1/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
2nd Advanced Fuels and Engine Efficiency Workshop / Nov. 1st 2016
TOYOTA
Effect of fuel components on abnormal combustion of the SI engine, - knocking under low speed to high speed
with high compression ratio engine -
Nozomi YOKOO
Toyota Motor Corporation
2/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
3/30
Automaker’s mission
Convenience
Alternative energy
Climate fluctuations
Pollution prevention
Fun-to-drive
Automaker
Energy Fuel
SustainableMobility
Customer’s Smiles
Safety
Reliability
Powertrain: Reduce tank-to-wheel energy consumption and minimize the burden on the environment.
4/30
Engine Thermal Efficiency and Output Performance
304050607080
90100
32 34 36 38 40 42 44Maximum engine thermal efficiency (%)
Max
imum
eng
ine
spec
ific
outp
ut (
kW /
L) Toyota HEVsToyota conventional vehiclesOther OEM HEVsOther OEM conventional vehicles
Future trendFuture trend
High compression ratio engines, turbocharged engines are required
“Fun to Drive”
5/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Fuel DiversificationAutomotive fuelsAutomotive fuels
Ener
gy s
avin
gEn
ergy
sav
ing
EV
FCV
Fuel
div
ersi
fica
tion
Fuel
div
ersi
fica
tion
Primary energiesPrimary energies PowertrainsPowertrains
Conventional vehicle
& HEV
Fuel diversification will progress moreover . However, conventional fuels from crude oil will be still mainstream for a few decades.
Natural gas
Coal
Biomass
Nuclear energy
Water/Wind/Solar power
Electricity
Hydrogen
Bio-fuel
CNG
Synthetic fuel
Gas oil
GasolineCrude oil
PHV
6/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Natural aspirated engine
Turbocharged engineTo
rque
(Nm
)
Engine speed (rpm)
Auto-ignitionRe-start Hot Condition
Low speed pre-ignitionHigh speed pre-ignition
Knocking
Knocking is occurs in the wide engine speed and load condition.→Knocking mitigation is essential for the engine development
Engine abnormal combustion
7/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Prediction of the knocking
Knocking initiation is influenced by the fuel auto-ignition characteristics.
What is Knocking・・・When temperature and pressure of the unburned mixture get
higher because of the compression from the flame propagation,parts of the mixture is auto ignited before the flame propagation
Knock prediction in EngineDevelopment of the chemical kinetics model
Point-Model selection for the gasoline-Calculation time
Point-Simple equation-Wide application
1970’s- Single molecule1990’s- PRF for SI knock prediction2000’s- Gasoline surrogate for knock prediction
1940’s- RON, MON1955- Livengood-Wu Integral1978- IFP ignition delay function
8/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
These day's high CR trend: Negative Temperature Coefficient(NTC) make an effect during the compression process
Knock condition: Compression Ratio Effect
300
400
500
600
700
800
900
0 5 10 15 20Te
mpe
ratu
re [K
]Time [ms]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 5 10 15 20
Pres
sure
[MPa
]
Time [ms]
Negative Temperature Coefficient(NTC)
CR 9
CR12
CR14
CR 5
CR 20
Engine Speed: 1200rpm CR: Compression RatioAdiabatic compression process
9/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
300
400
500
600
700
800
900
0 5 10 15 20Te
mpe
ratu
re [K
]Time [ms]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 5 10 15 20
Pres
sure
[MPa
]
Time [ms]
Low engine speed: Longer NTC duration
Knock condition: Engine speed effect
1200rpm6000rpm
1200rpm6000rpmEngine Speed
Engine Speed
NTC
CR 9
CR 12
CR 14
10/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Knock condition: Effect of the Combustion Phase
To avoid the severe knock conditionRetard the ignition timing→longer NTC duration
0
2
4
6Pr
essu
re
[MPa
]
200
400
600
800
1000
0 5 10 15 20
Tem
pera
ture
[K]
Time [ms]
Ignition Timing Combustion Pressure
NTC
knockknock
Engine Speed: 2000rpm
11/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
To improve the knock prediction accuracy・To extract the issues of Livengood-Wu integral prediction of high compression ratio engine with various octane number’s fuels.・To clear the effect of cycle-to-cycle variation for 1D model development.
NTC impact gets larger
High compression ratio enginesHigh boosted engines
Fuel diversification
Preparation for the low RON fuel is
required
Objective
12/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
13/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Test Engine: 1.8L, L4
Test Fuels: similar characteristics to conventional gasoline
Engine Operating Condition
Engine Experimental Condition
Engine CR12 CR13 CR14Bore(mm) 80.5 ← ←
Stroke(mm) 88.3 ← ←St/B ratio 1.10 ← ←
Cylinder Number 4 ← ←Displacement (cc) 1797 ← ←
Compression Ratio 12 13 14Valvetrain System DOHC 4valve ← ←
Injector position Port ← ←
Fuel 1 Fuel 2 Fuel 3 Fuel 4RON 75 83 91 100MON 70 76 83 87
Engine Speed 1300rpm 2000rpm 4000rpm 5200rpmLoad
Air Excess Ratio
WOT or Auto Ignition LimitStoichiometric or
Rich to meat exhaust gas temperature
14/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Livengood-Wu Integral
Ignition delay time by IFP group*
A 0.01869RON100
.
