deer12_kleeberg.pdf (1.65 mb)
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Detroit, October 16-19, 2012 [email protected]
Combustion Development Methodologies and Challenges for Smaller Boosted Engines
H. Kleeberg, S. Bowyer, D. Tomazic (FEV, Inc.) J. Dohmen, C. Schernus, B. Haake (FEV GmbH)
18th DEER Conference 2012
© by FEV – all rights reserved. Confidential – no passing on to third parties
Content
Introduction
Downsizing Challenges – Boosting – Oil Dilution – EGR
Summary
Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16 2
© by FEV – all rights reserved. Confidential – no passing on to third parties
Coping with CO2 targets: Load point shift by Downsizing
Ways of Downsizing: Smaller Displacement by Smaller cylinders Less cylinders
– 6 4 – 4 3 – 3 2 or 4 2 (e.g. Fiat Cinquecento)
Engines with less cylinders expected in many places City cars Compact cars … Full size + luxury vehicles: e.g. some V8 T/C 6-cyl.
Cutting cylinders will be applied more frequently
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Introduction
© by FEV – all rights reserved. Confidential – no passing on to third parties
Downsized Engine Boosting Tool Chain
4 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting
Same torque & power, smaller displacement Similar amount of air per cycle
⇒ air density ↑
Single stage turbo with limited full load speed range
2-stage turbo or super-turbo enables larger spread from low-end to rated speed
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Ref.: Schernus, Wedowski, Sauerstein et al., “Vehicle Demonstrator w/ 2-stage turbo SI engine”, GT-SUITE Conf. 2009
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
2-stage boosting ⇒ same wide-range torque and power from even smaller displacements
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5
10
15
20
25
30
0 2000 4000 6000 8000
Scatter bandFEV
Engine Speed / rpm
BM
EP
/ ba
r
Target
GDI
PFI
Scatterband T/C-Engines 80 kW/l
100 kW/l
120 kW/l
Large Turbocharger = LP-Stage
compressor mass flow
com
pres
sor
pres
sure
rat
io
nTC = const.
surge line
choke line
large compressor
compressor mass flow
com
pres
sor
pres
sure
rat
io
nTC = const.
surge line
choke line
large compressor
Small Turbocharger =
HP-Stage
compressor mass flow
com
pres
sor
pres
sure
rat
io
nTC = const.
surgeline
chokeline
small compressor
compressor mass flow
com
pres
sor
pres
sure
rat
io
nTC = const.
surgeline
chokeline
small compressor
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting: Influence of cylinder number
7 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
90 180 270 360 450 540 6300,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
0
2
4
6
8
10
°Crank Angle
Val
ve L
ift /
mm
pcyl
pExh
pInt
Valv
e Li
ft / m
m
Example 1500 rpm 4-Cyl.
pExh < pInt → pExh > pInt
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting: Influence of cylinder number
8 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
3-Cylinder engine ideal for turbocharging ⇒ high scavenging potential ⇒ very low residual gas fraction ⇒ good for knock mitigation
90 180 270 360 450 540 6300,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
0
2
4
6
8
10
Pre
ssur
e / b
ar
°Crank Angle
90 180 270 360 450 540 6300,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
0
2
4
6
8
10
°Crank Angle
Val
ve L
ift /
mm
pcyl
pExh
pInt
pExh << pInt
Pre
ssur
e / b
ar
Valv
e Li
ft / m
m
Example 1500 rpm 3-Cyl. Example 1500 rpm 4-Cyl.
pExh < pInt → pExh > pInt
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting: Influence of cylinder number
Compressor loop of a 2-cylinder engine Less than 3 cylinders:
9
Discontinuous sequence of intake strokes
Turbo compressor operating point shifts toward surge in breathing pauses
Counteraction increasing intake volume delays response
Supercharger alternative solution for PR ≤ 2.5
Boosting small cylinder numbers requires special attention
Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting: Turbo Maps Pressure pulsation of a 4 cylinder engine
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0 180 360 540 720Crank Angle
Exha
ust G
as P
ress
ure
high energy content at pressure peaks Standard turbine measurement
Extrapolation of turbine operation
Extrapolation ⇒ simulation errors B
SFC
[ %
] 100
95
90
85
105
Mea
sure
men
t
Sim
ulat
ion
with
ext
rapo
latio
n
Simulation Results (here: @ low end torque)
Simulations play an important role in TC engine development
Proper input data required
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Extended Turbine Mapping Toolkit
11 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Compressor Closed Loop Turbine Dynamometer
Run Away Measurement TC Friction Testing
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Boosting: Obtaining the right maps for simulation
Hot Gas Test Bench w/ Compressor Closed Loop (CCL) Benefits from CCL
12
CCL enables higher/lower inlet pressure CCL LP (low pressure):
– compressor inlet density ↓ – Less turbine power, p5/p6 ↓
CCL HP (high pressure): – compressor inlet density ↑ – More turbine power, p5/p6 ↑
Significant increase of p5/p6 range
Reliable data for predicting turbine power in pressure peaks (pulse turbocharging)
Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Special Turbocharger Measurement Techniques Example
�̇�𝑟𝑟𝑟
𝜼
CCL LP CCL HP
Downsizing Challenges: Boosting
Standard
∆PR * 5
