lean gasoline system development for fuel efficient small car · for fuel efficient small car halim...
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GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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Lean Gasoline System Development for Fuel Efficient Small Car
Halim Santoso - Presenter Stuart R. Smith - Principal Investigator GM Powertrain 2012 DOE Vehicle Technologies Annual Merit Review May 18, 2012
Project ID: ACE063
GM Powertrain Advanced Engineering
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• Project start: May 2010 • Project end: Sept 2013 • Project duration: 3 yrs 4m • Percent complete: 60%
• Improve the efficiency of light-duty passenger vehicles through:
– Engine Efficiency Improvement – Effective Engine Controls – Cost Effective Emission Control
• Total project funding: $15,411,724 – DOE share: $7,705,862 – GM share: $7,705,862 – Funding in 2011 $4,426,336
• Ricardo (combustion) • Bosch (fuel system) • Umicore (aftertreatment)
Timeline
Partners Budget
Barriers
Lean Gasoline System Development Overview
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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Demonstrate a lean gasoline engine system that achieves 25% fuel economy improvement compared to a 4-cylinder PFI engine in a mid-size sedan, while meeting T2B2 emissions.
• Fundamental combustion analysis and experimental investigation to generate knowledge that would support implementation across engine families
• Novel Lean after-treatment hardware and strategy developed
• Engine and after-treatment controls development within production controls constraints
3
Lean Gasoline System Development Relevance – Program Objective
GM Powertrain Advanced Engineering
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Lean Gasoline System Development Approach / Strategy – Targeted Efficiency Improvement
Advanced Dilute Combustion (direct injection, cool EGR,
high energy ignition) 3-5%
Lean Dilute Combustion and Aftertreatment
(closely-spaced multiple pulse injection)
6-10%
Vehicle Integration (12V stop/start, active thermal management)
4-6%
Downsizing (2.4L PFI to
1.4L DI Turbo) 6-10%
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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Lean Gasoline System Development Approach / Strategy – Technology Development Progression
Pha
se 1
In
itial
Con
cept
P
hase
2
Ref
inem
ent
Pha
se 3
O
ptim
izat
ion
May ‘10
May ‘11
May ‘12
Sep ‘13
May ‘13
2.2L NA Lean Engine
Lean Boost Controls
Engine & Aftertreatment Controls
Vehicle Integration & Calibration
Gen 1 Passive SCR Development
2.2L Experimental Lean Boost
Downsize Boost Simulation
1.4L Lean Boost Design
Active SCR Development Gen 2 Passive SCR Development
12v S/S & ATM Integration
Vehicle FE Optimization FE Demo
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GM Powertrain Advanced Engineering
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Combustion
Use CFD, spray lab and single cylinder dynamometer to define boosted lean combustion system prior to multi-cylinder engine design, procurement & development
Aftertreatment
Intake Temp = 60
C •Flame follows rich mixture and flow • Rich mixture position varies w/ temp • Flame motion f(heat release, flow)
Use system level engine and aftertreatment modeling techniques to drive refined exhaust architecture selection and aftertreatment emission control development
Lean Gasoline System Development Approach / Strategy – Development Process
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Lean Gasoline System Development Accomplishments – Phase 1: Lean Combustion Controls
Strategies for lean combustion and passive SCR implemented into production controls Transition from homogeneous to stratified without significant torque disturbance
