European GT-SUITE Conference 2009 · 9th November 2009 European GT-SUITE Conference 2009 Mechanisms...
Transcript of European GT-SUITE Conference 2009 · 9th November 2009 European GT-SUITE Conference 2009 Mechanisms...
Frankfurt,9th November 2009
European GT-SUITE Conference 2009
Mechanisms of the Mixture Preparation and Combustion for an Engine Operation with
the Ethanol Blend E85
Thomas Lauer1 , Markus Klein2
1Institute for Internal Combustion Engines and Automotive Engineering, Vienna University of Technology
2GM – Powertrain Germany GmbH
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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• Efforts will have to be made in the future to reduce the greenhouse gas CO2. A fleet emission limit of 120 g/km will be introduced by the European Union by 2012.
• In addition a steadily growing number of vehicles faces limited oil resources.
• Therefore low carbon fuels and fuels from biomass with an improved CO2-balance like ethanol are considered as an important alternative to conventional fuels for SI engines.
• Because of different physical and chemical properties compared to conventional fuels a detailed analysis of the engine process is necessary.
Introduction
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Fuel Characteristics of RON95 and Ethanol E100 (I)
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Fuel Characteristics of RON95 and Ethanol E100 (II)
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Correction of the Lower Heating Value
• In a bomb calorimeter the lower heating value at constant volume (ΔU)V,T‘ ismeasured. GT-Power expects the lower heating value at constant pressure(ΔH)p,T‘ . There is a difference between both values if the number of moleschanges during the reaction:
(ΔH)p,T‘ – (ΔU)V,T‘ = Rm · (nP – nR) · T‘
• For liquid fuels the lower heating value is reduced by the heat of vaporization.
2.490.63Deviation [%]29.7042.33(ΔH)p,T‘ + HOV
28.8641.983(ΔH)p,T‘
28.9642.063(ΔU)V,T‘
E85RON 95Chemical Energy [MJ/kg]
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Engine Specification GM Z14XEP
125 Nm @ 4,200 rpmMax. Torque
RON95, E85 (85 Vol.-% Ethanol, 15 Vol.-% RON95)Fuels
66 kW @ 5,600 rpmMax. Power
80.6 mmStroke
73.4 mmBore
1364 cm³Displacement
1.4 L Gasoline EngineEcotec Family 0, Generation 2,Multi Point Fuel Injection
Engine Type
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Numerical Model and Test Equipment
High-pressure sensors in the combustion chambers
Low-pressure senors in the inlet- and exhaust-manifold
Test EquipmentNumerical Model
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Gasdynamics @ Full Load –Comparison with Measurements
n = 2,800 rpm
n = 4,400 rpm
n = 6,000 rpm
Measurement location
pInlet
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Full Load Performance w/ RON95 –Comparison with Measurements
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Expected Impact of E85-Fuel on the Engine Operation
Two effects must be considered when operating the engine with E85:
• Because of the lower stoichiometric air/fuel-ratio of E85 its vapourdisplaces more air during intake. Therefore the volumetric efficiencyshould be DECREASED.
• The higher heat of vaporization of E85 combined with the lower air/fuel-ratio causes an intense cooling of the mixture during intake. Thereforethe density of the mixture and the volumetric efficiency should beINCREASED.
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Full Load Performance w/ E85 –Comparison with Measurements
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1000 2000 3000 4000 5000 6000Speed [rpm]
Volu
met
ricA
ir-Ef
ficie
ncy
[-]Measurement RON95
Measurement E85
Simulation RON95
Simulation E85
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Full Load Performance E85 –Comparison with Measurements
8
9
10
11
12
13
1000 2000 3000 4000 5000 6000Speed [rpm]
Bra
ke M
ean
Effe
ctiv
ePr
essu
reB
MEP
[bar
]
Measurement RON95
Measurement E85
Simulation RON95
Simulation E85
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0
10
20
30
40
50
60
70
0 0.2 0.4 0.6 0.8 1 1.2Volume / Vmax [-]
Cyl
inde
rPre
ssur
e[b
ar]
Measurement
Simulation E85 (30% Vaporized Fuel Fraction)
Simulation E85(100% Vaporized Fuel Fraction)
Influence of the Fraction of EvaporatedFuel on the Compression Curve
nMOT = 2,000 rpm
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Specific Heat Capacity for Liquid and Evaporated Fuels
0.0
1.0
2.0
3.0
4.0
5.0
6.0
200 400 600 800 1000 1200Temperature [K]
Spec
ific
Hea
tCap
acity
c p[k
J/kg
K]
Heptane1 Benzene1
Iso-Octane2 Indolene (GT-Power)Ethanol1 Ethanol2
Liquids
Vapours
1 VDI-Wärmeatlas2 NASA Thermobuild
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Specific Heat Ratios for Different Fractions of Evaporated Fuel
1.1
1.15
1.2
1.25
1.3
1.35
1.4
-180 -90 0 90 180 270 360 450 540Crank Angle [°CAaTDC]
Spec
ific
Hea
tRat
io κ
= c
p/ c
v[-]
RON95 (100% Vapour)RON95 (30% Vapour)
E85 (100% Vapour)
E85 (30% Vapour)
Compression
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0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1000 2000 3000 4000 5000 6000Speed [rpm]
Volu
met
ricA
ir-Ef
ficie
ncy
[-]Measurement E85
Sim. 30% Vapour (default)
Sim. 50% Vapour
Sim. 100% Vapour
Volumetric Efficiencies for Different Fractions of Evaporated E85
Further increase of the volumetricefficiency and therefore higherdiscrepancy to the measurements
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Conclusions and Model Adaptations
• A comparison with the measured compression curves indicates that most
of the fuel is obviously evaporated at inlet valve closing i.e. the fraction of
evaporated fuel should be close to 1.
