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DOT-TSC-RSPA-81-13
0S82184961 ~.
S -t- -t- !, III 11111111111111111111 IIII!III - ~ensl IVI les t,-.-'.-.-"~.-I lUI--
Combustion AutomotiveEngines to Variations inFuel Prope.rties
- - " --;
N.A. Henein
Center for Automotive.ResearchWayne State UniversityDetroit MI 48202
February 1982Final Repon
This document is available to the publicthrough the National Technical InformationService. Springfield. Virginia 22161.
ous. DeporTmenf of TronsporTOtiOn
IIesearch and Special Pn:9UftbAdministratIon
Transportation Programs BureauOffice of Systems Engineering'~:=C-~-=-====_NTSIWashington DC 20500 .~EPRODUCEOBY: Nos.
u.s. Oepartmen1 of Commerce _Nal;onal TeChnic:al.lnf~r:matlonService
Springfield, Virginia 22161
... '
NOTICE
This document is disseminated under the sponsorshipof the Department of Transportation in the interestof information exchange. The United States Government assumes no liability for its contents or usethereof ..
NOTICE
The United States -Government does not endorse products or manufacturers. Trade or manufacturers'names appear herein solely because they are considered essential to the object of this report.
GENERAL DISCLAIMER
This document may be affected by one or more of the following statements
• This document has been reproduced from the best copy furnished bythe sponsoring agency. It is being released in the interest of makingavailable as much information as possible.
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1. ~.,.." No. .-
DOT-TSC-RSPA-81-13
Tec:hnical R.,ort Documentation Page
3. ~.cipi_t·. C.'olov No.
SENSITIVITIES OF INTERNAL COMBUSTIONAUTOMOTIVE ENGINES TO VARIATIONS INFUEL PROPERTIES
S. Report Oot.
February 19826. P.,fo""inv o'V...; 10"0" Cod.
DTS-321
DOT-TSC-RSPA-8l-13~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~8.P..~_i~O~_il~_~~"N~
7........or'sl
N.A. Henein
C~nter for Automotive Research*Wayne State UniversityDetroit MI 48202
.12, 5.-......inv "'v_c., N_ ..d ...dd,o..if.S. l'epartment of TransportationResearch and Special Programs AuministrationTransportation Programs BureauOffice of Systems EngineeringWashington DC 20590
10. w... Uni' No. CTRAISI
RS2l2/R25l711. ContrMt 0' G,., No.
.~ DTRS-57-80-P-80733
Final ReportApr-Dec 81
14. s,-....inv ....one., Cocl.
DPB-25
*Under contract to:
16. ...• .,r.ct
U.S. Department of TransportationResearch and Special Programs AdministrationTransportation Systems CenterCambrir=rop MA 02;47
" An assessment of the sensitivity of the automotive gasoline anddiesel engines to variations in fuel propertie's has been made. Thevariables studied' include H/C ratio, distillation range, aromatic content,ignition quality as determined by the octane number, and. the autoignition quality as determined by the cetane number. The sensitivity ofthe engine is 'measured' against its power output, fuel economy, emis-
~ sians, and degradation of lubricants. The sensitivity to the. use ofalternate fuels such as neat fuels or fuel extenders is discussed. Thealternate fuels studied include shale oil derivatives, coal liquefactionderivatives, and alcohols. The impact of using emergency fuels inautomotive gasoline and diesel engines is discussedo:;-f--"~'
.. 17. 1C0., Words
Sensitivity of Gasoline Engines;Sensitivity of Diesel Engines;Alternate Fuels; Fuel Characteristics.
DOCUMENT IS AVAILABLE TO THE PUBLICTHROUGH THE NATIONAL TECHNICALINFORMATION SERVICE. SPRINGFIELD.VIRGINIA 22161
19. s.a,n,., Clouif. (0' ",i. ,~"l
Unclassified
Fo"" COT F 1700.1 (8-72)
20. S.cu,i ,., Closs. I. <01 'hi. P0901
Unclassified
Reproduction of comple,ed pave au'horized
21. No. 01 Pov.. 22. P"".
240
•
•
"
PREFACE
• The purpose of this report is to assess the sensitivity ofautomotive gasoline and diesel engines to variations in fuel
properties. Engines have different degrees of sensitivity to the
different fuel properties. This report discusses the fuel
properties which have major effects on engine sensitivities.
Published results of past work in this area are included and
analyzed. Areas which need new or additional research are also
identified in this report .
..
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iv
Section
TABLE OF CONTENTS
1. SU~Y••••••••••••••••• o.lleo ••• e •• CI ••••••••••••••• 1-1
1.1 Introduct.ion ·· oo.D •• o 1-11.2 Probable Future Alternate Fuels ..•••••.•••••.• 1-21.3 Sensitivity of Gasoline Engines ••••••••••••••• 1-2
" 1.3.1 Gasoline Engine Alternate Fuel Options. 1-2
1.4 Sensitivity of Diesel Engines................. 1-6
1.4.1 Diesel Engine Alternate Fuel Options .•• 1-6
1.S Emergency Fuels ••••.••••••.•• o~ ••• o.OQ ••• ••••• 1-81.6 Recommendations II ~ ••• 0". 11 •• 0 •• 0 •• 0.0 1-9
1.6.11.6.21. 6.3
Future Fuel Characterization ••.•••••.•.Gasoline Engines 0000 ••••••••
Die 5 e 1 En gin e s. II 0 II • .. II II • .. • • • .. • II • • • .. II • • • •
1-91-91-10
2. INTRODUCTION AND BACKGROPND........................ 2-1
3. FUEL PROPERTIES AND THEIR EFFECTS ••.•••"............ 3-1
3. 1 Fu t ur e Fue Is II • II ••• 0 II • e .. II II • II •• II •• 0 • 0 e 0 ill II • 3-1
3.1.1 General ooo.•••••••• " ••••• e •• o. 3-13.1.2 Properties of Future Fuels............. 3-3
3.2 Sto ichiometry and Combustion.................. 3 - 5
3.2.1 Effect of HIC Ratio on Stoichiometry ••• 3-83.2.2 Effect of HIC Ratio on the Adibatic
Flame Temperature ••.........•.•.•..••.. 3-113.2~3 Effect of HIC Ratio on the (F-A)
Standard Cy~le .......•••...•.........•. 3-11
3.3 Gasoline Engine Fuels ...•....•....•........••. 3-11
3.3.1 Volatility and Distillation Range .•..•. 3-143.3.2 Detonation and Preignition .
Characteristics .•.•.•.••...•.....•..... 3-173.3.3 Energy Density ...............••.....•.• 3-193.3.4 Latent Heat of Evaporation............. 3-20
3.4 Diesel Engine Fuels ...............•..•...••.•. 3-21
3.4.1 Augoignition Quality ................•.. 3-213.4.2 Volatility and Distillation Range...... 3-29
v
TABLE OF CONTENTS (CONTINUED)
4.2 ~1ethanol Neat." 0 0 00" ••• 11 •• 0.
4.1 Alcohol-Indolene Blends ...•.....•••.•••••..•.•
4.3 Shale-Derived and Coal Derived Gasoline in
Section',,--
Page
3-293-29
4-1
4-1
4-14-1
4-5
4-13 ,.
4-16
4-23
4-314-32
4-34
4-34
4-36.4-40
4-46
4-514-51
4-534-664-664-664-674-674-67
Effect of Blending on a 3-Way CatalystCar with Closed Loop Emission ControlSystem at Constant Speed .Effect on a 3-Way Catalyst Car withClosed Loop Control System on FTPeye1e .. 0 0 CI ••• 0 CII •• 0 •• CI II •• 0 ••••••
Effect of Exhaust Aldehydes and AcetoneEmissions II ••••••••••••••••
Phase Separation .....•...............•.
-Effect of Blending Gasoline and Alcoholson Octane Number •....... ~ •.•.•.•••....•Effe ct on Fl arne Speed .........•.•.....•Effect on a Single Cylinder Engine'sPerformance, Thermal Efficiency andEffi'i S 5 ion S 0 0 • • • 0 !t II • • • • G • • • eo. II • • • • 0 ct 0 D • 00
Effect of Alcohols on a Non-CatalyticCar,. .•• CI •••••••••••••••••••••••••••••••
Effect on Reid Vapor Pressure ......•...Effect on API Gravity ...............•..Effect on Octane Number .............•..Effect on Power Index .Effect on Conservation Index .Effect on Tradeoff Index .Effect on Emissions Index .
Single Cylinder Engine Sensitivity .....Comparison Between the Single CylinderEngine Results and Cycle Computations ..Mu1ticy1inder Engine Sensitivity .•.....Sensitivity of a Vehicle to NeatAlcohol G ••••••••••
4.1. 7
4.1. 8
4.1. 6
4.1.1
4.1. 24.1. 3
4.1. 4
4.1. 5
4.2.14.2.2
4.2. 34.2.4
4.4.14.4.24.4.34.4.44.4.54.4.64.4. 7
Gasoline Engines.ooo CI ••••••
4.4 Gasoline Emergency Blends ...•....•.••..•.•.••.
3.4.3 ViscosityooCl.ra ....•.•... G •••••••••••••••
3.4.4 Specific Gravity .....•..•..•.•..•••.••.
4. ()SENSITIVITY OF AUTOMOTIVE GASOLINE ENGINES ItOVARIATIONS IN FUEL PROPERTIES •.•••.•.•.••.••.•.••.•
vi
Section
TABLE OF CONTENTS (CONTINUED)
5. SENSITIVITY OF AUTOMOTIVE DIESEL ENGINES TOVARIATIONS IN FUEL PROPERTIES...................... 5-1
5.1 D.I. Four-Stroke-Cyc1e Diesel Engine .••••••.•• 5-1
5.1.15.1. 25.1. 3
5.1. 4
5.1. 55.1. 6
5.1. 75.1.8
5.1.9
Effect of Cetane Number ..•••.••••••••••Effect of Aromatic Content •••.•.•••.•••Effect of Mixing DF-2 with ShaleDistillates a ••••••••••••••••••••••• a II ••
Effect of Mixing DF2 with CoalDistillates 0 ••••
Effect of' Using Alcohols ••.•.•.••.••..•Effect of Mixing DF-2 wit~ VegetableOils c •• a ••••••••
Effect of Mixing DF-2 with Gasoline •••.Effect of Using Two Separate InjectionSystems in a Diesel/Gasoline FueledEngine II ••••
Effect of Using Wide Cut Distillates ...
5-15-2
5-2
5-45-8
5-185-18
5-245-24
.. '
5.2 D.I. Two-Stroke-Cyc1e Diesel Engine ••••••••••• 5-26
5.2.1 Effect of Using Off-Specification DieselFuels 5-26
5.2.2 Effect of Using Fuels Derived from TarSands and Shale Oil ...•..••.••.....•.•. 5-36
5.3 I.D.I. Swirl Type 4-Stroke-Cycle Engine ......• 5-50
5.3.1 Effect of Fuel Properties on FuelEconomy and on Particulates andOther Emissions........................ 5-50
5.3.2 Effect of Fuel Properties onParticula tes 0 0 ••• 0 • 0 II III' 5 - S4
5.4 Diesel Emergency Blends ........... 0 •••• 0 ••• II e II 5-59
5.4.1 Effect on Cetane Number .•.•..• II ........ o- S-595 . 4• 2 Effect on API Gravity ........ o. C1 ••••••• 5-595.4. 3 Effect of Heat on Combustion ..•.•...•.. 5-595.4.4 Effect on Viscosity .................... 5-635.4. 5 Effect on Power I nde x .................. 5~63
5.4. 6 Effect on Conservation Index ....... 0 • Il • 5-635. 4. 7 Effect on Tradeoff I n de x ............... 5-635.4. 8 Effect on Emissions Indexe s ............ 5-63
vii
TABLE OF CONTENTS (CONTINUED)
7 • 2 Die 5 e 1 En gin e 5" 0 0 • II " III Q (I • 0 iii • • • 0 ••• 0 • 0 •• CI III III • • • • 0
7 e CONCLUSIONS •.• II •••••• 0 ••• II ••• 0 0 ••• 0 0 II 0 ...... 0 •••• 0 ••
6 • 3 Die 5 e 1 En gin e s. 0 0 0 • 0 0 tI ••• 0 0 • e g •••••••••••• e eo.
...Page
6-1
6-16-b
6-26-2
6-26-36-4
6-4
6-5
6-56-5
7-1
7-1
7-37-37-5
7-7
7-9
7-15
7-157-15
8-1
8-18-18-2
A-I
B-1
Alternate Fuel Option~......•..•.......Gasoline - Alcohol Blends ......•....•..Neat Alcohols.Cl.o CI.ee.IIl." .
Ni trogen Oxides o ••••••••••••••••
Sulfur Compounds ~ .Partial and Complete OxidationProducts .- 0 0 .
Hydrocarbons. 0 ••••••••• 0 •••••••••••••••
Corrosion .................•. e ••••••• o ••
Effect of Alcohol Fuels on Lubricationand Engine Wearae'oaooDoo.ao.oo ••••••••
Gasoline Engine Emergency Fuels .....•.•Diesel Engine Emergency Fuels .
7.1. J_7.1. 27.1. 3
6.2.16.2.26.2.3
6.2.46.2.56.2.6
7.3.17.3.2
6 . 3• 1 Soot Par t.i cuIate s .....•.....•••. '•..•.••6.3.2 Sulfur .
7.2.1 Alternate Diesel Fuel Options •.•••.•••.
701 Gasoline Engines ...•. o ••••••••••••••••••••••••
6.1 Introduction oo •••••••••• t1 •••• o ••••
6.2 Gasoline Engines ...........•.........•.•..•...
APPENDIX A - REFERENCES .......................•....
APPENDIX B - REPORt OF INVENTIONS .
8.1 Future Fuel Characteristics ..............•....8.2 Gasoline Engines " o •••• o ••• e •••••••
8.3 Diesel Engines o ••• ooc.Il.II •••• ooooo •••••••
8 • RE COrvn·lENDATION Sill •. e •••••••• III • III " • 0 • 0 • III •• 0 0 III • II •••••••
6. SENSITIVITY OF ENGINE LUBRICATION TO VARIATIONSIN FUEL PROPERTIES ...••.•••.••.•••••••••••.••••.•••
Section
viii
LIST OF ILLUSTRATIONS
Figure.
3.1 TRENDS OF THE END-POINT AND CETANE NUMBER FOR U.S.AND EUROPEAN-PRODUCED DIESEL FUEL.................. 3-6
3.2 TRENDS OF THE CLOUD-POINT OF U.S. AND EUROPEANPRODUCED DIESEL FUELS ...••••.•..•...••••..•.• ~ .•••• 3-7
3.3 EFFECT OF HYDROGEN-TO-CARBON RATIO ON THEORETICALAIR-FUEL RATIO..................................... 3-9
3.4 EFFECT OF FUEL STRUCTURE fu~D NUMBER OF CARBON ATOMSON THEORETICAL AIR-FUEL RATIO...................... 3-10
3.5 EFFECT OF HIC RATIO ON ADIABATIC FLAME TEMPERATURE. 3-12
3.6 EFFECT OF HIC RATIO ON (F-A) STANDARD CONSTANTVO LUME C'lCLE....................................... 3-13
3~7 TYPICAL ASTM DISTILLATION CURVES ....••.•.......•..• 3-15
3.8 EFFECT OF DISTILLATION RANGE ON ENGINE PERFORMANCE. 3-16
3.9 VAPOR-AIR VERSUS FUEL-AIR RATIOS FOR OCTANE(C8H1S) AT 1 ATM................................... 3-18
3.10 RELATIONSHIP BETWEEN THE C.N. AND C.R. IN THE CFRENGINE WITH HMN AND XMN AS REFERENCE FUELS 3-23
3.11 CORRELATION BETI~EEN THE C.N. AND O.N. OF DIFFERENTFUE LS 0 •• 0 u a .. • • 3 - 2 5
3.12 A ·MODIFIED CETANE SCALE FOR RATING LOW IGNITIONQUAL I TY FUE LS II • 0 •••••• 0 • • • • 3 - 26
3.13 CYCLE-TO-CYCLE VARIATION IN THE AUTOIGNITION OFFUELS OF DI FFERENT CETANE NUMBERS.................. 3-27
3.14 PROBLEMS ASSOCIATED WITH VARIATIONS IN DIESEL FUELVOLATILITy 0 0.. 0...... 3,-30
3.15 PROBLEMS ASSOCIATED WITH VARIATIONS IN DIESEL FUELVI S COS I TY a II • • • • • .. • • 3 - 30
3.. 16 RELATIVE PERFORHANCE OF A DIESEL ENGINE AT CONSTANTFUEL-PUMP SETTINGS VERSUS SPECIFIC GRAVITY OF FUEL. 3-31
4.1 OCTANE CHARACTERISTICS OF GASOLINE HETHANOL BLENDS. 4-2
4.2 CORRELATION BETWEEN OCTANE INCREMENT AND BASE FUELOCTANE NUf\lRER..•.•...••.••...••...•.•.•.•.•• III •••••• 4-3
1.X
LIST OF ILLUSTRATIONS (CONTINUED)
Figure
4.3 EFFECT OF BLENDING METHANOL WITH INDOLENE ON THE
4.10
FL.Al\1E SPEED. II • • • • • • • • • • • • • • • • 0 • • • a • • • • • • • • • • • • • • • • • 4 .. 4
4.4 EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBHP AND MBT •.••.....•••••...•..•••.•••• &I • e-. • • • • • • • • 4 - 6
4.5 EFFECT OF MIXING METHANOL WITH INDOLENE ON BRAKESPECIFIC FUEL CONSUMPTION.......................... 4-7
4.n EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC ENERGY CONSUMPTION 4-8
4.7 EFFECT OF MIXING METf~NOLWITH INDOLENE FUEL ONBRAKE SPECIFIC UNBURNED HyDROCARBONS ..•.....•. :.... 4-10
4.8 EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC CARBON MONOXIDE .............•...•... 4-11
4. 9 EFFECT OF }.1! XI NG METHANOL WI Tf-! IlmOLENE FUEL ONBRAKE SPECIFIC NITRIC OXIDES 4-12
EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONPEAK BRAKE SPECIFIC NITRIC OXIDES.................. 4-14
4.11 OfANGES IN FTP RESULTS FOR 10% METHANOL-ADDED TOINDOLENE IN A NON-CATALYTIC CAR 4-15
4.12 EFFECT OF REID VAPOR PRESSURE ON THE TOTALEVAPORATIVE EMISSIONS.............................. 4-21
4.13 EFFECT OF METHANOL ON. THE PERFORMANCE AND EMISSIONSOF A 3-WAY CATALYST CLOSED LOOP CAR AT CONSTANTSPEED ......••...........•.......••.•..•.••..•..•••. 4-22
4.14 ISO FUEL-ENERGY CONTOURS FOR METI-IANOL-GASOLINEBLENDS 4-24
4.15 3-WAY CATALYST CONVERSION EFFICIENCY FOR HC, CO ANDNOx AS A FUNCTION OF LAMBDA........................ 4-25
4.16. OXYGEN SENSOR MILLIVOLT OUTPUT AS A FUNCTION OFEXHAUST GAS COMPOSITION (LAMBDA)................... 4-25
4.17 EMISSIONS ON THE FTP AS A FUNCTION OF ETHANOL IN ANETHANOL/GASOLINE BLEND 4-29
4.18 CLOUD POINT FOR VARIOUS METHANOL-GASOLINE BLENDS 4-33
x
LIST OF ILLUSTRATIONS (CONTINUED)
Figure
4.19 EFFECT OF C.R. ON POWER AND EFFICIENCy ..•.......... 4-35
4.20 EFFECT OF C.R. ON SAVINGS IN FUEL-ENERGY, AT37 MPH AND AT 62 MPH ROAD LOADS 4-37
4.21 PERCENTAGE DECREASE IN FUEL-ENERGY IN A METHAl'JOLFUELED ENGINE IN RELATION TO A PRODUCTION GASOLINEENGINE ' . . -e.................. 4-37
4.22 HC AND NOx EMISSIONS VERSUS C.R ; 4-38
4.23 HIXTURE TEMPERATURE WITH METHANOL AND GASOLINE 4-41
4.24 ENGINE OUTPUT WITH METHANOL AND GASOLINE 4-41
4.25 BRAKE THERNAL EfFICIENCY WITH METHANOL ANDGASOLINE · 4-43
4.26 EXHAUST NOx WITH METH.ANOL Al'JD GASOLINE 4-44
4.27 EXHAUST CO WITH METHAt'JOL AND GASOLINE.............. 4-45
4.28 EXHAUST HC WITH METHANOL AND GASOLINE 4-45
4.29 EXHAUST ALDEHYDES WITH METHANOL AND GASOLINE 4-47
4.30 EFFECT OF WATER ADDITION TO METHANOL ON EXHAUSTEMISSIONS AND ENGINE POWER......................... 4-48
.4.31 PNA HYDROCARBONS WITH METHANOL AND GASOLINE 4-49
4.32 EXHAUST EMISSIONS WITH METHANOL AND GASOLINE ATFULL THROTTLE ................•..' •......•...•.•.•... 4-StJ
4.33 EFFECT OF GASOLINE EXTENDERS ON RVP 4-54
4.34 EFFECT OF GASOLINE EXTENDERS ON API GRAVITy 4-55
4.35 EFFECT OF GASOLINE EXTENDERS ON OCTANE Nill1BER 4-56
4.36 EFFECT OF GASOLINE EXTENDERS ON POWER INDEX 4-57
4.37 EFFECT OF GASOLINE EXTENDERS ON CONSERVATION INDEX. 4-58
4.38 EFFECT OF GASOLINE EXTENDERS ON TRADEOFF INDEX ..... 4-59
4.39 EFFECT OF GASOLINE EXTENDERS ON THE HYDROCARBONSINDEX AT IDLE...................................... 4-60
Xl
LIST OF ILLUSTRATIUNS (CUNTINUED)
Figure
4.40 EFFECT OF GASOLINE EXTENDERS ON CO INDEX AT IDLE ... 4-61
4.41 EFFECT OF GASOLINE EXTENDERS ON NOx INDEX AT IDLE.. 4-62
4.42 EFFECT OF GASOLINE EXTENDERS ON HYDRC~ARBON INDEXAT ROAD LOAD....................................... 4 - 63
4.43 EFFECT OF GASOLINE EXTENDERS ON CO INDEX AT ROADLOAD 4-64
4.44 EFFECT OF GASOLINE EXTENDERS ON NOx INDEX AT ROADLOAD............................................... 4-65
5.1 PREDICTED WEIBULL FAILURE PROFILE FOR ENGINESOPERATING ON DILUTED DIESEL FUELS.................. 5-5
5.2 CETANE NUMBER VERSUS PERCENTAGE OF CETANOX INr"IETHAN,O L••••••••••.•..... ". • . . • . • . . . • • • • . • • • • • . • • • • • 5 -1 0
5.3 EFFECT OF THE AMOUNT OF CENTANOX IN HETHANOL ON HCEM! 55 IONS II •• • ' • ~ •••• 0 ••••••• 0 0 II • II II ••••••• I!I ••• II • • • • • • 5 -1 0
5.4 EFFECT OF THE BACK PRESSURE ON HC EMISSIONS 5-13
5.5 PERCENTAGE NEEDED OF CETANOX IN METHANOL AND CETANENUMBER TO MINIMIZE HC EMISSIONS TO 400 PPM 5-13
5.6 HC-EMISSIONS VERSUS DRIVING TIME AT NO-LOAD AFTERFULL LOAD AT ENGINE SPEED 1500 RPM................. 5-15
5.7 EFFECT OF DIESEL DYNAMIC INJECTION TIMING ON SMOKEAND HC EMISSIONS WITH FIXED METHANOL TIMING 5-15
5.8 COMPARISON OF PART LOAD PERFORMANCE BETWEEN STANDARDDIESEL AND DIESEL/METHANOL ENGINES AT 1500 RPM ..... 5-17
5.9 PART LOAD PERFORMANCE WITH DIESEL/ETHANOL ENGINEAT 1500 RPM........................................ 5-1 7
5.10 CETANE NUMBER OF DIESEL-GASOLINE MIXTURES.......... 5-20
5.11 EFFECT OF MIXING GASOLINE WITH DIESEL FUEL ONIGNITION DELAy , 5-21
5.12 TYPICAL DIESEL FUEL AND GASOLINE LOAD RANGE CURVESFROM A 6 CYLINDER 300 CID DIESEL ENGINE 5-i2
5.13 COMPARISON OF PART LOAD PERFORMANCE WITH DIESEL/CRUDEGASOLINE AND CRUDE GASOLINE AT 900 RPM ' 5-25
Xll
LIST OF ILLUSTRATIO~S (CONTINUED)
Figure
5.14, EFFECT OF C.N. VARIATIONS ON LD. AND RATE OFPRESSURE RISE (2-CYLINDER ENGINE).................. 5-27
,5.15 EFFECT OF C. N. ON ENGINE PERFORMANCE (2 - CYCLEENGIN E) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 • • • • • • 5 - 2 8
5.16 EFFECT OF C.N. ON EMISSIONS IN A 2-CYCLE ENGINE .... 5-30
5.17 EFFECT OF VISCOSITY ON EMISSIONS IN A 2-CYCLEENGINE ....................................•· .••..... 5-31
5.18 EFFECT OF C.N. ON LD. FOR VARIOUS DISTILLATIONRANGE FUELS........................................ 5-33
5.19
5.20
EFFECT OF C.N. ON RATE OF PRESSURE RISE-DISTILLATIONRANGE· SERI ES -. . . . . . . . . . . 5 - 33
EFFECT OF API GRAVITY ON BRAKE THERr·1AL EFFICIENCYDISTILLATION RANGE SERIES ...............•.......... 5-34
5.22
5.21
~.
.=
EFFECT OF API GRAVITY ON BRAKE HORSEPOWER -DISTILLATION RANGE SERIES 00 ~....... 5-34
EFFECT OF VISCOSITY ON BRAKE THEID·1AL EFFICIENCYDISTILLATION RANGE SERIES 5-35
5.23 EFFECT OF VISCOSITY ON BRAKE HORSEPOWERDISTILLATION RANGE SERIES 00_...... 5-35
5.24 RELATIONSHIP BETWEEN VISCOSITY AND API GRAVITY FORDIFFERENT DISTILLATES 5-37
5.25. EFFECT OF API GRAVITY ON BRAKE SPECIFIC HC -DI STI LLATI ON RANGE SERI ES. . . . . . . . . . . . . . . . . . . . . . . . . . 5- 38
5.26 EFFECT OF VISCOSITY ON BRAKE SPECIFIC HC -DISTILLATION RANGE SERIES 5-38
5.27 EFFECT OF TOTAL BTU INPUT ON BRAKE SPECIFIC CARBONMONOXIDE EMISSIONS - DISTILLATIO~ RANGE SERIES ..... 5-39
5.28 EFFECT OF C. N. ON BRAKE SPECI FI C CARBON ~1ONOXI DE -DISTILLATION RANGE SERIES 5-39
5.29 COMPARISON OF I.D. WITH REGULAR DIESEL FUEL ANDFUELS DERIVED FROM SHALE AND TAR SANDS 5-42
xiii
LIST OF ILLUSTRATIONS (CONTINUED)
Figure
5.30 COMPARISON OF MAXIMUM RATE OF PRESSURE RISE WITHREGU~AR DIESEL FUEL AND FUELS FROM SHALE AND TARSANDS .....••.•••••.•.••••• 0 0 ••••••• " • 0 •• II •• 0 ••••• II II 5- 43
5.31 BSFC WITH SHALE AND TAR SANDS FUELS RELATIVE TORE GU LAR FUEL •• Cl • ,.:) ••••••••••••• 0 •• 0 •••• II •• II II II II • • • • • 5- 44
5.32 COMPARISON OF SMOKE WITH REGULAR DIESEL FUEL ANDFUELS DERIVED ,FROM SHALE AND TAR SANDS............. 5-45
5.33 NOx EMISSION BY MASS WITH SHALE AND TAR SANDS FUELSRELATIVE TO REGULAR DIESEL FUEL 5-47
5.34 HC EMISSIONS BY ~~SS WITH TAR SANDS FUEL RELATIVETO REGULAR DIESEL FUEL............................. 5-48
5.35 CO EMISSION BY MASS WITH SHALE AND TAR SANDS FUELSRELATIVE TO REGULAR DIESEL FUEL 5-49
5.36 CONTRIBUTION OF VARIOUS COMPONENTS OF DIESEL FUELTO PARTICULATE EMISSIONS •.......................... 5-53
5.37 DISTILLATION RANGE OF SONE OF THE FUELS TESTED .•... 5-53
5.38 PARTICULATE INDEX IN ARBITRARY UNITS VS. FUELAROMATIC CONTENT................................... 5-57
5.39 PARTICULATE INDEX IN ARBITRARY UNITS VS. FUEL 90%BOILING POINT...................................... 5-57
5.40 EMISSIONS AND ECONO~~ VARIATION WITH FUEL BLENDS OFINCREASING AROMATICITY fu~D SPECIFIC GRAVITYSTARTING WITH D-2 FUEL 5-58
5.41 EMISSION AND ECONOMY VARIATION WITH FUEL BLENDS OFINCREASING AROMATICITY AND SPECIFIC GRAVITYSTARTING WITH LOW-AROMATIC NARROW CUT PRODUCT 5-58
5.42 EFFECT OF DIESEL EXTENDERS ON C.N 5-61
5.43 EFFECT OF DIESEL EXTENDERS ON API GRAVITy 5-62
5.44 EFFECT OF DIESEL EXTENDERS ON THE HEAT OFCOMB US TION II .... 0 •• I ••••••• II •• II •• 0 • 0 • Cl •• 0 • 0 •• II 0 •• 0 CI • e 5 - 64
5.45 EFFECT OF DIESEL EXTENDERS ON VISCOSITY 5-65
XIV
LIST OF ILLUSTRATIONS "(CUNTINUED)
Figure Page
5.46 EFFECT OF DIESEL EXTENDERS ON POWER INDEX .....•.... 5-66
5.47 EFFECT OF DIESEL EXTENDERS ON CONSERVATION INDEX ... 5-67
5.48 EFFECT OF DIESEL EXTENDERS ON TRADEOFF INDEX...•.... · 5-68
"5.49 EFFECT OF DIESEL EXTENDERS ON HC I N'DEX ...... 0 ••••• III 5-69
5.50 EFFECT OF DIESEL EXTENDERS ON CO INDEX ............. 5-70.
5.51 EFFECT OF DIESEL EXTENDERS ON NO x INDEX............. 5-71
5.52 EFFECT OF DIESEL EXTENDERS ON SMOKE INDEX ..•....... 5-72
6-l. EFFECT OF SULFUR CONTENT ON WEAR................... 6-7
LIST OF TABLES
c.- Table
1.l.
1. 2.
