mv20n021992p67

7/29/2019 mv20n021992p67

1/13

67

Research on Methano1-fueled

Marine Diesel Engine*

By Yoichi Nakamura'hk, Tadahiro Ozu**, Hisashi YanLashita***,Nobuyoshi Nakayamab'< and Tatsuo Fujii**

Nowadays concerns about methanol has increased from the viewpoints of environrnental protection andversatility of fuels at a global scale. Desire for saving of maintenance cost and lobour prevails as well as theenvironmental problems in the field of marine engines. From these rnotives we have carried out research anddevelopment of a methanol fueled marine diesel engine which is quite different from automobile en9ines inthe size, main particulars, working condition and durability.Although we have made a great use of invaluableknowledge from automotive techno1ogy, sorne special studies were neccessary due to these differences.Ignition method is a typical one. Dual fuel injection system was tried for trouble-free ignition of methanol fuel.

This system is thought to be the most favourable ignition method for marine diesel engines which have towithstand quick load change and accept no mis-firing. Under the leadership of Ministry of Transportation andwith the aid from The J apan Shipbuilding Industries Foundation and The J apan Marine MachineryDeveloprnent Association the work has proceeded from elementary studies of injection and tribo1ogy to therunning test. In this article the effects of configurations as to fuel injection system on the engine perforrnanceare described. Fundamental running test with a single cylindered 4-stroke test engine reveals that the marinedeisel engine can afford to have such a good performance as an original diesel engine has, when suitablereconditioning of fuel injection-and governing systems being applied to.

1. Introduction

Energetic research on methano1-fueledautomobile engines has been forwarded from theviewpoints of low environmental pollution and theuse of alternate fuel since the oil crisis, and they arenow being tested on vehicles in variousCountries in the world. Various technical issueshave already been solved or the prospect is brightfor them. It can be said that this type of engine isvery c1ose to completion at present. On the otherhand, it is an actual situation in the marine enginefield that the research on this type of engine hashardly been tested so far, since it has seldom been

evaluated from the viewpoint of environmentalpollution control because it is used at sea and theidea tO use methano1 on marine engines is notestablished yet. * Translated from J ournal of MESJ Vo1.26, No.9

(manuscript received J une 7, 1991) Lectured May16, 1991

**KAWASAKI Heavy Industries, Ltd. (3-1-1,Higashi-kawasaki-cho, Chuo-ku, Kobe, 650

J apan)***K AWASAKI Heavy Industries, Ltd. (1-1,

Kawasaki -cho, Akashi, 673 J apan)However, IM0 (International Maritime

0rgan-ization) is now investigating to includeexhaust gas from ships in the objects to becontrolled from the viewpoint of environmentalprotection on a worldwide scale that has been loudlyemphasized recentlyl). In case clean methanol isused as fuel,work for handling complicatedmachines such as centrifuges for heavy fuel oil andfor treating sludge discharged from them can beavoided, and further it can be expected to lessenfrequent engine maintenance work. It has thereforebeen strongly desired to use methanol on marinediesel engines from main1y the viewpoint of

pursuing ec0nomy.Though knowledge which has been gained with

automobile engines can be used in principle,manysubjects to be so1ved still remain, since marinediesel engines have large bores and mean effectivepressures of more than two times as much, theiroperating conditions are extremely severe and theyneed high reliability and durability in comparisonwith automobile engines. The authors haveconducted the above captioned R&D for the purposeof gaining knowledge which can so1ve theseissues and contribute to engine

October 1992 (1)

7/29/2019 mv20n021992p67

2/13

68 Yoichi Nakamura, Tadahiro Ozu, Hisashi Yamashita, Nobuyoshi Nakayama, Tatsuo Fujii

design. Methano1 has a cetane number of threehand,consequently, extremely low ignitability.For automobile engines, ordinary technologies cancope with the issues on ignition, since ignition plugshave actual service results over prolonged periodson Otto engines and starting plugs have also beenused to date on. diesel engines. On the other hand,

rnarine engines with spark ignition can not exhibitmean effective pressures as high as those ofordinary diesel engines because of the high rate ofpressure rise during ignition and they can notperrnit misfiring because of the large volume oftheir exhaust systems. The dual fuel injectionsystem which has actual service results onlarge-sized gas engines has therefore been selectedas the ignition system for this research.