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Extended Turbine Models for Reliable Performance Prediction in any Operation
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Compressor Closed Loop Turbine Dynamometer
Run Away Measurement TC Friction Testing
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 turbine pressure ratio
redu
ced
mas
s flo
w /
kgK
0.5 /s
bar
Downsizing Challenges: Boosting
© by FEV – all rights reserved. Confidential – no passing on to third parties
Fuel Injection
Same torque & power, smaller displacement Similar amount of fuel per cycle
– Similar injection amount with same cylinder number – Larger injection amount with less cylinders
Fuel spray length / bore ↑ ⇒ risk of wall wetting – Oil dilution – HC and soot – Higher risk of pre-ignition from stripped fuel-oil droplets
Injection technology needs adaptation – Injection pressure – Multiple injections
Approach: Experimental and Computational Analysis and Experimental Validation
14 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Downsizing Challenges: Fuel Injection & Oil dilution
© by FEV – all rights reserved. Confidential – no passing on to third parties
Charge Motion Design for heavily downsized gasoline engines
Charge motion must involve all of the charge to provide a homogenous mixture
15 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
GT² Base
Hig
her v
eloc
ities
Bet
ter c
onse
rvat
ion
Filling port concept High Tumble Concept
Downsizing Challenges: Charge Motion
© by FEV – all rights reserved. Confidential – no passing on to third parties
CFD Evaluation of Wall Wetting
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0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4Full Load @ 5000 rpm
Swirl Injector Multi Hole Injector
Weig
hted W
all C
onta
ct [-]
360 420 480 BDC 600 660 7200.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4Full Load @ 5000 rpm
Swirl Injector Multi Hole Injector
Weig
hted W
all C
ontac
t [-]
[°CA ATDC]
Liner
All Surfaces
Cylinder center line piston @ BDC
Valve center line
Swirl Injector
Multihole Injector
Downsizing Challenges: Fuel Injection & Oil dilution
© by FEV – all rights reserved. Confidential – no passing on to third parties
Injection and Oil Dilution
Standardized Test Procedure
17 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
Downsizing Challenges: Fuel Injection & Oil dilution
- Dilution analysis method: Gravimetry for Gasoline Fuels
- Operating duration: 1 h- Coolant temperature: 50 °C- Oil temperature: uncontrolled- Production PCV system- Oil/Fuel acc. to OEM specs
Oil Dilution
2500 rpm / BMEP = 10 bar
Oil
Dilu
tion
/ h [%
]
0
2
4
6
8
10
12
14
16
18
20
Rel. AFR [-]0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10
Scatter bandFEV
B15004a
Lower limitSolenoid DI
Example DISI T/C Injector Type A High Penetration
Example DISI T/C Injector Type B Low Penetration
© by FEV – all rights reserved. Confidential – no passing on to third parties
Cooled EGR benefit
CR increase by 2 units and fuel consumption benefit of 5% possible n = 1500 1/min, IMEP = 35 bar, rel. AFR= 1.0, with scavenging, RON 95
18 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
0
10
20
30
4033.6 34.4
Peak Pressure Position / °CA ATDC
80
100
120
140
112119
Peak Pressure / bar
0
2
4
6
8
1.5
COV of IMEP / %
1.1
230
240
250
260
270262
247
ISFC / (g/kWh)
-5%
CR: 8 CR: 10 6% cooled EGR
CR: 8 CR: 10 6% cooled EGR
Downsizing Challenges: EGR
© by FEV – all rights reserved. Confidential – no passing on to third parties
Cooled HP/LP EGR
19 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
EGR & increased backpressure reduce volumetric efficiency
Higher boost pressure required
Higher turbine power required Higher backpressure: turbine power
Increase of ∆p ?
EAT / Routing ?
T2-max to be protected w/ EGR
5 6
1 2 3
4
Exhm
InmCm
TmpBack
Vol. Effic.
λ LPmHPm
Downsizing Challenges: EGR
© by FEV – all rights reserved. Confidential – no passing on to third parties
EGR = F.E. benefit for T/C GDI Map = example for turbocharged gasoline engine 2.0l class
20 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
BM
EP /
bar
Engine Speed / rpm
Target: knock reduction FC benefit Solution: Cooled external EGR Challenges: Interaction with scavenging (HP – EGR) Transient boosting affected by additional HP EGR volumes only LP solution if best low end torque demanded
rel. A/F-Ratio=1
Physical effect: Dethrottle engine Solution: Internal or external (uncooled) EGR Challenges: none (state of the art)
0.9
0.85 0.8
Physical effect: knock reduction + reduced enrichment Solution: Cooled external EGR (HP or LP) Challenges: EGR cooling capacity Transient boosting affected by additional HP EGR volumes
Downsizing Challenges: EGR
© by FEV – all rights reserved. Confidential – no passing on to third parties
Conclusion
Future improvement of Downsizing engines Further reduction in size
– Advanced boosting systems – Appropriate cylinder dimensions – Matched injection technology
Proper control of auto-ignition (pre-ignition, knock, HCCI/RCCI) – Cooled LP+HP EGR – Thermodynamic cycle
Thermal management Friction
21 Kleeberg, DEER2012_FEV_BoostingSmallEngines.pptx, 2012-10-16
DEER Conference, Detroit, October 16-19, 2012 [email protected]
Combustion Development Methodologies and Challenges for Smaller Boosted Engines
Thank you for your attention!
Questions?