Effect of fuel components on abnormal combustion of the SI

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


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”


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


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


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


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


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


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


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



1. Introduction


5. Summary


Contents


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


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


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


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



1. Introduction


5. Summary


Contents


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


It seems that prediction accuracy is not enhanced with module optimization.

Comparison of experimental results and prediction results


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 = -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


-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


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



1. Introduction


5. Summary


Contents


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


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.



1. Introduction


5. Summary


Contents


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


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


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



1. Introduction


5. Summary


Contents


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


Thank you for your kind attention


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


詳細反応計算による着火遅れ期間

1.00E‐04

1.00E‐03

1.00E‐02

1.00E‐01

600 700 800 900 1,000 1,100

着火

遅れ

時間

[ms]

初期温度 [K]

LLNL_PRF91_fai=1

1 bar10 bar20 bar30 bar40 bar50 bar60 bar70 bar80 bar

NTC（Negative Temperature Coefficient）

Documents

Effect of fuel components on abnormal combustion of the SI