Since methanol is not only corrosive but alsoinsufficient in lubricating ability, elementalresea-rch has been neededto so1ve these

issues.However, elemental research will beexplained at another opportunity and this paperdescribes the operating performance of a methanoldiesel engine without touching elemental research.

2. Experimental Engine

A single-,cylinder, four-stroke, direct-injectiontype diese1 engine having a cylinder bore of250mrn has been modified so as to be suitable forthis experiment. The rated speed of thisexperim-ental engine has been set lower than that

of the original type so that the results of thisresearch can be utilized as widely as possible.

Table l and Fig.1 show the principal particulars ofthe expeimental engine and the schematic drawing

Fig.1 Schematic Drawing of Experimental Engine

The combustion system of the experimentalengine is of a dual fuel injection type such that themain fuel injection valve (methano1) is 1ocated atthe center of the combustion chamber and atomizedfuel from this va1ve is ignited by the pilot oilinjection frorn the secondary injection valve (oil)1ocated on the cylinder head near the periphery ofthe combustion space. This system has beenadopted from the reasons that it has the highstability of ignition, good low load perform-ance andhigh reliability, and that it serves as a rneasure toprevent corrosion, since combustion deposits made

by pilot oil injection cover the inside surface of thecombustion chamber. The rnethanol injection pumpis of a forced lubrication type to prevent lubricationtroubles. Since metha-nol is highly vo1ati1e, theauxiliary equipment of

(2)

Bulletin of the M.E.S.J ., Vo1. 20, No.2

7/29/2019 mv20n021992p67

3/13

Research on Methano1-fueled Marine Diesel Engine 69

Fig. 3 Schematic Drawing of Fuel RegulatingLinkage of E xperimental Engine

the methano1 system such as the fuel tank,strainer, supply pump and valves havebeen installed in an enclosed chamber (a fuelsupply unit) as shown in Fig.2. A fan and a gasdetector have been installed to sufficientlyventilate the inside of the unit for safety.

Pipe joints are also of speciaI structure toprevent fueI leakage.

Though the dual fuel injection systeminvo1-ves such a demerit that its fuel systembecomes complicated, auxiliary machinery such asgenerat-ing engines and a boiler burn fuel oil onboard in case of a ship, and large gain can not beexpected even though only the main engine adoptsa system of burning only methanol unless theseauxiliary machines also burn only methano1. Thedual fuel system is therefore considered proper.

Fig.3 shows the schematic drawing of the fuelregulating linkage of the experimental

engine. In this drawing, l is the methanol injecti-onpump, 2 is the pilot oil injection pump, 5 is thegovernor and 31 is the actuator necessary forcontrolling the ratio of the quantity of methanoland pilot oil to be injected. To grasp the condition ofdeposits in the combustion chamber, methanol withpurity of 99.9% and J IS No.2 gas oil for pilotinjection have been used.

3. Operation Test under Normal Condition

Under the full 1oad condition of the

above-m-entioned experimental engine (meaneffective pressure Pe : 16.13kgf/cm), influence onengine performance, the contaminationcondition of engine inside and Iubricating oil, andthe propert-ies of exhaust gas have beeninvestigated by changing the specifications of thepilot oil injecti-on nozzle, main fuel injection nozzleand main fuel injection pump, fuel injection timingand the quantity of pilot oil.

3.I Influence of Pilot Oil Injection Nozzle

The effect of the pilot oil injection nozzle hasbeen confirmed by changing the nurnber anddiameter of nozzle holes and the direCtion of

injection in the range shown in Fig.4.As a result, the one-hole nozzle Is the best in terms of fuel consumption, the stabilityof cylin-der pressure and the reduction in thequantity of pilot oil. However, the difference inperf0rmance among various types of nozzles is notremarkable. As mentioned later, when priority isgiven to the issues of startability, acceleratingability and sudden load change like the engagementof a clutch, or to the problem when the pilot oilinjection nozzle ho1es have been c1osed, it can besaid that the three-hole nozzle is the best and the

October 1992 (3)

7/29/2019 mv20n021992p67

4/13


Fig.5 Engine Performance vs Number ofPilot Oil Nozzle Holes

1argest possible nozzle hole diameter isdesirable.Though the influence of the direction ofthe pilot oil injection nozzle in relation to the mainfuel injection nozzle has also beenconfirmed, no improvement has been found. It isconjectured that the reasons for the above are thatswirls in the combustion chamber of theexperimental engine are not strong and thequantity of pilot oil is enough.