3.1
3.2
3.3
3.4
3.5
4.1
4.2
4.3
4.4
Page
PROBABLE FUTURE ALTERNATE FUELS ................•... 1-3
SOURCES OF ALCOHOLS i-4
PROPERTIES OF SYNTHETIC MOTOR FUELS PRODUCED FROMSI-I~I\.LEO I L. • • • • • • • • • • III .. • • III II • • III • • • • • • • • • • • • .' • • • • III .. III • • 3 - 4
PROPERTIES OF U.S. AND NON-U.S. DIESEL FUELS 3-8
OCTANE RATING METHODS .. ;........................... 3-19
SPECIFIC GRAVITY AND ENERGY-DENSITY FOR DIFFERENTFUELS. It •••••••••• o. -II 0.0 III III II ••• CI III 3-20
LATENT HEAT OF EVAPORATION OF DIFFERENT FUELS 3-21
COMPRESSION RATIOS CORRESPONDING TO VARIOUSINDOLENE-METHANOL BLENDS........................... 4-5
PROPERTIES OF THE DIFFERENT FUELS 4-17
PROPERTIES OF BLENDS OF INDOLENE AND ALCOHOLS 4-18
SUMMARY OF THE EXHAUST EHISSIONS, EVAPORATIVEEMISSIONS, AND FUEL ECONOMY 4-19
xv
LIST OF TABLES (CONTINUED)
Table
4. 5 FUEL ECONOMY WI TH DI FFERENT BLENDS BASED ON THEI RENERGY CONTENT g •••••••••••• oc ••••••••• 4-20
(\
4.6 EMISSIONS FOR FTP PROCEDURE WITH ETHANOL -GASOLINE BLENDS ...•....•.• ".....•.....•.•••.•..••. C1 4-28
4.7 EMISSIONS OF FTP PROCEDURE FOR A 3-WAY CATALYST CARWITH CLOSED LOOP CONTROL, WITH BLENDS OF GASOLINE,DIESEL FUEL AND WATER ..•........................... 4-30
4.8 CHART CALCULATIONS OF CYCLE CHARACTERISTICS 4-39
4.9 PROPERTIES OF SHALE OIL-DERIVED GASOLINE 4-52
4.10 EMISSIONS AND FUEL ECONO~~ RESULTS WITH SHALE- .DERIVED GASOLINE 00 4-52
4.11 EMERGENCY GASOLINE EXTENDERS....................... 4- 66
5.1 TYPICAL PERFOR~~NCE DEGRADATION OF SHALE OILDI LUT ION •• II'. 0 • 0 ••••••• 0'•••• II • • e.•••• Cl •• 0 • 0 0 • II 0 •••• e e 5 - 3
5.2 SELECTED PROPERTIES OF COAL DISTILLATES 5-6
5.3 TYPICAL PERFORMANCE DEGRADATION WITH TAR OIL ANDHYDROGENATED CREOSOTE OIL~ 5-7
5.4 POUR POINT (ASTM D975) OF DIESEL OILS DILUTED WITHCOAL DERIVED CRUDE................................. 5-9
S. 5 PERFOro.~NCE IMPACT OF ETHANOL FUELING.............. 5-12
5.6 PERFORMANCE IMPACT OF EXTENSION WITH VEGETABLE OIL. 5-19
5.7 PERFORMANCE IMPACT OF COTTON-SEED OIL EXTENSION 5-19
5.8 NO.2 DIESEL. FUEL PROPERTIES 5-29
5.9 PROPERTIES OF REGULAR DF-2 FUELS DERIVED FROM SHALEAND TAR SANDS ... G ••••••••• o ••••••••••••••• o .. eo ••• IiIG 5-41
5.10 PERFORMANCE IMPACT OF ETHANOL FUELING 5-51
5.11 PHYSICAL PROPERTIES OF G.M. STUDY FUELS 5-52
XVl
Table
5.12
5.13
5.14
7.1
7.2
7.3
7.4
7 ~ 5
7.6
2: 7. 7
LIST OF TABLES (CONTINUED)
Page
PROPERTIES OF D-1, D-2 &C-40 .....................• ~-55
PARTICULATES WITH D-2 AND C-40 FUELS - FTP CYCLE 5-56
EMERGENCY DIESEL EXTENDERS 5-60
IMPORTANT FUEL PROPERTIES FOR GASOLINE ENGINES 7-2
GASOLINE ENGINE ALTERNATE FUELS: GASOLINE - ALCOHOLBLENDS 7-4
GASOLINE ENGINE NEAT ALCOHOLS COMPARED TOIr~DOLENE........................................... 7-6
IMPORTANT FUEL PROPERTIES FOR DIESEL ENGINES 7-8
DP-2 GASOLINE BLENDS 7-11
DIESEL ENGINE ALTERNATE FUELS (DF-2/SYNFUELS'B LENDS) .......................•.............. .' ....' .' . 7 -12
DF-2/ALCOHOL BLENDS 7-13
xvii/xviii
1. SUMMARY
1.1 INTRODUCTION
The properties of automotive fuels are expected to change
in the future as efforts continue~to extend the petroleum reserves
and produce alternate fuels to replace the petroleum derived
fuels. These efforts are being made to reduce imports and achieve
energy self reliance. Automotive engines are sensitive to many
of the fuel properties which are expected to change. This report
deals with the sensitivities of the present, mass produced internal
combustion, automotive gasolini and diesel engines to variations
in fuel properties. Other types of automotive engines, such as
stratified charge or gas turbine, are still in the research anddevelopment stage and are not included in this report.
The introduction of alternate fuels may take one of the
following forms:
1. Varying the distillation range of currently produced
fuels (gasoline and diesels) in order to increase the
yeild of crude petroleum.
2. Mixing gasoline and diesel fuels with liquid synthetic
fuels such as shale oil derivatives, coal derivatives
or biomass derivatives.
3. Replacing gasoline and diesel fuels with alternate
fuels.
The gradual shift from regular automotive fuels to alternate
fuels in any of the above forms will result in variations in fuel
properties which affect combustion, lubrication, engine performance~
fuel economy,· emissions and reliability. This report emphasizes
the projected impact of those alternate fuels which are expected
to be available in the future on automotive engines.
1-1
1.2 PROBABLE FUTURE ALTERNATE FUELS
A pDssible scenario for future automotive fuels is given in
Table 1.1. This table is a result of studies made of reports
published by DOE, oil refining companies, research institutions
and automotive companies. For the immediate term (1980-1990),
current types of mass produced automotive fuels will be available
and are expected to be extended by alcohols or alcohol based
additives. For the near term (1990-2000), in addition to alcohols,it is probable that syncrudes derived from shale oil and coal
derivatives will be mixed with feedstocks of the refineries. For
the midterm future (2000-2020), the production of syncrudes is
expected to increase and reach about 10 percent of the U.S.
petroleum demand. For the long term future (2020-2040), new
engines may be mass produced to match the fuels which will then be
available. The contribution of syncrudes in the production of
these fuels is expected to reach 30 to 40 percent. For the farfuture (2040-2060),syncrude production is expected to equal that
of natural petroleum ~rude and gradually replace it. For post
2060, fuels (such as hydrogen) produced using inexhaus"tible energysources (such as solar energy or fusion energy) are expected to be
introduced. The use of hydrogen in automotive engines is con
tingent on the development of safe and economically competitivedistribution and storage systems.
1.3 SENSITIVITY OF GASOLINE ENGINES
Gasoline engines are mainly sensitive to the following fuel
properties: volatility, octane number, Hie ratio, latent heat of
evaporation, volumetric energy content, and sulfur and nitrogen
content.
1.3.1 Gasoline Engine Alternate Fuel Options
1.3.1.1 Synthetic Gasoline - Synthetic gasoline can be produced
from oil shale or coal derivatives. Synthetic gasoline from shale
oil is mainly paraffinic and is low in octane number. Synthetic
1-2
TABLE 1.1 PROBABLE FUTURE ALTERNATE FUELS
IMMEDIATETERM
NEAR-TERN
MID-TERN
LONG-TERN
FAR-TERM
POST-2060
1980
1990
12000
12020
12040
12060
Adequate supply of petroleum derived gasoline anddiesel fuels.Introduction of ethanol as octane improver or asa blend in gasohol (10%), and introduction ofmethanol.Production of gasoline from methanol (Mobil Process)Production of MTBE octane improver from methanol(Arco Process)
Introduction of syncrudes from shale oil and coalderivatives in the feedstocks of the refineries.The product depends upon the amount and composition of the syncrude and the degree of refinipg.
Production of syncrudes equivalent to about 10%of the -potential U. S'. petroleum demand.
Possible production of new engines to match thenew fuels.Production of sy~crudes equivalent to about 30%or 40% of the potential U.s. petroleum demand.
Possible introduction of hydrogen from inexhaustable energy sources.Production of syncrudes equivalent to more than50% of the potential U.S. petroleum demand.
Alternate non-petroleum fuels dominate.
1-3
gasoline from coal derivatives is rich in aromatic content and is
high in octane numb.er. It is expected that the a1 ternate fuels
will be introduced in the form of syncrude added to the refinery
feedstock. The quality of the produced fuel will depend upon the
quality of the feedstock, and energy expenditure in the refinery.
The increase in the octane number of the fuel (by using more
coal derived fuels) will allow the use of higher compression
ratios and improve the thermal efficiency of the gasoline engine.
The control of sulfur and nitrogen content of the final product
is crucial for limiting the emission of NO· and sulfates from the. xgasoline engine. In addition to emissions, the nitrogen ,and sul-
fur content of the gasoline from syncrude should be reduced to
avoid oil contamination, with resulting engine wear and'deterior
tion.
1.3.1.2 Alcohols - Alcohols are practical extenders or substitutes
for petroleum fuels. Methanol and ethanol, which are the least
expensive alcohols, can be produced from many sources as indicated
in Table 1.2.
TABLE 1.2 SOURCES OF ALCOHOLS
!t Source
! Methanol CoaljJ ! Natural gasII
,I \ Wood biomassi ~
I Municipal waste•
Ethanol Biomass: grain
sugar cane
other plants
Ethanol is currently marketed as an extender to gasoline in
gasohol which consists of 90 percent gasoline and 10 percentethanol. In a recent study. by T. Austin and G. Rubenstein (3.26)*,
*References are listed in Appendix A.
1-4
..--,:':: '.....~~!~. ,
the use of gasohol manufactured from u.s. grown corn was found to
be uneconomical from an energy point of view, and will increase,
rather than decrease the dependence of the United States on crude
oil. This is an alarming finding and requires immediate action
for further research.
The use of alcohols can take one of the following forms:
a. Alcohol-Gasoline Blends
Blends with a methanol content ?f up to 20 percent have
been found by VW (4.18) to require only minor engine
and vehicle modifications. The high octane number of
the blend allows the use of a higher compression ratio
(C.R.) resulting in a higher thermal efficiency. Using
methanol without increasing the C.R. or optimizing the
spark advance has no effect on the thermal efficiency.
The disadvantages are:
Drop in fuel economy measured in miles per gallon,
caused by the lower volumetric energy content of
the alcohols.
Increase in evaporative emissions, caused by the
increase in the volatility of the alcohol - gasoline
blends.
Increase in NOx exhaust emissions caused by the
leaning of the charge due to blending with alcohols.
(Alcohols have a lower stoichiometric air - fuel
ratio.)
Other problems related to lack of compatibility of
the engine and vehicle materials with alcohol-gasoline blends, and phase separation of the methanol
gasoline blends.
b. Neat Alcohols
Neai alcohols allow the use of a high compression ratioresulting in high thermal efficiency. Also, neat alcohols
1-5
with MBT (minimum advance for best torque); spark
timing, and optimum C.R. can produce less NO , HC and CO.x
Problems associated with the use of neat alcohols are:
A cold starting aid is absolutely essential for
starting the engines at temperatures below goC (46°F).
The fuel economy measured in miles per gallon, drops.
1.4 SENSITIVITY OF DIESEL ENGINES
Automotive diesel engines are mainly sensitive to the following fuel properties: cetane number (which affects every aspect
of the diesel combustion process), distillation range, aromaticity,
viscosity, sulfur content, nitrogen content, and energy density.
1.4.1 Diesel Engine Alternate Fuel Options
1.4.1.1 Broad or Wide Cut Distillates from Petroleum Crude
The increa.se in demand for jet fuel and heating oil is puttingpressure on refineries to produce wide cut distillates or diesel
fuels with more, heavier compounds. DF-3, which is heavier and
has a lower cetane number than diesel fuel (DF-2), is being considered for transportation diesel engines. The anticipated main
problems with DF-3 are related to increase in smoke information
and the resulting limitation on power to keep smoke emissions
within bounds.
The wide cut distillates contain lighter compounds than DF-2,
which cause a drop in cetane number and an increase in volatility.No work has been done to study the sensitivity of automotive
diesel engines to broad or wide cut distillates.
1.4.1.2 Synthetic Diesel Fuel from Oil Shale or Coal - Very
limited studies have been made on blends of DF-2 and synfuels
derived from shale oil and coal derivatives.
1-6
1.4.1.3 Alcohols in Diesel Engines - The use of alcohols in
diesel engines may take one of the following forms:
a. Alcohol - Diesel Blends
Mixing alcohols with diesel fuel has been found to re
ducethe smoke emission, and increase the smoke limited
power. It increases the BSFC, and the hydrocarbon,
aldehyde and noise)emissions.~~
Problem areas are related to:
.Co1d starting caused by the low cetane number of
alcohols,
Lubricating oil contamination by alcohols and their
combustion products, which causes engine wear, and
injection system wear.
b. Alcohol - DF-2 Emulsions
The cold starting problems experienced in the DF-2
alcohol blends, may be reduced by using alcohols as
emulsions. Pure DF-2 is used for cold starting. The
, concentration of the emulsified alcohol increases with
load. This will increase the smoke-limited power.
Problem areas are related to:
The need for an emulsifier and an extra tank.
Complicated techniques needed to control the two
fuels, particularly under transient modes.
c. Alcohol Carburet ion or Manifold Injection and Autoigni
tion of Diesel Fuel
The engine starts on diesel fuel. Alcohols are intro
duced into the intake manifold by carburetion or manifold
injection. The fraction of alcohols increases with load.
Problem areas are related to:
Misfiring at light loads,
Self-ignition at high loads,
1-7
The need for elaborate control systems to optimize
the timing and metering of the two fuels,
Excessive increase in the hydrocarbon and aldehyde
emissions.
d. Two Separate Injection Systems
The engine starts on diesel fuel. The alcohol injection
starts after warm up, the amount increasing with load.
Problem areas are related to:
The need for two high pressure injection systems.
The need for elaborate control systems.
e. Neat Alcohols
Neat alcohols have very low cetane numbers and need to
be mixed with two additives: i) cetane improvers to
increase their cetane number, and ii) lubricating oil to
improve their lubricity.
Problem areas are related to:
The absolute need for a starting aid. The aid can
be in the form of an intake air heater, or starting
on diesel fuel. The research work conducted so faron the use of alcohols in automotive diesel engines
has been very limited, and definite conclusionscannot yet be reached in this area. Further workis needed.
1.5 EMERGENCY FUELS
In case of a national emergency, vehicles to conduct certain
essential services would be required. Automotive gasoline and
diesel engines would be required to run on emergency fuels formed
from the available stock of basic fuels, extended with other liquid
fuels. One program was conducted on the use of emergency fuelsin automotive engines in a very limited number of vehicles. The
results of this program showed the following.
1-8
o
) .
a. Only alcohols can be used in automotive gasoline engineswithout the need to reduce the engine compression ratio
in order to avoid knock. The other emergency blends
studied are DF-2, marine diesel fuel, kerosene and
maphtha and their blends with alcohols.
b. For diesel engines: jet fuels, kerosene, medium naphtha
and No.4 fuel oil were used without any significant
()differences in engine operation being observed. Blend
ing with gasoline and alcohols decreased cetane number,
and smoke. This would probably increase the engine noise,
dilution of lubrication oil, and wear, particularly in the
injection system.
1.6 RECOMMENDATIONS
1.6.1 Future Fuel Characterization
Develop the following:
a. Scenarios for probable future fuels based on the availa
bility ·of new technologies and energy sources.
b. Data base for the variations in fuel properties caused by
blending the base fuels with different extenders.
c. Data base for the effect of variations in the fuel
properties on cetane number and octane number.
d. Information on the impact of alternate fuels on the
lubrication. of automotive engines.
1.6.2 Gasoline Engines
a. Investigate the sensitivity of gasoline engines to varia
tions in base fuel properties.
b. Assess tradeoffs in economy, performance and emissions
with variations in the fuel properties which affect cost
and energy savings in the refinery.
1-9
c. Assess the impact of mass-producing gasohols on the U.S.
energy situation, and the U.S. dependence on importedcrude.
d. Study of the use of neat alcohols, and their blends with
gasoline, in automotive gasoline engines. Engines should
be optimized for the alcohols.
e. Find techniques to solve the cold starting problems of
gasoline engines wi!h alcohols.
1.6.3 Diesel Engines.
a. Investigate the sensitivity of diesel engines to varia
tions in the base DF-2 by varying the fractioni of ~he
1ight and heavy c.ompounds.
b. Assess the tradeoffs in economy, performance, emissions
and variations in fuel properties which have an impact
on cost and energy savings in the refinery.
c. Develop a cetane scale suitable for rating the alternate
fuels.
d. Study the problem of instability of the autoignition
process of low-ignition-quality alternate fuels in dieselengines. Develop techniques to reduce its effect on
engine reliability.
e. Determine techniques to improve the cetane number of
alcohols.
f. Investigate the use of neat alcohols and their blends in
automotive D.I. and I.D.I. diesel engines.
The above recommendations are made to develop basic technicalinformation which is currently lacking.. This information is
essential for utilizing future alternate fuels in automotive
gasoline and diesel engines.
1-10
.,....~.
2. INTRODUCTION AND BACKGROUND
The future supply of automotive fuels, and changes that may
occur in their properties are matters of concern. While today
there are ample supplies of automotive fuels derived from petroleum,
the rate at which the world petroleum demand is increasing is such
that adequate supplies can only reasonably be assured until approxi
mately 1990 (2.1). Beyond 1990, it will be necessary to introduce
alternative sources of liquid automotive fuels in increasing
quantities. It will also be necessary for the United States to
produce alternative automotive fuels from the more plentiful
domestic energy sources available in order to reduce imports, and
achieve greater energy independence.
Coal and oil shale are the most promising sources in the
United States for the supplemental crude materials (syncrude)
needed for automotive fuel production. The syncrudes may either
be used separately as, refinery feedstock, or fed to the refinery
as part of a mixed charge of natural and synthetic crudes. The
product characteristics will depend on the applicable refining
- technology, as well as on the material in the feedstock.
Alcohols such as methanol and ethanol represent another type
of alternate fuel, which can be produced from coal or biomass.
Fermentation of biomass has been used for thousands of years to
produce methanol and ethanol. More recently, enzymes have been
used to convert cellulose to sugar, which is then processed intoethanol.
The criteria which will affect the future automotive fuels
concern the energy source, conversion technology, environmental
concerns, energy,efficiency, fuel distribution and storage costs,
and certain properties of fuels which control their compatibility
with future automotive engines.
The present types of gasoline and diesel engines are expected
to power vehicles for the rest of the 20th century. The gasolineengine is the most widely used engine for passenger cars.
2-1
The diesel engine, the most efficient transportation engine, is
used in heavy duty trucks and is penetrating the medium duty
truck and passenger car field. Other alternative types of engines
are being considered but are not currently in mass production.
Alternative engines include various types of stratified charge
engines, the gas turbine, the Stirling engine, and the steam
engine.
This report will deal only with the sensitivity of the
currently produced gasoline and diesel engines to variations in
fuel properties. The sensitivity of alternative engines to
variations in fuel properties is beyond the scope of this report.
2 - 2
3. FUEL PROPERTIES AND THEIR EFFECTS
3.1 FUTURE FUELS
3.1.1 General
There is no clear picture of what the future automotive
fuels will be. Published reports by DOE, oil companies, and
automotive companies indicate that the properties of future fuels
might change with time according to the availability of the energy
resources and refining technologies. A possible' scenario of
future automotive fuels, developed from the available information
in the literature is as follows:
1. Immediate term (1980-1990): Alcohols represent the
first alternate fuels which are expected to be introduced in
limited amounts. The currently mass produced au'tomotive fuels
will be available and are expected to be extended by alcohols or
alcohol-derived additives.
Alcohols have been used as fuels for internal combustion
engines for many decades. Methanol and ethanol have been con
sidered as motor fuels more so than other alcohols because they
are less expensive to manufacture from a numher of different raw
materials. Isopropanol has been used in fuels primarily as an
icing inhibitor and for ~ater scavenging during cold seasons.
Tertiary butanol is currently added,to gasoline by one company as
an octane booster (3.24).
Gasohol, which is a mixture of 10 percent ethanol and 90
percent gasoline, has already been consider.ed by many workers arid
DOE officials as a viable alternative gasoline engine fuel which
can reduce the reliance on imported foreign crude petroleum. In
fact, the price of gasohol has been subsidized by the Federal
Government to make it competitive with the price of gasoline
(3.25). In a recent study (3.26) made hy T. Austin and G.
Rubenstein of California Air Resources Board, questions were
3-1
raised about the validity of the use of gasohol as a more econom
ical alternate fuel. Austin and Rubenstein indicated that the
use of gasohol manufactured from u.s. grown corn has increased
rather than decreased the nation's dependence on crude oil. Also,they considered that it is more econOmical to make synthetic
fuels from coa~)than to use the same amount of coal to run an
ethanol production facility.
It is clear that a detailed study is rieeded to evaluate the
validity of the arguments used in the Austin/Rubenstein paper,
and to evaluate the economy of the production of eth~nolcand its
use as a gasoline extender.
2. Near-term future (1990-2000): In addition to al~ohols,
. i~ is probable that syncrudes derived from shale oil and coal
derivatives will be mixed with the feedstock of refineries (3.23).The quality of the final product depends on the fraction of
alternate syncrude in the feedstock, the properties of the basic
feedstock and the degree of refining. (3.23)
3. Mid-term future (2000-2020): The production of syncrudesis expected to increase and reach about 10 percent of the u.s.petroleum demand. (2.1)
4. Long-term future (2020-2040): New engine technologies
may be developed in the future to match the fuels which will than
be available. New engine candidates are the gas turbine and
Stirling engine. These engines utilize continuous combustionsystems which have different sensitivities to variations in fuel
properties: These new engines are not covered in this report.
It is expected that the syncrude contribution at the end of thistime frame will reach up to 30 or 40 percent.
5. Far Future (2040-2060): The syncrude production is
expected to equal that of the natural petroleum crude, and grad
ually replace it. Fuels such as hydrogen, produced using in
exhaustible energy sources, are expected to be introduced. Cur
rently, the use of hydrogen as an alternate automotive fuel IS
3-2
contingent on the development of safe and economically competi
tive distribution and storage systems.
6. Post 2060: Alternate fuels from inexhaustible energy
sources are expected to dominate.
3.1.2 Properties of Future Fuels
The fuel properties important to engine operation are octane
quality (for gasoline engines), cetane quality (for diesel
engines), volatility, viscosity, volumetric energy density, and
impurity content, e.g., sulfur and/or nitrogen.
Establishing the properties of future alternate fuels
is very difficult. However, general trends may be establishedbased on the currently available data on the properties of dif
ferent sources of fuels. For example, distillates derived from
coal are highly aromatic in nature (3.1) (3.2) (3.3) (3.23) and
are of a high octane quality. But, distillates derived from oilshale are highly paraffinic in nature (3.4) (3.5) (3.6)
(3.7) (3.23) and would likely have high cetane quali ty and low
octane quality. The less-refined fuels from coal and oil shale
are likely to have high nitrogen and/or sulfur contents (3.4)
(3.6) (3.7) (3.8) (3.9) (3.10) (3.23). The presence of nitrogencompounds can lead to instability resulting in the formation of
gums and ~articulate matter in storage, and the formation of deleterious deposits in vehicle engines (3.23). The coal-derived
fuels, such as solvent-refined coal and synthetic oils, may also
contain appreciable amounts of ash (3.8) (:L9) (3.11).
Table 3~1 gives the properties of automotive gasoline, diesel,
and jet fuels, processed from shale oil, by Laramie Energy ResearchCenter, Energy Research and Development Administration (3.12).
Gary (3.12) indicated that technology is available to producemotor fuels meeting existing motor fuel specifications from
Western oil shale, but more severe and extensive processing isrequired than for fuels produced from conventional crude oils.
As a result, the synthetic motor fuels will be more costly and their.production more energy consuming than todays petroleum based fuels.
3-3
TABL
E3
.1.
PRO
PER
TIES
OF
SYN
THET
ICM
OTOR
FUEL
SPR
OD
UCE
DFR
OMSH
ALE
OIL
,_..
......_
----
----
Dis
till
ati
on
,O
F
10%
20%
50%
9U%
EP
Dis
t.R
esi
du
e,
%~
IRV
P,
psia
(Max
)~
RON
l-10N
Cu
Str
ipC
orr
osio
nG
um,
mg
/lO
Om
lS
ulf
ur,
ppm
Nit
rog
en
,pp
mF
lash
po
int,
OF
Po
ur
po
int,
OF
Gra
vit
y,
°AP
IC
arb
on
Resi
du
eo
n10
%R
esi
dA
sh,
Wt%
Vis
.@
10
0o
P,
cst
Ceta
ne
Ind
ex
Net
heat
of
co
mb
ust
ion
,B
tu~romatics,
Vo
l%
Ole
fin
s,
Vo
l%
I'.~
Die
sel
Fu
el
Jet
Fu
el
---,---~._.._
_._...
Gaso
lin
e1
-02
-D4
-0JP
5/
JP
4/
Jet
AJet
~
----1
-0-._
_•••••-
.......--
----
13
04
00
422"
45
03
76
23
21
48
40
94
54
46
83
87
25
02
15
42
24
84
50
74
22
29
23
26
46
95
37
60
54
82
36
83
85
51
75
54
62
85
18
40
5
1.0
2.0
1.0
2.0
1.0
1.0
,8
.82
.08
29
1[)
lAIB
lB2
.83
01
00
20
0~
20
02
71
31
41
16
62
02
18
82
12
~2
65
14
0<
00
Ii2
0-2
6-9
14
1.9
39
.8II
39
.04
4.0
57
.00
.14
0.1
60
.36
<0
.00
1<
0.0
01
<0
.00
11
.6
62
.40
2.9
648
54
56
/Ib
18
,16
0_
18
,34
02
1.0
11
.7.
40
30
.4--
Ref
.3
.12
~.}
1,~~~
..!
Figure 3-2 shows that the minimum values for cl?ud-point for
u.s. produced No.2 diesel fuels have been consistently lower than
for diesel fuels produced in Europe. The maximum values, however,
are appro~imately the same. According to EMA (2.1), diesel No.1
~""" fuel or kerosene have been added to No.2 diesel fuel to achieve
the necessary filterability. rhe importation of No. 2 fuel pro
duced abroad, a trend toward higher end-point for u.s. producedfuel, and diminishing availability of No. lifuel suggest increas
ing winter operational pro~lems.
Table 3-2 from reference (2.1) summarizes the important
characteristics of u.s. and non-U.S. produced diesel fuels. The
information in Table 3-2 reflects, primarily, the difference in the
refining procedures used. U.S. refiners crack heavy residuals to
increase gasoline yield, whereas cracking is not as prevalent
abroad. The difference in practice accounts for the difference
in cloud-points and cetane numbers.
3.2 STOICHIOMETRY AND COMBUSTION
Stoichiometry and" combustion are related to the HIC ratio of
the fuel. For Indolene, HIC is 1.86, for diesel fuel, HIC is
3-5
360 -- --- - TYPICAL---- EUROPEAN-340
,/
c.J ./ ('j/'
,.: /'
z 320 ,/
- ;I'0 U.S. PR 0 OUCED ;I'a.. /'
Q./
./·z ,/14.1
~/300
NO.2 DIESEL FUEL
70
o'Z
60 .
50
40·
U.S. PROD UCEO
30 ..,....---""":I~---_----r----_----1960 1970 1980 1990 2000
Ref 2-1
YEARFIGURE 3.1. TRENDS OF THE END-POINT AND CETANE NUMBER FOR
U.S. AND EUROPEAN-PRODUCED DIESEL FUEL
3-6
60
40
20 o
uV
I..
Ir
---J
z-2
0- 0 Q
.
0 :> 0 .J-4
0\,
)
.:'.
-6~91o
r19~O
I1
9h
oI
19~O
I2
0b
O
Ref.
2-1
FIG
UR
E3
.2.
YE
AR
TREN
DS
OF
THE
CLO
UD
-PO
INT
OF
U.S
.AN
DEU
ROPE
AN
PRO
DU
CED
DIE
SEL
FUEL
S
G
TABLE 3.2. PROPERTIES OF'U.S. AND NON-U.S. DIESEL FUELSUSE. . uropean
Gravity, API 30-36(31) 36-47(38)
Cetane No. 39-60(47) 55-65
Distillation Range °C 175-332 175-371
Cloud Poi~t °C -16 to -9(-15) -20 to -7~
Pour Point °C -40 to -15(-23) -20 to ~9
( ) = typical value
1.875. The H/C ratio of the fuel may change with the introduction
of alternative fuels.
3.2.1 Effect of H/C Ratio on Stoichiometry
The stoichiometric air-fuel ratio depends upon the H/C ratio
of the fuel. The theoretical AIF ratio varies from 11.491 for
pure carbon to 17.233 for H/C = 4, as shown in Figure 3-3.
Figure 3-4 is a replot of Figure 3-3 showing the stoichiometric
AIF ratio plotted against the number of carbon atoms for different
types of hydrocarbons. For the same number of carbon atoms,
aromatics have the lowest theoretical AIF ratio. Therefore, an
increase in the percentage of aromatics in a distillate fuel
results in an increase in its density, and a reduction in its
stoichiometrIc AIF ratio. The use of such a fuel in an engine
designed for low aromatic fuels may affect fuel metering, the
mixture strength, and the exhaust emissions (3.14).
Figure 3-4 also shows that the stoichiometric AIF ratio drops
at a decreasing rate with the increase in the number of carbon
atoms, n , in the paraffins CnH Zn + Z' For olefins, CnH Zn ' thestoichiometric AIF ratio is the same for all values of n. For the
diolefins, C H2 2' and aromatics, C HZ 6' the theoretical AIFn n- n n-ratio increases at a decreasing rate with the increase in n.
Figure 3-4 shows that the difference between the AIF ratio for the
several hydrocarbon families diminishes as n increases.
3-8
,'tI-~
12
17
16
I 0 'n +-J
C\j~
15
I-I-L
;.., -<
Hr-
iC
Th
eo
r.A
IrC
\j u 'n0
11
."9
1+-
J
14\]
0.7
51
2.-
86
1V
II
11
3.2
76
U)
f-<2
1".7
86
~
16~090
:r3
f-o1
3~
..1
7.2
33
HIC
11
I,
B,
,,
Ie
I,'
o1
23
..
FIG
UR
E3.
3.EF
FEC
TO
FH
YD
ROG
EN-T
O-C
ARB
ON
RA
TIO
ONTH
EOR
ETIC
AL
AIR~FUEL
RA
TIO
18
•
Cnl
l:>
n•
2
Cn"2
n
Cn"2
n-6
/
17 1'-
r-~ c-J U ·rl~ Q
) 81
5Q
) ...c:
E-<o 'rl~ CO ~ ~
16
......... «
'J'l I t--' o
13
II
II
II
~_
IL
",
o5
10
15
20
NUM
BER
orCA
RBO
NA
TOM
S
jl~
:w:1
5
FIG
UR
E3
.4.
EFFE
CT
OF
FUEL
STR
UC
TUR
EAN
DNU
MBE
RO
FCA
RBO
NAT
OMS
ONTH
EOR
ETIC
AL
AIR
-FU
EL
RA
TIO
t J.j
!r
Theoretically, at n = 00, the theoretical AIF ratio for all the
hydrocarbons is that of olefins, which is 14.786.
3.Z.Z Effect of H/C Ratio on the Adiabatic Flame Temperature
Figure 3-5 shows the adiabatic flame temperature calculated
for the stoichiometric mixture at the end of a constant volume
combustion, with chemical equilibrium (3.15). The original pres-~ dsure before combustion is 10 atmospheres, and the original tem-
perature is 77°C. It is clear that the adiabatic flame tempera
ture increases w!th the de~rease in H/C ratio.
3.Z.3 Effect of H/C Ratio on the (F-A) Standard Cycle
The effect of H/C ratio on the (F-A) standard constant-volume
cycle is shown in Figure 3-6 (3.16). The cycle conditions are as
follows: compression ratio = 8.5, equivalence ratio ¢=l, initialtemperature = Z94.3°K (Zl.3°C), initial pressure = 1 atm.
Figure 3-6 shows that, for the hydrocarbon fuels, the
decrease in H/C ratio has the following general effects: increases
the maximum cycle temperature, decreases the thermal efficiency,
increases the maximum cycle pressure, and increases the meaneffective pressure. Most of these effects are the results of the
variations in the stoichiometric A/F ratio, which decreases with
the drop in the H/C ratio.
For alcohols (CH 30H and CZHsOH) the increase in H/C ratro has
effects similar to those on the hydrocarbons, except that the
stoichiometric AIF ratio increases with the decrease in H/C ratio.
For example, methanol, CH30H, with an H/C ratio of 4, has a
stoichiometric A/F ratio of 6.45, while ethanol, CZHSOH, with anH/C ratio of 3, has a stoichiometric A/F ratio of 9.0
3.3 GASOLINE ENGINE FUELS
Automotive gasoline engines are sensitive to many fuel properties particularly the following:
1. Volatility and distillation range,
3-11
3000
2900VOLUME COMBUSTIONCONSTANT
2800INITI AL PRESSURE - 10 ATM
u INITIAL TEMP. - 70·C•a: '-12 2700&&J~
l.IJ 2600:&<.J
2500......a:J< 2400-Q<
2'300
2 3 4
Hie
Re f. 3. IS.
