Potential of the Mild HCCI Combustion for Worldwide Applications

Future Fuels for IC EnginesERC Research Symposium – Madison – June 6-7, 2007

P.Gastaldi – M.Besson – JP.HardyRenault Powertrain Division

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Overview

• The Diesel engine : a customer oriented product within the planetary challenge for reducing CO2

• Potentials and threatens

• The Mild HCCI as a promising Low Temperature Combustion system.

• Mild HCCI and available fuels

• Future combustion systems for future fuels or future fuels for future combustion systems ?

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The Diesel engine : a customer oriented productwithin

the planetary challenge for reducing CO2

Part 1

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Satisfying customers is the main task for automotive manufacturers

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The Diesel Engine : a large success in Europe linked to upgraded technologies

0%

10%

20%

30%

40%

50%

60%

1990 1992 1994 1996 1998 2000 2002 2004 2006

VariableTurbo

Commonrail

1st gen.

Commonrail

2nd gen.

TurboDIE

urop

ean

Die

sel m

arke

t sha

re(d

ata

from

AC

EA)

Fuel EconomyPerformances

Noise

Emissions

Technological advances deeply linked to customer requirements

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By its high fuel efficiency, the Diesel engine is up to now the best

contributor for reducing the CO2 rejections due to road transport

The Diesel engine and the environment

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140

150

160

170

180

190

200

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

CO

2 (g/

km)

0%

10%

20%

30%

40%

50%

60%

gasolineDieseltotalDiesel market share

Improvement of averaged CO2 emissions(Western Europe – ACEA data)

Higher market share

Stronger reduction of

the fuelconsumption

Contribution of both

and

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Part2 : Potentials… and threatens

CO2Driving pleasure

Low noise

PotentialsCost

Andthreatens

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0

0,1

0,2

0,3

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0,7

0,8

1995-2000 2000-2005 2005-2008 2008-2011 2011- ?

NO

x &

10*

PM (g

/km

)

NOx

Soot

Euro 3

Euro 4Euro 5

?

NOx trap ?

Oxycat

CSF

0

50

100

150

200

Euro 3 Euro 5 Euro 3 Euro 5

Injection system

turbocharger

aftertreatment

Base engine

1.5 dCi66kW / 200Nm

1.6 MPI72kW / 127Nm

0

50

100

150

200

Euro 3 Euro 5 Euro 3 Euro 5

Injection system

turbocharger

aftertreatment

Base engine

1.5 dCi66kW / 200Nm

1.6 MPI72kW / 127Nm

Strategies for Euro5/6/US

Advanced after-treatment

NOx-trap, SCR

ReductionReduction ofof EngineEngineout out EmissionsEmissions

New combustionNew combustion

Two different strategies for the future

A challenge for the future : protecting the environmentat an acceptable cost…

25% of the engine cost is due to the after-treatment

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… on worldwide markets

Low CO2High performances

High fuel quality

High torqueSUV

Very low emissionsDifficult conditions

Low costlow fuel quality

The combustion system must be compatible with worldwideapplications to reduce costs

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Part 3

The Mild HCCIas a promising

Low Temperature Combustion system

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A low temperature combustion : the key for the future ?

0

0,5

1

1,5

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3,5

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4,5

5

1200 1400 1600 1800 2000 2200 2400 2600 2800Combustion temp. [K]

Loca

l Equ

ival

ence

Rat

io [-

]

#2cold & stratified

#3cold & lean

#1rich & hotMaterialreliability

Stability,HC

Rich

"conventional" combustion

Lean

Soot

NOx

Only solution #3 seems to be feasible in the near future

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The split injection as a way of realising a low temperature combustion

BTC Heat release

Combustion due to the first injection

Fuel vaporised during the second injection is cooling the first combustion

Combustion due tothe second injection

Fuel quantities and respective phasing of the two injections aregoverning the noise/soot trade off

The combustion is actively controlled by the injection

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Mechanism of the split injection

-5,0 2,5 10,0 17,5 25,0 32,5 40,0Crank Angle CA

dQ(k

J/m

3.D

eg)