Fig.5 shows engine performance when the total

nozzle hole area of the pilot oil injection valve hasbeen kept constant (35% of the total nozzle holearea of the injection valve for burning only oil) andthe number of nozzle holes has been changed. Thetwo-hole nozzle shows slightly better fuelconsumption. However, it is not preferablefrom the viewpoint of ignition stability,since thevariation of maximum cylinder pressure (Pmax) islarge.

Fig.6 shows engine performance when the totalnozzle hole area of the pilot oil injection valve hasbeen changed. It has turned out that,

Fig.6 Engine Performance vs Total Pi1otNozzle Hole Area

when the total area is made too sma11, it becomesdifficult to start the engine, and that it is alsodifficult to continue the operation of the engine onmethano1/oil even if it could be started and theengine finally stops, since the quantity of pilot oil

necessary for causing perfect ignition can not besupplied. However, when keeping the quantity ofpilot oil constant, smaller total nozzle hole areagives the better stabil ity of pilot injection.3.2 Influence of Methanol Injection Nozzle

Engine performance has been confirrned usingmethanol injection nozzles of which the number ofnozzle holes are 8, 9, 10 and 12, and nozzle holediameters have been selected in the range from0.39mm to 0.48mm (90% to 200% of the nozzle

(4) Bul letin of the M.E.S.J ., Vo1. 20, No.2

7/29/2019 mv20n021992p67

5/13


Fig. 7 Engine Performance vs Number ofMethano1 Injection Nozzle Holes

area of the injection nozzle for burning only oil).As aresult, it has turned out that, in case of theexperimental engine, the injection nozzle which hasten nozzle holes of 0.46mm in diameter, i.e.150% ofthe nozzle area of the injection nozzle for burningonly oil, shows the best fuel consumption.

Fig.7 shows engine performance against thenumber of injection nozzle holes using intake airpressure as a parameter when using injectionnozzles of which areas have been kept constant(130% of the nozzle area of the injection nozzle forburning only oil) and the number of nozzle holes hasbeen 8, 10 and 12.

Though the 8-hole nozzle shows the specific fuelconsumption on almost the same level as that forthe lO-hole nozzle, the former shows betterperformance, since both Pmax and exhausttemperature are 1ower. However, it is considered inthis case that thermal 1oads on the combustionchamber components become high due to the longerfuel spray travel by about 7% than that for gas oilaccording to the calculation using theexperimental formula of YAMASHITAetal.y,since the nozzle diameter of the 8-hole nozzleis larger. Fig.8 shows measured temperatures on the

Fig. 8 Liner Temperature vs the Number ofMethano1 Injection Nozzle Holes

inner surface of the cylinder liner (above TDC

position of the top ring). It shows thattemperatu-res for the 8-hole nozzle are higher bynearly 401C than those for other nozzles and theabovementio-ned conjecture is correct.

When considering the ignition characteristic ofmethanol burning from the periphery of a spray,issues remain from the viewpoint ofreliability including sliding conditions, since thequantity of atomized fue1 reaching the surface ofthe cylinder liner is estimated to be more. The12-hole nozzle shows slightly worse fuelconsump-tion probably due to the interference of

sprays.According to the research by WAKURI et al.u,the spray angle in this case becomes 17 or 18degrees and sprays do not directly touch eachother.However, when taking account of the behaviorof sprays after impinging on the surface of the linerand the entrainment of air into sprays, it isthought that the limit of the number of nozzle holesis 12 or so.

Fig.9 shows test results in the case where thenozzle diameters of the 10-hole and the 12-holemethanol injection nozzles have been changed. No

large change of characteristics has been found

October 1992 (5)

7/29/2019 mv20n021992p67

6/13


Fig.9 Engine Performance vs Methano1Injection Nozzle Hole Diameter

even though the diameters of nozzle holes have beenchanged except injection pressure. In order to obtainsprays similar to those of gas oil, it is necessary touse a methanol injection nozzle with the number ofholes of l.5 to 2 times and a hole diameter of 1.l to1.2 times of those of a gas oi1 injection nozzle,taking account of the spray characteristic ofmethanol having a shorter fuel travel and adifference in calorific value between gas oil andmethano1. However, the number of holes islimited to 12 or so in terms of themachining of injection nozzles in practice andinjection duration for methanol becomes relativelylonger than that for gas oil. I t is likely that thischaracteristic is cancelled out by the highcombu-stion speed of methanol and doesnot badly influence the heat release periOd of arunning engine so much.