n 1.7B 3800
τ s , p kg/cm , T K
τ Ap expBT
1τ dt 1.0
1.0E-04
1.0E-02
1.0E+00
1.0E+02
Igni
tion
dela
y tim
e [s
]
0.00.51.01.52.02.53.0
-90 -60 -30 0 30 60 90
Live
ngoo
d-W
u In
t. [-]
CA [ATDC]
0
2000
4000
6000
Pres
sure
[k
Pa]
0
500
1000
Tem
pera
ture
[K
]Knock
Predicted Timing
*A.M.Douaud et al: Four-Octane-Number Method for Predicting the Anti-Knock Behavior of Fuels and Engine,SAE Technical paper(1978), 780080
Knock prediction by the Livengood-Wu Integral
15/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Pressure, Initial mixture temperature: Experimental Results・200cycle averaged pressure・Mixture composition and mass fraction
Temperature Calculation (Tad , Tchem)① Tad :Calculate with adiabatic compression equation
② Tchem :Calculate with kinetic model(consider the heat production in compression process)
Mechanism LLNL Gasoline Surrogate Detailed mechanism*Reactor Closed Homogenious bach ReactorProblem Type Constrain Pressure And Solve Energy EquationPressure Experimental data measured by Pressure sensorHeat Loss noneEquivalence Ratio Same as Experimental Data
【Configuration】CHEMKIN-PRO
【Fuel Specification】 PRF75RON 83RON 91RON 100RONPRF75 PRF83 PRF91 PRF100
iso-octane (IC8H18) [mol %] 72.7 81.2 90 100n-heptane (NC7H16) [mol %] 27.3 18.8 10 0
【Air】O2 21 vol.%N2 79 vol.%
*Mehl M.et al: Kinetic modeling of gasoline surrogate components and mixtures under engine condition,Proc.Combust.Inst., 33,193-200 (2011) https://combustion.llnl.gov/mechanisms/surrogates/gasoline-surrogate
・Heat loss with the wall→no consideration・Ratio of specific heat of fuels→use iso-octane value
・Initial mixture temperaturecalculated by the state equation
Calculation method of the cylinder Temperature
16/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
①Tad :Calculate with adiabatic compression equation②Tchem: Calculate with kinetic model
(consider the heat production in compression process)
1300rpm
5200rpm
Calculation method of the cylinder temperature
300400500600700800900
1,000
-90 -60 -30 0 30 60 90
Tem
pera
ture
[K]
CA [ATDC]
0200400600800
1,000
0 2,000 4,000 6,000
Tem
pera
ture
[K]
Pressure [kPa]
300400500600700800900
1,000
-90 -60 -30 0 30 60 90
Tem
pera
ture
[K]
CA [ATDC]
0200400600800
1,000
0 2,000 4,000 6,000
Tem
pera
ture
[K]
Pressure [kPa]
Tchem
Tad
17/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
18/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Optimization to minimize variance
y = 1.11 x + 4.89 Prediction case:18/48
y = -0.30 x + 19.68 Prediction case:48/48
-10
0
10
20
30
40
50
60
70
80
0 20 40 60
θ pre
dict
ion
[ATD
C]
θexp [ATDC]
TadTchem
Low prediction accuracy is found with both Tad and Tchem→Optimization to minimize variance is conducted.
Comparison between experimental results and prediction results
Ⅴ=1N
1τ dt 1
Tad Tchem
A
n 1.7B 3800V 0.19 5.42
0.01869RON100
.
τ Ap expBT
19/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
It seems that prediction accuracy is not enhanced with module optimization.
Comparison of experimental results and prediction results
y = 0.73 x + 10.90 Prediction case:44/48
y = -0.03 x + 28.24 Prediction case:31/48
-10
0
10
20
30
40
50
60
70
80
0 20 40 60θ p
redi
ctio
n[A
TDC
]
θexp [ATDC]
Tad-fittingTchem-fitting
Before optimization After Optimization
y = 1.11 x + 4.89 Prediction case:18/48
y = -0.30 x + 19.68 Prediction case:48/48-10
0
10
20
30
40
50
60
70
80
0 20 40 60
θ pre
dict
ion
[ATD
C]
θexp [ATDC]
TadTchem
Tad fitting Tchem fittingA
n 1.8 1.3B 3700 3850V 0.08 0.20
0.017RON100
.
0.011RON100
.