-10

15

40

65

90

115

140

3

5

7

SOI after TDC (CA)(2nd injection) Mass burnt rate

2 “almost” independentcombustions

2nd one late in burnt gasesCool flame

High cooling due to 2nd injection

late “fully” premixed combustion

2nd diffusive combustion

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Mild HCCI definition

HCCI because a noticeable part of the fuel is injectedearly in the compression cycle to get a homogeneousmixture and to secure a quasi fully premixed combustion

mild because the second part of the fuel is injected later onin the cycle and can burn as a diffusive flame

associated to a quite conventional Euro4 chamber design andtherefore allowing competitive full load performances

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Mild HCCI results: simulation on a NMVEG cycle (hot)Renault Laguna, 6 gear manual transmission

1061044804003505022Mild HCCI

100100100100100100100conventional

f.c.(l/100km)

CO2COCH4HCIOFNOx

Calculated engine out emissionsnoise level equivalent to Euro4 version

(rough estimation of transitions between combustion modes)

HCCI strategy is successfully reducingboth NOx and soot Engine Out Emission High penalty on hydrocarbons

and especially methane

Fuel consumption mustbe reduced

Euro4 / 10 ppm S

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Part 4

Mild HCCI and available fuels

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Mild HCCI and worldwide representative fuels

Test engine :4 cylinder 2.0 liter 84x90 mm CR 16 engine with HP and LP EGR

Fuels

29028025728050% vaporized(°C)

0.007000O/C

103001010Sulfur level(ppm)

54544454Cetane

41.442.542.942.9Heating value(MJ/kg)

B30(30% Diester)

Euro 3USEuro 4

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Full load results

No noticeable difference between Euro4, Euro3 and US fuels even with thesame tuning

For B30, low reduction of performance ( ~3%) due to a lower heating Valuebut lower smoke level at 4000 rpm ( ~0.5 FSN)

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The longer delay dueto the low CN iscompensated by thehigher combustionvelocity in pre-mixedmode.

Detailed comparison between US and Euro4 at 4000 rpm full load

-15.0 -7.5 0.0 7.5 15.0 22.5 30.0 37.5Angle vilebrequin [deg]

EVL1

[V]

-20

0

20

40

Th2d

Q1

[kJ/

m3d

eg]

-100.0

12.5

125.0

237.5

350.0

Th2I

nt1

[kJ/

m3]

1000

3750

6500

9250

12000D2344271.003D2344269.003

Gazole USEuro4

Same injection timing

0

0.5

1

1.5

2

2.5

0.65 0.7 0.75 0.8R

Fum

ée [F

SN]

Euro4

Gazole US

Same smoke vs equiv.ratio

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Part load results US versus Euro4 analysis at 2000 rpm 6 bars BMEP same engine tuning same moderate EGR rate

-15.0 -7.5 0.0 7.5 15.0 22.5 30.0 37.5Angle vilebrequin [deg]

EVL1

[V]

-30

80

190

300

Th2d

Q1

[kJ/

m3d

eg]

-20

30

80

130

180

Th2I

nt1

[kJ/

m3]

400

850

1300

1750

2200D2344243.002D2344280.007

gazole Euro4gazole US

With Euro4 fuel, the firstcombustion is effectivelyslowed down by the secondinjection

With US fuel, the lowcetane leads to a highdelay => there’s onlyone retarded combustion

US versus Euro4 :- 25% NOx- 10 dBA+ 100 % HC+ 15% BSFC

Two injections

Too late combustion leading to unacceptable BSFC

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Conclusion for US fuel

NOx [g/kWh]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

2 3 4 5 6

CO2rg [%]

Covariance PME

0

0.5

1

1.5

2

2.5

2 3 4 5 6

CO2rg [%]

This late combustion leads to a poor acceptance of EGR rates compatible witha fuel neutral target > necessity to move to earlier injection timing for the 2 injections

NOx target Sigma BMEP

Combustion becomesunstable with US fuel

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Part load results Euro3 versus Euro4 analysis at 1750 rpm 7 bars BMEP same engine tuning same moderate EGR rate

Very close combustionBehavior

no difference foremissions and BSFC

soot +30% due to Sulfur level

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Conclusion for Euro3 fuel

IOFCL [mg/s]

0

1

2

3

4

5

0 0.5 1 1.5 2 2.5 3

NOx [mg/s]

N O x [mg /s]

1.0

2.0

3.0

4.0

Euro4

Euro3

For Euro3 fuel, high EGR rates are forbidden due to important soot emissions⇒ NOx reduction and compliance with Fuel Neutral is impossible⇒ Engine tuning has to be modified