• A simulation with an increased fraction of instantaneously evaporated fuel
results in a further overestimation of the volumetric efficiency and full load
performance for E85 due to its high heat of vaporization. There is obviously
no solution that fulfills both demands.
• From video observations in the inlet ports it became obvious that a
considerable part of the fuel puddles on the walls. The heat of vaporization
is therefore taken rather from the structure than from the air.
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Conclusions and Model Adaptations
Sensing massflow and fuel vapour fraction
Actuate externalheat source
HOVFraction of fuel thatevaporates in the puddle
1. Approach (Heat Fluxes): Sensing and actuation of the heat of vaporizationthat is „lost“ to the structure (see picture above)
2. Approach (Reduced HOV): Reduction of the fuel‘s heat of vaporization in accordance to the mass fraction that evaporates in the puddles
Additional parameter to tune the model to the measurements
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Full Load Results for E85-Operation –85% Vaporized Fuel Fraction, 80% Heat
of Vaporization from Structure
Constant values for:Vaporized fuel fraction: 85%Vaporized in Puddle: 80%
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Cyl. Pressure Curve for E85-Operation –85% Vaporized Fuel Fraction, 80% Heat of
Vaporization from Structure
0
10
20
30
40
50
60
70
0 0.2 0.4 0.6 0.8 1 1.2Volume / V max [-]
Cyl
inde
rPre
ssur
e[b
ar]
Measurement
30% Vapour
Reduced HOV
nMOT = 2,000 rpm
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Content
1. Introduction
2. Specifics of Ethanol Compared to Conventional Fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Full Load Results for E85-Operation –Comparison with Test Results
The model predicts a moderately increased mean effective pressure in spite of a lower volumetric efficiency and is in good agreement with the measurements. The results can be explained with a moderately higherheating value of the mixture and a higher efficiency of the process.
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NO-Emissions for both Fuels –Comparison with Test Results
A constant NOx calibration multiplier of 1.1 was used for both fuels
Difference ExhaustTemperature RON95-E85 NO-Emissions
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Content
1. Introduction
2. Specifics of Ethanol compared to conventional fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Outlook and Conclusion
• When simulating engines operated with alcohol blends like E85 a higher impact of the fluid properties on the volumetric efficiency and compression curve was observed.
• With the integration of the heat fluxes in the inlet port a good correlation with the engine performance could be achieved. The differences in combustion temperature and efficiency for an engineoperated with RON95 and E85 could be shown.
• However, it must be considered that this approach is not predictive butmust be tuned to measurements.
• Investigations with a more predictive model of the wall film in the inletports that is provided by GT-Power and thermal models of the portwalls are carried out right at the moment.
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Content
1. Introduction
2. Specifics of Ethanol compared to conventional fuel
3. Model Setup and Calibration
4. Simulation Results
4.1. Full Load Results for both Fuels and Comparison with Test Results
4.2. Conclusions and Model Adaptations
4.3. Impact of E85 Fuel on Combustion and Efficiency
5. Outlook and Conclusion
6. Summary
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Summary
• Because of the higher market share of alternative fuels like ethanol in the future an analysis of their impact on the engine process is necessary.
• Investigations were carried out with a 4-cylinder gasoline engine with portfuel injection regarding full load performance. It could be shown that the fuel‘s fluid properties and wall film effects have a higher impact on the quality of the simulation results than for conventional fuels.
• Modifications of the engine model concerning puddling and fuel evaporationimproved the correlation with the measurements in terms of volumetricefficiency and torque. The differences in engine operation between the twofuels RON95 and E85 could be understood with the adapted model.
• Investigations with a more detailed model regarding the thermodynamicbehaviour of the wall film and the inlet port walls are carried out right at the moment.
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Thank You Very Much
For Your Attention!