Lean stratified torque model integrated into production torque structure • Hi Flow EGR control • Fuel mode transitions • Passive SCR NH3 generation
control strategies • Initial 12V Stop / Start
controls for lean combustion
Homogeneous to Lean Stratified Transition
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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Improvement
0 to -2%
5%
10%
10 to 20%
20 to 30%
Lean operation shows significant fuel economy improvement at light to medium loads Need to extend the lean operating range to higher loads Lean combustion systems is not very efficient in stoichiometric homogenous mode
Lean Gasoline System Development Accomplishments – Phase 1: Naturally Aspirated Fuel Economy
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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Boosted combustion enables leaner operation at higher loads through increased trapped air mass capacity while maintaining high EGR level for NOx emission control Fuel economy improvement from: • Lower heat transfer to
coolant • Lower exhaust gas
enthalpy
9
Lean Gasoline System Development Accomplishments – Phase 2: Exploratory Boosted Lean Combustion
2500 RPM 8 bar BMEP
Fuel
ene
rgy
(%)
Boost is key enabler to run lean at higher loads
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Lean Gasoline System Development Accomplishments – Phase 2: Exploratory Boosted Lean Combustion
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1565/28 1805/29 1410/51 1821/80 1530/95 1692/100 1461/114 1700/120 2000/175
2.4L PFI
2.2L Lean Stratified
2.2L Boosted Lean Stratified
Nor
mal
ized
BSF
C
RPM/Tq (Nm)
The fuel economy improvement of the naturally aspirated lean stratified engine reduces from 20% to 10% as the load increases from 25 Nm to 50 Nm The highest naturally aspirated load that can be operated in lean stratified is ~85 Nm Boosting the engine allows us to run lean up to 175 Nm
BSFC comparison: PFI to Lean to Boosted Lean
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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5
7
10
10
15
0 5 10 15
2.2L NA SG5 Swirl widely-spacedsolenoid multi-hole
2.2L Boosted Swirl SG5 widely-spaced solenoid multi-hole
2.2L Boosted Swirl SG5 closely-spaced solenoid multi-hole
1.4 L 1st-stage Boosted Swirl SGEclosely-spaced solenoid multi-hole
Reference 2.0L Boosted Low-Tumble Multi-Pulse Bosch A-cone
BMEP
11
Lean Gasoline System Development Accomplishments – Phase 2: Closely-Spaced Injection
Sep ‘11
Aug ‘11
Jan ‘11
reference development
Boosted combustion with closely-spaced solenoid injection enables 90% of FTP and Hwy cycles to be operated in lean stratified with 1.4L boosted engine
Phase 3 Plan
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High energy ignition enables higher EGR tolerance at low and mid load • EGR tolerance was increased from
15 to 35% with constant AFR
• 4% BSFC reduction can be achieved at lower load condition
12
Lean Gasoline System Development Accomplishments – Phase 2: High Energy Ignition
0
3
6
9
12
0 10 20 30 40 50 60
CoV
of I
MEP
(%)
EGR Rate [%]
COV of IMEP
1500 RPM, 3 bar BMEP, 27 AFR
High energy ignition will enable improved fuel economy at the same engine out NOx levels
92
96
100
0 10 20 30 40 50 60
Nor
mal
ixed
BSF
C (%
)
EGR Rate [%]
BSFC Comparison
HE IgnitionStock Ign
1500 RPM, 3 bar BMEP, 27 AFR
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Boosted Stratified
Boosted Homogeneous (turbo speed limited)
Lean Gasoline System Development Accomplishments – Phase 2: Turbo Matching for Boosted Lean
Turbocharger is aggressively sized to provide the maximum potential efficiency gain while providing the large mass flow required to support lean operation
Turbo Matching • Restricted selection to single stage turbo, biased selection to meet low speed stratified rather than
peak power charging requirements. System solution may eventually drive multi-stage charging.