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Part load results B30 versus Euro4 analysis at 2000 rpm 6 bars BMEP same engine tuning same moderate EGR rate

-7.5 -0.0 7.5 15.0 22.5 30.0 37.5 45.0Angle vilebrequin [deg]

EVL1

[V]

-30

40

110

180

Th2d

Q1

[kJ/

m3d

eg]

-15

30

75

120

165

Th2I

nt1

[kJ/

m3]

450

875

1300

1725

2150D2344368.004D2344381.004

B30 iso CO2rg=4,6%Euro4 iso CO2rg=4,6%

Reduced ignition delayfor the first combustion

Slightly higher noiselevel (+ 2 dBA)

Lower smoke level dueto Oxygen in the fuel

BSFC higher with B30but efficiency is the same

Engine tuning could be common for both Euro4 and B30 fuels

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B30 fuel results: simulation on a NMVEG cycle (hot)Renault Laguna, 6 gear manual transmission

B30/Euro4 optis

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-5%

0%

5%

10%

15%

20%

25%

30%

Nox IOF HC CO CO2 CH4 CSE

B30/Euro4 optis

But lowerspec.heatingvalue > sameefficiency

NOx level compatible with “fuel neutral” hypothesisNoise level equivalent to Euro4

Only one penalty on CH4 > oxycat light off to be secured

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Part load optimisation with Euro4 and US fuels analysis at 2000 rpm 6 bars BMEP constant very low NOx level

Retarded combustionfor Euro4 fuel

Slightly higher BSFC

Roughly one advancedcombustion allowed bythe low soot level for US

Low cetane and highvolatility compensatesthe earlier injection

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Part load optimisation with Euro4 and US fuels analysis at 2000 rpm 6 bars BMEP constant very low NOx level

y = 0.8092x + 4.9938R2 = 0.9917

y = 0.6667x + 3.6667R2 = 0.9383

0

5

10

15

20

25

0 5 10 15 20 25

tuning Euro4

tuni

ng U

S

Timing inj.1

dwell

Slightly delayedinj1 timing for US

Linear correction on injection timing easily achievablein the ECU

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US fuel results: simulation on a NMVEG cycle (hot)Renault Laguna, 6 gear manual transmission

NOx level compatible with “fuel neutral” hypothesisNoise level equivalent to Euro4

HC and CO penalties on cycle (overmixing effect due toa high volatility ?)

US versus EU4 fuel

-20%

0%

20%

40%

60%

80%

100%

120%

Nox IOF HC CO CSE

US/Euro4 at NOx target

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Part load optimisation with Euro4 and Euro3 fuels analysis at 2000 rpm 6 bars BMEP

constant very low NOx level

y = 1.0091x + 0.3148R2 = 0.9913

y = 1.1053x - 0.9474R2 = 0.9671

0

5

10

15

20

25

0 5 10 15 20 25

Euro4 tuning

Euro

3 tu

ning

Timing inj1

dwell

y = 1.7616x - 0.642R2 = 0.9941

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00

Euro4 tuning

Euro

3 tu

ning

Ti1/Ti2

NOx level compatible with “fuel neutral” hypothesisNoise level equivalent to Euro4

Linear corrections for Euro3versus Euro4 tuning

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• The mild HCCI combustion system is compatible with fuels representative of worldwide availability as with 1st generation bio. ones– At full load eg for down-sizing strategies– within a “fuel neutral” hypothesis (simulation result –

transitions to be optimised)

• HC, CH4 and CO have nevertheless to be secured, especially for cold start

• Fuel consumption has still to be reduced for all the fuels (Euro4 vehicles still the target)

Conclusion

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Fuels and combustion for the future

(tests achieved on a Renault Megane on New European Driving Cycle)

The Well to Wheel approach is the key parameter to quantifythe actual interest on new fuels…

as for thecurrentlyexisting B30

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Part 5: New combustion systems and new fuels…

…are like tango couples

They could be the best if they remain togetherBut they still have to be performantif they change partner and orchestra

Thank you for your attention

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Fun to drive and economic

-30%

-20%

-10%

0%

10%

20%

30%

40%

Euro2(1996)

Euro3(2002)

Euro4(2007)

K9K 1.5l DI TC 106ch

VehiclePerformanceindex

FuelConsumption

F9Q 1.9l DI TC 100ch

Euro5?(???)

G8T 2.2l IDI NA 87ch

Improved technologies and down-sizing