3.3 lnfluence of P1unger Diameter of Methano1Injection Pump

Fig.10 shows engine performance in

case where the plunger diameter of the

methanol injection pump has been changed in therange from 22mm to 28mm.

The test has been carried out with injectiontiming being set at 23 degrees before

TDC (statically) for pumps having plungerdiameters from 22mm to 27mm and at 20 degreesbefore TDC (statically)for the pump havingplunger diameter of 28mm, since maximumcylinder pressure has been predicted to exceed anal1ow-able limit in this case. As seen in this figure,the

(6) Bul letin of the M.E.S.J ., Vo1. 20, No.2

7/29/2019 mv20n021992p67

7/13


injection duration and the specific fuelconsumpti-on are almost constant in the range ofplunger diameter from 26mm to 28mm. Since Pmaxhas an allowable limit and injection timing must bechanged when the rate of injection is increased,theimprovement in fuel consumption is small eventhough the plunger diameter of the metha-nolinjection pump is made too large. I t can therefore besaid that the limit to the plunger diameter is aboutl.3 times of that for only oil burning.

It can be seen from Figs.11 and 12 that theinfluence of the plunger diameter on thedistribut-ion of heat release rates and on injectionpressure and the lift pattern of the needle valvebecomes smal1.

3.4 Influence of Injection Timing

Fig.13 shows engine performance in casewhere the injection timing for methanol has beenkept constant and that for pilot oil has been

changed. As seen in this figure, the engine

performance becomes better in case where pilot oilis injected earlier by two degrees than metha-no1.

Though the test where pilot oil is injeCted laterthan methanol has also been carried out,combustionhas not stabilized and continuous runninghas been difficult. Another test has also beencarried out, where the relative difference ininjection timing between methanol and pilot oil hasbeen fixed and the timing for both fuels has beenadvanced in parallel. However it haS turned outthat the improvement in fuel consumption is smal1.

3.5 Influence of the Quantity of pilot Oi1

Fig.14 shows engine performance in casewhere the quantity of pilot oil has been changed for

each pilot oil injection nozzle. It can be seen fromthis figure that the lowest points of specific fuelconsumption differ with the specifications of pilot oilinjection valves. That is, the percentage of pilot oilin total consumed fuel for the lowest point of specificfuel consumption is between l1 and 12% for theone-hole nozzle and that is near 15% for thethree-hole nozzle. Thus, the lowest point shiftstoward the larger percentage of pilot oil. Though thequanttty ot piLot aiL can be decreased down toabout 4% by making the pilot oil injection nozzlearea smaller, proper quantity.is

October 1992 (7)

7/29/2019 mv20n021992p67

8/13


considered to be 12-15% in practice, since thestartability of an engine must be considered asmentioned later.

Smoke density and NOx have also beenmeasured during these tests. Though detailedresults will be explained later, the results can besummarized as fol1ows. Compared with a diese1engine being operated on gas oil, the smoke densityis 1ower by one order by Bosch scale and NOx issbout half under the same load condition.Thus,exhaust gas characteristics have beenconfirmed to be superior. Furthermore, overhaulinspection and the results of lubricating oilanalysis after tests have shown less contaminationof the engine inside. As mentioned above, it hasbeen confirmed that the possibility of loweringenvironmental pollution and decreasing

maintenan-ce work for diesel engines is large.