FIGURE 3. S. EFFECT OF HIC RATIO ON ADIABATIC FLAME TEMPERATURE
3-12
16
%o•%v1
---. - - ""'It ALCOHOLS15
CaL 14-~
~- 13
HYDROCARBONS
,..----'llo~ 7u.-CL'"
44 _::::lc( -I.,..---
~ 42 3000f'..
~
40 2900 :..c(I
""--- 2800 ~- ..... '"p
2700
20u......
ISc(
~u 10 .-0 --~ -....\I) 5
2 3 4
Ref. 3.16
FIGURE 3.6. EFFECT OF HIC RATIO ON THE (F-A)STANDARD CONSTANT VOLUME CYCLE
3-13
2. Detonation and preignition characteristics,
3. Energy Density on both a mass and volume basis,
4. Latent heat of evaporation.
Other fuel properties which affect engine performance, and
which will not be discussed in this report are: chemical
stability, corrosiveness, safety and cost.
Gasoline engines are sensitive to many fuel properties
particularly the following:
3.3.1 Volatility and Distillation Range
Volatility is measured by the Reid Vapor Pressure (RVP) , the
lighter part of the fuel on the ASTM distillation curve, or theEquilibrium Air Distillation (EAD).
Ideally, the fuel shou1~ be equally distributed among thecylinders of the engine, and completely evaporated before ignition.During cold starting, only the volatile portion of the supplied
fuel will evaporate. At the .same time the mass ratio of theevaporated fuel to the total supplied fuel is low. Choking is
applied to increase the mass ratio of the "total fuel supplied"
to the "air" (FT/A), which, in turn, will bring the ratio of
evaporated fuel to air (Fv/A) above the lean ignition limit.
Figure 3-7 shows the distillation curves -for the differentfuels produced from the petroleum crude for use in automotive
engines. Wide cut fuels will have a distillation range which
combines that of gasoline and diesel fuels. The shape and level
of the distillation curve affect gasoline engine performance. The
characteristic indicating the starting quality of a fuel is gen-
eral1y considered to be represented by the percentage vaporized at
a fixed temperature of 158°F. The warm-up characteristic isrelated to the temperature at which SO percent of the fuel isvaporized. Fuel economy is related to the temperature at which
90 percent of the fuel is vaporized, because the heavy ends havehigher heating values. Figure 3-8 shows the relationship betweenthe different portions of the distillation curve and the engine
3-14
lO 40 10 .._., ••11' g,.foll.' ..., V.._o
00 ~
y V
l.--~t.,.......oo00
~V
0/......
~2,
~P' '"- :.-- I
~~ ~..- VI.J""'" l--l--
l~V Y VV 1/ )/
00
./[..7'V 6V
V '--"~I,....--
.-00
.J' -:::;;.- i,....o"'" 7't/Y --7 ../' R
r./
- -0
2
l'
•
1. Heavy Diesel oil2. Distillate3. Kerosene4. Summer gasolinp
5. Wintp.T gasoline6. Aviatinn ~asoline .7. Ethyl ~lcohol
8. BPozr>nE'
Ref. 3.17.
FIGURE 3.7. TYPICAL ASTM DISTILLATION CURVES
3-15
- lONG ntIP fCOtto.' -----
DR"'''''DI'O"'I
-- U"""TOI C"Nor IfAlUNO ---
- G"M_._•.__ WAI",.U' _ __ _ - 'tUO -
'OULING•.- ACCIU .... '.OH & 'own -----• .• - $MOO'HNUI -----
---- SHOIt 'I., ICONO"" ----
VA'OI- LOCI •
fE.....,
o 10 20--' ,40 ..J~---J'80 90 100
" EVAPORATED
Re f. 3.18.
FIGURE 3.8. EFFECT OF DISTILLATION RANGE ONENGINE PERFORMANCE
3-16
problems.
In gasoline engines, the unburned hydrocarbons and carbon
monoxide emissions are reduced with more volatile fuels, because
leaner mixtures can be used during warm-up. The lower the whole
range of temperatures on the ASTM curve, the shorter is the warm
up period.
The heavy portions of the fuel, which are represented by
temperatures above the 90 percent point on the distillation curve,
may be deposited on the cylinder wall, and get mixed with the
lubricating oil in the crankcase, affecting its lubricity. Wide
cut fuels, which contain a larger portion of the heavy compounds,
can cause more crankcase oil dilution. This will be discussed in
Section 6 of this report.
For single compound fuels such as methanol and ethanol, the
ratio of (Fv/FT) depends only on the temperature, and cannot be
increased by increasing (FT/A) beyond the point of complete
evaporation. This is illustrated in Figure 3-9. and explains the
difficulty in cold starting with single compound fuels (such as
alcohols) which have low vapor pressure at the low starting
temperatures.
3.3.2 Detonation and Preignition Characteristics
3.3.2.1 Octane Rating - The tendency of any fuel to produce knock
in a gasoline engine depends upon many design and operating
parameters. The knock rating of a fuel is determined by measure
ments on a standard engine (CFR) , under standard operating condi
tions (motoring or research conditions), using a standard knock
intensity (measured by a standard knock meter) and a pair of
standard reference fuels (100 for isooctane, and zero for n
heptane). The octane number of the fuel is equal to the percentage
of isooctane in a mixture of isooctane and n-heptane which pro
duces the same knock intensity as the tested fuel under the
standard operating conditions. The different standard conditions
for the two octane methods are given in Tahle 3-3.
3 -17 ..
.0
.5
o
0.300.20F
0.\0o
V tJI 100·~
14
/ 2
II
.12
11-t 90°F10
.~I..
8.06 80·F,
/ I.roOF.06
/
/ 60 OF
II ""'OF ore
2 I 30·F
/oV
Q
QO
0.
o
o
a:.~'0:0.~
&A
~o
Re f. 3.19.
FIGURE 3.9. VAPOR-AIR VERSUS FUEL-AIR RATIOSFOR OCTANE (C 8H18 ) AT 1 ATM
3-18
TABLE 3.3. OCTANE RATING METHODS
Motor Method Research Method(MaN) (RON).
Inlet Temperature 300°F 125°F
Speed 900 R.P.M. 600 R.P.M.. I
The motor method is considered more severe because of its higher
inlet temperature and speed requirements.
3.3.2.2 Fuel Sensitivity - The fuel sensitivity is defined as
equal to (RON-MaN). The paraffins show near zero sensitivity
because they are similar in structure to the two reference fuels.
Therefore, the more the paraffinic content of the fuel, the lower
~ts sensitivity. For alternate fuels, the sensitivity depends on
the fuel sources. For example, fuels from coal-derived-liquids
will have a higher percentage of aromatic compounds and a higher
sensitivity than those derived from shale oil. At the same time,
the octane number of the coal derived fuels is higher than that of
the 5hale oil derived fuels. Sensitive fuels tend to knock sooner
= as the inlet temperature is increased.
The use of high octane fuels will not improve the performanceand efficiency of the gasoline engine unless the compression ratio
is raised, or the -spark timing is advanced. It should be noted
that increasing the compression ratio and/or advancing the timing
may increase the NOx and the hydrocarbon emissions.
·3.3.3 Energy Density
Fuel economy is usually expressed in terms of BSFC for
engines, and kilometers per liter or miles per gallon for vehicles.The BSFC is a function of the energy-mass density in 8ddition to
other thermodynamic parameters which affect the efficiency of
- conversion of the chemical energy of comhustion to useful mech
anical work. The energy-mass density of sever~l fuels is given In
3-19
Table 3-4. Table 3-4 shows that methanol has 49 percent of the
energy-volume de~sity of gasoline, and ethanol has 65.6 percent
of the energy-volume density of gasoline.
TABLE 3.4. SPECIFIC GRAVITY AND ENERGY-DENSITYFOR DIFFERENT FUELS
SpecifiG Ener~-Mass Energy-VolumeGravi ty') . De sity Density
(Dens i ty) * ,I BTU/Ibm BTU/Gallon
High Low . Low
Gasoline 0.739 20,300 19,070 117,400(6.156)
Kerosene 0.825 19,750 18,510 127,200(6.872)
Light Diesel Fuel 0.876 19,240 I 18,250 133,200(7.297) I
! I!
Medium Diesel Fuel 0.920 I 19,110 , 18,000 138,000(7.663) ! I, I ,
Methanol 0.796 9,750 8,570 56,800(6.630)
Ethanol 0.794 12,800 11,500 76,100(6.614)
i
* IDensity-Pound/U.S. Gallon. '-
The energy-volume density is directly proportional to the
product of the energy-mass density and the specific gravity.
Diesel fuel has the highest energy volume density, followed by
gasoline, ethanol and methanol.
The energy density of the fuel affects the storage and
transportation related costs which contribute to the final market
price of the fuel.
3.3.4 Latent Heat of Evaporation
Table 3-5 shows the latent heat of evaporation for several
fuels, and the drop in the inlet air temperature (6T) with
3-20
..
complete evaporation of the fuel in ait to a stoichiometric A/F
ratio.
TABLE 3.5. LATENT HEAT OF EVAPORATION OF DIFFERENT FUELS
H BTU I~T of,)
fg Ibm
Gasoline 150 40
Ethyl Alcohol 361 I 153 !I
I
Me'thyl Alcohol 474 ! 300I
Light Diesel 115 30
3.4 DIESEL ENGINE FUELS
Automotive diesel engines are sensitive to many fuel proper
ties, in particular the following:
1. Autoignition Quality
2. Volatility
3. Viscosity
4. Specific Gravity
3.4.1 Autoignition Quality
3.4.1.1 Centane Rating - The autoignition quality of the fuel is
related to the rates of the preignition processes which take place
in the period of time between fuel injection and combustion.
These processes can be divided into two major types: physical and
chemical processes. The physical processes are: (1) spray dis
integration and droplet formation, (2) heating of the liquid and
evaporation, and (3) diffusion of the vapor into air to form a
combustible mixture. The chemical .processes are: (1) the decomposition of the fuel molecule to lighter compounds, and (2) the
oxidation reactions which release the chemical energy. These
processes overlap, but the early processes are mainly physical and
3-21
the latter processes are chemical. The fuel properties affect
both the physical and chemical preignition reactions.
The autoignition quality of the fuel is measured by theperiod of time between the start of injection and the start of
pressure rise or illumination due to combustion. In diesel
engines, the start of pressure rise due to combustion is the cri
teria used to indicate combustion. The autoignition quality is
indicated by the cetane number of the fuel wH)ch is measured in
a standard engine (CFR) , under standard operating conditions(RPM = 900, T. = 150°F), by using a pair-of standard reference. a J.rfuels (100 for cetane, and 15 for hepta-methyl-nonane). In the
CPR engine, the C.R. is varied to produce an ignition delay of
l3°C.A., with the dynamic injection timing at l3°C.A. BTDC. Therelationship between the C.R. and C.N. is given in curve 1 of
F'igure 3-10. The cetane nlDTIber of the fuel, according to the
ASTM D-6l3 method, is given by the following equation:
C.N. = % n-cetane + 0.15 (%I1MN)
According to the above ASTM method, fuels can be rated between
C.N. 100 and C.N. 15. But below C.N. 15, fuels cannot be ratedby this standard method.
3.4.1.2 Problems Related to the Autoignition of Some Aiternate
Fuels
a. ASTM D-6l3 Rating Method
Alternate fuels which have cetane nlDTIbers less than IS can
not be rated by using the ASTM D-6l3 method. These fuels includegasoline, ethanol and ethanol. For such fuels, the low standardreference fuel should have a C.N. of zero rather than the C.N. of
15 used in ASTM D-6l3. In earlier methods, alpha-methyl
naphthalane (ctMN) was used as a zero C. N. reference fuel. Curve
number 2 of Figure 3-10 is a scale obtained by using n-centaneand aMN as reference fuels. It is noted that a C.R. higher
3-22
10 20 30 40 SO 60 70 80 eo 100CETANE NUMBE~
RELATIONSHIP BETWEEN THE C.N. AND C.R. IN THE CFRENGINE WITH HMN AND XMN AS REFERENCE FUELS
CETANE SCALE BASED ON BLENOS2 OF n-CETANE 8 aMN, lj= I~OoF,
1.0.• 13 0
o
CURRENT ASTMCETANE SCAl.E RANGE
i n -CETANEa HMN, T II 150°F
1.0.• 13°
:IiU1ft
30.0
29.0
2B.0
21.0
26.0
2e.0
24.0
23.0
22.0
21.0
20.0
0 19.0-t:tQ: 18.0
ZQ 17.0tntn 16.0UJa::Q.:E 15.00U
14.0
'3.0
12.0
11.0
10.0
~.O
8.0
7.00
Ref. 3.2l.
FIGURE 3.10.
3-23
than 29:1 is needed for C.N. = 10. For lower cetane fuels, aC.R. exceeding the highest C.R. of the CFR engine is needed.
Many attempts have been made by the U.S. Army Fuels and
Lubricants Research Laboratory to extend the scale to lower than
C.N. = 15. These are summarized in a comprehensive SAE paper by
Urban and Gray (3.20) a~tl include the following:
i. Blend normal cetane with the sample, and then, calcu~)
late the sample cetane number from the cetane number
of the blend.
11. Correlate the cetane and octane numbers of the sampleas shown in Figure 3-11.
iii.. Use an I.D. = l7 C C.A. instead of the standard I.D. of
l3°C.A.
All these methods proved to be unsatisfactory. In a more recent
study (3.21), a modified cetane scale was developed by increasing
the inlet air temperature from 150°F to 350°F, which allowed fuels
of C.N. as low as zero to be rated at a C.R. of 19.5:1. This
modified scale is shown in Figure 3-12.
There is a need for an extensive study of the modified scale
by using inlet temperatures between the standard temperature of
150°F and 350°F. This study is needed to determine the most
suitable inlet air temperature for the cetane rating of fuels in
the CFR engine.
b. Cycle-to-Cycle Variation in the Ignition Delay
Low ignition quality fuels having C.N. <20 have been observed
to produce cycle-to-cycle variations in the ignition delay asindicated in the pressure traces shown in Figure 3-13. It should
be noted that for all the fuels shown in Figure 3-13, the start
of needle lift was at 13° BTDC according to the ASTM D-6l3method, and cycle-to-cycle variations in the needle lift were not
observed. The cycle-to-cycle variations in the pressure trace,
at the point of pressure rise due to combustion, increased with
the decrease in the cetane number of the fuel from 20 to zero.
3-24
20
•
•
eN = 146. 0 - 1. 48 (ON)
SEE = =1.6
.'•
••
8
6
16
18
14
1 2
10
...1/
.D
E::lZI/'CIII...&I
L>
84 86 88 90 9Z 94 96
Motor Octane Number
Each point represents the average of several determinations.
FIGURE 3,11. CORRELATION BETWEEN THE C.N. ANDO.N. OF DIFFERENT FUELS
3-25
!C.O
29.0
2e.o
21.0
26.0
2~.0
24.0
23.0
22.0
21.0
20.0
19.0
C- Iaoi=it(
17.0a::zQ 18.0VIU')
I~OL&Ja::0- 14.0:t0U I~O
12.0
1/.0
10.0
8.0
8.0
Ref. 3. 21. 7.00
FIGURE 3. 12.
o AVERAGE OF :s RUNS USINGBLENDS OF n-C£TANE a ALPHAMETHYLNAPHTHALENEC.MH)REF'ERENCf: FUELS.
CETANE SCALE BASED ON Bl.ENDSOF n-CETANE 8 QtMH, T1.1~OoF,I.D. lII3 o. .~.. .
~ EXPEnEMENTAl. CETANESCALE BASED ON BL.ENDSOF n-CETANE 8exMN
1j • 3~0OF , I.D.= 13~
Cl..~ "".. er.uc....--- Ic..u..r; • .uta ---......
_ ..l... L I I I
10 20 ::Ie 40 ~ GO TO 80 eo 10c)
CETANi: NUMBERA MODIFIED CETANE SCALE FOR RATING LOWIGNITION QUALITY FUELS
3-26
(b)
(e)
(d)
,",,:n,§
.~
_~(L
1P
/L1
t)p
re
"""~:
;:,,.j=
jP
inj
(a)
~ I N ----I
(c)
Ref.
3.2
1.
(f)
FIG
UR
E3
.13
.CYCLE~TO-CYCLE
VA
RIA
TIO
NIN
THE
AU
TOIG
NIT
TON
OF
FUEL
SOF
DIF
FER
ENT
CETA
NE
Nill
1BER
S
"-J
This cycle-to-cycle variation in the I.D. explains the erratic
operation of the I.D. meter used in the ASTM D-613 method, reported
by Urban and Gray (3.20), during the rating of low C.N. fuels.
There is a need to study the source of the cycle-to-cycle
variation in the autoignition of low C.N. fuels~ and methods to
control it.
3.4.1.3 Ignition Delay Correlations - Many correlations have been
developed between the ignition delay and the air properties in
diesel engines for the regular fuels. These" correlations are
reviewed in reference (3.22).
There correlations are of the general form
I •D D =
E
AeRT
np
where
1. D. is in units of time
A is a pre-exponential factor
E is the global activation energy-R is the universal gas constant
T is the absolute temperature
p is the absolute pressure
n is an exponent
There is a need to develop such correlations for the other"alter
nate fuels which might be used in the future in diesel engines.
The effects of increasing the aromaticity and the distillation
range of the petroleum fuels, and blending the diesel fuel with
alcohols, and coal and shale derived distillates, need to be
determined. These correlations will be needed in the future to
3-28
determine the sensitivity of the I.D. to fuel properties and the
most effective techniques to reduce the ignition delay.
3.4.2 Volatility and Distillation Range
The sensitivity of the diesel engine to variations in fuel
volatility are summarized in Figure 3-14.
3.4.3 Viscosity
The sensitivity of diesel engines to variations in the fuel
viscosity are illustrated in Figure 3-15.
3.4.4 Specific Gravity
Figure 3-16 shows the relative performance versus fuel
specific gravity, and BTU per gallon when operated in a particular
engine at constant fuel pump setting. The increase in efficiency
as the -fuel becomes lighter is due to reduced F/A ratio. At a
constant efficiency, the effect on power is due entirely to t~e
changes in heat of combustion per unit volume.
3-29
- Low rates of mass diffusionresulting in poor mixingand exhaust smoke.
:; .-l
High content of heavy ~polycyclic aromatics .~
which are slow in burning~~__ o~and produce exhaust smoke. ~
cl1J1-41-4:lU
- Long ignition delayscausing high rates ofpressure rise, noise,and vibrations.
Vapor lock on the lowpressure side of theinjection pump.
- Excessively high diffusionrates resulting in poorcombustible mixtures andincreased He anc aldehydeemissions.
Volatility
FIGURE 3. 14. PROBLEMS ASSOCIATED WITH VARIATIONSIN DIESEL FUEL VOLATILITY
~
Eoor lubrication and ~fuel leakage I particularly .~at low speeds. _ ..-.....,.::0 ~
~ l1JC :ll1JtL.1-41-4::lU
- Poor handling by thefuel injection pump
__~.-requiring heating.
- Poor spray atomization.
Viscosity
FIGURE 3.15. PROBLEMS ASSOCIATED WITH VARIATIONSIN DIESEL FUEL VISCOSITY
3-30
SOtt,1 'e ,raw",Q 090 08~ 080
1..'_.......I.__L.-_...L..._...J.._---J'I-..._...L..._.....L._--1__.L-__'L.-_...L...__
~18.~00 18.600Qe , Blu/lDm
111.100 111,1100 111.900
I • I I, • Full 'ood -I
!~ - ~/."
I I I ~ r--::: " 11z'\ 00 I I
II' r-r-~I II I" : r1I I
Oil ,7~ ~
,5 I
,2 'II F..., ""mh',
0ii
II0
oc
..•o0.
" 8.e<C~ 7
! I I !....J I II "'_-------- ---
I.--~~ i II.... I i
II
I
1-D,fc •
027
026 .,
o 2~
O~O
28 30 32 3<1 36 38
API "OW",40 42 44 46
13~ 130Blu oe' 90110" llllOullO""')
NOTE: BSFC Points are average for all loads
Re f. 3.19.
FIGURE 3.16. RELATIVE P~RFORMANCE OF A DIESEL ENGINE ATCONSTANT FUEL-PUMP SETTINGS VERSUS SPECIFICGRAVITY OF FUEL.
3-31/3-32
4. SENSITIVITY OF AUTOMOTIVE GASOLINE ENGINESTO VARIATIONS IN FUEL PROPERTIES
4.1 ALCOHOL-INDOLENE BLENDS
4.1.1 Effect of Blending Gf~oline and Alcohols on Octane Number
Figure 4.1 sh~ws the effect on the octane number of addingmethanol to Indo1ene (4.1). Methanol improved RON more than MON.
This observation has been made by many investigators. Johnsonand Riley (4.1) developed the following correlation to describe
the effect of methanol on fuel octane rating:
ONB = Nt + 6N[1-exp(-Kx)]
where
ONB = octane number of blend
x = volume % methanol in blend
Nt = RON or MaN of base fuel
liN = octane increment from addition of methanol
K = base fuel response factor
6N is fixed for any given base fuel and indicates how effectivemethanol will be in raising the O.N. of the base fuel. The varia
tion in 6N with the base fuel O.N., obtairied by Johnson (4.1), is
given in Figure 4.2. This Figure shows that the higher the octanenumber of the base fuel, the lower the antiknock achieved by adding methanol. Also, the MaN curve shows significantly smaller
octane increases than those found for the RON. Base fuels with aMaN greater than 83 gave virtually no change in MaN when blendedwith methanol.
4.1.2 Effect on Flame Speed
The effect of blending Indo1ene and methanol on the flamespeed in a CFR engine is shown in Figure 4.3. The flame speed 1S
measured by using an ionization gap probe. This figure shows that
4-1
120,..---.,..-----------.-.---
lASE FUEL' D (".llItON. I.,., MON)METHANOL.' (.09.5 IlION. '6.0 WON)
110
_OTOR
61li1 e 0.66". 0.0345
• RESEARCH
6N • 12.00K·00ZI'6
10020 40 60 80VOLUME % METHA,NOL.
10-_--1__.........__........__.-1-__""""
o
Ref. 4.1.
FIGURE 4.1. OCTANE CHARACTERISTICS OF GASOLINE METHANOL BLENDS
4-2
oL-_-.J..__J......_.-L.--==--...L-_--.l.__~
- 70 80 90 100lASE FUEL OCTANE NUMBER
Ref. 4-1.
FIGURE 4.2. CORRELATION BETWEEN OCTANE INCREMENT AND BASEFUEL OCTANE NUMBER
4-3
)(3
0%
ME
TH
AN
OL
04
0%
ME
TH
AN
OL
.9
00
RPI
,,1.
C.R
.:5
toI
SP
AR
I(T
IMIN
G:
180
BT
OC
oB
AS
ELI
NE
.v10
%M
ETH
AN
OL
21
00
-1!3
200/
0M
ETH
AN
OL
18
00
. u w Ul
17
00
".~ U1
90
0,
N'7
~"",..-
)f
...
0+>
-W
I .j::
.W 0
-1
50
0U
l
W11
00~ <
t-J lL
10
0
1.00
1.80
_2D
O
Ref.
4.2
EQ
UIV
ALE
NC
ER
AT
IOFI
GU
RE
4.3
EFFE
CT
OFBL
END
ING
MET
HANO
LW
ITH
IND
OLE
NE
ONTH
EFL
AME
SPEE
D
t~L
a blend, having 20 percent methanol, produced the highest maximum
flame speed.
4.1. 3 Effect on a Single Cylinder Engine's Performance, Thermal
Efficiency and Emissions
4.1.3.1 Power Output and Minimum Advance for Best Torque - Add
ing methanol to Indo1ene allowed higher compression ratios to beused without knock and resulted in a horsepower increase as shownin Figure 4.4. The maximum gain in power output is with 25 per
cent methanol; higher percentages of methanol do not further increase the power output. In fact, the output with 40 percent
methanol is less than that with 25 percent methanol. The MBT
(minimum advance for best torque) for each blend is also shown in
Figure 4.4. The compression ratio that corresponds to each ofthe Indo1ene-methanol blends is given in Table 4.1.
TABLE 4.1. COMPRESSION RATIOS CORRESPONDING TO VARIOUSINDOLENE-METHANOL BLENDS
PERCENT 0 5 10 15 20 25 40METHANOLI
jCOMP. 7.2:1 7.5: 1 7.62:1 7.73:1 8.1: 1 8.0:1 8.0:1jRATIO
4.1.3.2 Fuel Economy - Brake specific fuel consumption resultsare given in Figure 4.5, and show an increase in fuel consumption
with the addition of methanol. This is caused by methanol's lowerheat of combustion (4800 k cal/kg) as compared to Indolene
(10,600 k cal/kg).
On an energy basis, the brake specific energy consumption inK cal/BHP hr is plotted in Figure 4.6 for different blends. Adding methanol to Indolene has a definite effect on decreasing the
4-5
WIDE OPEN THROTTLE 900 RPM
c 25~oMETHANOL
.to 40/o METHANOL
•o
...\l
•
c:w~0~
w(f.l
c:0:I:
w...::.:::c::{Q::.CD
3.6 .-u0
3.4 ~
a:l
3.20w0..."
3.0 wuz
2.8 ~0c::{
2.6 ::.:::Q::.
~2.4 (/)
402.2
302.0
20
10
0
.7
. Ref. 4.2.
.8 .9 1.0 1.1 1.2
EQUIVALENCE RATIO q,1.3
FIGURE 4.4. EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBHP AND MBT
4-6
SPARK ADVANCE MBT
WIDE OPEN THROTTLE 900 RPM
1.3.8 .9 1.0 /.1 1.2
EQUIVALENCE RATIO P
• INDOLENEo 5%METHANOL
~ 10% METHANOL
v 15% METHANOL
• 20% METHANOLc 25/0 METHANOL
z .9o-.....a..~ .8(f)
zou .7-1W~I.J... .6
u~
u .5wQ..(f)
w .4-t----,r---r---r-..,..---,.-.,......--r--,..-...,...-,.-....,......-.
~ .7c::coRef. 4.2.FIGURE 4.5. EFFECT OF MIXING METHANOL WITH INDOLENE ON
BRAKE SPECIFIC FUEL CONSUMPTION
4-7
.,
WIDE OPEN THROTTLE
900 RPMSPARK ADVANCE MBT
• INDOLENEo 5 °h METHANOL'Y 10% METHANOL~ 15% METHANOL
"• 20"0 METHANOLo 25% METHANOL
4000a::~,~
~
m"--J<U~
z3500o-~Cl.:E:::>CJ)
zou
G 3000a::I.LJZ~
U-IJ..-ULLJ£l.fI) 2500
1.20 1.301.101.00.90.80
2000 --L.__--L..__........__""""-- ~
.70
Ref. 4.2. EQUIVALENCE RATIO
FIGURE 4.6. EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC ENERGY CONSUMPTION
4-8
specific energy consumption or improving the brake thermal effi
ciency for equivalent ratios between the lean limit and the stoichiometric. This is attributed to many factors including the in
crease in the allowable compression ratio with methanol, the
lower time losses caused by the higher flame speeds, and the
lower heat losses caused by the lower combustion temperatures.
4.1.3.3 Hydrocarbons - The effect of adding methanol to Indoleneon the brake specific hydrocarbons (HC) is shown in Figure 4.7for different equivalence ratios. It is noticed that, in general,
the HC emissions tend to increase with methanol, particularly inthe lean mixtures. This increase is expected to be more significant if the response of the HFID (Heated Flame Ionization De
tector) to methanol is into consideration.
The increase in (HC) emissions with methanol is attributedto the higher volatility of the methanol-Indo1ene blend (as com
pared to that of pure Indo1ene) and to the presence of more fuel
per pound of air for a given blend. These factors lead to higherconcentrations of HC in the quench layers and crevices.
4.1.3.4 carbon Monoxide - Figure 4~8 shows emissions of carbonmonoxide as a function of ¢ for various blends. This follows the
expected trend that (with and without methanol) very little CO is
emitted on the fuel-lean side down to ¢ = 0.7, and the concentration of CO increases as ¢ increases on the fuel-rich side. At a
given fuel-air equivalence ratio, the brake specific CO slightlyincreases with methanol.
4.1.3.5 Nitrogen Oxides - The effect of methanol on the brakespecific NO emissions is shown in Figure 4.9 for different meth-
xano1 ratios as a function of the equivalence ratio. It is noticed
that the specific NO x emissions increase with methanol for richmixtures having ¢ more 1.1. For leaner mixtures, the specific
NO x is reduced to different degrees with methanol content. The
brake specific NO x peaks at richer mixtures with the addition ofmethanol.
4-9
1.31.21.1
RATIO <p.8 .9 1.0
EQUIVALENCE
--
.7
5
10
WIDE OPEN THROTTLE 900 RPMSPARK ADVANCE MBT
"1"')
• rNDOLENEo 5 % METHANOL• 10% METHANOLV 15% METHANOL
20 • 20% METHANOL
C 25% METHANOL15 & 40 rio METHANOL
a:::Id..:r:~(j)
~«a:<.9
UI
UlJ..
UWa..(f)
. _w.~
«a::.CD
. Ref. 4.2.
FIGURE 4.7. EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC UNBURNED HYDROCARBONS.
4-10
EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC CARBON HONOXIDE.
.8 .9 1.0 1.1 1.2 1.3
EQUIVALENCE RATIO <p
"
900 RPMWIDE OPEN THROTTLE
SPARK ADVANCE MBT
420 • INDOLENEo 5 ~o METHANOL~ I 0 % MET HAN aLv I 5 % MET HAN 0 L
• 20 0/ 0 'METHANOL
c 25;to MET HAN 0 L
A 40% METHANOL
:/0::I
I
§:340OJ
"(/)
~300<t:0::0
2400u
u l801...l--U
~ 120(J)
w~ 60<t:0:::.co
0.7
Ref. 4.2.
FIGURE 4.8.
4-11
. 1.3
900 RPM
METHANOLMETHANOLMETHANOL.,METHANOLMETHANOLMETHANOL
o 5 %
... 10 %
V 15 %
• 20/0·0·25/0
40%
.8 .9 1.0 1.1 1.2
EQUIVALENCE RA TIO <P
WIDE OPEN THROTTLESPARK ADVANCE MBT
elNDOLENE
.7
40
350
0:::I:
30ICl..ICD
~ 25~<!a::e,:) 20
x0z
15u-lJ....-Uw 100...enw~ 5<x:cr.C!J
Ref. 4.2.
FIGURE 4.9. EFFECT OF MIXING METHANOL WITH INDOLENE FUEL ONBRAKE SPECIFIC NITRIC OXIDES.
4-12
The peak values of the specific NO x curves are plotted in
Figure 4.10, and show a definite reduction in specific NO x withthe increase in percentage methanol up to about 30%.
4.1.4 Effect of Alcohols on a Non-Catalytic Car
The effect of using a blend of 10 percent methanol/gasolinefuel in a non-cat~lytic car has been reported by Johnson and Riley
and is given in Figure 4.11. The baseline fuel is Indolene. Based
on this figure and other results reported by Wigg and Lung (4.3)
and Brinkman et al (4.4), the following conclusions are made:
(i) Adding 10 percent methanol to unleaded gasoline will
reduce the CO emissions by approcimeately 30 percent.
(ii) Adding 10 percent methanol to unleaded gasoline does
not substantially change the HC or NO x emissions.
(iii) The miles per gallon of fuel is less forblends than for the unmodified gasoline.caused by the low energy content per unit
methanol as compared with Indolene.
the methanol
This isvolume of
(iv) However, there was a slight increase in the milestraveled per million BTU's, indicating a slight in
crease in the energy efficiency.
4.1.4.1 Effect of Alcohols on 1978 Catalytic Cars - Naman and
Allsup (4.15) of DOE reported the results of~hassis dynamometer
test on eight 1978 vehicles. Five vehicles had oxidation catalystsand 49-state emission control systems, and three vehicles were
equipped with 3-way catalysts and California emission control systems. The spark timing and idle speeds were adjusted to the manufacturer's specifications (which probably were optimized for In
dolene fuel). The extenders were 10 percent ethanol, 10 percent
methanol, 7 percent methyl tertiary butyl ether, and 7 percenttertiary butyl alcohol. The exhaust emissions and fuel economies
were measured on the 1978 Federal Test Procedure (FTP), using achassis dynamometer. Fuel economy was measured using the carbon
4-13
c
Q,
.•~=
.B65
•<{
>=.8
85<1
>=.8
95-
16-1
.~=.970
28
2040
32
24
36
1015
20
25
30
35
40
Ref.