GM Powertrain Advanced Engineering
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GM Powertrain Advanced Engineering
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0
200
400
600
0 250 500 750 1000 1250 1500 1750
Tem
p de
g-C
FTP test time (sec)
SCR temperatures during the FTP
R Rear SCR Rear
UF SCR Mid
Lean Gasoline System Development Accomplishments – Phase 1: Passive SCR Aftertreatment
Passive SCR – NH3 is generated across three way catalyst • Passive SCR system installed and currently being calibrated • Front SCR too hot to store NH3 effectively, may require exhaust thermal management • Not able to meet target NOx efficiencies at high loads • Need to be able to generate NH3 more efficiently at high loads (FE penalty increasing)
Passive SCR currently has thermal limitations resulting in missing T2B2 emission target
RICH: LEAN:
NH3
NOx
RICH
LEAN
H2O
N2
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Lean Gasoline System Development Accomplishments – Phase 1: Passive SCR CO reduction Passive SCR system generates excess CO during NH3 generation event • Continuing to investigate washcoat
formulations to improve NH3/CO ratio • Currently require additional CO clean-up
catalyst downstream of TWC
00.5
11.5
22.5
33.5
44.5
5
0 500 1000 1500 2000
TP CO [g/mile]
CO Breakthrough during NH3 generation
NH3 generation
FTP Test time (sec)
Passive SCR currently generates excess CO resulting in missing T2B2 emission target
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Lean Gasoline System Development Accomplishments – Phase 2: Active SCR Aftertreatment
Active SCR is more capable than passive and without fuel economy penalty Phase 2 will leverage passive SCR at light loads to reduce urea consumption
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 100 200 300 400 500 600 700 Temperature in SCR1 Brick [
C]
NO
x C
onve
rsio
n Ef
ficie
ncy
[-]
0
50
100
150
200
250
300
350
400
NH
3 Sl
ip SCR-4 Passive Sys
GM SCR-5 Supplier Data
SCR-5 Modified SCR 1 Cone
SCR-6 "Torpedo" SCR eta
SCR-4 NH3 slip Post SCR1
SCR-5 NH3 slip Post SCR1
SCR-6 "Torpedo" Slip ;
NOx conversion and NH3 slip vs SCR Temperature Passive and Active (urea) SCR systems
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Lean Gasoline System Development Collaboration – Key Supplier Involvement
The program is partnering with the following suppliers in order to develop a common understanding of the integration challenges to implement lean gasoline systems in to production
• Ricardo - Combustion knowledge and analysis techniques as well as a broad knowledge of lean combustion systems
• Bosch – Injector hardware including spray geometry and small closely-spaced pulse capability
• Umicore – Aftertreatment knowledge for lean gasoline and diesel systems, analytical and production field experience
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Lean Gasoline System Development Future Activities – Phase 3: 1.4L Downsized Lean Boost Engine
Cooled High-Flow EGR System
Closed Coupled Catalyst Exhaust
Compact Turbocharger Assembly
Split Port Swirl Cylinder Head
Port De-Activation
Optimized Spray Guided Pistons
Central Direct Injection w/ Close-Spaced Pulses
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Lean Gasoline System Development Future Activities – Phase 3: Vehicle Integration and Aftertreatment
Vehicle Integration • Integrate 12V stop/start into lean combustion
system and controls • Develop and calibrate lean boosted controls for
refined drivability Thermal Management • Integrate “controlled flow” water pump concept
into 1.4L lean boost engine • Develop and integrate the automatic
transmission thermal system Aftertreatment • Integrate passive and active aftertreatment to
optimize emission performance and minimized urea consumption
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Lean Gasoline System Development Summary Phase 1 – Initial Development – FY10 to FY12 • Controls strategies for lean combustion and passive SCR are implemented on the
naturally aspirated lean combustion engine and exhaust system • Lean operation shows significant fuel consumption improvements at light to medium
load, though did not meet target with naturally aspirated engine Phase 2 – Experimental Refinement – FY11 to FY12 • Fundamental analysis and hardware experimentation undertaken to explore boosted
lean combustion with substantial efficiency gains realized • The passive SCR aftertreatment was refined to provide significant NH3 production,
though generates excessive CO and lacks sufficient thermal operating range • The active SCR aftertreatment demonstrates a significant NOx reduction Phase 3 – Future Optimized System – FY12 to FY13 • Fuel economy optimization with a 1.4L downsized lean boost engine • Lean combustion controls development for boosted operation • Vehicle optimization with 12V stop/start and thermal management integration • Aftertreatment optimization to achieve target of T2B2