τ Ap expBT
20/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
-101030507090
θkno
ck [A
TDC
] Experimental ResultsPredicted withTadPredicted with Tchem
Engine Speed 1300rpm 2000rpm 4000rpm 5200rpm
RON 75 83 91 100 75 83 91 100 75 83 91 100 75 83 91 100CR 121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314
Before Optimization
Prediction results(before optimization)
Tad:Prediction of Low Engine Speed → Better predictionPrediction of High Engine Speed → Difficult
Tchem:Prediction of 100RON → Better predictionPrediction of low RON → Difficult
※No data: Predictions are failed
21/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Engine Speed 1300 2000 4000 5200
RON 75 83 91 100 75 83 91 100 75 83 91 100 75 83 91 100CR 121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314
-101030507090
θkno
ck [
ATD
C]
Experimental ResultsPredicted withTad-fittingPredicted with Tchem-fitting
After Optimization
Prediction results(After optimization)
Knock prediction with Tad, Tchem w/optimization→ High accuracy area is shifted
Issue of Livengood-Wu Integral prediction is high accuracy of wide range condition.
※No data: Predictions are failed
22/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
23/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
200
400
600
800
1,000
Tem
pera
ture
[K
]
0.0
2.0
4.0
6.0
Pres
sure
[M
Pa]
1300rpm2000rpm5200rpm
0.0
0.5
1.0
1.5
2.0
0 10 20 30
Live
ngoo
d-W
u In
t. [-]
time [s]
Livengood-Wu Integral of 75RON fuel
Solid line:Experimental Knocking TimingDash line:Predicted Knocking Timing
Prediction Accuracy is Low
Temperature and the pressure of the knocking occurrence timing is low.→Gradient of the Livengood-Wu
integral becomes small.
Ignition retarded operation:-High compression ratio engine-Turbocharged downsized engine
Ignition delay time under 700K~800K is important
24/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
200
400
600
800
1,000
Tem
pera
ture
[K
]
0.0
2.0
4.0
6.0
Pres
sure
[M
Pa]
1300rpm2000rpm5200rpm
0.0
0.5
1.0
1.5
2.0
0 10 20 30
Live
ngoo
d-W
u In
t. [-]
time [s]
Livengood-Wu Integral of 100RON fuel
Solid line:Experimental Knocking TimingDash line:Predicted Knocking Timing
Prediction Accuracy gets high
Temperature and the pressure of the knock occurrence timing is high.→Gradient of the Livengood-Wu
integral becomes large.
25/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
26/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Knock and cycle-to-cycle variation
TemperaturePressure Mixture(Air excess
ratio)
Tumble flow
Heat exchange at wall
Mixture formation
Combustion speed
Direction of flame propagation
Variation which effect on the
knock
Cause of cycle-to-cycle variation
27/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Knocking and cycle-to-cycle variation
Should we know the effect of the initial temperature variations on the knocking occurrence timing?
Initial temperature variation
0
1000
2000
3000
4000
5000
6000
-90 -60 -30 0 30 60 90
Pres
sure
[kPa
]
CA [ATDC]
Pressure variation
average200 cycle
200400600800
1000120014001600
0.000 0.005 0.010 0.015 0.020 0.025Te
mpe
ratu
re [K
]Time [s]
∆10K
∆3.5CA
Experimental condition:91RON, CR13, 1300rpmCalculation condition:CHEMKIN-PRO, LLNL-mech, PRF91
28/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
0.0
1.0
2.0
3.0
4.0
∆C
A / ∆
T [C
A/K
]
The effect of the initial temperature variations on the knocking timing
The effect of the initial temperature on knocking timing becomes large with low RON fuels and high compression ratio.
Engine Speed 1300 2000 4000 5200
RON 75 83 91 100 75 83 91 100 75 83 91 100 75 83 91 100CR 121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314121314
∆T: Rate of initial temperature variation [K]∆CA:Rate of knocking timing variation [CA]
Increase with high CR Increase with low RON
29/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
4. Discussion(1) Issue of low RON fuels for LW integral prediction(2) Effect of the cycle-to-cycle variation
1. Introduction
2. Engine experiment and analysis method
5. Summary
3. Results of Livengood-Wu integral for knocking prediction
Contents
30/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
2. Future direction2. Future direction
• High compression ratio engines and turbocharged engines are being introduced into the market. With these engines, knocking prediction accuracy becomes low because the impact of NTC becomes large.
• With low RON fuels and high compression ratio condition, knocking occurrence timing is affected by the long time low temperature oxidation reactions. This factors make the accuracy of LW- integral prediction low.
• With those condition, the effect of cycle-to cycle variation also need to be considered.
Summary
• Verify the knocking prediction from low compression ratio to high compression ratio (CR5-CR20) to improve the knocking prediction accuracy.
Future research plan
32/302nd Advanced Fuels and Engine Efficiency Workshop TOYOTA
Douautらによる着火遅れ期間
1.00E‐04
1.00E‐03
1.00E‐02
1.00E‐01
6.00E+02 7.00E+02 8.00E+02 9.00E+02 1.00E+03 1.10E+03
着火
遅れ
[ms]
初期温度 [K]
IFP_91RON_fai=1_Tad‐fit
1 bar10 bar20 bar30 bar40 bar50 bar60 bar70 bar80 bar