Lean Gasoline System Development for Fuel Efficient Small Car · for Fuel Efficient Small Car Halim...

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




This presentation does not contain any proprietary, confidential, or otherwise restricted information 2

• 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





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





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%





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





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





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





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





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





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





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





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





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.





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





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





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





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





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





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





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

Lean Gasoline System Development for Fuel Efficient Small Car · for Fuel Efficient Small Car Halim...

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