4.2
.P
ER
CE
NT
ME
TH
AN
OL
.FIG
UR
E4
.10
.EF
FEC
TO
FM
IXIN
GM
ETHA
NOL
WIT
HIN
DO
LEN
EFU
ELON
PEA
KBR
AK
ESP
EC
IFIC
NIT
RIC
OX
IDES
0:: :r I 0... :r m ~.
en ~ <{ a: 0
x 0 Z U - l.L. -
+:>
0I
·wt-
'+:
>Q
.. en w ~ <{
0:: m ~ <{
·w n..
Q,
""-JCD<ir<[
>-20
Z
38.5
4.2
CIPfMJ9Jf MR FlPRflS: IrcxuNE eN),
JICD.EJ£ • lei Pnwo..\tMJQ£:
JDJ Ct~ AInt.1\10 WI'" 6ltJa.J lIE.
, 275C La IIG'TIA ItT.M. D'USSI~. ~ A.£L.:
I( -1.99~,
m- 36.6 PI"',Illx - 2.70 ew~,
~-17.2
. 1)(;7(;
Ref. 4.1-FIGURE 4.11. CHANGES IN FTP RESULTS FOR 10% HETHANOL ADDED
TO INDOLENE IN A NON-CATALYTIC CAR
4-15
balance method. The evaporative emissions were measured usingthe 1978 Sealed Housing for Evaporative Determination (SHED).
The properties of the fuel and alcohols used in this inves
tigation are given in Table 4.2. The properties of the blends
are given in Table 4.3. The results 'reported by Naman (4.15) aregiven in Table 4.4). These results show the following:
,
1. The fuel economy, on a mpg basis, decreased from 2,7
to 7.6 percent with each blend from that of the base
fuel. But from an energy point of view the miles per
million BTU decreased from 0.5 to 2.02 percent from
that of the base 'fuel. In one case, the ethanol ex
tender increased the miles per million BTU by 0.5percent. The results computed on an energy basis are
given in Table (4.5).
2. CO emissions decreased from 8 to 46 percent dependingon the emissions control syst~m used.
3. HC emissions decreased from 5 to 32 perc~nt.
4. NO x emissions were either unaffected or increased.
5. Evaporative emissions increased proportional to the increase in RVP as shown in Figure 4.12. The 10 percentmethanol blend has the highest evaporative emissions
and RVP.
4.1.5 Effect of Blending on a 3-Way Catalyst Car with Closed
Loop Emission Control System at Constant Speed
The effect of' blending gasoline with methanol was determi~ed
by Lawson, et. a1. (4.5) in a Volvo 244 DL car, with ~-sond
emission control system. The sensor is designed to control the
F/A ratio at the stoichiometric value. The effect of increasingthe percentage of methanol in the gasoline/methanol blend on
engine performance and emissions is shown in Figure 4.13. Theoxygen sensor was found to continue to maintain stoichiometric
F/A control with increasing methanol content in the blend up to
4-16
TABLE 4.2. PROPERTIES OF THE DIFFERENT FUELS
Indo1ene Ethanol Methanol !'!TBE TBAC8H15 C2H6O CH 40 C5H12O C4H10O
Molecular Weight 99.65 46.07 32.04 88.14 74.12
Specific Gravity 0.739 0.794 0.791 Q 0.741 0.784
Density 1b/gal. 6.15 6.62 6.60 6.18 6.54
Heat of Combustion 18,558 11,613 8,495 ·15,100 14,025BTU/lb
Heat of Combustion 114,132 76,878 56,067 93,318 91,724BTU/gallon
Stoichiometric A 14.8/1 9.0/1 6.45/1 11. 7/1 11/1F
Ref. 4. IS.
4-17
TABLE 4.3. PROPERTIES OF BLENDS OF INDOLENE AND ALCOHOLS
2 3Fuel No. 1
Specific gravity, @ 60 o /60 o F••••
API gravity, degrees ••••..••••••
Sulfur, wt pct •. ~ ..•••••.•.•..••
F.I.A., pct:Aromatics••.......•••••....••.01efins ••.••......••••......••Saturates .•..•....••••...• : •••
Reid vapor pressure, psi •••..•..
Hydrogen/carbon ......•••••••.••.
Oxygen/carbon•••....•••••••.•••.
Distillation, OF:
I ElP •••••••••••••••••••••••••••5%•••••••••••••••••••••••••••
10% .•..........•.......••.•••.20 %•••••••••••••••••••••••••••30 %•••••••••••••••••••••••••••40\.g._ ••••••••••••••• ~ ••••••••50\ 0 •••••••••
60% •••.•••••••••••••• e ••••••••
70% .•....•••.....••.••.•.•.•..80 %•••••••••••••••••••••••••••90% ..................•........ '95% ..•...............•........End point .
Recovery, pet .........•....•....
Residue, pct ....•........••••.•.
Loss, pct ••......•••......••••..
1
0.739
60.0
.002
251
74
8.6
1.90
9212213816719'3214229242259294326335356
98.0
1.0
1.0
0.744
58.7
.002
251
74
9.7
1. 97
.034
102120130143152182222238250284320334346
98.0
1.0
1.0
0.744
,58.7
.002
251
74
11. 9
2.00
.049
96110116123131191219235252283321332345
98.0
1.0
1.0
4
0.740
59.7
.001
241
75
8.7
1. 93
.012
93120133157178200228238252282322330348
98.5
.5
1.0
5
0.741
59.5
.002
241
75
9.1
1. 93
.014
96123131\153172195218234250284322331350
98.0
1.0
1.0
IFuel No.1 = Indolene (base fuel}.Fuel No. 2 = Fuel No. 1 + 10% ethanol.Fuel No. 3 = Fuel No. 1 + 10% methanol.Fuel No. 4 = Fuel No. 1 + 7% MTElE.Fuel No. 5 = Fuel No. 1 + 7% TEA.
Ref. 4.15.
4-18
f:{
TABL
E4
.4.
SUM
MAR
YO
FTH
EEX
HA
UST
EM
ISSI
ON
S,EV
APO
RA
TIV
EE
MIS
SI6N
S,AN
DFU
ELEC
ONOM
Y
Fu
el
Descri
pti
on
Fu
el
Eco
no
my
,m
pgU
rban
Em
issio
ns,
gm
/mil
eH
CC
O.
NO
xA
ldeh
yaes
.m
g/m
ile
To
tal
Ev
ap
ora
tiv
eE
mis
sio
ns,
gm
OX
IDA
TIO
NC
AT
AL
YST
VE
HIC
LE
S(5
-CA
RA
VE
RA
GE
)----------------------
Fu
el
No
.1
(In
do
len
e)
18
.60
.85
8.5
61
.6
31
82
.8
Fu
el
No
.2
(In
do
len
e+
10%
eth
an
ol)
17
.9.5
84
.66
1.
63
18
4.0
Fu
el
No
.3
(In
do
len
e+
10%
meth
an
ol
17
.5.6
24
.64
1.
89
27
5.4
Fu
el
No
.4
(In
do
len
e+
7%M
'I'B
E)
18
.0.6
85
.78
1.6
21
43
.5
Fu
el
No
.5
(In
do
len
e.j:
::.
+7
%'I'
SA)
18
.0.7
87
.88
1.
75
17
3.0
I f-'
I.Q
)-W
AY
CA
TA
LY
STV
EH
ICL
ES
(3-C
AR
AV
ER
AG
E)
-----------
Fu
el
No
.1
(In
do
len
e)
18
.5.4
36
.23
0.4
84
2.0
Fu
el
No
.2
(In
do
len
e+
10%
eth
an
ol'
18
.0.3
94
.55
.59
82
.3
Fu
el
No
.3
(In
do
len
e+
10%
meth
an
ol)
17
.1.4
14
.47
.71
43
.8
Fu
el
No
.4
(In
do
len
e+
7%M
TB
E)
17
.9.
31
4.5
1.6
57
2.2
Fu
el
No
.5
(In
do
len
e+
7%T
BA
)1
7.7
.32
4.8
9.5
89
2.1
D
TABLE 4.5. FUEL ECONOMY WITH DIFFERENT BLENDS BASED ONTHEIR ENERGY CONTENT
Blend1 2 3 4 5
Heat of Combustion c)BTU/gallon 114132 110407 108326 112675 112564
% Change in Heatof Combustion 0 -3.26 -5.09 -1.3 -1.4
Miles per millionBTU(a) Oxidation ca-
talyst cars(average o.f 5) 163 162.1 161. 6 159.8 159.9
(b) 3-way catalystcars (averageof 3) H2.1 163 157.9 158.9 157.2
% Cnange in milesper million BTU(a) Oxidation ca-
talyst cars 0 -0.5% -0.9% -1.96% -1. 9%
(b) 3-way catalystcars 0 0.56~ -2.59% -1. 97% -3.02%
4 -2 0 .
3-W
ayC
ata
lyst
Veh
icle
__
_
/o/.'
o./'
./'
./
:ft'"
/
.,0
gm•
60
,I
II
,I
IOx
idat
ion
Cata
lyst
Veh
icle
.---
To
tal
Ev
apo
rati
ve
Em
issi
on
s5
0
.j::> I N f-'
30~
20
1-
,.
~0
/0
/.
o/e
0/0
/"
,/'
CJ
1°1
I,
,,
'I
7.0
R.O
'1.0
I0.0
1.0f2
bp
si
Rei
dV
apor
Pre
ssu
re
FIG
UR
E4
.12
.EF
FEC
TO
FR
EID
VA
POR
PRES
SUR
EON
THE
TOTA
LEV
APO
RA
TIV
EE
MIS
SIO
NS.
!)fISSIONS M!AStTRlIl AT 2800 !.PM. SO rr. US. TORQUE
. _ 100Fr. LIS. I
1St - 95 MAX.I
90 TORQUE.J1,r.OO I AI
14 85 2800- .,II
,80_I
1.lOO 13 ~ J 75, jI
\.1,~00 12 ' 4.300~
I I
I,I
1.100I
11 ;. - 4.200
I10 lI,ROO 11.0 _ 4.100
!I BTUI !I
TBC JOO 9 ~I I
1.9 KIN. 4. OOO~.:, "."PPM
: % C02l!OO 8 .8 3.900
; % O2
! 1I II I:zoo :r
,.7 3.800-
I % CO
~ 3.700I
600 I .6- J -~OO J I
.5 i
of
I
I!!oo
,I I
.4 I
]I,I,
;loo 3: .3- I r I
I
1~OO 2 .2
i.100 1O2 .1
o 15 25 35 45 65
I I!m'BAJIOL ~Ref. 4-.5. •
FIGURE 4.13. EFFECT OF METHANOL ON THE PERFORMANCE AND EMISSIONSOF A 3-WAY CATALYST CLOSED LOOP CAR AT CONSTANTSPEED.
4-22
about 30 percent. Up to this point, there was no change in maxi
mum torque, but the energy required to achieve this maximum power
decreased, as did the CO and hydrocarbon emissions. Between 30
and 55 percent methanol blend, the limit of the increased volumetric fuel injection was reached, and a leaning-out of the F/A
ratio became evident in the form of decreased power output and
increased oxygen content of the exhaust. Lawson reported that"the
engine continu~9 to perform well as the efficiency continued to
improve. At methanol concentrations greater than 55 percent, it
was apparent, from the increas~d hydrocarbons that the lean .mis
fire limit had been reached. Figure 4.14 is a plot of iso-fuelenergy contours obtained from operating the engine on zero to 55
percent methanol blends. This figure indicates that as the
methanol content of the blend increases up to 45 percent, less
BTU/min were re~uired to achieve the same load/speed conditions.
Similar results have been obtained on VW cars fueled with 15
percent methanol and 85 percent gasoline, as reported by Bernhardtand Lee (4.13). A reduction in energy consumption of 12 percent
was achieved during the ECE cold start test as compared to the
gasoline operation.
4.1.6 Effect on a 3-Way Catalyst Car With Closed Loop Control
"System on FTP Cycle
Three-way conversion catalyst systems provide control of
three types of emissions: hydrocarb6ns, carboR monoxide, and
oxides of nitrogen. The conversion efficiency depends on theair-fuel ratio (4.6) as shown in Figure 4.15." A conversionefficiency of 80 percent or higher is possible if the A/F ratio
remains, on the average, within a narrow band around the stoichiometric ratio mixture. Although the A/F ratio may vary considerablyover very short periods, the average A/F within each interval of
a few seconds duration must lie within a band of 1 or 2 percentagepoints on either side of the stoichiometric to achieve high conversion efficiency. The A/F ratio control can be achieved by a
closed loop control system by which the oxygen content of the
4-23
VOLVO ENGINE. ISO nJEL~!!tCY CONTOUKS (ITU/MIN)POR 0 - )SI METHANOL IL!MDS
IIUT CiASOLIRE____ MJS
MlS
IISS
~M41bs~ MJS
~H2S KlSHEAT
6700 BTU/MIN
"
20
70
30 •
10
90 •
80
40
'0
60
TORQUEft. 1.15.
1500 zoooSIlEO IPK
3000 noo
Ref. 4. S.FIGURE 4.14. ISO FUEL-ENERGY CONTOURS FOR METHANOL-GASOLINE
BLENDS.
4-24
fUEL. RICH
0.99FUEL. L.EAN
1.00 1.01
A: TOTAL Oz IN EXHAUST
STOICHIOMETRIC 02 .
Ref. 4.6.
FIGURE 4.15. 3-WAY CATALYST CONVERSION EFFICIENCYFOR HC, CO AND NO x AS A FUNCTION OFLAMBDA.
__ J.. .._~
I II__~_-J
II I
- -:--...,, I
-~--""'1,
1000 .~--",t_-:.J-_l _!°rl-!·~4. , • ,I
I I I100 r---....--
I , I800 L.. - _1- - -t - -
I I I.I I
400 t---- _.L_I I ,I I ,
100 r- -- t - -t-I , I
o L._.I __ L_~ o..M OM ·tOO Htl t.&4
. 'UIL RICH 'UlL LEAN
Ref. 4.6.
FIGURE 4.16. OXYGEN SENSOR MILLIVOLT OUTPUT AS AFUNCTION OF EXHAUST GAS COMPOSITION(LAMBDA) .
4-25
exhaust is continuously monitored and the A/F ratio adjusted to
maintain the stoichiometric A/F ratio. For unleaded gasoline,
the average A/F ratio is controlled between 14.45:1 and 14.75:1.The oxygen content of the exhaust, which is related to the A/F
ratio, is determined by an oxygen sensor placed in the exit ofthe exhaust manifold (4.7) (4.8). The oxygen sensor producesa signal of a to 500 mv when the A/F ratio is slightly lean,and
'SOO to 800 mv when slightly rich as shown in Figure 4.16. Theresponse of the oxygen sensor is very rapid, detecting changes
in the exhaust gas within a few milliseconds and responding with
a very steep voltage characteristic at ¢=1. The response of theoxygen sensor to the stoichiometric mixture is independent offuel composition (4.6).
The effect of blending gasoline with alcohols on the type
'of emission control using a 3-way catalyst was studied by Mooneyet al .(4.6), on a Volvo 244 car. The car had a 4-speed manual
transmission and a 2.1 liter, 4-cylinder engin~, without EGR.
The fuel-metering was by a R. Bosch K-Jetronic fuel injectionsystem contro"lled by a closed-loop system with an oxygen sensor.
The fuels used in Mooney's tests were:
Ethanol:
Ethyl Alcohol. Ethyl Acetate
Methyl Iso-Butyl Ketone
Aviation Gasriline
Methanol:
Reagent Grade
97%
1.%1%
1%
99.9%
Unleaded Gasoline
Research Octane NumberAPI Gravity 60/60°F
Vapor Pressure (100°F)
LeadSulfurPhosphorous
Distillation ASTMD-86
IBP50%
EP
91.8%648.4 psi
0.023gm/gal.
300 ppm0.5 ppm
4-26
The results of the emissions produced from the vehicle with
the baseline gasoline fuel, and with different 'blends of gasoline
and alcohols are given for FTP in Table 4.6, and plotted in
Figure 4.17. The FTP results indicate the following:
(a) For Ethanol-Gasoline Blends
(i) At 10 percent ethanol, HC and CO increased significantly from the baseline while NO remained constant., x
(ii) At higher ethanol concentrations, the emissions be
haved in different ways: (a) the CO emissions de
creased to values lower than the baseline, 3.19gm/mile, and reached a minimum of 0.78 gm/mile at
40% ethanol, (b) the HC emissions decreased andreached a minimum of 0.11 gm/mile at 30% ethanol,
(c) the NO x emissions increased from 0.11 gm/mile
at the baseline to 0.14 gm/mile with 20 percentethanol, after which it dropped to 0.07 gm/mile at
30 percent ethanol and reached 1.55 gm/mile at
50 percent ethanol.
The emissions results indicate that the 3-way catalyst withthe closed loop control system was able to produce a high conver
sion efficiency for HC/CO/NO for ethanol mixtures of 30 percent.,xFor higher percentage mixtures, it appears that the closed-loopsystem (as set) could not maintain maximum conversion efficiency
for HC/CO/NO x .
(b) For Methanol-Gasoline Blends
Mooney's (4.6) tests on methanol-gasoline mixtures demonstrated that the system can operate satisfactorily with blends of
up to 20 percent methanol. Similar results have been recentlyreported by Seiffert of VW (4.18).
(c) For Ethanol-Diesel-Gasoline Blends
The results of tests conducted with blends of gasoline,ethanol, diesel fuel, and water are given in Table 4.7. These
results indicate that adding 30 percent ethanol increased the RON
4-27
TABLE 4.6. EMISSIONS FOR FTP PROCEDURE WITH ETHANOL GASOLINE BLENDS
HC CO NOr) x
gm/mi gm/mi gm/mi Blend
Baseline No C;:atalyst
0.93 13.68 2.47 100% Gasoline
Ethanol/Gasoline Blends
0.14 3.19 0.11 100% Gasoline
0.31 3.90 0.11 10% Eth./90% Gas
0.24 2.77 0.14 20% Eth./BO% Gas
0.11 2.61 0.07 30% Eth./70% Gas
0.14 0.78 1. 77 40% Eth./60% Gas
0.22 0.90 1. 56 50% Eth./50% Gas
Methanol/Gasoline Blends
0.14
0.16
.0.15
3.19
3.20
3.20'
0.11
0.09
0.05
100% Gasoline
10% Meth./90% Gas
20% Meth./80% Gas
Note: Data for car having 3-way catalyst with closed loop control.
Ref. 4.6
4-28
"
./.~"----
i I....••c'"
J0 10 10
o
i...o. 1
•cz
o
Ref. 4.6.
FIGURE 4.17. EMISSIONS ON THE FTP AS A FUNCTION OF ETHANOL INAN ETHANOL/GASOLINE BLEND.
4-29
TABL
E4
.7.
EM
ISSI
ON
SO
FFT
PPR
OCE
DU
REFO
RA
3-W
AY
CATA
LYST
CAR
WIT
HCL
OSE
DLO
OP
CON
TRO
L,W
ITH
BLEN
DS
OF
GA
SOLI
NE,
DIE
SEL
FUEL
AND
WAT
ER
HC
CO
·N
OR
ese
arc
hx
Octa
ne
Fu
el
Vis
co
sit
yg
m/m
ig
m/m
ig
m/m
iB
len
dN
um
ber
(Cen
tip
ois
e)
0.3
25
.74
0.0
810
0%G
aso
lin
e9
2.9
0.4
1
Wit
ho
ut
Cata
lyst
1.
221
7.9
92
.70
100%
Gaso
lin
e9
2.9
0.4
1
0.3
33
.55
0.1
070
%G
aso
lin
e°9
8.6
0.5
7.j
O.
23%
Eth
an
ol
I Vl
7%D
iesel
Fu
el
0
- Wit
ho
ut
Cata
lyst
I
1.
391
5.8
72
.34
Sam
eas
Ab
ov
e9
8.6
0.5
7
0.3
85
.76
0.0
970
%G
aso
lin
eN
AN
A25
%E
than
ol
.2.5
%D
iesel
Fu
el
2~%
Wate
r
0.3
03
.83
0.1
670
%G
aso
lin
e1
02
.60
.57
30%
Eth
an
ol
Refe
ren
ce
4.6
.
:~l~ "
.j~;
~l1t
:
of gasoline from 92.9 to 102.6. Also, 23 percent ethanol could
offset the poor octane characteristics of 7 percent diesel fuel.
Mooney concluded from his studies that the closed loop control system automatically provided a stoichiometric A/F ratio .of
12.8 for the 30 percent ethanol/gasoline blend and a 14.6 A/F
ratio for the 100 percent gasoline. Also, methanol/gasoline fuelblends containing up to 20 percent methanol provided excellent 0
vehicle operation and l~w HC, CO and NOx exhaust emissions.
4~1.l Effect of Exhaust, Aldehydes and Acetone Emissions
The effect of blending gasoline with methanol or ethanol on
the individual aldehydes and acetone was reported by Harrenstein,.et al (4.9). The engine used was a 1963, four-cylinder Pontiac
engine, which had been modified to simulate a modern engine, using
a 1974 cylinder head and camshaft. The C.R. was 8.1:1. Duringexhaust sampling, the engine was operated at steady-state condi
tions, 2000 rpm, MBT spark advance, and with F/A equivalence
ratios (t) of 0.9~, 0.90 and 0.82. During operation at ~ = 0.82,
the engine experienced lean-limit misfiring. The DNPH method with
a gas chromatographic finish was employed to obtain exhaust gasconcentrations of aldehydes and acetone.
Harenstein's experiments indicated that the use of alcohol
gasoline blends results in the following effects:
i. An increase in total aldehydes (including acetone)levels. The increase is 25 percent for 20 percentethanol, 10 percent for 20 percent methanol, and
30 percent for 30 percent methanol.
11. The aldehyde emissions are generally a strongerfunction of fuel blend-than of equivalence ratio.
iii. Formaldehyde is the -largest cQmponent of the total
aldehydes; up to 70-90 mole % of the total.
iv. The emissions of formaldehyde and acetaldehyde_arestrongly controlled by the content of methanol and
ethanol in the fuel respectively.
4-31
v. Acetone concentration increases as the lean misfire
limi t is approached. (rt> = 0.82).
vi. Acrolein concentration decreases slightly with increasing alcohol blend level.
vii. Aldehydes and acetone are partially destroyed in the
exhaust system and virtually completely destroyedin the catalyst.
4.1.8 Phase Separation
4.1.8.1 Nature of the Problem - A study of the methanol/gasoline.
phase separation problem was conducted by Lawson et al (4.5).Reagent grade methanol was dried and used in various proportions.
Mixtures of dry gasoline, dry methanol and water were mixed in a
'sealed conical flask, fitted with a thermometer and a magneticstirring bar. This flask was cooled until the cloud point temper
ature was reached as observed by the eye. Figure 4.18 shows the
cloud point expressed as grams of water added per 100 g'rams fuelto reach cloud point (or onset of phase separation) at selected
temperatures and for various methanol contents. Figure 4.18 indi
cates that at above-freezing temperatures, the presence of moremethanol imparts a greater water tolerance to the mixture. At
lower temperatures in the range -10°C to -20°C, there is relatively little difference in the behaviour of blends with methanolcontent of up to 45 perc.ent. The cloud point is approximately
at 0.05 gram per 100 grams of fuel. Lawson attributed this separation at 30 percent and 45 percent methanol to the drop in tempera
ture rather than to the presence of water. For example, a 30
percent methanol blend will phase separate at approximately -20°Ceven if no water is present. Increasing the methanol content to
4S percent provides greater phase separation, increasing that tem
perature to -15°C. Lawson, et. al., concluded that phase separation phenomena below the freezing point is controlled by the combined tendency toward immiscibility exhibited by both the waterand the methanol.
4-32
20
~-til10c
~CICIII~ 02III~
-10
-20
0'1 0'2 0·3 0·4 O'~ 0'6 0·7 o·aGRAMS OF WATER PER 100Q OF FUEL
0·9 1·0
Ref. 4.5.
20.~
u 10 .../• ./.
/r"'" 7~ "0WII:
0;:) •I- ./4II:III -10~
./:tw...
-20
.// , I •2 3 4
GRAMS OF' WATER PER 1009 OF FUEL
FIGURE 4.18. CLOUD POINT FOR VARIOUS METHANOL-GASOLINE BLENDS
4-33
At higher methanol contents of 60 percent and 70 percent,
there is a reversal towards more miscibility which can be interpreted as the solubility of the gasoline in the methanol. This
solubility becomes relatively insensitive to the water content asis illustrated by the low slopes of the 60 and 70 percent curves.
The "crossover" temperature at which methanol insolubilityequals that of wa;er (where the cloud point lines intersect) is
0etween -10°C and -15°C. This has been found by Lawson et al toagree well with the range -12 to -18°C reported by Ecclestonand Cox (4.10) for 30 percent aromatic gasoline.
4.1.8.2 Effect of Aromatic Contents on Phase Separation - Lower
ing the aromatic content tends to induce more phase separation,i.e., the same effect occurs at a higher temperature. Ecclestonand Cox (4.10), found that a 25 percent aromatic gasoline had a
crQ...ss~ver at 0 to SoC, and IS and 20 percent aromatic gasoline at7 to 13°C. The presence of aromatics causes a marked increase in
solubility of methanol in gasoline and of gasoline in methanol.
4.2 METHANOL NEAT
The main differences in the fuel properties of neat methanolas compared to the current production gasoline are:
(i) high octane number
(ii) low heating value
(iii) high latent heat of evaporation
(iv) low vapor pressure
4.2.1 Single Cylinder Engine Sensitivity
The high octane number of methanol allows the engine to runat compression ratios higher than 8:1 to 9:1 used in the current
production gasoline englne. This results in higher brake thermalefficiency and mean effective pressure. Figure 4.19 shows theeffect of increasing the C.R. in a single cylinder engine, with
4-34
Pe 60HP!
I i
5.8 1~i1, I
0 I I II
Itil
56/: ,
I .,..._.-. ....- ! I- -~ .....- -...,-
51. ' ,.' ,....I ",, ",
I /I ""5.2 ' •
I x-x AFER 1.0I .--- AFER '12;
E ILO .
I , .% I
! I38
I,I
36
1
I II
i I: i
34 , f-J8 10 12 11.
COMPRESSION RATIO l
Ref. 4.11-
FIGURE 4.19. EFFECT OF C.R. ON POWER AND EFFICIENCY
4-35
MBT spark timing and full throttle opening, on the power outputand brake thermal efficiency. The results are shown for A/F
equ~valence ratios of 1.0 (stoichiometric) and 1.12 (lean). For
both the A/F ratios, best brake thermal efficiency is at a C.R.
between 12:1 and 13:.1. The power output of the lean mixture peaks
at about 12:1. For the stoichiometric mixture, the power output
increases at a decreasing rate as the C.R. increases. The savingin specific energy consumption with the increase in C.R. is given
(';J in Figure 4.2 a aft loads equivalent to 37 mph and 62 mph road loads.
At 37 mph load, the fuel consumption can be reduced up to 5 percentby increasing'the C.R. from 8.2:1 to 13:1. At a 62 mph equivalent
load, the saving in fuel consumption amounts to 11 percent.
Figure 4.21 shows the improvement in specific energy consumption
at a load equivalent to that of 37 mph, with increasing compression ratio for methanol fueled engines in comparison to ,the current
production gasoline engine. The gain in efficiency ranges from
18 to 23 percent according to compression ratio.
The effect of C.R. on the emissions was reported by Meurad(4.11) as follows:
(i) CO is mainly a function of A/F ratio and not on
the C.R.
(ii) HC (UBF) increased with C.R. as indicated in Figure4.22. This increase is a result of the increase in
the effective 5/V ratio which results in more HC in
the quench zone, and the drop in the exhaust temper':lture which results in a reduction in the oxidationreactions during exhaust.
(iii) The increase in NO x /with C.R. was insignigicant.
4.2.2 Comparison Between the Single Cylinder Engine Results and
Cycle Computations
The increase in power output of gasoline engines has beencalculated for methanol as compared to isooctane by 'detailed computer analysis. An example of the cycle analysis results is shown
4-36
y • 100 1rnI'I'l162mphl
~SEC:ao'o
-s
--0
-15
Ref. 4.11.
10 11 E
FIGURE 4.20. EFFECT OF C.R. ON SAVINGS IN FUEL-ENERGY, AT37 MPH AND AT 62 MPH ROAD LOADS.
Ref. 4. 11.
~SEC
-
18 1DID
·2C
- 22
8 10
'V = 60 km/h
I 37mph I
FIGURE 4.21. PERCENTAGE DECREASE IN FUEL-ENERGY IN A METHANOLFUELED ENGINE IN RELATION TO A PRODUCTION GASOLINEENGINE.
4-37
A
• 1.. 11 tpo,r~"
5OJ: \\wi• SO lr",',.
27 rr.:po
c;
c
c
'IiII ... .... ..-. .... --.11I
I£I-I
JII
2~
II
o ,-I_--:-__--:-:- _
10 1~
B
Ref. 4.11-
FIGURE 4.22. HC AND NO EMISSIONS VERSUS C.R..x
4-38
TABLE 4.8. CHART CALCULATIONS OF CYCLE CHARACTERISTICS
Cu. Ft.Peak Peak of Mixture Compression
Temperature Pressure per 1b of WorkOR psia 0 Air BTU/1b
Isooctane 5200 1240 13.92 130
Methanol' 4870 1300 13.92 101 .
Ethanol 5000 1255 14.09 111
C.R. = 9.1, Intake Air = 1000F14.7 psia, ¢ = 1
4-39
in Table 4.8. This example shows that at equal equivalence ratio
(¢ = 1) and C.R. =.9:1 the calculated compression work for methanolis 101 BTU/1b as compared to 130 BTU/1b for isooctane. The peak
combustion temperature is lower: 4870 0 R for methanol compared
to 5200 0 R for isooctane. The peak pressure is higher: 1300 psiafor methanol as compared to 1240 psia for isooctane. Thus, it
follows that a methanol-fueled engine can achieve power boostover a gasoline-fueled engine at the same equivalence ratio, orequal power at a leaner equivalence ratio. e)
These computed results agree with the experimental work on
the single cylinder engine discussed earlier.
4.2.3. Mu1ticy1inder Engine Sensitivity
Berhardt and Lee of VW (4.13) reported the results of laboratory and road tests on a number of VW product~on vehicles whichhave been converted to methanol operation through the use of a
modified carburetor and an exhaust-heated intake manifold combined with a heating feature using engine coolant. The enginesused were water-cooled 4-cy1inder, 1.6 liter VW engines. The
standard carburetor was modified to improve the atomization of thefuel-air spray. The intake manifold was heated by a constant
flow of hot exhaust gases, and, in addition, by hot engine coolant
after warm-up. In spite of this heating, Bernhardt reported thatit was impossible to get completely identical mixture temperatureswith methanol and gasoline. Figure 4.23 shows the results reported
by Berhardt for the intake charge temperature for methanol andgasoline.
4.2.3.1 Effect on Power Output ~ Figure 4.24 shows the enginebrake power with methanol and with gasoline at different enginespeeds. The methanol engine had about 10% higher output than
the gasoline engine, both with MBT spark. This is related to theincrease in the mass of the fuel-air charge with methanol caused
by its higher latent heat of evaporation. This results in lower
charge temperatures as indicated in Figure 4.22.
4-40
o
6000
--- GASOLINE-METHANOL
\«\\\\\\\\.b
\\ ..
\\ ..
\.\
\\
\
'" '"............... 0-''''
CR =9.7. WOT.MA): POWERSPARK TIMINGI
I
o1_--J-._...I-.....-~_-.l.I_......l...._o 2000 4000
ENGINE SPEED - RPM
u30o
Ref. 4.13.
FIGURE 4.23. MIXTURE TEMPERATURE WITH METHANOL AND GASOLINE
-·"J;.:<'~I· - 60
.~--- GASOLINE~"'~ -METHANOL
50 ?'"