4. Starting Test

4.l Test MethodThe stable combustion of dual fuel engines

under normal operation can be ensured by pilot oilof several percent of total fuel which is injectedunder full 1oad condition. However, a considerablylarge quantity of fuel is needed when startingengines, since accelerating torque is

necessary in addition to normal running torque.For this reason, starting tests have been carried outunder the fol1owing conditions.

a) Constant quantity of methano1 (full 1oad)and varying quantity of pilot oi1

b) Constant quantity of pilot oil and varyingquantity of methano1

c) Operation on only pilot oi1d) Starting on pilot oil and injection of metha-

nol after thate) Constant quantity of methano1 (50%) and

varying quantity of pilot oi1For al1 conditions except e), cold conditions ofintake air temperature ts # 191C , cooling watertemperature tw t 191C , 1ubricating oiltemperatu-re to #201C and liner temperature tL #201C have been adopted. For a part of e)condition,warm conditions of ts t 301C , tw #58 C ,

to #50 t and tL #391C have been adopted.

4.2 Test ResultsFig.15 shows the summaries of test results

(8) Bulletin of the M.E.S.J ., Vo1. 20, No.2

7/29/2019 mv20n021992p67

9/13


taking the quantity of pilot oil on the abscissa andthat of methanol1 on the ordinate. . mark showsthat no ignition has been detected. }and J marksshow that, though ignition has beendetected, it has not been continued and torque hasnot been generated. > and O marks show thatignition has been detected and continued stably and

engine speed has risen up to its set speed. Suffixesshow test numbers.

As can be seen from this figure, under the coldcondition (0 J .), ignition has not been detected at alllike Test Nos. 1-5 in case where a large quantity ofmethanol has been injected together with oil. Onthe other hand, under the warm condition (O }) likeengines just after operation, starting has beenpossible like Test Nos. 21, 22 and 13. However, therehas been an example such as Test No.12 whereoperation

could not be continued due to pilot oilless by fewpercent than that of Test No.13. When pilot oil isplenty, starting even under the cold condition is

possible like Test No.25 even though a considera-bly1arge quantity of methanol is injected. Test Nos.8, 9and l0 have been carried out in such a way that theengine has been started on only pilot oil andmethanol has been injected after detecting ignition.

These are examples where the engine has misfiredand not generated effective torque and

operatiOn could not be continued because ofmuch methanol and less pilot oil. It has turned outthat, since pilot flames are blown out by theinjection of meth1no1, energy necessary for startingcan not be made up by methanol and a necessaryquantity of pilot oil must be inj:?cted under the coldcondition.

Fig.16 shows the transition of engine speed forTest Nos.3, 7, 11 and 13 which have been carriedout under typical starting conditions. Test No.3shows the case where methano1 of the

quantity corresponding to the limit of the injectionpump rack has been injected under thecold condition. Engine speed rises up to only that bystarting air. Test No.7 shows that acceleratingtorque is not generated though slight ignition isdetected, because the quantity of methanol has beendecreased to 30%.

Test No.11 shows the case where only pilot oil isinjected. Though the rate of speed increase is smal1,engine speed rises up to the set speed.Test No.13shows the case where methanol of the quantity of50% has been injected under the warm condition. It

can be seen that engine speed quickly risesby the combustion of methano1.Fig.17summarizes the results of starting tests usingaccelerating time and mean effective pressure(Pmi) obtained from indicator diagrams ascoordinates. O and X marks show cases wherestarting has succeeded and failed respectively.Thesolid line shows the relationship between minimummean effective pressure necessary for acceleratingengine speed which has been calcula-ted from meanaccelerating torque and accelerat-ing time. I t can beseen from this figure that,apart from the length of

accelerating time related to inertial mass, Pmi of atleast 4 or 5 kgf/cm2 must be generated for startingengines.

5. Quick Load Throw-in Test

5.l Test Method

Tests simulating the condition of engagingclutches which are often installed on medium to

October 1992 (9)

7/29/2019 mv20n021992p67

10/13


Fig. 18 Procedure8 of Quick Load Throw-in Test

high speed engines have been carried out byquickly throwing-in 1oads on the dynamometer(eddy current type) according to the procedures

shown in Fig.18. Rotating mass is added betweenthe engine shown in Fig.l and the dynamometer tobe able to simulate a shafting of a marine engine.

The engine has been imposed with a load duringfour or five seconds after changing over from oiloperation to methano1/oil operation under nolobd condition, and engine speed and pressure inthe cylinder have been recorded.Supposingthe loaded condition of an engine after engaging aclutch, 1oads (40-150 kgf ) correspondi-ng to 20-70%of the load at full engine output and also thequantity of fuel to be injected corresponding

to these loads have been selected.For intake airpressure, two cases of naturally aspirated andsupercharged (0.35 kgf/cm) conditions have beenselected. Since intake air of this experimentalengine is supplied by an indep-endent motor drivenblower, the transient chara-cteristics of aturbocharged engine can not be simulated exactly.However, it is considered that engine characteristicscan qualitatively be grasped by this test.

