Low-Temperature Combustion for High-Efficiency, Ultra … · Low-Temperature Combustion for High-Efficiency, Ultra-Low Emission Engines. LTC University Consortium ... Point2 Point1

LTC University ConsortiumLTC University Consortium

University Consortium

University of MichiganMassachusetts Institute of Technology

Stanford UniversityUniversity of California, Berkeley

Dennis Assanis (UM)

12th Diesel Engine-Efficiency and Emissions Research (DEER) ConferenceAugust 20-24, 2006, Detroit, Michigan

Low-Temperature Combustion for High-Efficiency,Ultra-Low Emission Engines


Big Picture

• HCCI university consortium concentrated on– developing workable control systems– obtaining experimental data– developing analytical tools to optimize and assess

implementation ideas• LTC university consortium will focus on

– extending the practical operating range of LTC engines at both low and high load

– improve system fuel economy benefits– include PPCI engines and alternate fuels


Low Temperature CombustionPrecisely Control Combustionto Expand LTC Operating Range

• Maintain High Thermal Efficiency• Avoid pollution forming regimes

PhysicsExperiments

ModelingChemical Kinetics

Engine System Management:

Boosting; Thermal

In-cylinder measures:

Fuels, Injection; Assisted Ignition

FuelVaporizer

N2

Intake Canister

SCV valve

Heater

External EGR Line

ExhaustCanister

ThrottlePlate

Air Cleaner

FuelTank

Accumulator

Direct Injection

Fully

Pre

mix

ed

HydraulicDYNO

MechanicalTelemetry

Exhaust Gate Valve

FuelVaporizer

N2

Intake Canister

SCV valve

Heater

External EGR Line

ExhaustCanister

ThrottlePlate

Air Cleaner

FuelTank

Accumulator

Direct Injection

Fully

Pre

mix

ed

HydraulicDYNO

MechanicalTelemetry

Exhaust Gate Valve


LTC Consortium Tasks

1. Thermal management (UM)2. Combustion stability at low load

(UM)3. Engine control for extended

operation (MIT)4. Increased power density (UCB)5. DI studies for low load (SU)6. Emission control devices for

PPCI (UM)7. Spark assisted HCCI (UM)8. Ignition properties of alternative

fuels (UM)


UM Optical Engine UM Heat Transfer Engine

Stanford Camless EngineMIT Camless Engine UCB Multi-cylinder engine

Engine University Consortium Set-UpsUM Camless Engine


PPCI combustion regime in (Z, η ) plane

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1Z (mixture fraction)

J (E

GR

frac

tion)

(i-1)-th flameleti-th flamelet(i+1)-th flamelet

OXIDIZER

η

FUEL

Upper bound of initial η distribution

Lower bound of initial η distribution

EGR

Thermal and Compositional Stratification:Near-wall Conditions and Mixture Preparation

Stanford VVA engine

INJECTOR

CONTROLLER

1 23

4

7

5

61 2

3

4

7

5

6

UM Heat Transfer and VVA Engine

ReactantsEGR

L

ReactantsEGR

L

EGR

L

EGR+Air Fuel

RegenerativeMultipleFlamelets


Spark-Assisted Concepts:Expand the LTC Operating Range

Spark Plug

Prechamber

Orifice

Main Chamber

Burned GasesFresh Mixture

Spark Plug

Prechamber

Orifice

Main Chamber

Burned GasesFresh Mixture

SA-HCCIOpen Chamber

SA-PrechamberConcept

UM Optical Engine


From In-cylinder to Systems

-5

0

5

10

15

0 2000 4000 6000

BM

EP

(bar

)

RPM

LTC

Nat. AspiratedTurbo / Supercharged

FTPMAP

RANGEEXTENSION


Expanding the LTC Range:Turbo-charging and Exhaust Heat Recuperation

Computer controller

Airtank

Compressor

Heater Chiller

P,TSensor

P,TSensor

Exhaust

EMV engine

Valve timing control Computer controller

Airtank

Compressor

Heater Chiller

P,TSensor

P,TSensor

Exhaust

EMV engine

Valve timing control Exh. Gas

Hot Air

Cyl.Block

FastFlap

Valves

Cold Air


Aftertreatment Options for LTC Engine

0

1

2

3

4

5

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700 800

Norm CONorm HC

Temperature

Nor

mal

ized

Em

issi

ons

Temperature Turbine O

utlet (C)

BMEP (kPa)

Closecoupled

DOC

LTC/PCIEngine

DOC/DPF

UreaDecomposition

Catalyst

CO(NH2)2 + H2O↔ 2NH3 + CO2

Urea SCR

Ureainjector

FuelPost

Injection

HC SCR

NAC/LNT

Low Temperature Combustionleads to higher HC, CO


Thermal Management:Predictive HCCI Engine System Simulation

-10

0

10

20

30

40

-8 -6 -4 -2 0 2

BURN DATA

CA

(Deg

ATC

)

CA0 (Deg ATC)