~ 40
//
I'~
~
~ 30~ j"0w~
/<t 20a:::l%l
10 CR = 9.7. WOT.I MAX POWER
~ SPARK TIMING
01000 2000 3000 4000 5000
Ref. 4. 13. ENGINF. SPEED - RPM
FIGURE 4.24. ENGINE OUTPUT WITH METHANOL AND GASOLINE
4-41
4.2.3.2 Effect on Brake Thermal Efficiency - Berhardt comparedthe brake thermal efficiency of the gasoline engine with that of
methanol engine,. both having the same compression ratio ~f 9.7:1.
The results are shown in Figure 4.25 for a speed of 2000 rpm, andWOT, at different air-fuel equivalence ratios, and show that themethanol engine is more efficient than the gasoline at the same CoRo
Because of the high octane rating of methanol (RON ~ 110,
MaN ~ 92) (21), the C.R. could be boosted to 14.0, resulting in 0higher brake thermal efficiency as indicated in Figure 4.25.
4.2.3.3 Cold Start Problems - With methanol, a cold startingaid is absolutely essential for starting the engine at temperatures below BOC (4.13). Cold start aids could be in the form of
volatile starting additives (such as butane, methyl ether, or
gasoline) to be sprayed into the intake air during startinG. Asmall methanol-fueled flame preheater may be used in the intake
manifold to solve the cold starting problem.
4.2.3.4 Effect of Methanol on Emissions
Figure 4.26 shows the effect, as reported by Bernhardt, ofair-fuel equivalence ratio on the NOx emissions of the gasoline
a~d methanol-fueled cars, at 2000 rpm, WOT, and MBT spark. The
methanol cars, with C.R. = 9.7:1, or C.R. = 14.1 had lower NOx
than the gasoline car. The reduction in NO is caused by the lowerxpeak temperature with methanol than with gasoline.
The CO emissions from the methanol-fueled engine correspondedI
approximately to those from the gasoline-fueled engine as indicatedby Bernhardt as shown in Figure 4.27. At 2000 rpm and a stoichiometric mixture ratio between ~ = 1 and ¢ = 0.9, methanol produced
less CO emissions.
The hydrocarbons In the methanol-fueled car consisted of theoriginal fuel, aldehydes and other hydrocarbons. The hydrocarbons
~
in the methanol-fueled car were found to be less than those from
the gasoline-fueled car as shown in Figure 4.28.
4-42
o
/ (I
;' ..LMETHANOI.........e CR = 9.7
:2000 RPM, WOT i14 CYL. ENGINE I
,,,--~---e,... ...."'. ...., ...
/~ e , ...... c
~/ GASOLINE "",o / CR =9.7 ',;
I • 0I ;
<;I~
35
JrMETHANOL
..,;;-_~I CR = 14.0
I
t; 30zwU~....ww
~ 25c:cc
20
~. LEAN LIMIT
RICH~-LEAN
0.8 , .0 , .2 , .4AIR-FUEL EQUIVALENCE RATIO
Ref. 4.13.
FIGURE 4.25. BRAKE THERMAL EFFICIENCY WITH METHANOL ANDGASOLINE.
4-43
:2000 RPM, WOT ',4 CYL ENGINE
RICH--LEAN-O .......... ...l....-__---"-__---J
0.8 1.0 1.2 1.4AIR· FUEL EQUIVALENCE RATIO
4000· .- \.
I .- ,\ GASOLINE
IJ. \
CR = 9.7J \
iI
I I.I
~\
METHANOLI
I II \
3000~I I, \
~ II ,
CR = 9.7 IJ Ia. ) \
1a. I , ~
~20j, i
II \
I!
,\ I\
\.
I"(/) , "--~--:
~
.1wlI(
0
. z 1000L
Ref. 4.13.
FIGURE 4.26. EXHAUST NO WITH MET[~NOL AND GASOLINE.x
4-44
4.---------------,- METHANOL--_. GASOLINE
3-
\\\~
1-
\\,
a ""'-_l...-I__~J,;;;"_~..:.... =---::.Q.IJ........__:-.-.J08 1 0 1 2 1 4
RICH --:- LEAN
AIR.FUEL EQUIVALENCE RATIORef. 4.13.
FIGURE 4.27. EXHAUST CO WITH METHANOL AND GASOLINE.
9 600
800 ,-----\------------,
~ --- GASOLINE\ -- METHANOL\\\.\-,,,,, .,-
\\.~,"" \
\ ~, ~
..... _-.;'
~ 400--:<,...-c:::o?; 200
O'--........ .....L...__---' ......._
Ref. 4.13.
FIGURE 4.28.
08 10 1.2 1 4
AIR·FUEL EQUIVALENCE RATIO
EXHAUST HC WITH METHANOL AND GASOLINE.
4-45
The total aldehydes emitted from the methanol-fueled engine
were higher than from the gasoline-fueled engine when the same C.R.
(C.R. = 9.7) was used, as shown in Figure 4.29. The total alde
hydes of the methanol-fueled car were reduced by increasing the
C.R. from 9.7:1 to 14:1 as shown in Figure 4.29. Bernhardt reported that the total aldehydes may be reduced by adding water to
methanol. This resulted in a NOx reduction as shown in Figure
4.30, with some sacrifice in power output.
Polynuclear aromatics (PNA) obtained from a gasoline-fueled
car were compared with those from a methanol-fueled car by
Bernhardt (4.13), on the European Test Procedure. The results
are shown in Fig. 4.31 and indicate a much lower level of PNAs
when methanol is used.
Figure 4.32 shows the variation in the emissions, withengine speed, at WOT, for methanol and for gasoline.
4.2.4 Sensitivity of a Vehicle to Neat Alcohol
VW reported the results of tests conducted on a number of
standard production vehicles which were converted from gasolineto methanol operation. To improve cold starting, gasoline orother volatile fuel was injected into the intake manifold.
Vehicle evaluation has been conducteft mainly under simulatedroad conditions using the CVS cold-hot emissions tests and theECE Test Procedure. The results for ~ethanol-fueled cars indi
cated an improvement in energy consumptiori of 4 percent when compared with gasoline operation during the ECE cold-start test,
and 12 percent for the hot start.
The effect of using methanol on the ECE cold test cycle is
to reduce the CO emissions by 25 percent, but to increase (HC)by 22 percent. In the hot-start test, the CO emissions were re
duced by 68 percent and HC by 28 percent (24), and NO by 20 per
cent.
4-46
,,I
METI'fANOLCR = 140
(j
300 ,..---------------------,
METI'fANOLCR = 97
I200 ~ I
~ /J(1..-_-lY(j--a()r';....-~I)r----
~~~ 100 to- I~_:.... _.-.--_...~-::~::-:==~::::-. ~~::~.==:2 40:=' !:-o-----
- • • -~---~ 'GASOLI~Ea-.....::r- eR = 97
."
I ." RICH --+,-- LEAN IO~.L. ..L- .._._ ~
oe 1 0 1.2 1 4
AIR-FUEL EOUIVALENCE RATiO
Ref. 4.13.
FIGURE 4.29. EXHAUST ALDEHYDES WITH METHANOL AND GASOLINE
4-47
2000
2
-OUTPUT
---- .... ... ... .... .... ....,,-,,,,,",-ALDEHYDES
....,,,....
....,....,
15
~ CO25-.,---------....;...-....::.;::..,
80KW
20
20
60
lJ')I.lJo>~40I.U
.9 10c::
o t:o
-HC FlO
5 10WATER - VOL ~o
co- l:::::7 0
. , 5 .
Ref. 4.13.
FIGURE 4.30. EFFECT OF WATER ADDITION TO METHANOL ONEXHAUST EMISSIONS AND ENGINE POWER.
4-48
TOTAL PNAWITH GASOLINE 2777035 ... \i:ll5 f '//i
WITH METHANOL. 303 ~g res:ENGINE· 15 ~ WATER COOLED
2400
O~~~~~~~~~~~~.a:.;:~.LJ,;~~~~LJPER IND BGHIP COR
-DAH ATC
~ 1200<z 800
400
(/l 2000z
O. '"' TEST2800r-------~------------.
Ref. 4.13
FIGURE 4.31. PNA HYDROCARBONS WITH f>1ETHANOL AND GASOLINE.
4-49
NO
NO
I ~ .III,,,
~.
(f',...... '-CO
~_:~-_:.._- ....... .. --·~HC ~FiD-
1000 2000 3000 4000 5000ENGINE SPEED - RPM
o
3000
1000
NO. HC5000 r----:---------..PPM ---GASOLINE ......v...
-METHANOL ,'7 '.a- ...vI ......
I v'I
II
II
II
III1.,
I .I~
I1
1I
2
o
CO10 4000%
~6o~ 2000
~4w
Ref. 4.13.
FIGURE 4.32. EXHAUST EMISSIONS WITH METHANOL AND GASOLINEAT FULL THROTTLE.
4.3 SHALE-DERIVED AND COAL DERIVED GASOLINE IN GASOLINE ENGINES
Hurn (4.14) reported experimental data concerning physical
properties and engine performance characteristics for a gasoline
derived from oil shale -and for a gasoline containing a coalderived component. The properties of gasoline derived from
shale oil are given in Table 4.9.° The emissions and fuel economy
results with shale-derived gasoline are compared with Indoleneand given in Table 4.10. Hurn reported that the differences be
tween the results with the shale-derived gasoline and the regulargasoline were mainly related to poor octane quality which resulted
in engine knock.
Hurn reported the results of tests on gasoline produced
from blends of coal derivative components and refinery stocks.The naphtha from catalytic reacting (51 percent yield) of a
coal syncrude, was blended with refinery stocks. The naphtha
was usable as 44 percent by volume of a finished, 96 RON, unleaded gasoline.
The results showed no significant differences between the
emissions and fuel economy characteristics of reference andtest fuels. The data show somewhat elevated CO and HC emissionsfor the fuel containing coal-derived components. Hurn indicated
that the differences may be attributable to a slight differencein the stoichiometry of the fuel mixtures.
4.4 GASOLINE EMERGENCY BLENDS
In case of a national emergency, the available gasolinefuel may need to be extended in order that gasoline engines pro
viding essential services continue operation. Under such
emergency conditions, blends of_gasoline and other fuels may beformed to stretch-out the base gasoline fuel. Russell, et al
(4.16) of Southwest Research Institute (SWRI) conducted an
extensive study of such emergency blends and published the results in a guidebook. Several blends of gasoline and extenders
were tested in single and multicylinder engines and in a very
4-51
TABLE 4.9. PROPERTIES OF SHALE OIL-DERIVED GASOLINE
API Gravity, 60°F.................................... 87ASTM Distillation, of:
IBP. D. II ••• a II 0 ••••••••••• II. II ••••• 11 ••••••••••••••••• 0.
10 percent ~ .30 percent .SO percent ' .70 percent o ••••••••• ~ ••••••••••••••
90 percent .End poin t .
Reid V.apor Pressure, psia .
Sulfur, wt. percent .
Nitrogen, wt. percent .
oxy gen, wt. perc en t. . . . . . . . .'. . . . . . . . . . . . . . . . . . . . . . . . .
Hydrocarbon types (FIA) , vol. percent:
Aromatics .Olefins ; : .Saturates ' .
Motor Octane No. (MON) .
Research Octane No. (RON) .
114125158194261328387
10.5
0.024
0.03
0.52
28.01L1 .n58.0
76.0
81.1Stability data:
ASTM induction period, min 1140-*ASTM existent gum. mg/100 mI. 25Accelerated gum (4 hr.) mg/IOO m1:
2 . 0 1b s DMD per 1. 000 bb 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 32
*40 lbs of pressure was lost during the entire 24-hr period:however, at no time did it lose 2 lbs in a l5-minute period.
Ref. 4.14.
TABLE 4.10. EMISSIONS AND FUEL ECONOMY RESULTS WITHSHALE-DERIVED GASOLINE
Fuel VehicleEmissions, g/rnile
CO HC NO x Aldehydes
Fuel Econorny,mpg
UrbanCycle Highway
Shale gasoline 1974 Model, 25.8 2.2 2 . 6 0.14 11. 2 17.4Indolene 351-CID 25.9 2.3 2.7 0.15 10.9 17.7
Shale gasoline 1975 Model, 7.4 1.3 2 . 7 0.18 12.3 21.1Indo1ene* 3l8-CID 8.7 1.2 2 . 5 0.17' 12.2 20.6
*Represents one analysis, all other data represent the average of 3replicates.Ref. 4.14. 4-52
limited number of vehicles, both on the road and by chassis
dynamometers. SWRI developed "Tradeoff Charts" for engine performance, fuel economy and emissions for each of the emergency
blends. Figures 4.33 to 4.44 are compiled from the charts developed by SWRI. The following indexes are used:
1. BSGC = BSFC x w gasoline
. where
a
BSGC = brake specific gasoline ~onsumption
BSFC = brake specific fuel (blend) consumption
m gasoline = mass fraction of gasoline
2 •
= mass of gaSOlinemass of lend
C t " I d l_BSGC (blend)onserva Ion n ex = B5Ft (base)
3. Power Index = BHP(blend)BHP(base)
4. Tradeoff Index = Conservation Index + Power Index
Russell et al (4.16) indicated that the tradeoff index re
flects the balance between increase in base fuel conservation anddrop in power (if any) with increasing extender concentration. Amaximum in the Tradeoff Index curve indicates a maximum advis
able extender concentration. Beyond this concentration, there
is reason to believe base fuel may be wasted.
5. Emission Index _ Emission (blend)- Emission (base)
The emergencey gasoline ,extenders tested by SWRI are shown inTable 4.11.
4.4.1 Effect on Reid Vapor Pressure
Figure 4.33 shows the effect of blending. gasoline with different extenders on the Reid Vapor Pressure CRVP). Alcohols
are the only extenders which result in an increase in the RVP atconcentrations less that 42 percent for methanol and 30 percent
4-53
REID VAPOR PRESSURE PSI
10 20 30 40 50 60 70 80 90 100
VOLUME %
1 Extender = No. 2 Diesel Fuel
2 = Marine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = Naphtha
6 = Kerosene
:3
4 I I I I
_I I III
2 f ,
~I 1,-"""""'"r---I I
'. I I I
0; :
;
~ ---~·4 I
I -f--..- I8 , I ~r---.. 1-2-5-6~ I
I I
6 : I I ........i
!II
~i4
I
I
, , I I I~i&. ! , 1 I I
,
i i !i
Ioo
Ref 4.16.
FIGURE 4.33. EFFECT OF GASOLINE EXTENDERS ON RVP.
4-54
API GRAVITY 60/60F70 r---...,.....-~--,.--....,----r--,.--...,.--.....,...----..,
I.6 51----+--~---+---+--+---+----+--+--~--i
:3 0 40 50 60 70 80 90 10 0
VOLUME %10 20
4 0 ~_...:__ ___" __..I__"""'__ ___'___"__ ___Io __
o
.,'- 1 Extender = No. 2 Diesel Fuel..._-2 = Marine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = Naphtha
6. = Kerosene
Reference 4.16.
FIGURE 4.34. EFFECT OF GASOLINE EXTENDERS ON APIGRAVITY.
4-55
6 01------+--4--..=.....::~...,....._--=~~-~--------__I
50 t----+------'---......-----I------>=r__--+-------............---!iI40 I--_.....I..-_....;..l.__"'--_--'-__"""-_......._--I.__..:..- ..-
o 10 2.Q :30 40 50 60 70 80 90 100
8 0 I--~t:=--~~........,~-_+_--r__-_+_-____:'------__;
OCTANE NUMBER12 0 r----:-----I-~-___r-_~-,.__-~-..,..._-~-...., :3
I I0 1--+----:.1----'+---+--+---+------1r--=:::::P-'~~-___::::13
.j
JPOI=:t~~Ft=1-4~~·.--r·::1-,,-- ~-, I• '4 I i
9 O~~+--~--d---=~--P--+--~--..;...---~
RON
MON
VOLUME %
1 Extender = No. 2 Diesel Fuel2 = Marine Diesel Fuel (DF1'1)3 = .Ethanol4 = Methanol5 = Naphtha6 = Kerosene
Reference 4.16.
FIGURE 4.35. EFFECT OF GASOLINE EXTENDERS ON OCTANE NUMBER
4-56
'-12
5045403530252015105
~ I II I! II, IiiI i
6-7- 8- 9,I
I -......... , i 4"'I . II
I:--:::- I
"- i I z
~. I "10
I
2.01.8
1.61.4
1.21.0
0.80.60.4
0.20.0o
POWERINDEX
VOLUME %
= Ethanol= Methanol
No. 2 Deisel Fuel
= Marine Diesel Fuel
= MBTE
= ,Naphtha-Ethanol
= DFM-Ethanol
= No. 2 Diesel FuelEthanol
1 Gasoline Emergency Blend Extender =2
3
4
5
6
7
8
9
10
1112
= Kerosene-Ethanol
= Ethanol Extendedwith Water
= Naphtha
= Kerosene
Reference 4.16.
FIGURE 4.36. EFFECT OF GASOLINE EXTENDERS ON POWER INDEX.
4-57
00
15
5040 453525 302015105
II I I
I Ii
. ,I
I
I " I~J:I
I III I I !;
Ii I ~ (I.C?.:.!,;
I ; I.I r ! (0.45,t i 3I
i "1 6 - 7- 8- 911-12
:'.:1 2
I I
i , I I,i
i! I II . 10
CONSERVATION INDEX2.0
1.81.61.4
1.2
1.0
0.80.60.4
0.20.0
"VOLUME %
1 Extender = Noo 2 Deisel Fuel
2 = Marine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = MTBE
6 = Naphtha-Ethanol
7 = DFM-Ethanol
8 = No. 2 Diesel Fuel-Ethanol
9 = Kerosene-Ethanol
10 = Ethanol Extended with Water
11 = Naphtha
12 = Kerosene
Reference 4.16.
FIGURE 4.37. EFFECT OF GASOLINE EXTENDERS ON CONSERVATIONINDEX.
4-58
I2
3I
504540353025.2015105
I I I
I I,
I I _1 6 - 7 - 89
,4.~
·1 I: I i I
1 '" --i
j t'--. I
II "10
ii
2.01.81.6
1.4
1.2\.0
0.80.60.4
0.20.0
o
TRADE-OFFINDEX
VOLUME %
1 Extender = No. 2 Diesel Fuel
2 = l1arine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = MTBE
6 = NaphthaEthanol
7 = DFM-Ethanol
8 = No. 2 Diesel Fuel-Ethanol
9 = Kerosene-Ethanol
10 = Ethanol Extended with Water
11 = Naphtha
12 = Kerosene
Reference 4.16.
FIGURE 4.38. EFFECT OF GASOLINE EXTENDERS ON TRADEOFF INDEX.
4-59
4 r-----.,I----.,I-----r---I---
I I Ii I I
·31-----~----_+_----+_---__l_----._.j
III; ! I
Me INDEX 2t-------- I 4
; -----~ -,-'-- ~j~~~ 1--- :5
- --7
i2
00 5 10 15 20 25 30 35 40 45 50
' "'T~~<-J
VOLUME %
1 Extender = No. 2 Diesel Fuel
2 = Marine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = Naphtha-Ethanol
6 = DFM-Ethanol
7 = Naphtha
Reference 4.16
FIGURE 4.39. EFFECT OF GASOLINE EXTENDERS ON THE HYDROCARBONSINDEX AT IDLE.
4-60
I I
I IIi ,
I II i
, I I:I
!,
I !,. ' ,'-2-7 5- 3"'-4
I
II I"
Ii iI I
4
3
CO INDEX 2
oo 5 10 15 20 25
VOLUME %30 35 40 45 50
Reference 4.16.
1 Extender = No. 2 Diesel Fuel
2 = Marine Diesel Fuel
3 = Ethanol
4 = Methanol
5 = Naphtha-Ethanol
6 = DFM-Ethanol
7 = Naphtha
FIGURE 4.40. EFFECT OF GASOLINE EXTENDERS ON CO INDEX AT IDLE.
fII
II
i II!
,
"I I
_/7,I
,
i
- i ,-=' I
!3
I·S
I -,~
4
o
NOX INDEX 2
oo 5 10 15 20 25
VOLUME %30 35 40 45 50
Reference 4.16.
1 Extender = No . . 2 Diesel Fuel2 = Marine Diesel Fuel3 = Ethanol4 = Methanol5 = Naphtha-Ethanol6 = DFM-Ethanol7 = Naphtha
FIGURE 4.41. EFFECT OF GASOLINE EXTENDERS ON NO INDEXAT IDLE. x
4-62
4,.....----.,------..,.....--~-~----~----__.
He INDEX 2t-------:~----___:: =---"-----i__---__t
Olo---_--'-__"'O"-_-""' -...010--~~-~-__=:"=_-~~~:"=_-""='o 5~ 10 15 20 25 45 50
VOLUME %
1 Extender = No. 2 Diesel Fuel2 = Marine Diesel Fuel3 = Ethanol
4 = Methanol
5 = Naphtha-Ethanol
6 = DFM-Ethanol
7 = Naphtha
Reference 4.16.
FIGURE 4.42. EFFECT OF GASOLINE EXTENDERS ON HYDROCARBONINDEX AT ROAD LOAD.
4-63
I I II .I I ii
, l II0
I
\
II
,i
II I
I I !,
! 14I. " I 7
- - --- 5""- 2...... 1I
II
4
3
2CO INDEX
oo 5 10 15 20 25 30 35 40
VOLUME %45 50
Reference 4.16.
1 Extender"= No. 2 Diesel Fuel2 = Marine Diesel Fuel3 = Ethanol4 = Methanol
5 = Naphtha-Ethanol6 = DFM-Ethanol
7 = Naphtha
FIGURE 4.43. EFFECT OF GASOLINE EXTENDERS ON CO INDEXAT ROAD LOAD.
4-64
I
III
I
IIIII III!
I ,!
iI
I
II II I
'1 17I :I
.2 I·
!1-
'5, :-=164 3
4
3
NO X INDEX 2
'0o 10 15 20 25 ~O
VOLUME %35 40 45 50
Reference 4.16.
1 Extender = No. 2 Diesel Fuel2 = Marine Diesel Fuel3 = Ethanol4 = Methanol5 = Naphtha-Ethanol6 = DFM-Ethanol7 = Naphtha
FIGURE 4.44. EFFECT OF GASOLINE EXTENDERS ON NO x INDEXAT ROAD LOAD.
4-65
for ethanol. Higher concentrations of alcohols cause a ~rop in
the RVP.
TABLE· 4.11. EMERGENCY GASOLINE EXTENDERS
(I)
(II)
(I I I)
(IV)
(V)
(VI)
(VI I I)
(IX)
(X)
(XI)
(XI I)
No. 2 Diesel Fuel 0
Marine Diesel Fuel (DFM)
EthanolMethanol
MTBE (Methyl Tert Butyl Ether)
Naphtha - EthanolNo. Z Diesel Fuel - Ethano1
Kerosene - Ethanol
Ethanol Extended with WaterNaphtha
Kerosene
Diesel
Alcohol
Ether
Complex Extender
(Lower Proof Ethanol)Solvent
(Solvent)
4.4.2 Effect on API Gravity
Figure 4.34 shows the effect of extender concentration onAPI gravity. All extenders used in this figure result in a
drop in the API gravity, or an increase in the blend specificgravity.
4.4.3 Effect on Octane Number
Figure 4.35 shows that only alcohols produce an increase in
the octane number of a blend. Blending with diesel fuel No. 2
has the worst effect on octane number of all the extenders shown.
4.4.4 Effect on Power Index
Figure 4.36 shows that gasoline extenders have either no
effect on, or decrease the power index of the blend.
4-66
4.4.5 Effect on Conservation Index
Figure 4.37 indicates that the conservation index increases
with the increase in the concentration of all the extenders except ethanol extended with water.
4.4.6 Effect on Tradeoff Index
Figure 4.37 indicates that all extenders, other than ethanolmixed with water, increase the tradeoff index, up to a volume
ratio of 25 percent. At higher volume ratios of diesel fuels,
naphtha and kerosene the tradeoff index decreases.
4.4.7 Effect on Emissions Index
The effects of the volume percent of the extenders on theemissions at idle are shown in Figure 4.39 for the unburned hydro
carbons, Figure 4.40 for CO, and Figure 4.41 for NO x .
The effects on the emissions at road load are shown in
Figure 4.42 for the unburned hydrocarbons, Fig~re 4.43 for CO,and Figure 4.44 for NO .x
4-67/4-68
,,,(,,
5. SENSITIVITY OF AUTOMOTIVE DIESEL ENGINES TO VARIATIONSIN FUEL PROPERTIES
5.1 D.I. FOUR-STROKE-CYCLE DIESEL ENGINE
5.1.1 Effect of Cetane Number
Tne major effect of cetane number is related to the length~
of the ignition delay. Lower C.N. fuels result in longer ignition delays, more fuel injected before autoignition, more premix
ing of the fuel with air, and higher rates of pressure rise. The
increased premIxIng results in more fuel in the lean flameout
region of the spray and increased unburned hydrocarbon exhaust
emissions. The increase in the HC emissions with the drop in C.N.has been observed by Bertodo (5.1) in tests on a 3.86 liter, 4
cylinder, 0.1., high swirl toroidal engine. The higher rates of
pressure rise resulting from the longer 1.0., result in higher
temperatures and more premixed combustion, which increase the NOxemissions. This effect has been observed by Bertodo (5.1).
Bertodo reported the sensitivity of the engine to variations inparameters which control the 1.0. as follows:
a. Delaying injection timing by 10°C.A. reduced the 1.0. by
about 30 percent, and allowed operation do~n to C.N. 40,
but resulted in increased smoke equivalent to a derate
requirement of 2.5 percent.
b. Increasing C.R. from 16:1 to 18:1 reduced the I.D. by
about IS percent, and allowed operation down to about
C.N. 45, but increased the NO x level by 5.7 percen~ to
9.5 percent.
~. Changing the mixing rate by using a "Squish Lip" combustion chamber design instead of the high swirl toroidal
design: (a) reduced the I.D. from 0.75 to 0.5 ms whentuned for best fuel economy, which allowed the operationdown to C.N. 42, and (b) reduced the r.D. by 50 percentwhen tuned for minimum emissions, and allowed operation
down to C.N. = 35.5-1
Bertodo (5.1) reported that reducing the C.N. from 55 to Z2
resulted in the following:
a. Acceptable operation down to C.N. 48, at which point,
severe white smoke and light load misfire occurred. This
trebled the HC level.
b. C.N. lower than 48 led to severe roughness and piston
erosion.
5.l.Z Effect of Aromatic Content
Aromatics are known to be low cetane number fuels, and to
contribute to the smoke particulate emissions. Bertodo (5.1)
reported that as the aromatic contents were raised from 15 to 30
percent, black smoke levels became unacceptable, and particulate
concentrations doubled. Similar effects are reported in I.D.I.
engines, which will be discussed later.
5.1.3 Effect of Mixing DF-Z With Shale Distillates
Bertodo (5.1) reported tests conducted on a D.I. high swirl,
toroidal diesel engine, with DF-Z mixed with shale distillates.The shale distillates had the following approximate split:
Light Distillates
Kerosenes
M~ddle Distillates
IBP < ZOO°C
IBP < 315°C
IBP < 375°C
10%ZO%
20%
The rest of the shale distillates were heavy fractions with IBP >
375°C and were not mixed with the DFZ. The cetane rating of shale
distillates with IBP < 375°C is about CN 25. The ASTM gums levelwas in the range 27-35 mg/ml. The DF2 was obtained from a refinerypracticing extensive cracking to maximize gasoline production.
The fuel contained 35 percent aromatics, and had the following
properties:
C6 - 190°C Raffinates 2%200 - 300°C Kerosenes 70%
200 - 300°C Hydrocrackates 4%300 - 350°C Distillates 24%
5-2
~;,:
i1
TABL
E5
.1.
TYPI
CA
LPE
RFO
RMA
NCE
DEG
RAD
ATI
ON
OF
SHA
LEO
ILD
ILU
TIO
N
En
gin
eB
aseli
ne
En
gin
e1
6:1
Co
mp
ress
ion
Rati
o2
2°
BTD
CD
yn
.In
j.T
imin
g
Baseli
ne
En
gin
e1
8:1
Co
mp
ress
ion
Rati
o8
°R
eta
rded
Po
wer,
KW
*un I
s/f
/c/.
ml/
Kw
hLN
Bla
ck
Sm
ok
e,%
USP
HS
.s
Part
icu
late
s,
mg
/m-5
No
ise,
dBre
-2
xl0
Fu
el
Sp
ecif
icati
on
Dil
uti
on
Aro
mati
cC
on
ten
t.,
%
Cen
tan
eR
ati
ng
AST
MD
97
5N
o.2
20%
Sh
ale
Oil
32
CN
39
-4
5
60
.3
28
2
14
.3
2.4
11
.7
91
/4
26
7
10
2
13
.1
2·.
6
10
.2
91
/4
22
0.
10
0
BS
28
69
Cla
ss
Al
Nil
-2
0
)C
N5
0
61
.6
28
1
N/m
2
g/K
wh
+
g/K
wh
+
g/K
wh
+
NO
,x
HC
,
CO
,
* +
~t
25
00
rev
/min
an
dB
S.A
ul4
la:
19
71
co
nd
itio
ns
~t
CA
RB
13
-mo
de
cy
cle
co
nd
itio
ns
The C.R. of the baseline engine had to be increased from 16:1 to
18:1, and the injection retarded by 8°C.A., in order to account
for the lower C.N. of the DF2-shale distillate mixture. The
results are given in Table 5.1, and indicate the following trends:
a. The power had to be derated by 2 percent from 61.6 kW
to 60.3 kW in order to keep black smoke at a constant
level of 9.25 percent USPHS opacity.
b. The specific fuel consumption was almost constant.
c .. NOx ' CO, particu~ates and noise increased ..d. HC decreased slightly
The operating problems experienced, after testing for 250 hours
on a mixed duty cycle, were restricted to lacquering and sticking
of precision components exposed to high temperatures, notably
injectors and needles. This was attributed to the high gum content
of the fuel.
5.1.4 Effect of Mixing DF2 With Coal Distillates
Bertodo (5.1) conducted tests on coal distillates-DF2 mixtureson a D.r. high swirl torodial type diesel engine. Two types of
coal distillates were used: low pressure pyrolysis tar oil, and
hydrogenated creosote oil. The properties of these coal distillates
are'shown in Table 5.2. The test results with blends of 25 perc~nt
coal distillates~and 75 percent BS2869 Class A2 diesel oil are
shown in Table 5.3. The results indicate the following:
a. Blending with 25 percent coal distilates lowered the
C.N. of the fuel. This results in a longer 1.5.
Operation with dilution above 25 percent straight tar
oil or above 50 percent hydrogenated creosote oil was
impossible.
b. Derating of the power was necessary to keep the blacksmoke at 10 percent US PHS capacity.
c. The NOx ' HC and CO increased.
5-4
~'
IBase Line Eng!.2!
and Fuel,_: ~I-
Witl'fShale Oil ==,=Dilution~ ~.
. ~'I -IWith Syncrude 4 ' /
Dilution I 7~"~?~65- -,
I
.-'........ B,·O-BO·75
Extrapolated from Ref. (13)(14)99·9
95
80
60
:! 40I
V'l 20l.LJc::: 10~-oJ
5Lt 3l.LJ 2>- ,~
<{-oJ 0·5~
~ 0·3~u
:. ....0·1
.,~~ - 0·05~ .-'.."':' ...
0·03
0·010·01 .0·1 '·0 10
OPE RAT ING LIFE - YEARS
Reference 5.1.
FIGURE 5.1. PREDICTED WEIBULL FAILURE PROFILE FORENGINES OPERATING ON DILUTED DIESEL FUELS.
5-5
TABLE 5.2. SELECTED PROPERTIES OF COAL DISTILLATES
PremiumDiesel
Oil
Low PressurePyrolysis
Tar Oil
HydrogenatedCreosote Oil
Specific Gravity 0.857 1. 06 0.87
Cetane Rating SO <20 40
Conradson Carbon, on 10%
residue, % wt. 0.05 0.26 0.19
Distillation temperature,
°C for 90% volume recovery 273 260 264
Flash point, closed cup Pensky-
Martens °C 90 112 107
Benzole Insolubles, % 0.05 4.8
Hard asphalt, % 0.11 2.5
Reference 5.1.
5-6
1<
.\
TABL
E5
.3.