The governor of this engine is WoodwardUG8 type with a torque limiter. The test has beencarried out by controlling the quantity of pilot oilwith the lever 34 and that of methanol by limitingthe output of the lever 6 with the torque limiter ofthe governor in Fig.3.

5.2 Test Results

Fig.19 shows the test results of the quick loadthrow-in test. Measured points are p1otted byselecting Pmi, which has been converted from adynamometer load, for the abscissa andthe percentage of methanol injected, which has beencalculated from the rack position of the injectionpump, for the ordinate.

In this figure, , O , O , and O' marks showcases where engine speed has returned to its set

values after quickly imposing loads ; ,., . and .'marks show cases where the engine has stalledand could not carry loads ; and J , J ' and > showcases where the engine had not sta1led but theengine speed has not returned to its set values.Suffixes show test numbers.

The magnitude of load which can be thrown-in iseffective only in the hatched range under naturallyaspirated condition and the engine output islimited to Pmi = 9-1Okgf/cm2. Since this limit cannot be raised even under the warm condition, it isnot influenced by the phenomenon of blowing out

pilot flames by methanol as


7/29/2019 mv20n021992p67

11/13

Research on Methano1-fueled 4arine Diesel Engine 77

detailed under the section of starting test, and it isthought that output can not be increased due to theshortage of intake air even though the quantity ofmethanol is increased. It can be seen from examplesmarked with O' that the limit of output canconsiderably be increased by d small degree ofsupercharging and Pmi of 12.5kgf/cm2 can bedeveloped. It means that the magnitude of loadwhich can be thrown-in, i.e. the speed of engagingthe c1utch (the rising speed of oil pressurefor operating the clutch), depends on theaccelerating ability of the turbocharger and it can besaid that the clutch must be operated linking withintake air pressHre. The quantity of pilot oil hasalmost no influence on the limit of output in the

range shown in Fig.19. Fig.20 and 21 show thetransitions of engine performance after loadthrow-in under naturally aspirated condition andunder supercharged condition wiht the intake airpressure of 0.35kgf/cm2 respectively. Though Pmi# 1Okgf/cm2 can be obtained just after loadacceptance in every case under naturally aspiratedcondition, the balance between generated enginetorque and load can not be maintained due to theshortage of air (small air/fuel ratio) and the coolingeffect by the latent heat of vaporization of methanolwhen the quantity of injected methanol is much.

Both Test Nos.19 and 25 have thistendency, and engine speed lowers halfway andcan not recover.

Under supercharged condition, the enginegenerates Pmi # 15kgf/cm2 and engine speedquickly returns to the set value, since aconside-rably large quantity of air, i.e. specific air

consu-mption 4kgf/PSh, is supplied to the engine.Test Nos.41 and 42 show the cases where the enginecan not develop enough output because of too littlequantity of injected methanol against the thrown-inengine load. As mentioned before, the experimentalengine does not represent the dynamiccharacteristics of actual turbocharged engines, sincethe experimental engine is not equipped with anexhaust turbocharger. However,it is expected thatthe above-mentioned load throw-in test can offermatters to be considered when methanol is applied

to diesel engines.

6. Conclusion

Tests have been carried out under static anddynamic conditions in order to graspengine performance when methanol is applied tomarine

October 1992 (11)

7/29/2019 mv20n021992p67

12/13


diesel engines. As a result, it has turned out thatthe performance of a methano1/oil burningengine can be improved near to the performancelevel of an oil burning engine by optimizing the fuelinjection sysytem and the combustion chamb-ergeometry and by adapting the fuel regualtingsystem and tbe intake air system of the former.

7. Acknowledgements

This research has been carried out inco-op-eration with KOKKA SANGYO, coastalShipping company, and HANSHIN Diesel Works,engine manufacturer for coasters. The authors wishto express our deep gratitude to people concerned.

DiscussionYasuhiro Ito (NIICATA ENGINEERING CO.,LTD.)