EXPERIMENTALDATA POINTS

CURVE FITS

CA0

CA10

CA50

CA90

Intake port

Fuelinjector

Intakevalves

Exhaustvalves

Exhaust port

Combustionchamber

AIR

EXHAUST

Intake port

Fuelinjector

Intakevalves

Exhaustvalves

Exhaust port

Combustionchamber

AIR

EXHAUST

Auto-ignition delay expression

)/33700exp(103.1 41.12

77.005.14 TRyP Oign ⋅⋅⋅⋅⋅⋅= −−−− φτ0.1)/1( =∫ dtignτ

])0(06.0)0(1.15.92,5.95min[(%) 2CACACeff ⋅−⋅−=

)])0(exp(1[ 1+

Δ−−−⋅= w

effCACACxθ

GT-Power based model

8.073.08.02.0 )()()()()( tWtTtPtLth scaling ⋅⋅⋅⋅= −−α )(6

)( 21 mot

rr

rdp PP

VPTVCSCtW −+=

Combustion efficiency and Burn rate correlation

Heat Transfer correlation

Finite Element Analysis of Wall Temperatures


400

410

420

430

440

450

460

470

0 20 40 60

Time[sec]

Wal

l tem

pera

ture

[K]

0

1

2

3

4

5

6

7

8

BM

EP [b

ar]

Twall

BMEP

Point4

Point3

Thermal Management:Wall Temperature Effects

0

10

20

30

40

50

60

-20 0 20 40Crank Angle [degree]

Pres

sure

[bar

]

Steady state at P3

Transient at P3 withhot walls of P4

370

375

380

385

390

395

400

0 20 40 60

Time[sec]

Wal

l tem

pera

ture

[K]

1.2

1.4

1.6

1.8

BM

EP [b

ar]

Twall

BMEP

Point2

Point1

Early ignition timing and excessive pressure rise rate

Hot to cold

Cold to hot

Misfire


0

1

2

3

4

5

0 1000 2000 3000 4000

RPM

BM

EP

[bar

]

HCCI operation depends on load history:Transient wall temperatures affect the range

0

1

2

3

4

5

0 1000 2000 3000 4000

RPM

BM

EP

[bar

]

RANGE WITH STEADY STATE WALL TEMP

RANGE WITH TRANSIENT WALL TEMP

INITIALLY COLD WALLS

INITIALLY HOT WALLS

0

1

2

3

4

5

0 1000 2000 3000 4000

RPM

BM

EP

[bar

]

INITIALLY MID-RANGE WALLS

• Engine with rebreathing:• Residual fraction adjusted for optimal combustion

• Compression ratio = 12.5


Target RGF =

RGFsteady + (ΔTwall x Gain),

ΔTwall = Twallcurrent – Twallsteady

RPM

BM

EP

[bar

]

Gain for RGF to compensate for Twall effects

500 1000 1500 2000 2500 3000 3500 4000 45000

1

2

3

4

5

6

7

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

RPM

BM

EP

[bar

]

Contour of Residual Gas Fraction [%]

500 1000 1500 2000 2500 3000 3500 4000 45000

1

2

3

4

5

6

7

20

25

30

35

40

45

50

55

RPM

BM

EP

[bar

]

Contour of Piston Surface Temperatures [K]

500 1000 1500 2000 2500 3000 3500 4000 45000

1

2

3

4

5

6

7

420

440

460

480

500

520

Current Twall Gain for RGF to compensate for ΔTwall

= f (rpm, bmep)

Steady Twall= f (rpm, bmep)

Optimal Steady RGFfor the best BSFC= f (rpm, bmep)

EngineEx. Pressure PID control

Fuel rate PID controlTarget

Load Torque

Schematic Diagram Twall Compensation


BSFC

210

220

230

240

250

260

270

5 10 15 20 25 30 35

Time [sec]

bsfc

[g/k

W.h

]

Transient Simulation in HCCI Regime – Cold Walls

• Brake specific fuel consumption– Overall better BSFC with

compensation for the cold Twall

Compensation

Piston surface temperature

400

410

420

430

440

450

460

470

5 10 15 20 25 30 35

Time [sec]

Wal

l tem

pera

ture

[K]

Mapped steady state piston surface temperature

Calculated transient piston surface temperature

No compensation

RPM

BM

EP

[bar

]

500 1000 1500 2000 2500 3000 3500 4000 45000

1

2

3

4

5

6

7


Acknowledgements• University of Michigan

Dr. Aris Babajimopoulos, Dr. George Lavoie, Dr. Zoran Filipi, Prof. Margaret Wooldridge, Dr. Chris Depcik,Brad Zigler, Jason Martz, Orgun Guralp, Mark Hoffman, Kyoung-Joon Chang, Yanbin Mo, Alex Knafl

• General Motors Research LaboratoriesRod Rask, Paul Najt, Tang Wei Kuo, Pat Szymkowicz

• Lawrence Livermore National LaboratoriesSalvador Aceves, Dan Flowers

• Sandia National LaboratoriesJohn Dec, Magnus Sjoberg


Thank you!

Documents

Low-Temperature Combustion for High-Efficiency, Ultra … · Low-Temperature Combustion for High-Efficiency, Ultra-Low Emission Engines. LTC University Consortium ... Point2 Point1