TYPI
CA
LPE
RFO
RMA
NCE
DEG
RAD
ATI
ON
WIT
HTA
RO
ILAN
DH
YD
ROG
ENA
TED
CREO
SOTE
OIL
"Base
lin
eE
ng
ine
16
:1C
om
pre
ssio
nR
ati
o22
°BT
DC
Dy
n.
Inj.
Tim
ing
Str
ati
fie
dD
iesel
18
:1C
om
pre
ssio
nR
ati
o8°
BT
DC
Dy
n.
In
j.T
imin
g
Baseli
ne
En
gin
e1
8:1
Co
mp
ress
ion
Rati
ol4
°BT
DC
Dy
n.
Inj.
Tim
ing
Fu
el
Sp
ecif
icati
on
BS
28
69
Cla
ssA
lB
S2
86
9C
lass
A2
BS
28
69
Cla
ss
A2
Dil
uti
on
Nil
25%
Tar
Oil
25
%H
yd
rog
enat
edC
reo
sote
Oil
Aro
mati
cC
on
ten
t,%
-20
N/A
N/A
Ceta
ne
Rati
ng
>CN
5036
41
*P
ow
er,
Kw
61
.6
58
.45
5.1
s.
f.c.,
m1/
Kw
h2
81
33
63
23
+1
4.8
NO
,g
/Kw
h1
3.1
16
.3x
+2
.64
HC
,g
/Kw
h2
.9+
CO
,g
/Kw
h1
0.2
12
11
.7
Bla
ck
Sm
ok
e,%
USP
HS
91
/41
01
0"
-52
10
0N
/AN
/AN
ois
e,
dBre
-2
xlO
N/m
*at
25
00
rev
/min
and
BS
Au
14
la:
19
71
co
nd
itio
ns
+at
CA
RB
1]-
mo
de
cy
cle
co
nd
itio
ns
Ref
eren
ce5
.1.
Ref
eren
ce5
.1.
d. The specific fuel consumption increased.
Problems reported by Bertodo are related to nozzle fouling,
lubricating oil sludging, and consequent wear. This resulted in
poorer reliability and durability as shown in Figure 5.1. The
low pour point of the coal-derived liquids, typically 4°C on the
a ASTM 975 test, made it nOcessary to introduce some fuel line
heating to minimize waxing, filter plugging and line blockage.
Table 5.4 shows the pour point of diesel oils diluted with coalderived crudes.
5.i.5 Effect of Using Alcohols
Alcohols can be utilized as fuels for diesel engines by using
the following techniques:
1. Neat alcohols mixed with a cetane improver.
2. Emulsion of alcohols with diesel fuel.
3. Carburetion of alcohols and ignition by diesel injection.
4. Two separate injection systems.
5. Spark ignited alcohols injected in diesel engines.
5.1.5.1 Neat Alcohols Mixed With a Cetane Improver
An improvement of the ignition quality of some alternate fuels
can be achieved by using cetane improving additives (5.2).Figure 5.2 shows the effect on cetane number of adding cetanox to
methanol. Cetane num~er increased linearly from 3 to 24 with the
addition of up to 10 percent cetanox. ' The rate of increase ofC.N. decreased as cetanox was 'added above 10 percent. FIgure 5.3
shows the effect of the additive on the hydrocarbon emissions at
part load in an automotive turbocharged direct injection dieselengine (displacement = 10 liters, C.R. = 15:1). At any BMEP, theincrease in the percentage additive resulted in a reduction in
the hydrocarbon emissions. This is probably due to the shorterignition delay periods and the decrease in the amount of fuel inthe lean flame-out regions. The probl~m.; associated with this
5-8
TABLE 5.4. POUR POINT (ASTM D975) OF DIESEL OILS DILUTED WITHCOAL DERIVED CRUDE
BS 2869 A2 Diluted Diluted DiluentDiesel Oil OnlY 2526 50'6 OnlY
Lov Pressure PyTo1ysis_17°C _12°C _6°C 4°CTar Oil as Diluent
Hydrogenated Creosote-17°C _14°C _9°C OOCOil as Diluent
Reference 5.1.
5-9
''0
10
Test on aCFR engine with equal contents of energy in themixed methanol and in the
,reference fuel.
°o::----""'!""""--T------,..--5 10 15 20
u-Ionox in. rr4':~n:')1 Yol %
Reference 5.2.
FIGURE 5.2. CETANE NUMBER VERSUS PERCENTAGE OF CETANOX IN METHANOL
Part loadat engine speed 2220 rpm.
1000 \ '. .\ '.
500
20 ~ol S Cet~no.
lS ~ol S •
10 ~ol S •S yo] : •
Reference 5.2.
FIGURE 5.3. EFFECT OF THE AMOUNT OF CENTANOX IN METHANOL ON HCEMISSIONS.
5-10
approach are related to low durability due to excessive wear.
The amount of additive needed can be reduced by preheating
the intake air by engine coolant. At partial loads, when the
coolant is relatively cool, the exhaust gases can be recirculated
by increasing the back pressure. This may reduce the hydrocarbon
emissions.
Cold starting represents a problem and calls for preheating
the intake air by an electrical element orJby using an intake air
burner.
The effect of increasing the back pressure on the hydrocarbon.
emissions at partial load is shown for the engine of Figure 5.2
in Figure 5.4. These results are for methanol with 5 percent
centox by volume. The reduction in the HC at any BMEP can be
attributed to two factors. The first is the reduction in the
ignition delay period caused by the increase in the gas tempera
ture. The second factor is th~ improvement ·in the oxidation
.. reactions caused by the higher mass average temperature.
Bertodo {5.1) conducted two types of tests with ethanol.
The first consisted of ethanol neat mixed with 8 percent ethyl
nitrate ~nd 2 percent lubricating oil. Mixing with ethyl nitrateincreased the C.N. to 45. In the second type, blends containing 30
percent ethanol were used, either premixed or manifold injected
with the injection timing retarded by 10cC.A. The results are
shown in Table 5.5 and indicate the following trends:
a. Mixing with ethanol ~educed the C.N.
b. Power decreased very slightly
c. Specific fuel consumption on a vo1ume/kW basis increased
due to the lower energy content of ethanol. On an
energy basis, the fuel economy did not change.
u. NO, CO, black smoke, decreased.x
e. HC increased.
5-11
TABLE 5.5. PERFORMANCE IMPACT OF ETHANOL FUELING
~ne
PUel Specification
DilutionAromatic Content. %Cetlllle Ra till8
. Power. ",.,.s.f.c •• ml/Kwh
NO • g/Kwh +BC~ g/Il:wh+CO. g/Kwh+Black smoke. " USPHS5 2Mohle, cill re - 2zl 0- !11m
Basel1ne ~e16:1 Compreeeion Ratio
220 M'DC D)m. Inj. TimJ.lljJ
BS 2869 Clan Al
!Iil- 20>CH 50
61.6281
l}.12.6
10.2en
100
Basel1ne &!gine16:1 Compreesion Ratio
120 BTDC Dyn. Inj. TiDlilljJ
9O'J' Ethanol'"' Ethyl !Iitrate2'J{, Lub. OU
C!I 40
60.1411
10.24.16.94~
Baseline ~e1611 Compreseion Ratio
120 M'DC 11).0. Inj. T1JIL1ng
BS 2869 Class Al
}OJ' Ethano1-15
CH }8 - 4}
60.4}40
12.82.99.01
•+
at 2500 rev/min and BS Au 141a I 1971 conditions
at CARS 1}-lDode cycle conditions
Reference 5.1.
Aldehydes were reported to increase. Bertodo reported problems
related to lubricating oil contamination by organic acids (mainly
formic) and unidentified aldehydes. This resulted in higher wear
in critical engine parts such as bearings.
5.1.5.2 Emulsions of Alcohols With Diesel Fuel - Injecting
methanol or ethanol under high pressure in diesel fuel was found
by Holmer, et.al. (5.2) to form an emulsion, which remains stable
long enough to be uniform until injected. This results in a dropin the cetane number of the fuel. The cetane number demand is
much lower at full load than at low load as as shown in Figure5.5. Therefore, a load-dependent emulsion can be used, which in
creases the amount of emulsified methanol with load. One such
system was developed in which the emulsion was produced. It was
found that with this system, emulsions of methanol and ethanol
5-12
Part--load at 1500rpm. Methanol ·~th 5 1 %
W.L VO •• centanox.
500
h"'"5thCilPP'essllre
250 175 0 kP., :. I
, P. ,\ ~. .'\ ~. ,
\ ". .., ....o~~~~"""-"--"""'::::;:::i==;:::::;:.-o 0.5 to
Bflol(P ~
1500e&:
1000(,)::I:
Reference 5.2.
FIGURE 5.4. EFFECT OF THE BACK PRESSURE ON HC EMSSIONS.
.""'", ...1 ~ ~art load at engine speed
2220, ambient air temperature25 C.
Reference 5.2.
2~~
• ~ -.oJ• - C'2
Ie ~....~
FIGURE 5.5. PERCENTAGE NEEDED OF CENTANOX IN METHANOL AND CETANENUMBER TO MINIMIZE HC EMISSIONS TO 400 PPM.
5-13
-with diesel fuel are only useful under steady state, full load
conditions. Under transient conditions, the capacity of thegallery of the injection pump does not allow the quick adjustment
of the methanol/diesel ratio to meet the cetane requirements at
different loads. Figure 5.6 shows the variation of the hydro
carbon emissions with time after unloading the engine. Holmer,
et.al. found that only 32 percent diesel fuel could ·be substituted
by methanol ~nder full load con8itions to avoid piaks of HC above~
1000 ppm. Holmer stated that with such e~ulsions, the diesel fuel
will give reasonable wear protection of the injectors and fuel
pump providing the alternative 1uel has a low·acid content ..
5.1.5:3 Carburetion or Manifold Injection of Alcohols and Ignitionby Diesel Injection - Alcohols have a latent heat of evaporation
much higher than gasoline. Therefore, carburet ion of alcohols re
sults in a larger drop in the intake air temperature which af
fects the autoignition process and tends to cause misfire at low
loads. At high loads the carburetted mixture tends to self-ignite
(5.3, 5.4, 5.5). Manifold injection of ethanol was found by
Bertodo (5.1) to require elaborate and expensive control ofthe metering and timing of the two fuels.
5.1.5.4 Two Separate Injection Systems - The methanol, ethanolor gasoline is injected, separate from the diesel fuel, by a
separate injection system. The relative timing of the start ofinjection in the two injection systems has a great effect on
performance and emissions. The effect of the dynamic injection
timing of diesel fuel on the HC and smoke is shown in Figure 5.7,
at a fixed injection timing for methanol. It is clear from this
figure that earlier diesel injection results in lowering the HC
at light loads and the smoke at the higher loads.
5-14
7000
e6000a5000
~LOOO
3000
~ooo
'000
. I [ng1n. lIissfirinQ, r... ll I.::a~ e;,;\;hilJlII, {33 vel I dill.1 In ~thlnelI - --- S4 .n'''91 I: !3~ vol Idiesel 1n ~thlnol
I - 59 ,n,,,S1 $, ~9 vol. dlu,l in _thlnel, _.- 68 enel'91 II
•,,,
PU"e diesel f ...el
Ref. 5-2.
FIGURE 5.6. HC-EMISSIONS VERSUS DRIVING TIME AT NO-LOAD AFTERFULL LOAD AT ENGINE SPEED 1500 RPM.
I
e't<:::>~\.,
0.5
ot-------C"'Part load
at engine speec 900 rpm.
os
- Oblt"Sfl - 7SaTDr- - - o.OIt Sf l =101:3'DC_. - otvl!SEL : 15BTDC20()O
~'H>J
E~~
~ 0 ~--_...L-_-";;;:-='==-_o6N[.P\ Mf'a
Ref. 5.1
FIGURE 5.7. EFFECT OF DIESEL DYNAMIC INJECTION TIMING ON SMOKEAND HC EMISSIONS WITH FIXED METHANOL TIMING.
5-15
The relative amounts of fuel injected can be varied accord
ing to the cetane requirements at the different loads. At idling
and light loads the fuel should be diesel fuel in order to reduce
He emissions and improve ·the cold starting characteristics.
A comparison between the performance of the standard diesel
engine and the diesel/methanol engine is given in Figure 5.8.
This figure also shows curves for methanol with 15 percent water,
which represents an alcohol distilled at a low concentration andrelatively lower cost. Figure 5.8 indicates that with methanol,
there is a slight improvement in thermal efficiincy, low load
hydrocarbons, and high load smoke.
Figure 5.9 is for.a diesel/ethanol engine and is similar to
the corresponding figure for methanol.
5.1.5.5. Spark Ignited Alcohols in Diesel Engines - A commercial
spark ignited diesel engine running on diesel fuel was used by
Vo1ve (5.2). To make a light engine, a low compression ratio (12:1)
was used. The prob1~ms with this engine were cold starting, high
emission of hydrocarbons at idling, and low reliability, as thespark plug could be wetted by the fuel, thus causing misfire.
Spark ignited diesel engines running on gasoline, methanol,
and ethanol have been developed (5.6) (5.7), but are not commer
cially available. In these engines, a much higher voltage isneeded for the spark because of the high compression ratio.
The effect of using methanol on the endurance of diesel
engines during two lOOO-hour cycling bench tests was reported by
Holmer, et.a1., (5.2). Wear was observed between the injection
needle and the spring washer causing the opening pressure to fallfrom 14.7 MPa to between 4.1 and 11.8 MPa. An attempt was made
to solve the wear problem in the injector by increasing the back
pressure in the fuel leakage pipe in order to maintain the
methanol in a liquid phase at the temperatures which exist in theinjector. This attempt did not solve the problem. Other problems
reported by Holmer are related to cracked plunger liners.
5-16
"
- ." ,'I.IJ: ,.~.(;) 1'/:'\.' l l '''6i'li-'.- - ,':!. '1/';'''[1/
- M~- ill.e.l\'Ol • 7!J % .....M [R
400
40~
30 •~
~~
70 ""'........0 "'"7,0
-'.e
~VI 0 "---~-....:::=r.;__.J
0.58,.t-P MPd
Reference 5.2.
FIGURE 5.8. COMPARISON OF PART LOAD PERFORMANCE BETWEEN STANDARDDIESEL AND DIESEL/METHANOL ENGINES AT 1500 RPM .
._- [7H""OL- - -nHAI...Ol .30"" hl.7l I(
- - [T HANOL 050 % 1''''',"[ R
7,0
Reference 5.2.
)0,
~ ~e ~~ W ~~ SMOKE ~
5, 0 '-----'---~.,....,,--~, ~o 0.58,.,£P !'1Pa
FIGURE 5.9. PART LOAD PERFORMANCE WITH DIESEL/ETHANOL ENGINE AT1500 RPM.
5-17
5.1.6 Effect of Mixing DF-2 With Vegetable Oils
Results of tests on blends of DF2 and several types of
vegetable oils are given in Table 5.6. The vegetable oils tested
are:
a Soya Oil
a Babco Oil
0 Palm Oil0 Peanut Oil
o
The results with 10 percent and 20 percent ~otton seed oil aregiven in Table 5.7. Bertodo concluded that:
i. Most vegetable oils except castor oil are directlymiscible with middle distillates.
ii. High viscosity and acidity were general problems with
all vegetable oils.
iii. Castor oil, readily mixed up to 2 percent concentration,
was too viscous (297.5 CS at 37.8°C) and tended to cause
fOUling (carbon residue 44 percnet), and proved
excessively acidic.
5.1.7 Effect of Mixing DF-2 with Gasoline - The main problem of
using gasoline as an alternate fuel in diesel engines is related
to its very poor ignition property resulting, in very long ignitiondelays. This results in late start of combustion at low speeds
and misfire at high speeds. Techniques to reduce ignition delayare heating the inlet air, raising the compression ratio, or
mixing a high ignition quality additive with the gasoline such as
diesel fuel or lubricating oil. Figure 5.10 gives the cetane
number drops from 50 to 32 as the percentage gasoline in the mix
ture increases from 0 to 50 percent. The effect of mixinggasoline and diesel fuels on the ignition delays is shown in
Figure 5.11. This figure shows that an inlet air temperature of
100°F, mlxlng with 30 percent gasoline increased the I.D. by 50
percent. Figure 5.12 shows results reported hy Scott for testsof a 300 cu. in., 6 cylinder D.I. truck engine, with diesel fuel·
5-18
TABLE 5.6. PERFORMANCE IMPACT OF EXTENSION WITH VEGETABLE OIL
lloaBeline Enginel§:l Compression Ratio
22 !'l'DC llyn. Inj. T1m1.:lg
BS 2869 Class Al lIS 2869 Class Al BS 2869 Class Al lIS 2869 Class Al BS 2869 Class AlNil 20% Soya Oil 2~ Baba~o Oil 20% Palm Oil 20% Peanut Oil
_20 -15 _15 _15 _15>C!l 50 CB 4S C!l 48 C!l 47 C!l 47
!Zlgine
Fuel SpecificationExtenderAromatic Content, ~
Cetane Rating..Power. Itws.I.c •• ml/Kwh
NO • gjKwr.+BC~ g/KwoCO. g/Kwh+B:acx SmoKe. ~ OSP~5 2Noise. dB re - 2xlO H/m
61.6261
13.12.6
10.2~
100
61.1286
8 - 9
61.1284
e - 9
61.1281
e - 9
61.0280
e - 9
• a~ 2;00 rev/min and BS Au 141a 1971 conditions
at C~ l}-mode cycle conditions
Reference 5.1.
TABLE 5.7.
Ec.gine
PERFORMANCE IMPACT OF COTTON-SEED OIL EXTENSION
Baseline Engine16:1 Compression Ratio
220 BTIlC' Dyn. Inj. Timing
Fuel SpecificationExtenderAromatic ContentCetane Rating
Power. K"'"s. f. c.. ml/Kwh
1:IS 2869 Class AlNil
-20>CN 50
61.6281
1:IS 2869 Class All~ Cotton Seed Oil
-18CN 49
61.0280
E5 2869 Class Al20% Cotton Seed Oil
...... 16CN 47
60.9278
NO • g/Kwh+ l~.lHC~ g/Kwh+ 2.6CO, g/Kwh+ 10.2Elack Smoke, %USPH§5 2 ~Noise, dll re - 2xlO N/m 100
• at 2500 rev/Min and 1:IS Au 141a : 1971 conditions
+ at CARE 13-mode cycle conditions
Reference 5.1.
5-19
8 - 9 8 - 9
60
50
40
0:30LIJm
2:;)
Z
IIJ20z
et....LLIU
10
o 10 30I
40I
50Percentage of Gasoline in Mixture
FIGURE 5.10. CETANE NUMBER OF DIESEL-GASOLINE MIXTURES
5- 2 a
4.0
3.6
03.2I.IJV')
~~
0 2.8Qa::t:2.4
~...J~2.0ozo;= 1.6ZL?-
1.2
.8
BLENDS OF DIESEL # 2AND GASOLINE
Pm=600 PSIO
<> CN-44e CN - 30I2J CN - 22CD CN- 6
50 100 150 200 250 300 350 400 450 500INLET AIR TEMPERATURE (OF)
FIGURE 5.11. EFFECT OF MIXING GASOLINE WITH DIESEL FUEL ONIGNITION DELAY.
5-21
- __ KUWdlt YdS oli 23· E SlanG;.!r,: n:~_: on t,m,n-,;_._.- Es~c, rl:'yulilr yasol,n", 32 E s:"nc:,,~:: ,n!"C!lon t,mlny---- -- MT8036 yilsolln" 32 E S:ii nn:: r:: '1 ',:,l tIOr"· (,m,ny
30 40 50 60 70 se 90 10C' 1 10Brit'·· M .. iln Etlt:'C!III.. Pr",ssu'," 'ps"
---,--- ._- ------ --- - .._---\
7r---~ -- --\ 2600 r\:l1'
~~__ \ :JV /- 61
~ __... >
- 5:'-, J V --=!"--=-=_--, \ .... J\''I \ - '- -\ - 1_·/
4;~- ----- ---6-, \ I _
j' 'So " 2000 ro", I _
; 3-~ __ J~ -~:~ ;5 ~6' .__ ._=::::..,.~-=?Ij(: I 4
JV i51--00'<..-----1500 rp,,·--J\ : 3 ~
~IV '\' I )~ oJ ~--"'::::::~SC;;~=_--I'--""::::':::"'::;-'~' -,/~-
----.~ ="=i .....
'.J13~~-""""-""'"
Reference 5.18.
FIGURE 5.12. TYPICAL DIESEL FUEL AND GASOLINE LOAD RANGE CURVESFROM A 6 CYLINDER 300 CID DIESEL ENGINE.
5-22
and two types of gasoline. TheC.R. was raised from 17 to 19:1.
The BMEP at which just visible smoke is indicated by the symbol
JV on the figure for each fuel. Figure 5.13 sho~s very clearly
that gasoline produced higher BMEP at the smoke limit. This is
caused by the incre~se in the portion of the fuel which is
injected during the longer ignition delay, and the increase in the
pre-evaporated and pre-mixed part of the charge. The deteriora
tion in fuel economy at high speed and light load is due tr.·) mis-~
firing due to the long ignition delays of gasoline. Combustion
photographs taken by Scott (5.8) indicated the occurenc~ of pre
mixed burning with long ignition delays.
One of the problems associated with the use of gasoline in
direct injection diesel engines is the formation of pockets of
ena gas outside the combustion.bowl, which detonate causing
damage to the piston crown.
The use of additives can reduce the ignition delay period.
Adding,S percent lubricating oil to the gasoline was found to
increase the cetane number of a primary reference fuel 'from 19
to 22 and to decrease the R.O.N. of gasoline from 93.1 to 89.5
(5.8). Adding 5 percent lubricating oil was found by Scott (5.8)
to eliminate the damage in the piston caused by detonation, and to
provide necessary lubricity to the gasoline in the fuel injection
pump.
Another problem associated with the use of highly volatile
fuels in'diesel engines is vapor lock in the fuel injection pump.
This may be avoided by using pressurized recirculating feed to the
pump gallery (5.8).
The use of gasoline in divided chamber automotive engines
was reported by Scott (5.8) to be far less successful than in D.!.
engines. This is attributed to the high rate of evaporation and
premixing, coupled with high rates of heat loss, which result in
excessive delay and unreliable ignition, particularly at partialloads.
5-23
5.1.8 Effect of Using Two Separate Injection Systems in a Diesel/
Gasoline Fueled Engine
A comparison between the partial load performance of a diesel/
·crude low octane gasoline engine and a diesel engine running on
gasoline has been reported by Holmer et.al., (5.2) and is given(j
in Figure 5.13. This figure shows an increase in the thermal
efficiency and reductioQ in smoke in the diesel engine when runon low-octane gasoline. However, the HC emissions are much higher
with pure gasoline, particularly at light loads. To reduce these
emissions and improve the cold starting characteristics, pilotinjection of diesel fuel is used at light loads and atstarting. At high loads, the pilot injection is stopped as the
cetane requirements are less.
5.1.9 Effect of Using Wide Cut Distillates
Holmer (5.2) indicated that wide cut fuels can be obtained
by mixing crude gasoline with diesel fuel, and can be produced at
the refinery with less energy than that required to produce highoctane gasoline. Broadening the distillation range of the fuel,
by including both lighter and heavier fractions than those nor
mally associated with DF2, is the simplest and most expedientmethod to increase the diesel fuel stocks (5.1). According to
Bertodo (5.1), the benefits f~om such a fuel are:
a. Reduce the refinery losses by 17-25 percent.
b .. Increase crude barrel yield as "road fuel" by 5-25
percent.
c. Improve the mileage potential per barrel of crude by
11-21 percent.
d. Raise crude to drive-wheel conversion efficiency by
about 30 percent.
5-24
- - (/(I.'Of" u':'$JL IN! :."'0 DlfSEL
- - - (t;uDf GtSOLII£
,1£.
Reference 5.2.
.k-'Q.
~OO....(XHAUS 7
,
o 0; 0,4BM[P MP.
0,6
FIGURE 5.13. COMPARISON OF PART LOAD PERFORMANCE WITH DIESEL!CRUDE GASOLINE AND CRUDE GASOLINE AT 900 RPM.
5-25
5.2 0.1. TWO-STROKE-CYCLE DIESEL ENGINE
5.2.1 Effect of Using Off-Specification Diesel Fuels
Baker (5.9) performed tests on a two-stroke-cycle medium
speed diesel engine by using off-specification diesel fuels. One
or more properties of these fuelscdid not lie in the currently
accepted range of specifications for Number 2 dies.el fuel. The
fuel properties ~aried were cetane number, viscosity and dis
tillation range.
The engine used was a'two-~ylinder version of the Electro
Motive Division (EMD): 8.5" bore, 10.0" stroke, 2-stroke-cycle,blower scavenged, maximum governed speed of 835 rpm, 16:1 C.R.
Fuels were produced by blending various components, and
compared to No.2 diesel fuel which met all requirements of ASTM
0-975 shown in Table 5.8.
Effect of Cetane Number. The effect of cetane number was to reduce
the 1.0. and rate of pressure rise as shown in Figure 5.14. For
fuels with a C.N. above 30, the decrease in 1.0. was not sufficient
to result in a significant penalty in engine performance, brakehorsepower, thermal efficiency, BSFC, and rate of pressure rise as
shown in Figure 5.15. Below a C.N. of 30, rate of pressure rise
increased dramatically. The effect of the variation in C.N. onthe emissions is shown in Figure 5.16. In this 'figure, Notch 8
indicates .full load rated speed and load. All other notches
indicate partial load conditions.
Effect of Viscosity. The viscosity was varied independently of
the other fuel properties by heating an extremely viscous lube
stock. Probably, heating the oil resulted in variations indensity. Engine power, fuel consumption, thermal efficiency, and
combustion characteristics were almost constant. The effect of
viscosity is shown in Figure 5.17. Brake specific particulatesincreased as viscosity increased from 38 to 65, at the high load.
(This load was limited by the inability of the injection system
to supply sufficient fuel for normal operation). At partial loads,
5-26
160
140 FUEL 8LENOS
120HAN/OIESEL FUEL
·,SOOCTANE/OIESEL FUEL··SECONOARV REF FUELS
100...IZ:::l 80'""'-"'1:'IZ: ... 60"'c... -Ou;... ~ 40~
«IZ: +-
20
0
12
"10
,.~~:.. 6 NOTCH 89
+ NOTCH 6.~":'~. > 8 C NOTCH 40<
~ 0 NOTCH 2... -co<ZU01:'- ...~c 6Z -~
5
4
315 20 25 30 35 40 45 50 55
CETAIIolE IIolUM8ER
Reference 5.9.
FIGURE 5.14. EFFECT OF C.N. VARIATIONS ON I.D. AND RATE OFPRESURE RISE (2-CYLINDER ENGINE).
5-27
Z 0750i=...~::::l
'"Z0 0.5 ....'-'-~CI: .e;g =6 • Co G"':r •:l .... !:'-'Ill- -"'11I 0.25- ..J'-'-'"...'"'":It«a:
0III
~
no A"· :0:""""4
~.Co6
200
180
a: 160...~0 140......
FU~L BLENOSIII 120a:0 MAN/OI ESE L I' UE L:r 100 -rSOOCTANE/OIESEL FUEL...lI: 80 ··SECONOARY REF FuELSCa:III 60
40
f20
0
30'
> 32'-' A"Z A'" A·· ~ :6q 30
/~...... 2B..J«~
26ct A NOTCH 8...:r~
'" 24lI:~ctIII 22
20
1815 20 25 30 35 40 45 50 55
CETANE NUMBER
Reference 5 _9.
FIGURE 5.15. EFFECT OF C.N. ON ENGINE PERFORHANCE (2-CYCLE ENGINE)
5-28
TABLE 5.8. NO. 2 DIESEL FUEL PROPERTIES
Reference: 5.9.
Bas~lin~
Fuel ASTM D975 No. 2 Dies~1 (IProperty Specifications Fuel
Celane Number min. 40 55API GravilY no spec:. 37.7
Kinemalic Viscosil)' min. - maA.(esl. al 40°C) 2.0 4.3 3.3
Heal of Comb.(BTU/lb) no sp~" 1968~
DisliJIalion (0 F)10'7. no spec:. 4609017. min. - maA,
540 675 64Q
Sulfur ('7. mass) 1.0 0.15Ash (llio mass) omWain. Sed. (17. voL) 0.10Flash PI. (OF) min.I:!5 161
5 - 29
Reference 5.9.
".==~
··..·
D •
,:~~
t•.. .;
. . .:::......." :::::::;;~: -
FIGURE 5.16. EFFECT OF C.N. ON EMISSIONS IN A 2-CYCLE ENGINE.
5-30
2
0.75
6 NOTCH B
+ NOTCH 6
o NOTCH 4o 'NOTCH 2
II!!:.;;....---+---~~-o
0.5
1.5
i:r 1.25~
:r~
~<IIZo=a:;5 0.75oc::Q>::t OS
0.25
o
.,y' .~.-------+
10
95
9
~ 8.5~
:rCIl
~ 8...!:ll( 7.50uit 70-
i
63D .a SO 60 70 SO 90 100 110
6.5
Ref erenc e 5.9. VISCOSITY (CST}
FIGURE 5.17. EFFECT OF VISCOSITY ON EMISSIONS IN A 2-CYCLE ENGINE
5-31
the brake specific particulates increased with viscosity up to 65
CS, after which they decreased. This variation in particulate
emissions is related to the change in the spray characteristicsand the degree of premixing of the fuel and air.
Brake specific hydrocarbons generally increased
particularly at the lightest loads (Notch 2). Brake
nitrogen oxides decreased with increased viscosity.
"oxide and sulfates did not show a definable relation
with viscosity,
specific
Carbon mon-
to viscosity.
Effect of Distillation Range. Fuels of different distillation
range were prodnced by blending various combinations of unleaded
gasoline, a lube stock, and No.2 diesel fuel. This resulted invariations in the other fuel properties, and a multi-variate
statistical analysis was used to find the effect of each fuel.property. This analysis indicated that the distillation range
was not a primary factor in B.H.P. and BSFC, but rather, the C.N.,
API gravity and the heating value are the major factors. In a
second analysis, each of the performance parameters was plotted
in terms of each fuel property, and the results were then cross
referenced to isolate the pertinent properties. The effect ofC.N. on I.D. is shown in Figure 5.18, and on the rate of pressure
rise in Figure 5.19. Below a C.N. of 30, the increase in I.D.resulted in a high rate of pTessuwe rise. The effect of API
gravity on brake thermal efficiency is shown in Figure 5.20. The
effects of API gravity on the brake horsepower are shown in
Figure 5.21. It should be noted that the engine was not optimized
for fuels of different distillation ranges. Accordingly, it is
expected that the engine thermal efficiency and power output are
not optimized for these fuels. Baker (5.9) observed that the
maximum brake horsepower and brake thermal efficiency resulted from
the use of fuels whose properties approximated those of the baseline diesel fuel.
The effect of viscosity on the brake thermal efficiency is
shown in Figure 5.22. The effect on brake horsepower is shown in
Figure 5.23. The relationship between the API gravity and theviscosity for the different blends used by Baker is given in
5-32
~i~
l~
\.<~
I.'.
,,
,'
~o
q
12
_I
lIiO
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A.
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...."
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"41
too..
....1/
1
10J.
411
20
41II
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c::l
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160
12r
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,....
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Ref
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ce5
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FIG
UR
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-1
8.
EFFE
CT
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.N.
ONI.
D.
FOR
FIG
UR
E5
.19
.EF
FEC
TO
FC
.N.
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TEO
FV
ARI
OU
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IST
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AT
ION
RANG
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ESSU
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RIS
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AT
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FUE
LS.
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ER
IES
.
35 JO 2!i
20
......
C1l
<:I"
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l
t:..·t
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200
<:I" I l:l. .. r· · ••
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o •
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i
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e
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o2
J4
56
89
10o
!i10
VIS
CO
SIT
YfC
ST~
4O"C
IR
efe
ren
ce
5.9
FIG
UR
E5
.22
EFFE
CT
OFV
ISC
OSI
TYON
BRAK
ETH
ERM
ALEF
FIC
IEN
CY
DIS
TIL
LA
TIO
NRA
NGE
SER
IES
Refe
ren
ce
5.~
FIG
UR
E5
.23
.
VIS
CO
SIT
YIC
ST
fil4
o"C
I
EFFE
CT
OF
VIS
CO
SIT
YON
BRAK
EH
ORS
EPO
WER
DIS
TIL
LA
TIO
NRA
NGE
SER
IES.