I pay my respects to you for your presentationof valuable research. I am happy if you give me youranswers to the fol1owing two questions.

1. How do you evaluate the properties ofexhaust gas from the viewpoint of lowenvironmental pollution ?

To what extent does NOx in particulardecrease in comparison with diesel engin-es ?I think soot is more or less influenced by pilotinjection. How do you think about thismatter ?

2. Please let me know if there is any point tobe particularly noted in the respect ofd urability.

Author'8 reply

1. Though exhaust emissions which areproblematical are formaldehyde andunbur-ned methano1, they are not so muchprobl-ematical in marine engines comparedwith automobile engines. NOx was from 2/3 to1/2 of that of gas oil burning engines,since the

combustion temperature of met-hanol was1ow.Soot was so little that it could hardly bemeasured by a Bosch smoke meter in spite ofpilot injection.

2. Though we were worried about the occur-rence of piston ring scuffing, we couldconfirm that no problem would occur byselecting proper lubricating oil. However,forthe durability of the methanol injectionsystem, we experienced the stick of theplunger and the corrosion and breakage of thespring.

On these troubles, we are scheduled topresent in detail at the autumn lecturemeeting. Pleae see this paper.

Keijiro Shiode (SHIP RESEARCH INSTITU-TE )

I pay my respects to you for your presentation

of very valuable experimental data. Please let meknow if you have experienced any trouble on thefue1 injection valve when alcohol fuel has beenused.

Author's reply

On the trouble of the methanolinjection system, we are scheduled to present indetail. Please see this paper. Though weexperienced the wear of the needle valve and

the corrosion and breakage of the springdue to the low viscosity and corrosiveness ofmethano1, we could solve these troubles bychanging their shapes and materials.

Hiromi Kondo (DAIHATSU DIESELMFG.CO., LTD.)

I pay my respects to you for your valuableresearch on the combustion of methano1. Pleasegive me your answers to the fol1owing questions.

1. What phenomenon can I think about by thedescription "In case the quantity of injected

oil is the same, smaller area of nozzle holesis ..." on Page 70 in the text ?

2. Please tell me the locations of measuringpoints for liner temperature and of the pilotoil nozzle in F ig.6.

3. Please tell me the process of calculatingPmi from mean accelerating torque shown inFig.6 on Page 70.

4. How should I consider compression ratiosfor methanol engines ? I should be obliged ifyou would tell me the compression ratio usedin this experiment.

Author's reply

l. The pilot injection system actuallyhas considerably larger capacity thanthat necessary for normal operation,taking account of engine starting and theengag-ement of a clutch. Consequently,injection characteristics under normaloperation tend to deteriorate. It is thereforenecessary to throttle nozzle area to maintainnecessary


7/29/2019 mv20n021992p67

13/13


injection pressure.

2. Eight sensors for measuring liner tempera-

ture are inserted on the periphery of the liner at

intervals of 45 degrees and the pilot oil injection

nozzle is located near the periphery of the

combustion chamber. The difference in linertemperature which was thought to be due to

pilot flame was not observed .

3. Though the rate of engine speed increase

after starting is not uniform, this minimum Pmi

curve has been made by the way of thinking of

the mean rate of acceleration for the sake of

simplification to investigate its tendency.

Friction torque has been made constant.

4. Though tests with various compression

ratios were not conducted, we think thecompression ratios for engines with pilot

injection can be considered in the same way as

those of oil burning engines. Tho-ugh the

compression ratio of the experimental engine is

the same as that for the case of burning only oil

( E = 13), the effective compression ratio

becomes higher than that for the case of burning

only oil,since the timing of intake valve c1osing

is advanced a little.

References

(1) Yonebayashi A., "Activities of IMO MEPC

regarding exhaust enlission fron-1 ships",

Pre-text of the 47th M.E.S.J -Conference,

p.l44,199l.

(2) Hikino K., et al, "Recent trends of

ignitability improvements on methanoI

diesel en9ines", J ournal of S.A.E.J , vo1.44,

No.8,p.92, 1990.(3) Yamashita H., et aI , J ournal of

M.E.S.J ,vo1.26, No.9, 1991.

(4) Wakuri Y., et al, Transaction of

J .S.M.E,256-156 (24-8), p.820.

October 1992 (13)

Documents

mv20n021992p67