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Washington, DC, March 2008
A Primer: Aircraft Emissions & Environmental Impact
Alan EpsteinVice PresidentTechnology & Environment
Aviation and the Environment
Impact of Aviation on The Environment
Ground Level:• NOx O3• Particulates
Troposphere:• CO2• NOx• H2O• Particulates
~3,000 ft (1000m)
~40,000 ft(12-17 km)
Local Air QualityLocal Air QualityNoise
Ozone Layer ChangeOzone Layer ChangeStratosphere:• NOx• Halogens
Climate ChangeClimate Change
Air
Engine Efficiency Vs. Combustor Technology
Fuel
Combustor
Air
Engine Efficiency Vs. Combustor Technology
Fuel
Combustor
Set By Engine EfficiencyCarbon Dioxide - CO2Water Vapor - H2O
Combustion Products
Air
Engine Efficiency Vs. Combustor Technology
Fuel
CombustorSet By Combustor TechnologyNitrogen Oxides – NOxCarbon Monoxide – COUnburned Hydrocarbons – UHCSmoke
Set By Engine EfficiencyCarbon Dioxide - CO2Water Vapor - H2O
Combustion Products
Air
Engine Efficiency Vs. Combustor Technology
Fuel
CombustorSet By Combustor TechnologyNitrogen Oxides – NOxCarbon Monoxide – COUnburned Hydrocarbons – UHCSmoke
Set By Engine EfficiencyCarbon Dioxide - CO2Water Vapor - H2O
Two Paths to Emission Reduction• Reduce emissions per kg of fuel• Reduce absolute amount of fuel
Improving Combustors to Reduce EmissionsCombustor Requirements
SAFETY
Emissions
Altitude Re-lightand Starting
Stability Endurance
Local Air Quality & Global Warming
LeanFuel RichCombustion
Mixing & Lean Combustion
Science Behind Low NOx TechnologyNOx Up With Temperature and Time
NO
x(E
I)
0
100
200
0.2 0.6 1 1.4 1.8
Equivalence Ratio ~ Fuel/Air
Rich Quick Quench Lean (RQL) Combustor Design
Rich
4 ms
1 ms
0.3 ms
Time
EI – Emission Index, grams NOx per kg of fuel
LeanFuel RichCombustion
Mixing & Lean Combustion
Science Behind Low NOx TechnologyNOx Up With Temperature and Time
NO
x(E
I)
0
100
200
0.2 0.6 1 1.4 1.8
Equivalence Ratio ~ Fuel/Air
Rich Quick Quench Lean (RQL) Combustor Design
Rich
4 ms
1 ms
0.3 ms
Time
Max Allowed
EI – Emission Index, grams NOx per kg of fuel
LeanFuel RichCombustion
Mixing & Lean Combustion
Science Behind Low NOx TechnologyNOx Up With Temperature and Time
NO
x(E
I)
0
100
200
0.2 0.6 1 1.4 1.8
Equivalence Ratio ~ Fuel/Air
Rich Quick Quench Lean (RQL) Combustor Design
Rich
4 ms
1 ms
0.3 ms
Time
Max Allowed
Too Leanto Burn
EI – Emission Index, grams NOx per kg of fuel
LeanFuel RichCombustion
Mixing & Lean Combustion
Science Behind Low NOx TechnologyNOx Up With Temperature and Time
NO
x(E
I)
0
100
200
0.2 0.6 1 1.4 1.8
Equivalence Ratio ~ Fuel/Air
Rich Quick Quench Lean (RQL) Combustor Design
Rich
4 ms
1 ms
0.3 ms
Time
EI – Emission Index, grams NOx per kg of fuel
Max Allowed
Too Leanto Burn
EngineAverage
0
100
200
300
400
500
600
pre 76 76-80 81-85 86-90 91-95Year of Engine Certification
% o
f CA
EP2
limit
HCCONOx
History of Regulated Emissions Reduction
NOx Reductions Continue to be MandatedCannot compromise CO, UHC, and Smoke
0
20
40
60
80
100
120
140
1988 1992 1996 2000 2004 2008 2012
% IC
AO C
AEP/
2 NO x
Stan
dard
Conventional
TALON I
TALON II
Original Standard
CAEP/2PW4090
PW4098
PW4168
CAEP/4
CAEP/6
TALON X
PW6000
CAEP: Committee on Aviation Environmental Protection
Reducing Fuel Burn to Reduce EmissionsThermal and Propulsive Efficiency Set Fuel Burn (SFC)
NOx - CO2 Engine Design TradeImproving Thermal Efficiency Can Increase NOx
0 10 20 30 40 50 60
NOXSFCImproving CombustorTechnology
Spe
c ifi c
Fue
l Con
sum
p tio
nS
FC (l
b /lb
-hr)
Overall Compressor Pressure Ratio (Thermal Efficiency)
Em
issions IndexE
I (grams N
Ox/kg fuel)
Improving Engine performance
NOx - CO2 Engine Design TradeImproving Thermal Efficiency Can Increase NOx
0 10 20 30 40 50 60
NOXSFCImproving CombustorTechnology
Spe
c ifi c
Fue
l Con
sum
p tio
nS
FC (l
b /lb
-hr)
Overall Compressor Pressure Ratio (Thermal Efficiency)
Em
issions IndexE
I (grams N
Ox/kg fuel)
Improving Engine performance
NOx - CO2 Engine Design TradeImproving Thermal Efficiency Can Increase NOx
0 10 20 30 40 50 60
NOXSFCImproving CombustorTechnology
Spe
c ifi c
Fue
l Con
sum
p tio
nS
FC (l
b /lb
-hr)
Overall Compressor Pressure Ratio (Thermal Efficiency)
Em
issions IndexE
I (grams N
Ox/kg fuel)
Improving Engine performance
•Lower fuel consumption so- Lower CO2- Lower NOx
Low by-pass – B707-320 (JT3D), B727 (JT8D)
1990 20001960 1970 1980 2010
Ultra high by-pass
TURBOFAN
B747 (JT9D) B777 (PW4084)
TURBOFAN
TURBOJET – B707 (JT3C)
Evolution in By-Pass Ratio & Efficiency
High by-pass -
History of 70-100 PAX Class Air Transport
3750 HP162” prop
Allison 501-D13Turboprop
38
3500
325/352
20,0009985
6535
116,000
1958
Electra
41,00017,00020,0006,000Cruise Altitude (ft)
81689037001450Range (NM)
447 / 470250/275260/325150 cruiseCruise/Max Speed(KCAS)
1200 HP138” prop
Pratt & Whitney Twin Wasps
20
9528720
25,200
1936
DC-3
3500 HP199” prop
Pratt & WhitneyWasp Major
23
14189
6900
145,800
1948
Boeing 377 Stratocruiser
2009 1998Entry into Service
2475 HP155” prop
PW127Turboprop
83
8968
1645
49,600
ATR 72
13,600 lbf46” fan
CF-34Turbofan
70
861002900
91,800
CRJ1000
Takeoff PowerDiameter (in.)
Engine
Fuel Efficiency (seat-st.mi / US gal)
Wing Span (ft)PassengersFuel Capacity (gals)
MTOGW (lbs)
Summary of Aircraft Emissions Primer
• Aircraft engines have unique requirements– Safety, weight, life in addition to low emissions
• Regulated emissions– Smoke, HC, CO are well in hand– NOX will stay a challenge as rules tighten & efficiency up
• Climate change concerns may add new constraints– CO2 is a concern– H20 may be a player if contrails important
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