Figure ~.24. This figure shows that heavy fuels are more viscous.
Accordingly, high viscosity fuels have more BTU per unit volume
and, in general, should produce more power for the same volumetricrate of fuel injection.
Effect of Fuel Properties on Emissions. The effect of API, gravity
on the brake specific hydrocarbons. is shown in Figure 5.25. In
general, lighter fuels produced more hydrocarbon emissions'. This
is caused by the longer I.D. of th~ lighter fuels~ i~ addition to
their higher vapor pressure and results in more HC in the lean
flame-out region of the spray.
The effect of viscosity on the brake specific hydrocarbon
emissions is given in Figure 5.26. This figure shows that the
fuel which has a viscosity slightly lower than diesel fuel pro
duced less BSHC. For less viscous fuels, BSHC were higher than for
diesel fuel. Fuels which are more viscous than diesel fuel produced
less BSHC, particularly at the lighter loads.
The effect of viscosity on the BSHC is related to the lean
flame-out region of the spray and to the fuel in the sac volume
of the nozzle.
Baker reported that neither particulates nor nitric oxide
emissions could be specifically defined in terms of the infl~ence
of a single fuel property. However, carbon monoxide displayed a
dependence on both cetane number and total BTU input; in both
cases, the trends observed were also a function of load (or notch
position), as indicated in Figures 5.27 and 5.28.
Baker concluded that no single fuel property could be classi
fied as the primary variable which affected performance and
emissions when all fuel properties were allowed to vary simultaneously; rather it was the combined influence of several variables
that ultimately determined engine behavior~
5.2.2 Effect of Using Fuels Derived From Tar Sands and Shale Oil
Tuteja and Clark (5.11) studied the sensitivity of a D.I.,
2-stroke-cycle diesel engine to variations in fuel source. Diesel
5-36
60
50 .
>t- 40-><a::
~
C)
CL 30ca:
20
o 2 4 6 8 10 12 14 16
VISCOSITY (CST,40·C)
18 20 22 24
FIGURE 5.24. RELATIONSHIP BETWEEN VISCOSITY AND API GRAVITY FORDIFFERENT DISTILLATES.
5-37
Q
oIi~
I:[.:
.l
12 10 II Ii 4 2 o
..... III III
NO
TC
HII
III 'M Q ,.1•
•
'1 10 8
..... III III
III OM QN
OT
CH
II
••
11 10
44 1 •
.. ..••
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TC
H4
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HIi
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• ..'" •
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efer
ence
5.9
FIG
UR
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.25
.R
efe
ren
ce
5.9
EFFE
CT
OF
API
GRA
VIT
YON
BRAK
EFI
GU
RE
5.2
6.
SPE
CIF
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IST
ILL
AT
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RANG
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RIE
S
VIS
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I
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FIG
UR
E5
.28
.EF
FEC
TO
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.N.
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AK
ES
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AKE
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CIF
ICCA
RBON
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S
fuels derived from oil shale and tar sands were compared with
the commercial DF-Z diesel fuel derived from crude petroleum. The
properties of these fuels are shown in Table .5.9. The DF-Z hasthe lowest viscosity and distillation range, while shale fuel has
the highest. Tar sands fuel has the lowest cetane number, sulfur
content and atomic HIe ratio while sha~~ fuel has the highest.
The fuel nitrggen content was low for regular DF-Z and tar sands
fuel, but substantially higher for the shale fuel. ~
The engine used was a three cylinder, D.I., 18.7 C.R.,
naturally aspirat~d, Z13 CID, Z-stroke-cycle diesel engine~ The
injectors used were of the N-60 needle valve type modified to
maintain constant beginning of injection. In this work, NO was
measured by using an NDIR analyzer, and NO Z by using a long path
NDUV. These values were corrected for temperature and humidity.
The effect of load on I.D. for the three fuels is shown in
Figure 5.Z9 for three different speeds. The I.D. decreased with
the increase in cetane number.
The maximum rates of pressure rise,shown in Figure 5.30followed a trend similar to the ignition delay.
The BSFC relative to DF-Z fuel is shown in Figure 5.31 and
shows a slight loss in fuel economy with the alternate fuels,
particularly at the high loads. This is believed to be caused by
the injection and combustion systems which were developed for the
DF-Z and not for the other two fuels. For example, in this work,the injection timing was kept constant and corresponds to the I.D.
of DF-Z fuel. The I.D.s for the alternate fuels are longer than
for the diesel fuel and a slight advance of the injection timingwould have improved the engine fuel economy.
The exhaust smoke obtained for the three fuels is given in
Figure 5.32. Tar sands fuel showed the highest smoke, followed
by regular DF-2, and shale fuel respectively. The differencesare generally small and possibly not significant at lower speeds.
At higher speeds, the fuel from tar sands produced the highestsmoke. In general, smoke is related to the injection timing,
5-40
DERIVEDFUELSREGULAR DF-2SANDS
OFAND TAR
PROPERTIESFROM SHALE
5', 9 ,TABLE
TAlI.!!m
!!!.....LsICR
Ar..utaa,IUM'M1Olaf I".....1111'11••h
0.160.0%2.7....U.'6'J.6'J. ~0.0U.7
0.2'0.010'7. J6U.87'2.6%0.00.5J2.3.0016
D.SO0.2'16.0ZU.79J).7
.001
\'.....C.R
'b
0.2O. J0.9O. :
CO. I<0.1
C.OI0.60.10.10.10.5
0.2J .•0.71.2
<0.1<0.1
mill:
AII111... 't. ('C)"/Cteta. Ikl.liP 'r1(1: or~ ·F~ 'rEP 'r'.,1
'uca.tt, CI .. 100" ,. J5
57.!I. 76'1.015 I425509605649J6. :
%.50
L.awer lIe.t1na Vel ...Un:flbl
11131 11:61 11107
~
PIO.tIl~lt5 Dr r~c.s ~SCl I' ~. OOPI.' TEns
5
•C
•Arcmel Joe
"'~P1I"""'"Oloh,..'.r.' t lnau.
.1,..ArOMt H
~
o. =~
0.0:. CO.9t1'!'. I_ll.. E''2 .•2•. 00.\J2. J.001t
Lo.ArOUt1:
~
0.250.01! (0.9:,16 IJ1~ 6:J5. \25.30.0".1.000..
OF';
.0:',001 (;.0:1It. C:11.1'IJ. C'2LlO. C61 ;.DOO.
Jp.eel.".
.OHoc .0... : (l ~:
8~ . ]..1. tl~
t.IH.C0.'6: .\.0008
nACE !lETAll.'
!'''''\'
••...CoIPb
•. 010.60.10.10.10.1
•. 011.20.010.23D. OJ0.25
c. C5. 1\.01.09.a~0.3'
O. :1. D:.~~.o~
.01
.11
""111M ... ('C)RICee,..,. Ie.liP 'r101 'r'01 "9ll'I "EP 'r'.,1
ST.81.76'J.OH7025
'09601649h.1
'02'7~
551
102. 01n.916!236)!I
51.IH1).6
5-41
- TAR SANDS FVEI.- REGULAR DIESEL FUEL- ~ FUEL FROM SHALE 01.
15 ... .• •
10 121DRPM
·I'-----------~
nDOIIPM
1100IIPM
.. I ....-.
~-.....------ -.---
10
•iii=15,.-------------Wc~ 1D
ii ·5
II 15,.---~~~-----......;.--....
. ~---....._-~s~~~-~- ......- .....- ....-..J
ZD .eo 10 -10 100%LOAD
Reference 5.11.
FIGURE 5.29. COMPARISON OF I.D. WITH REGULAR DIESEL FUEL ANDFUELS DERIVED FROM SHALE AND TAR SANDS.
5-42
--.J REGULAR DIESEL FUEL-- TAR SANDS FUEL-- SHALE FUEL
zoo
150
..•."',/~, .---~- .•" ....
----~--
1Z60RPM
. .
2100RPM
'100RPM
................-_ .. .
'OO'-_-'-_......_--I._-""_--I_~a .ao 10 10 100
" LOAD
150
c~~ 100'--------- ....1III..,E
§ 200..,..,III
~ 150 ............................1:1 fIf""" ......__•.$ 100~-----------"'"KIeC
• ZOO
Reference 5.11.
FIGURE 5.30. COMPARISON OF MAXIMUM RATE OF PRESSURE RISE WITHREGULAR DIESEL FUEL AND FUELS FROM SHALE, AND TARSANDS.
5-43
e __•• TAR SANDS FUEL-- SHALE AIEL1JU.------.....;,;.-------,
12&0RPM
fe:= 1.02w
!ciZ 1.00II:
fe1.02 ::
w
!1.00 ~
wII:
O.98~;::::========~,... 1.0.
~/" _-0,"............ 1100'
....•. RPM.'
-==='-'========:0.111JUOr-
fe:h.020w!~1.000
*
Reference 5.11.
.'..'................;;;;.
RPM
20 .to 10% LOAD
..'........
100
FIGURE 5.31. BSFC WITH SHALE AND TAR SANDS FUELS RELATIVE TOREGULAR FUEL.
5-44
- REGULAR DIESEL FUEL...- •.•• TAR SANDS FUEL .~)
--FUEL FROM SHALE2
1~
~12&0RPM
..~O~
Z...-.:CI 1&00•III 1 RPMz
~~CIt
i 0..............::.:.:.:... ~
2 2100RPM
1
0
0
Reference 5.11.
FIGURE 5.32. COMPARISON OF SMOKE WITH REGULAR DIESEL FUEL ANDFUELS DERIVED FROM SHALE AND TAR SANDS.
5-45
injection pressure, 95 percent, and aromatic contents. Table 5.9
indicates that the fuel from tar sands has an aromatic content
slightly higher than DF-2 and much higher than the shale-derived
fuel. The 95 percent point does not indicate a trend in these
tests. It appears that the reason for the highest smoke with the
fuel from tar sands is related to the unoptimized injection timing.
The longer ignition delay with this fuel, without advancing thev 0
timing allows the combustion to take part later in the expansion
stroke and result in higher smoke concentrations.
The ~Ox emissions are given in Figure. 5.33 for the two fuelsrelative to DF-2 fuel. In general, over the speed range, NOxemissions were highest with tar sands fuel, and least with the
shale-fuel, except at full load at the 'highest speed. The
difference between DF-2 and shale fuel is small. However, the
difference between NO emissions from regular DF-2 and. tar sands
fuels is significant. The differences between the two fuels which
contribute to the high NOxemissions are: (i) the lower cetane
number of tar sands fuel, which results in longer I.D., and premixed combustion, (ii) the slightly higher aromatic content of thetar sands fuel as compared to that of DF-2 and the resulting
higher combustion temperature, (iii) the higher nitrogen content
of the tar sands fuel as compared to that of DF-2.
The unburned hydrocarbons from the tar sands fuel and shale
fuel are given by Tuteja and Clark· (5.11) in Figure 5.34, relative
to the hydrocarbons from DF-2. The HC emissions with tar sands
fuel are about 60-70 percent of HC emissions with regular DF-2,
whereas, with shale fuel, these emissions are about 30-40 percentof those with regular DF-2, over all the speed and load ranges.
The factors that might have contributed to the lower HC emissions
from the alternate fuels are related to the higher viscosity and
SO percent points of these fuels, which reduces the HC related
to the volume of fuel in the sac and injection nozzle.
The CO emissions are shown in Figure 5.35 for the alternate
fuels relative to the CO from the regular DF-2. In general, tarsands fuel shows the highest CO followed by regular DF-2 and shale
5-46
-- SHALE FUEL- TAR SANDS RIEL• • EXPECTED RELATIVE NOX EMISSION BASED ON TOTAL
CONVERSION OF .24% N IN REGULAR DIESEL RIEL1.20r--------------1.00 -0.10..•Ii..
I...Ie 1.00a•...~ 0.10c.......e
1:l0-~
...".'
1.D0,~ ....
0.80
Reference 5.11.
~..............--...............-
,--e-_.....~.--
20 40 10 ID 1DC% LOAD
12&0RPM
1100'RPM
2100RPM
FIGURE 5.33. NOx EMISSION BY MASS WITH SHALE AND TAR SANDS FUELSRELATIVE TO REGULAR DIESEL FUEL
5-47
1&00 RPM
2100 RPM
- TAR SANDS FUEl.-- SHALE RIEL
,,·1 I., 12&0 RPM-.,I 0.7-w
!I!.w 0.5-!~ ------ _..-.=O.3'---------------_...J
r--------------O.l-zIi!..
0.7;w
• Ur--------------...I! 0.7'" .... --------.....'"
~ ?! 0.5- /c /~ '--1--'-/1 I~ 0.3"-_......._ ......._ ...._---......._ ....._ ...
20 40 60 10 100% LDAD
Reference 5.11
FIGURE 5.34. He EMISSIONS BY MASS WITH TAR SANDS FUEL RELATIVETO REGULAR DIESEL FUEL.
5-48
1210 RPM
10 100,
11G0 RPM
---'TAR SANDS FUEL.--- SHALE RIEL.. Ur-------~....,;.----;.,
11.51M
8! 1.0c-~ 0.5;==============Ui
.5i1M
8.oi
c
~-----------""'D.5$.. z.ar----------~--I.,• 1.51Moc.a
~ 1.0~ ------~c·........ .-.i:l '--c 0.51.--~-....--.l.-....l--'----l
Reference 5.11.
FIGURE 5.35. CO EMISSION BY MASS WITH SHALE AND TAR SANDS FUELSRELATIVE TO REGULAR DIESEL FUEL.
5-49
fuel. The factors which contributBd to this behaviour are
related to the cetane number of the fuel. According to Broering
and Holtman (5.12), and Gross and Murphy (5.13), CO increases
with the increase in the 90 percent distillation point.
Tuteja, et. al., observed no significant contribution duea
to fuel bound nitrogen in NO emissions. Their tests were conducted
at an injection timing of 18:6 0 BTDC, and they attributed theinsignificant N conversion due to NO attaining its equilibrium
concentration in the main NO producing regions. However, at
relatively retarded timing necessary for low emission engines,
significant conversion of fuel bound nitrogen might take place.
5.3 I.D.I. SWIRL TYPE 4-STROKE-CYCLE ENGINE
5.3.1 Effect of Fuel Properties on Fuel Economy and on
Particulates and Other Emissions
Many attempts have been made to find out which constituents
of the fuel (i.e. paraffins, aromatics or olefins) were mostresponsible for particulates.
Burley and Rosebrock (5.14) reported the results of a carbon14 fuel tracer study, in which radioactive C-14 tagged fuel
constituents were blended, one at a time, with the standard base
line D-2 fuel. These fuels were run in a 2.1 liter I.D.I. 4
. cylinder Opel engin~, modified to run on one cylinder. All theparticulates were collected on an 8 x 10 inch filter mounted in a
tunnel and analyzed for the presence of C-14. Tests were at the
equivalent of 25 mph road load and 55 mph road load for each fuel.
The petroleum compounds used in C-14 fuel tracer· studies are
shown in Table 5.10. The quantity of C-14 compound added to the
test fuel was so small that the general physical properties of the
fuel were unchanged. The results of these tests, given inFigure 5.36, show the following:
1. Each of the compounds (paraffins, olefins and aromatics)made a contribution to particulates.
5-50
TABLE 5.10. PERFORMANCE IMPACT OF ETHANOL FUELING
CA~ION
CCMI'OUND ~ FORMULA. STIUJC'TURE
DECANE Co1O CltrCC"2~ 14cH,
MEXADECANE Co1l CMJ-ICHzI1"McH,
OC'TADECANE Co1l CMrlCHzl1r~
DKENE Co10 CM:z"'CM-ICHzlrMcHzC?43
ORTHO IIETHYL XYL.ENE C·I $=14cH,Ci"2
1~ETH"LIlUMTNALDlE Con
@J;~(lUIIfG LAaE LI
'~ETH"LNAI'KTHALINE Con"'ETHYL. LAlELI
00
Reference 5.1.
5-51
2. Particulate emissions from the paraffins were independent
. of boiling point over the range 174°C to 317°C.
3. Aromatics, as a group, were the greatest contributors to
particulates. The ring-labeled I-methyl naphthalene was thelargest contributor.
()
4. Most of the C-14 appeared in the insoluble fraction. Less
than 20 percent appeared in the soluble fraction.
In another extensive study, Burley and Rosebrock found the
effect of fuel composition on fuel economy and emiss~.o~s. Forty
six fuels including D-l and D-2 fuels were tested. The range of
distillation characteristics of these fuels is shown in Figure 5.37.The engine used was an Oldsmobile, 5.7 liter, I.)n.I. V-8, 4-stroke
cycle, C.R. = 22.5:1 light duty diesel, with C.A.V. poppet-type
injectors. Each fuel was tested at the standard timing, 5 engine
degrees advance, and 5 engine degrees retard. The tests were con
ducted under steady state conditions at 5 speed-torque points in the
FTP cycle, and a weighting factor applied to calculate the performance and emission parameters. Particulates were collectedfrom the exhaust of one cylinder diluted in a 300 CHI constant
volume tunnel. The sampling time was 20 minutes at each point.The HC and NO emissions and the fuel economy were also measured.x
The physical properties of the fuels and their range are
shown in Table 5.11.
TABLE 5.11. PHYSICAL PROPERTIES OF G.M. STUDY FUELS
'.
Physical Property Range of Test Fuels
Specific Gravity 0.678 - 0.879
Viscosity O. 50 - 3.5 CS at 40°C
10% Boiling Point 48 - 233°C
50% Boiling Point 71 - 267°C
90% Boiling Point 92 - 365°C
Cetane Number 21 - 80
Aromatic Con tent 0 - 95%
API Gravity 27.13 77.20
Sulfur Con tent O. 002 - 1. 25~5-52
G _
--,
I
--
-
Reference 5.14.
FIGURE 5.36. CONTRIBUTION OF VARIOUS COMPONENTS OF DIESEL FUEL, TO PARTICUL.ATE EMISSIONS.
,.._->-5..
II • • • • _
fWICDff I'IA1'GM....
Reference 5.14.
FIGURE 5.37. DISTILLATION RANGE OF SOME OF THE FUELS TESTED.
5-53
A multiple linear stepwise regression analysis was employed
to relate the fuel properties to the various emissions, and fuel
economy.
5.3.2 Effect of Fuel Properties on Particulates
The regression analysis sho~~d the following:
1. Aromatic content and 90 percent boiling point were the
fuel properties most closely related to particulates, as shown in
Figures 5.38 and 5.39.
2. Fuel volatility factors such as the 10 percent and SO per
cent boiling point showed a weaker correlation to particulates
than the 90 percent boiling point.
3. Particulate emissions increased with addition of cetane
improvers to the light fuels.
4. A typical D-l fuel produces 25 percent less particulate
emissions than D-2 fuel.
Burley and Rosebrock tested a light,narrow distillation
range, low aromatic fuel (C-40) in two vehicles on the FTP cycle.The vehicles were equipped with 5.7 liter engines similar to the
ones used in the fuel test program· conducted on the dynamometer.
The injectors in the engines were conventional two-hole pencil
injectors rather than the CAV poppet type injectors previously
used. The properties of the C-40 fuel are given in Table 5.12
together with those for D-l and D-2 fuels. The particulates formedon the FTP cycle from the C-40 fuel are reduced to 57.4 percent
of those from the reg~lar D-2 fuel (Table 5.13).
Burley and Rosebrock. (5.14) studied the effect of aromaticson the 5.7 liter Oldsmobile diesel engine on a dynamometer under
5 different steady load-speed points with the.two-hole, penciltype injectors. The armoatic contents of the fuel were changed
5-54
TABLE 5.12. PROPERTIES OF D-l, D-2 &C-40
5-55
TABLE 5.13 PARTICULATES WITH D-2 AND C-40 FUELS FTP CYCLE.
Diesel No.2
C-40
0.826 grams/mile
0.474 grams/nile
by blending various amount~ of 95 percent aromatic fuel (C-42:
solvent #150) to D-2 fuel. The results given by :b~ur1ey and Rose
brock are shown .in Figure 5.40. From this figure, it is noted
that:
1. Increase in the aromatic contents up to 55 percent had
little effect on the particulates and. hydrocarbons. Above
55 percent, the particulates and hydrocarbons increasedat a very high rate. .
2. NOx increased continuously with the increase in the
aromatic contents.
3. The increase in aromatic contents improved the fuel
economy (on a volume basis) up to an aromatic content of
45 percent, above which there was no effect.
In another test, Burley and Rosebrock (5.14) found the effect
of increasing the aromatic content o~ the fuel by blending the95 percent aromatic product (C-42) with the low aromatic narrow
distillation range fuel (C-40). The tests were at steady state at
5 sFeed-torque points of the FTP cycle. The results are shown in
Figure 5.41.
The NOx ' HC and particulates increased steadily with increasing aromaticity, while the fuel consumption remained relatively
constant on a volume basis in spite of a density change.
Burley and Rosebrock concluded that the soluble content of theparticulates did not correlate well with fuel properties. Soluble
contents tend to decrease as cetane number increases. Also, the
hydrocarbons decrease with the increase in specific gravity,
viscosity, 90 percent boiling point and cetane number. The NO didxnot correlate well with the fuel properties, but appeared to
decrease with the drop in the aromatic content, specific gravity,and 90 percent boiling point. The fuel economy, on a work done per
5-S6
•
u
I• • •• I •• • •-. I .-• • • •u ,- w- I.-•... • •u • •
u
" I •_1S__.•
Reference 5.14.
FIGURE 5.38. PARTICULATE INDEX IN ARBITRARY UNITS VS. FUELAROMATIC CONTENT.
-7.:,-"
-- a, .. ...U I I II I
• e ...'C'.' •u •.. -t::.
• • II,.. • II~ft •• • '10-.a • •r •,.. •
U
I, - - - -...... ..-r.~
Reference 5.14.
FIGURE 5.39. PARTICULATE INDEX IN ARBITRARY UNITS VS. FUEL 90%BOI LING POINT.
5-57
•N
O.
•IN
DEX
7
HeIN
DEX
..PA
RnC
ULA
TEIN
DEX
a
,.. 0' ..
He
PA
Rl1
CU
UT
EI
7 ..• • •
HCIN
DEX
3
NO
.IN
DEX
IPA
RTI
CU
LATE
IND
EX
U1 I U1
00
2I
EC
ON
OM
Y
EC
ON
OM
YIN
DEX
"(B
YV
OLU
ME. 0
'L
9I
11,
P15
4555
15A
RO
MA
TIC
S.%
EC
ON
OM
Y
(BYl~g~~ME)
1J.
EC
O;)
YY
V--
--
o·,
,,
,9
o10
20ao
4010
AA
OM
AT
,tS
.%
Refe
ren
ce
5.1
4.
Refe
ren
ce
5.1
4.
FIG
UR
E5
.40
.E
r.lIS
SIO
NS
AND
ECON
Gr.lY
VA
RIA
TIO
NFI
GU
RE
5.4
1.
WIT
HFU
ELBL
END
SOF
INC
REA
SIN
GA
RG
r.lA
TIC
ITY
AND
SPE
CI
FIC
GRA
VIT
YST
AR
TIN
GW
ITH
D-2
FUEL
.
EMIS
SIO
NAN
DEC
ONOM
YV
AR
IATI
ON
WIT
HFU
ELBL
END
SO
FIN
CR
EASI
NG
AR
OM
ATI
CIT
YAN
DS
PE
CIF
ICG
RAV
ITY
STA
RTI
NG
WIT
HLO
W-A
ROM
ATI
CNA
RROW
CUT
PRO
DU
CT:>
unit volume basis, improved with the increase in specific gravity,
90 percent boiling point, cetane number and viscosity.
5.4 DIESEL EMERGENCY BLENDS
Similar to the gasoline emergency blends discussed in section
4.4 of this report, diesel blends were tested by Russell et.al.
(4.16) and the :?results reported in the "Emergency Fuels Utiliza
tion Guidebook". The tests were conducted on a DD4-53 Detroit
diesel 2-stroke~cycle engine, and LD-465-l multifuel "engine. The
diesel extenders are listed in Table 5.14. The indexes used in
this section are the same as those in Section 4.4 except for the
BSDC.
BSDC = BSFC x wdiesel
whereBSDC = Brake specific diesel consumption
wdiesel = mass fraction of diesel fuel
mass of diesel fuel= mass of blend
5.4.1 Effect on Cetane Number
The effect of blending diesel fuel with different extenders
on C.N. is shown in Figure (5.42). All the extenders useddecreased the C.N. except"No. 4 fuel oil which resulted in a slight
increase in C.N. The worst extender is gasoline which resulted in
a sharp decrease in C.N.
5.4.2 Effect on API Gravity_
Figure 5.43 shows that all the extenders used by Russell et.al.,
(4.16), except No.6 fuel oil and South Texas sour crude, increased
the API gravity of the blend.
5.4.3 Effect of Heat on Combustion
Figure 5.44 shows that all the extenders used increased the
heat of combustion except No. 6 fuel oil.
5-59
TABLE 5.14. EMERGENCY DIESEL EXTENDERS
l. Gasoline
2. Ethanol Alcohol3. Medium Naphtha
4. Heavy Naphtha Solvent
5. Jet A Jet Fuel6. Jet A-I
7. Kerosene Kerosene (Solvent)8. No. 4 Fuel Oil Heating Oil
9. No. 5 Burner Oil
10. No. 6 Fuel Oil Residual Fuel
11. TX Sour
12. LA Sweet
13. CA Sour Crude Oil
14. UT Sweet
15. Peanut Oil
16. Soy Oil
17. Sunflower Oil Vegetable Oil
18. Corn Oil
The reference fuel used is neat baseline fuel (CAT 1 H reference
diesel fuel).
Reference 4.16.
5-60
CETANE NUMBER6 0 r---r---.,--~-~----,r----:---~-----.---
I 0 &--_-I-_--"__...l...--_-J..__.l........;_...... ......_-J;.._----'
o
Reference 4.16.
FIGURE 5.42. EFFECT OF DIESEL EXTENDERS ON C.N.
5 - 61
"
API GRAVITY 60/60F80
II
70 i
60 . , III
iI 2
50 4
5
403
S
30 ~"'-
B .~,_.
20
100I
10 20 30 40 50 60 70 90 100 -.VOLUME %
1 Extender = Gasoline
2 = Medium Naphtha
3 = Jet A
4 = Jet A-I
5 = Kerosene. 6 = No. 4 Fuel Oil
7 = No. 6 Fuel Oil
8 = South Texas Sour Crude
Reference 4.16.
FIGURE 5.43. EFFECT OF DIESEL EXTENDERS ON API GRAVITY
5-62
5.4.4 Effect on.Viscosity
Figure 5.45 shows that all the extenders used reduced the
viscosity of the blend except No. 6 fuel oil and South Texas sour
crude.
5.4.5 Effect on Power Index
Figure 5.46 shows that all the extenders used reduced thepower index at concentrations highe~ than 65 percent. The gasoline
and ethanol caused the sharpest drop in power index at all con
cent~ations. Some extenders, such as No.6 fuel oil resulted ina slight increase in the power index at concentrations less than
65 percent.
5.4.6 Effect on Conservation Index
Figure 5.47 indicates that extending the diesel fuel with any
extender results in an increase in the conservation index.
5.4.7 Effect on Tradeoff Index
Figure 5.48 indicates that the tradeoff index increases withall the extenders~ except with gasoline "at concentrations higher
than 60 percent.
5".4.8 Effect on Emissions Indexes
The effect of blending diesel fuel with different extenders
is shown in Figure 5.49 for hydrocarbons, Figure 5.50 for CO,
Figure 5.51 for NO , and Figure 5.52 for smoke. It is clear fromxthese figures that the hydrocarbons are the most sensitive, and
increase with the use of extenders. The CO increases when heavier
fuels such as No.6 fuel oil, No.5 burner oil, No.4 fuel oil,and heavy naphtha fuels, are used. The NO x index increases with
the lighter fuels, and remains almost constant with the heavier
fuels. The smoke index decreases with gasoline and ethanol, and,
tends to increase with the heavier fuels.
5-63
BTU/LB
21 000 __-~-----r-----r---:----:---~--"'-""'"
2 0 500 t----T---+--..-..----T----+-----!---I-----r-:---+-~::I'f
4200 0 Ot--------l...--~-"'"""----+--~---±=;;...".e.---___:~~ 3
~~__+:~~~::::~~~tt=_:J 2
19000 ,., I
i
185007
180000 10 20 30 40 50 60 70 80 90 100
VOLUME %
I Extender = Gasoline2 = Medium Naphtha3 = Jet A4 = Jet A-I5 = Kerosene6 = No. 4 Fuel Oil7 = No. 6 Fuel Oil
Reference 4.16.
FIGURE 5.44. EFFECT OF DIESEL EXTENDERS ON THE HEAT OF COMBUSTION
5-64
7
90 10070 8030 40 50 60
VOLUME %2010
CENTISTOKES 40c4---"""-~----""""-------~-----+--'
o
30
90
120
• .l~...
1 Extender = Gasoline
2 = Medium Naphtha
3 = Jet.A
4 = Jet A-l
·5 = Kerosene
6 = No. 4 Fuel Oil
7 = No. G Fuel Oil
8 = South Texas Sour Crude
Reference 4.16.
FIGURE 5.45. EFFECT OF DIESEL EXTENDERS ON VISCOSITY
5-65
2.0
-s7 -II
! I II : ij !
II
i
iI
frog-IO
II !I ! ~eI
I :7 4
Ij I
:z
~~ I 3'I , II
I j !II
I1---
,
I I I II I'
i
I I
I I II I II I I
I
1.2
1.6
0.8
0.4
cPOWERINDEX
10 20 30 40 50 60 70 80
VOLUME %90 100
1 Diesel Emergency Blend Extender = Gasoline
2 = Ethanol (Dieselhol)3 = Medium Naphtha
4 = Heavy Naphtha
S = Jet A
6 = Jet A-l
7 = Kerosene
8 = No. 4 Fuel Oil
9 = No. S Burner Oil
10 = No. 6 Fuel Oil
11 = South Texas Sour Crude
Reference 4.16.
FIGURE 5.46. EFFECT OF DIESEL EXTENDERS ON POWER INDEX.
5-66
CONSERVATION INDEX
50 60 70 80 90 10030 4010 20
! I II
I- I
I iI
I I
, I
I i II I I II
I
I I
/ II
I !
II
I I I ____L.---I
i
I I, 9-10
I I
II I,~!
I I
I~............ r-....... 2
.-J.--::::I ....... ,o
O.
12
1.6
0.4
2.0
0.8
tilVOLUME 10
1 Extender = Gasoline.~
2 = Ethanol (Dieselhol)3 = Medium Naphtha4 = Heavy NaphthaS = Jet A
6 = Jet A-I7 = Kerosene8 = No. 4 Fuel Oil9 = No. S Burner Oil10 = No. 6 Fuel Oil11 = South Texas Sour Crude
Reference 4.16.
FIGURE 5.47. EFFECT OF DIESEL EXTENDERS ON CONSERVATION INDEX.
5-67
90 10040 50 60 70 80
VOLUME %302010
: Ir4-10
:::J:jl
!i 4i ---c--- 3-6
, i~!I
I .i , I I I
I I ~ ! I
II
I i I "'J 2, I I I
I ,,
I I !""" .I ,I II , I
i I II i I I I
i I I
! Ii I I
II
I , I j IIoo
1.2
.1.6
0.8
0.4
2.0
TRADEOFFINDEX
..1 Extender = Gasoline2 = Ethanol3 = Medium Naphtha4 = Heavy NaphthaS = Jet A6 = Jet A-l7 = Kerosene8 = No. 4 Fuel Oil9 = No. S Burner Oil10 = No. 6 Fuel Oil11 = South Texas Sour Crude
Reference 4.16.
FIGURE 5.48. EFFECT OF DIESEL EXTENDERS ON TRADEOFF INDEX
5-68
HeINDEX
4-------.-----...,.--~-___r--r___:::~-_:_-....,
3~----l___-~--4~::.....-+.,...c::::::..._+--~-_+_-_+-___f6
oL---J_--L_--!..._~_~_...;..I_~_~_~~o 10 20 "30 40 50 60 70 80 90 100
VOLUME %
.. 1 Extender = Gasoline2 = Ethanol
.~._-
3 = Medium Naphtha4 = Heavy NaphthaS = Jet A
6 = Jet A-I7 - Kerosene8 = No. 4 Fuel Oil9 = No. S Burner Oil10 = No. 6 Fuel Oil
Reference 4.16.
