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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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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0
0,1
0,2
0,3
0,4
0,5
0,6
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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A low temperature combustion : the key for the future ?
0
0,5
1
1,5
2
2,5
3
3,5
4
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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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
-10%
-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