FIGURE 5.49. EFFECT OF DIESEL EXTENDERS ON HC INDEX
5-69
COINDEX
4~-r--r--.,.......-.,...---r---r---------
103t---+--+--+-+----+--~-___,,~~~-..l--__J
2r--r---t--b~T_-+_-+=:=_~~~-+_~
VOLUME %
..1 Extender = Gasoline
2 = Ethanol
3 = Medium Naphtha
4 = Heavy Naphtha
5 = Jet A
6 = Jet A-17 = Kerosene
8 = No. 4 Fuel Oil
9 = No. S Burner Oil10 = No. 6 Fuel Oil
Reference 4.16.
FIGURE 5.50. EFFECT OF DIESEL EXTENDERS ON CO INDEX.
5-70
Ii j Ij I ,
I :
i
:\
"
2.
I! .
I ~ : ! ,I
,
II
i i I , I : I, I ; I j
4
N\)x 2INDEX
oo 10 20 30 40 50 60 70 80 90 100
VOLUME %
1 Extender = Gasoline.• ' 2.,\<Vo.'" = Ethanol
3 = Medium Naphtha
4 = Heavy Naphtha
5 = Jet A
6 = Jet A-I7 = Kerosene
8 = No. 4 Fuel Oil
9 = No. S Burner
10 = No. 6 Fuel Oil
Reference 4.16.
FIGURE 5.51. EFFECT OF DIESEL EXTENDERS ON NO INDEX.x
5-71
-6·7
e
40 50 60 70- 80 90 100
VOLUME %20 3010
I!
II, I
I I !
I I I II
I!
I
II
II
I
I!i
!I I
I,,
iI !I I
I, ! ;I
I II I I IOi:
----':::::i5
--2l1
4
i---r--...- I - 9 I 3
II i!
3
oo
4
SMOKEINDEX 2
I Extender
2
3
4
5
6
7
8
9
10
= Gasoline
= Ethanol
= Medium Naphtha
= Heavy Naphtha
= Jet A
= Jet A-I
= Kerosene
= No. 4 Fuel Oil
= No. 5 Burner Oil
= No. 6 Fuel Oil
Reference 4.16.
FIGURE 5.52. EFFECT OF DIESEL EXTENDERS ON SMOKE INDEX.
5- 72
6. SENSITIVITY OF ENGINE LUBRICATION TOVARIATIONS IN FUEL PROPERTIES
6.1 INTRODUCTION
Variations in fuel properties might result in increased oil
contamination and intensify some of the lubrication problems such
as lubricant de grarl"ation, depos its, corro s i on and wear. Crankcase'J
oil contamination is caused by one or a combination of the
following:
a. Direct contact of the combustion products with the lub
ricating oil film on the cylinder walls past the piston ring or
along the valve stems. This contaminated oil returns to the
crankcase.
b~ Blow-by gases in contact with the lubricating oil in the
crankcase. The blow-by gases, during the compression stroke ingasoline engines, contain fuel vapors. During the expansion
stroke the blow-by ~ases contain combustion products.
c. Exhaust gas recirculation.
d. In some engine models, the fuel vapors are vented in the
crankcase.
The PCV valve directs the crankcase gases into the intake mani
fold, which reduces the lubricant contamination problems.
The fuel properties which affect the concentration of con
tanimants are related to nigrog'en and sulfur contents, and the
incomplete and complete combustion products. The type of contamination depends on the combustion process, and is different in
gasoline and diesel engines.
6.2 GASOLINE ENGINES
The main lubricating oil contaminants in gasoline engines arelisted in paragraphs 6.2.1 and 6.2.5. Effects of alcohol fuelson lubrication and engine wear are described in paiagraph 6.2.6.
6-1
6.2.1 Nitrogen Oxides
The nitrogen oxides are formed as a result of the high tem
peratures reached in the combustion process, from the atmospheric
nitrogen, or from nitrogen in the fuel. Most of the nitrogenoxides are in the form of nitric oxide, and the rest is nitrogen
dioxide. The latter is more reactive than nitric oxide, in con
taminating the' oil (6.1).
If the nitrogen content of the fuel increases, the nitrogen
oxides concentration in the blow-by gases and in the exhaust gases
use~ for EGR will increase, resulting in more oil contaminatiori.
6.2.2 Sulfur Compounds
The sulfur compounds are mainly sUlf~r dioxide (S02) and
sulfur trioxide (S03). These are formed during the combustion
process, and depend mainly on the sulfur content of the fuel arid
the air-fuel ratio. The sulfur content of the conventional
crude petroleum based gasoline is 0.07 percent.
The sulfur compounds contribute to the corrosive wear causedby the condensation of acids on the cylinder walls with subsequent
chemical attack of the metal and removal of corrosion productsby the wiping action of the rings. The corrosive wear ,is dif
ferent from abrasive or rubbing wear caused by mechanical inter
action between two metallic surfaces with relative sliding motion.
The corrosive wear is significant during low temperature opera
tion.
Syncrudes are known to contain more sulfur than conventional
crudes. Reducing the sulfur content of gasoline made from syn
crude will require the expenditure of more energy and money in
the refinery.
6.2.3 Partial and Complete Oxidation Products
The partial oxidation products consist of aldehydes, RCHO(mainly formaldehyde, HCHO) , ketones (R 2C=O) and acids (RCOOH).These are products of preflame reactions and partial comhustion
6-2
problems in the form of depositsof the engine is not achieved,
These deposits appear as "varnish"
which takes place as a result of flame quenching near the walls
or of incomplete flame propagation.
The complete combustion products, water and carbon oxides,
are, of course, present in higher concentrations in the blow-by
and EGR contaminants.(j
It is expected that the partial and complete oxidation pro-
ducts of future fuels will be nearly the same as those of conven("
tional gasoline. J
6.2.4 Hydrocarbons
The higher boiling point hydrocarbons of fuels represent a
major contaminant because of their lower molecular weight as com
pared with that of the lubricating oil molecules. These higher
boiling point hydrocarbons adhere to the cylinder wall, particularly under cold starting and warmup periods, and are mixed with
the lubricating oil film.
If the end-point of future gasolines is increased, more oil
contamination can be expected--:z: .-.';&~~'.. ' Low temperature operat ion
occur whenever complete warmupparticularly in cold weather.
and sludge.
Varnishes which coat various engine parts such as valvelifters, pistons, piston rings, and pev valves, may cause trouhle
some adhesion of parts or interference between close-fitting
parts. These varnishes have been found to contain significant
amounts of nitrogen, sulfur and oxygen.
Sludge is colloidal in nature and separates from the crankcase oil in the more stagnant regions of the engine, or is
deposited in places critical to oil supply and distribution, suchas the piston oil control ring or the oil screen in the sump.The sludge forms as a water-in-oil emulsion, stabilized andthickened by finely divided solids, such as lead salts, soot, and
resin forming surfactants.
6-3
6.2.5 Corrosion
Corrosion occurs on ferrous surfaces, particularly if gaso
line engines are operated under light-duty conditions and with
frequent shut-down periods. The factors favoring corrosion are
a dispersed water phase in the oil, the presence of sulfur com
pounds in the fuel, and high dilution of the crankcase lubricant
wi th raw fuel.
The high temperature operation problems result from exposing
the lubricant to high temperatures and to high nitrogen oxide
concentration, in the combustion chanber or as a result of contractwith the blow-by gases. Oil oxidation under high temperature oper
ation result in carbonyl-type compounds, which are acidic incharacter and may attack and dissolve corrodible metals. Also,
nitrogen oxides can be involved in high temperature accelerated
oxidative degradation. This is particularly true with increased
blow-by rates (6.1).
6.2.6 Effect of Alcohol Fuels on Lubrication ~nd .Engine Wear
Owens and co-workers (6.6) of the U.S. Army Fuels and Lubricants Research Laboratory at S.W.R.I. investigated the effects
of methanol fuel on spark ignition engine wear and deposits. Theengine used was a 2-3 liter Ford overhead cam, four-cylinder
design and was tested on a dynamometer, according to a modified
ASTM sequence V-D test procedure. Owens, et al., indicated thatthe use of pure methanol as a fuel can result in large increases
in engine wear and wear-metal accumulation during low temperature
operating periods. This increased wear occurs primarily in the
piston ring and upper cylinder bore area. In addition to wear,
methanol was found to form rust. The extent of rust formation is
dependent on the materials present and the metal and lubricanttemperatures during engine operation. Therefore, this rusting
phenomena would be design dependent and vary in intensity from
engine to engine. Owens, et al indicated that the blow-by producedfrom methanol contains at least formaldehyde and formic acid,
which are capable of corrosive attack within the ring zone, the
6-4
......; ..
area of highest concentration. The methanol, or its intermediate
combustion products, directly attack the piston ring and cylinder
bore area rather than first degrading the lubricant.
6.3 DIESEL ENGINES
Diesel lubrication problems are mainly related to the oil
contamination by soot particulates, in addition to the factorsdescribed in 6.2., Gasoline Engines. ()
6.3.1 Soot Particulates
The soot particulate formation is one of the characteristics
of the diffusion type flame in heterogeneous, combustible mixtures.The particulates formed during the different stages of co~bustion
can be picked up by the lubricating oil and contaminate the crank
case lubricating oil by the approaches discussed in Section 6.2.
The lubricating oil can be contaminated by soot particulates,
even when the final engine exhaust is clear (6.2).
The fuel properties which affect the soot particulates havebeen explained in detail in another part of this report.
The soot contrihutes to the formation of different types of
deposits in the engine, such as piston groove carbon, piston
lacquer, and crankcase sludge. The piston groove carbon and
lacquer are the result of combinations between the soot particulates and resins. The sludge is the result of combinations between
soot, oil, oxygenates and water (6.3). Formation of deposit
resins arises both from partial combustion products of the fuel,and from oxidative-thermal degradation of the luhricating oil and
its additives.
6.3.2 Sulfur
The problem of the contamination of the lubricating oil with
sulfur is much more serious in the diesel engines than in gasolineengines because of the much higher sulfur content of diesel fuels.
6-5
There is some evidence that formation of deposit resins is
favored by increases in fuel sulfur except at very high tempera
tures where thermal effects predominate. Increasing the fuelsulfur content from 0.4 to 1.0 percent was reported to. increase
the level of piston deposits by 100 percent, in Caterpillar L-1
Test procedures by Deen and Schetelich (6.4).
Figure 6-1 shows the effect of sulfur on wear, obtained by
Moore and Kent (6.5), using a single cylinder 5-3/4 inch bore,
4-inch stroke, Caterpillar test engine. The sulfur content of
the fuel was varied from a to 1.3 percent by adding di£ferent
amounts of thiophene to the light commercial fuel of originallylow sulfur content. Figure 6-1 also shows the wear rates of two
heavy diesel fuels, and it is seen that the points fall reason
ably well on the curve. Figure 6-1 shows that, with all. otherconditions constant, the rate of wear with a diesel fuel of 100
percent sulfur content is approximately 400 percent greater than
that with a fuel of a percent sulfur content.
6-6
1200
.(/)
~ 1000oto0:::W 800a..z0::o 600~
(f)
~<r 400::-~-....J--l-~ 200
o 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Ref. 6.5. PERCENT SULFUR
FIGURE 6 -1. EFFECT OF 'SULFUR CONTENT ON WEAR
6-7/6-8
7. CONCLUSIONS
Automotive gasoline and diesel engines are sensitive to
certain fuel properties. Currently, the baseline automotive
gasoline and diesel fuels are highly processed to the American
Society of Testing Material (ASTM) specifications from natural
crude petroleum. The ~rrent a~tomotive engines are tailored to
meet certain performance and emission goals when run on these
fuels. Some variations in the properties of the baseline automo-
·tive fuels are anticipated in the future because of the expected
depletion of natural crude resources, the increase in the price ofimported crude and the desirability of reducing the nation's
reliance on foreign fuels. In the United States, alternate fuels
can be produced from the abundant coal and shale oif reserves, or
from biomass. At the present time, the properties of futurealternate fuels cannot be well defined, because they have not
been established; although, it is known that the distillates from
shale oil are highly paraffinic in nature while those from coal
are highly aeromatic in nature. Also, syncrudes from coal and
shale oil contain impurities such as nitrogen and sulfur.
Reducing these impurities in the final product will require expenditure of energy and ~ollars at the refinery. Less refined
fuels are likely to have high nitrogen and sulfur contents.
The following conclusions are based on the available datapublished in the literature. The areas which need further
research are noted.
7.1 GASOLINE ENGINES
The important fuel properties which affect gasoline engines
are summarized in Table 7-1. The gasoline engines are sensitive
to the fuel volatility, octane number, HIC ratio, latent heat of
evaporation '. energy content, and sulfur and ni trogen contents.The engine parameters which are sensitive' to each of the aboveproperties are also listed in Table 7-1.
7=1
TABLE 7-1. IMPORTANT FUEL PROPERTIES FOR GASOLINE ENGINES
Fuel economy
Acceleration.~;'
Power
Fuel Property
1 - Distillation range
o - 20% point
20 - 80% point
80 - 100% point
2 -·Octane number
3 - Hie ratio
4 - Latent heat of
evaporation
5 - Gravimetric energy
content
6 - Volumetric energy
content7 - Nitrogen content
8 - Sulfur content
Dependent Engine Parameter
Cold starting
Hot starting
Vapor lock
Evaporative emissionsWarm up
Hot stalling
Carburetor icing
Crank-case oil dilutionDeposits -
Gum
Plug fouling
Hydrocarbon emissionsCompression rat1u
Enpine efficiency
Stoichiometry
Combustion temperatureCold starting
Volumetric efficiency and powerBrake specific fuel consumption
Storag~ costTransportation cost
NO emissionsxLubricating oil contamination
Corrosion and wearSulfates emissions
Lubricating oil contamination
Corrosion and wear
7 -2
,". '~.
7.1.1 Alternate Fuel Options
The gasoline engine alternate fuel may be one of the follow
ing options, or their blends with gasoline:
1. Synthetic gasoline from syncrude produced from oil shale
or coal
2. Alcohols:
,) i. methanol produced from coal, biomass or wastes
ii. ethanol produced from biomass.
3. Hydrogen produced from coal.
The synthetic gasoline in the first option is expected to be pro
duced at specifications close to those of baseline gasoline. The
synthetic gasoline produced from shale is low in octane number
a~d needs to be improved by high octane extenders such as MTBEor TBA. The synthetic gasoline produced from coal is highly
aromatic and has a high octane number. Gasoline engines can bedesigned to run on these gasolines with relatively higher compres
sion ratios. in order to improve their fuel economy. The effect.. - of the use of the extenders MTBE and TBA will be stnnmarized in the
following item.
The hydrogen in the third option is ~onstrained in its use
as an alternate fuel by the development of safe and economically
competitive distribution and storage systems. Hydrogen is not
expected to be a viable alternate fuel in the near term (1980
2000), or mid-term time frame (2000-2020). This report has notdealt with hydrogen as a fuel for automotive engines.
7.1.2 Gasoline - Alcohol Blends
The effects of blending gasoline with methanol, ethanol,
MTBE and TBA on the fuel physical properties, and the performance
of gasoline cars is summarized in Table 7-2. This table indicatesthe fo llowing:
7-3
TABLE 7-2. GASOLINE ENGINE ALTERNATE FUELS:GASOLINE - ALCOHOL BLENDS
Fuel or Engine Parameter Gasol~ne ExtenderMethanol Ethanol MTBE* TBA*
Volat~l~ty:10% 10% 7% 7%
RVP t t t t
10% point .j. .j. 1- 1-
t/) Specific gravity III t t t t(1)
~,,.,j H/C ratio t t t tra~
tJ lo.l.,.,j (1) Volumetric Energy content 1- i- 1- i-en Q.>'0 Octane number t
.t-= lo.l t t
c..c..Latent Heat of evaporation t t t t
Miles per gallon 1- 1- 1- 1-
~ Miles per BTU 1- 1- 1- 1-en>, Emissions g/m~
rac.. HC i- .j. .j. .j.-.lE-;rar:..U CO ..j.. i- .j. i-..C tr.l NO "t t i- ta lo.l -~,.,j ra x~u
Aldehydes N/A N/A N/Ara N/A"Ceo'.-1 I"'- Acetone N/A N/A N/A N/Ax 0'1o~
Evaporative g t t t t
Miles per gallon i- i- .j. .j.
Miles per BTU i- t .j. ..j..
Emissions g/m-.lc..mE-; HC .j. .j. .j. .j.>.r:..~
ra .. CO 1- .j. i- .j.~ enra lo.l NO t t t tU ra
U x>,
Aldehydes N/A. N/A N/A N/Araeo~I"'-I 0'1 Acetone N/A N/A N/A N/AM~
Evaporative t t t t
':".-
* MTBE:
TBA:
Methyl tetriarybutyl ether
Tetriarybutyl alcohol
7-4
..
1. The fuel economy in miles per gallon decreaied mainly
because of the lower volumetric energy content of the
blends.
2. The fuel economy in miles per BTU decreased because the
cars used were not calibrated for the blends. A major{j
adjustment which would have improved the fuel economy is
the spark timing (which could have been slightlyadvanced) .
3. The NO x and evaporative emissions increased with the
blends.
It is clear from Table 7-2 that both the volatility and octanenumber of a fuel increased after blending with alc~hols. The
results shown are for baseline cars and do not reflect the full
potential of the blends since the cars were tailored to run on the
baseline gasoline. For example, the baseline cars have C.R. less
or equal to 8.5:1, which is limited by the octane number ofIndolene ().N.=9l). The C.R. could be increased to 9.5 or 10
with these blends without producing knock. Increasing the C.R. of
the engine improves the fuel economy of the vehicle.
The major problems associated with the use of alcohol - gasoline blends are:
1. Phase separation with methanol - gasoline blends
2. Cold starting problems caused by the higher latent heatof the blends
3. Increase of the NOx exhaust emissions and the hydrocarbon
evaporative emissions
4. Incompatibility of some materials which are used success
fully with gasoline and deteriorate seriously withalcohol - gasoline blends.
7.1.3 Neat Alcohols
The sensitivity of gasoline engines to the use of neat
alcohols, contrasted with Indolene is given in Table 7-3.
7-5
TABLE 7-3. GASOLINE ENGINE NEAT ALCO~OLS COMPAPED TO INDOLENE
Fuel or Engine Parameter Methanol Ethanol
Volatility 1- 1-
Specific gravity t t
In H/C ratio t tQJ
t"""I •.-I Volumetric Energy Content -t -trtI~
tJ ~ Octane Number..-fQJ t tIn c..>to Latent Heat of evaporation t t.cl-lc.c. Stoichiometric A/F 1- ~
Power t N/ABrake Thermal t N/AEmissions
HC ... ~ *CO - ... ... *NOx ... - -t *Aldehydes t t *PNA ..j.
Evaporative
* CVS - Hot Drivingcycle only.
7-6
•
Most of the work conducted has been on methanol, and showed
the following advantages for methanol:
1. Methanol has a high octane rating (RON = 110,-MON = 92)which allow th~ C.R. of the gasoline engine to reach
13:1 or 14:1 and achieve better thermal efficiency than
the current gasoline engine. VW reported an improvement
of 4 percent during the ECE cold start test, and 12 per
cent for the hot start test.
2. Tests over the whole speed range indicated that with
methanol, the brake output ot the engines is 10 percenthigher than for gasoline engines, both with MBT spark.
3. Tests over the operating range of the equivalence ratio(0.8 to 1.2) indicated that the methanol-fueled engine
produced less NO , CO and HC than the gasoline fueledx .
engine. However, the aldehydes emissions were higher
with methanol than with gasoline.
Operation on methanol on the ECE cold test system resulted in a
reduction of 22 percent in CO, but an increase of 22 percent inHC. In the hot-start test, the CO emissions were reduced by 68
percent HC by 28 percent, and NO by 20 percent.x
Problems
A cold starting aid is absolutely essential for starting the
engine at temperatures below 8°C. Cold starting aid could be in
the form of volatile starting additives (such as butane, methylether, or gasoline) to be sprayed into the intake air during
starting. A small methanol-fueled flame preheater can also be
used in the intake manifold.
7.2 DIESEL ENGINES
The important fuel properties which affect the automotive
diesel engine are summarized in Table 7-4. Automotive diesel·engines are sensitive primarily to the cetane number which affects
almost every aspect of combustion such as: ignition delay,
7-7
TABLE 7-4.
Fuel Property
IMPORTANT FUEL PROPERTIES FOR DIESEL ENGINES
Dependent.Engine Parameter
1 - Cetane Number
()
2 - Distillation range
Light ends
Heavy ends
3 - Aromatic content
4 - Viscosity
5 - Sulfur content
6 - Nitrogen content
7 - Gravimetric
energy content
8 - Volumetric ener y content
Ignition delay
engine noiseHydrocarbon emissionsNOx em~ssions
exhaust smoke, and particulates
cold starting
cold startingHycrocarbon and aldehyde emissions
Vapor lockCavitation in the injection system
Smoke emissions
particulate emissions
waxing and filter plugging
Smoke and particulate emissions
Polynuclear aromatic hydrocarbons
Spray formation and combustion
Injection system lubricationFlow through the fuel system
Sulfate emissions
corrosion and wear
NO emissionsxcorrosion and wear
B.S.F.C.
Miles per allon
7-8
•
•
engine noise, cold starting problems, and emission of hydro
carbons, nitrogen oxides, smoke, and particulates. Automotive
diesel engines are also sensitive to the distillation range,
aromatic content, viscosity, sulfur content, nitrogen content,
gravimetric energy content and volumetric energy content of their
fuels.
7.2.1 Alternate Diesel Fuel Options
The diesel engine alternate fuels may be one of the following:
1. Wide cut distillates from petroleum crude
2. Synthetic diesel fuel from syncrude produced from oil
shale or coal
3. Alcohols.
7.2.1.1 Distillates from Petroleum Crude - The increase in demand
for jet fuel and heating oil will put pressure on the diesel fuel.production to include heavier compounds. To this effect, DF-3 isbeing considered for transportation diesel engines. No work has
J~,"
been conducted so far to find the sensitivity of automotive dieselengines to DF-3 fuel. Another approach to reduce energy expenditure in the refinery is to produce a wide cut fuel which will con
tain lighter and heavier compounds than DF-2. Very limited work
has been reported so far on the performance of automotive dieselengines on wide cut fuels. The following applies:
1. D.I. truck engines are more sensitive to variations in
fuel properties than I.D.I. engines used in passenger cars.
2. The increase in the volatility of the distillate by
lowering the .10 percent point results in a drop in C.N., increasein I.D., increase in HC and NO emissions and increase in combus-
xtion noise. Some of these problems can be solved by increasing theC.R. of the D.I. engine, retarding the injection timing, turbo
charging, or redesigning the combustion chamber. The increase involatility is usually associated with a reduction in viscositywhich might result in poor lubrication and fuel leakage in the
injection pump, particularly at low speeds.
7-9
3. The increase in the heavy components of the distillate,
by increasing the 90 percent point, results in more smoke. Derat
ing the engine power may be needed to limit the smoke. Heavyfuels, which need to be heated to flow readily, increase the
ignition delay, He, NO , and smoke particulate emissions andxnoise. These effect are more pronounced in D.I. engines than In
I.D.I. engines.
()
7.2.1.2 DF-2 Gasoline Blends - Some work has been conducted on
DF-2 gasoline blends and the results are summarized in Table 7-5.
The main advantage of DF-2 gasoline blends is the drop in smoke
formation resulting from the increased portion of premixed combus
tion. This results, however, in increasing the combustiongenerated noise, and the unburned hydr~arbon emissions. Other
problems associated with the use of diesel-gasoline blends are the
difficulty in cold starting, misfire at light loads and high
speeds, vapor lock in the fuel injection system, crankcase oil
dilution and lack of proper lubrication of the fuel injection
parts.
7.2.1.3 DF-2/Synfuels Blends - The effect of blending DF-2 with
synfuels from shale oil and coal - derived crude have not beenwell studied. The limited studies conducted in this area show
unfavorable results as summerized in Table 7-6. The major prob
lems with shale-derived synfuels are lacquering, needle sticking
and poor reliability. The major problems with coal-derived syn
fuels are filter plugging, waxing, nozzle fouiing, lubricating oil
sludging and poor reliability.
7.2.1.4 DF-2/Alcohol Blends - The third option is to use alcohols,
as blends with DF-2 or as neat compounds. Very little work has
been conducted in this area. The limited work completed so fQr
showed some effects which are summarized in Table 7-7.
The major problems associated with the use of alcohols to
extend the diesel fuel are:
7-10
•
TABLE 7-5. DF-2 GASOLINE BLENDS
1 - Cetane Rating
2 - Smoke limited power
" 3 - BSFC
4 - BSEC5 - Emissions
HC
CO
NOxNoise
SmokeAldehydes
Major Problems:
7-11
i-
t)
t-t
-t
t
..j.
N/A
· Cold starting
· Misfire at high speedsand light loads
· Vapor .lock in fuelinjection system
· Crankcase oil dilution· Lack of proper lubrication
of the fuel injection parts
· increase in combustiongenerated noise
TABLE 7-6. DIESEL ENGINE ALTERNATE FUELS(DF-2/SYNFUELS BLENDS)
Shale Derived Coal DerivedSynfuel Synfuel
1 - Cetane Ratl.ng .j. .j.
2 - Gum Content t 0 N/A
3 - Smoke-limited Power .j. ..j..
4 - BSFC - t
5 - Aromaticity .j. t
6 - Emissions
HC - t t
CO t t
NO t tx
Noise t t
Smoke t t
7 - Pour Point N/A t
8 - Major Problems Lacquering Filter plug-
Needle stick- ing
ing Waxing
Poor reliability Nozzle foul-ingLub. oil sludg-ing
IPoor reliability
7-12
TABLE 7-7. DF-2/ALCOHOL BLENDS
Methanol Ethanol
•
1 - Cetane Rati~g ~') '" '".2 - Smoke-limited Power - oj; - i-
3 BSFC t t
4 - BSEC - -5 - Emissions
HC t t
CO i- i-
NO i- i-x
Noise t t
Smoke .j. .j.
Aldehydes t t
7-13
a. Blends of Alcohols - DF-2
i. cold starting
ii. lubricating oil contamination and engine wear
iii. injection system wear
b. Alcohols - DF-2 Emulsions
Some of the above problems can be reduced by using p~e
DF-2 at cold starting and increasing the emulsion con
centration with load. This requires difficult controltechniques particularly under transient modes.
c. Alcohol Carburetion or Manifold Injection and DieselInjection
This results in a large drop in the intake air tempera
ture which causes misfire at low loads. On the other
hand, self-ignition may occur at high loads. Also,
elaborate control techniques are needed to optimize the
timing and metering of the two fuels
d. Two Separate Injection Systems
. This allows varying the relative amounts of the two
fuels. The main problem associated with two high pres
sure injection systems is the initial cost, and the
elaborate and expensive control systems needed tooptimize the timing and metering of the two systems.
The major problems associated with the use of neat alcohols
in diesel engines are:
a. Autoignited Alcohols
~.
1. Alcohols have a very low C.N. (about 3).
require to be mixed with cetane improving
such as 8 percent ethyl nitrate.
They
additives,
2. Alcohols have very poor lubricity. They must bemixed with about 2 percent lubricating oil.
3. Lubricating oil contamination with alcohols may cause
7-14
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increased engine wear.
4. A starting aid such as intake air heating or using
diesel fuel is required under cold starting conditions.
b. Spark Ignited Alcohols in Diesel Engines
The major problems are:
1. Alcohols have high l\tent heats of~evaporation which
result in severe cold starting problems.
2. High emission of hydrQcarbons at idling and low loads.
3. Low reliability due to wetting of spark plugs andmisfiring.
4. Requires a much higher voltage for ignition because
of the high compression ratios used.
5. Wear due to cavitation in the injection system.
6. High hydrocarbon and aldehyde emissions.
7.3 EMERGENCY FUELS
7.3.1 Gasoline Engine Emergency Fuels
One research program conducted on the use of emergency fuels
in a limited number of automotive gasoline engines indicated that
only alcohols can be used as gasoline extenders without the need
to reduce the compression ratio of the engine. The emergency
fuels, studied are DF-2, marine diesel fuel, ethanol, methanol,
MTBE (Methyl Tert Butyl Ether), naphtha - ethanol, DF-2 ethanol,
kerosene - ethanol, ethanol extended with water, naphtha, and
kerosene.
7.3.2 Diesel Engines Emergency Fuels
Tests on a limited number of diesel engines showed the
following results:
1. The following fuels were found to be suitable emergency
7-15
fuels for diesel engines and had minor effects on smoke
emissions: Jet A, Jet A-I, medium naphtha, and kerosene.
2. Blending with gasoline and alcohols decreased the C.N.sharply, however, it decreased smoke. The problems with
these fuels are mainly related to their poor lubricity,
particularly in the fuel injection system, and theincrease in combustion noise and cold starting diffi
culties.
3. Blending with heavier distillates such as No.4,' and No.
S fuel oil, resulted "in an increase ln smoke.
7-16
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8. RECOMMENDATIONS
Research is needed in the following areas to determine the
sensitivity of automotive engines to variations in fuel proper
ties.
8.1 FUTURE FUEL CHARACTERISTICS.,1. Develop scenarios for future automotive fuels based on
the most energy- and cost-efficient refining techniques, and the
availability of the energy sources.
2. Develop a data base for the variation in fuel properties
·as a function of blending the base fuels with different types of
extenders.
3 .. Develop a data base for the effect of variations in fuel
properties on their autoignition properties (cetnne number and
octane number). The fuels should cover a wide range of the
following:,:'
i. CarJ10n to hydrogen ratio,
i i . aromatic content,
iii . distillation range,
iv. density,
v. sulfur content
vi. ni trogen content.
4. Study the impact of the use of alternate fuels on the
lubrication process in automotive engines and find techniques to
reduce lubricating oil contamination.
8.2 GASOLINE ENGINES
1. Investigate the effect of variations in the base fuel
properties on gasoline engine performance, fuel economy andemissions. Develop engine maps to cover the expected variations
in future fuel properties.
8-1
Emphasis should be on the properties which cost more to controlin the refinery.
3. Study the economy of producing ethanol from U.S. grown
grain, the energy expenditure, and the efficiency of converting
the source energy into useful mechanical work. A system approachI..;
should be taken in this study.
4. Study the use of neat alcohols and blends with gasoline
in gasoline engines. The following should be optimized: com
pression ratio, spark timing, and fuel metering ... Most of thestudies conducted so far are on mass produced engines calibrated
for gasoline (Indolene).
s. Investigate techniques ~o solve the cold starting prob
lems of gasoline engines when run on neat alcohols or alcoholgasoline blends.
8.3 DIESEL ENGINES
1. Investigate the effect of variations in the base fuel
properties on the automotive diesel engine (D.I. and I.D.I) per
formance, economy and emissions. Develop engine maps to cover
the expected variations in future fuel properties. The engine
systems should be optimized for each fuel.
2. Make an assessment of the tradeoffs in economy, performance, emissions and variations in fuel properties which cost
more to control in the refinery;
3. Develop a modified cetane scale to rate the autoignitionquality of alternate fuels. The current scale is unsuitable for
alternate fuels.
4. Study the problem of cycle-to-cycle variation in the
autoignition of alternate fuels in diesel engines, and methods ofreducing their effect on engine reliabjlity.
s. Determine the effect of cetane improvers on increasing
the C.N. of alcohols. These improvers include commercjally
8-2
'"
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available additives, diesel fuel, and lubricating oil. This study
needs to be done on a CFR-Cetane engine with the Modified Cetane
Scale which is capable of measuring the C.N. of fuels in the range0-20.
6. Study the use of neat alcohols, and alcohol-diesel blends
in optimized diesel engines. The main design parameters which
should be optbnized are: compression ratio, injection pressure,
injection nozzle, intake system, and combustion chamber design.
8-3/8-4
....
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3.20
3.21
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A-3
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..
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A-4
,./~~ .
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4.11
4.12
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-'
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A- 5
4.15
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4.18
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A-6
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:)
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5.12
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A-7
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'.
,,
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APPENDIX BREPORT OF INVENTIONS
The work presented in this report is of a review nature.
No invention or application for patent rights evolved from theaperformance of this work.
100 copies
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