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Engine, Emissions and Vehicle Research Division Southwest Research Institute Engine, Emissions and Vehicle Research Division Engine, Emissions and Vehicle Research Division Southwest Research Institute Southwest Research Institute Cooled EGR and alternative fuels Solutions for improved fuel economy Dr. Terry Alger November, 2007
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Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

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Page 1: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

Engine, Emissions and Vehicle Research DivisionSouthwest Research Institute

Engine, Emissions and Vehicle Research DivisionEngine, Emissions and Vehicle Research DivisionSouthwest Research InstituteSouthwest Research Institute

Cooled EGR and alternative fuelsSolutions for improved fuel economy

Dr. Terry Alger

November, 2007

Page 2: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

2

• Emissions standards have been getting more strict on an approximately 4 year cycle– HD standards are less strict, but getting tighter quickly – Light duty standards are already fairly strict, but there is

always potential for further reductions

• New concerns regarding “global climate change” and energy security have resulted in a renewed focus on fuel economy

• Customers are concerned about fuel consumption– Cost of gasoline is getting higher– Social aspects– CO2 regulation increasing

• High mileage vehicles offer a significant marketing opportunity

Motivation and Market Forces

Page 3: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

3

The Route to High Efficiency• Gasoline engines have the potential to be intrinsically more

efficient than diesel engines– Otto cycle has significantly higher ideal efficiencies than Diesel cycle

• In the “real world” gasoline engines suffer from some drawbacks

– Pumping losses• Emissions standards require TWC and a fixed A/F ratio – throttle is

required– Knock

• Limits compression ratio• Spark retard to combat knock severely reduces efficiency• Spark retard also increases exhaust temperatures

– Requires overfuelling– Engine cannot meet emissions at high load

• 2 routes to high efficiency:1. Downsize and boost at “normal compression ratio”2. Increase compression ratio and maintain or increase displacement

Page 4: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

4

A Solution for High Efficiency• Reduce or eliminate pumping

losses– Use cam phasing and/or hot

EGR at low load to increase internal residual

– Reduce engine displacement• Requires higher manifold

pressures for the same torque as the larger engine

• Increase compression ratio– Better thermal efficiency

• Boost to increase specific power– Overcomes small displacement– Improved marginal efficiencies

Ignition and flame propagation

difficult

Increased exhaust

temperatures require

overfuelling

KNOCK

Page 5: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

5

Overcoming Obstacles to High Efficiency• Advanced ignition systems

– Improve EGR tolerance– Increase knock tolerance

• Cooled EGR– Reduces knock

• Combustion phasing improves for high efficiency• Enables high CR and/or loads

– Reduces exhaust temperatures• More effective dilution than overfuelling• Combustion phasing improvement also helps with combustion

temperatures

• Change the chemical composition of the charge– H2 reformer– Alternative fuels

Page 6: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

6

Improving ignitability

Fine Iridium ElectrodeHT lossesRequired breakdown voltage

Large GapHT lossesQuenching

Required breakdown voltageFlow CouplingEMI

Higher Energy LevelsFlame kernel volumeSecondary currents

Proportional heat lossesSpark “blow-out”Durability(?)

Long Duration / Multiple SparksProbability of ignitionFlow couplingInitial flame volume

Knock tendencyEffect of cylinder pressure

on spark event

Top systems to date:

• Dual fine electrode spark plugs

• High energy, long duration spark systems

Page 7: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

7

Ignition System Improvement at Low Loads• Very low loads present

challenges to ignition with EGR– High levels of in-

cylinder residual– Relatively cooler

temperatures• Residual• “Hot” EGR• Engine surfaces

• MS System V2.1 has the best EGR tolerance– Best low load EGR

tolerance– Burn duration and

stability very good 0 5 10 15 200

2

4

6

8

EGR [%]

Stock System MS system V1.0 MS System V1.1

MS System V2.0 MS System V2.1

CoV

IMEP

[%]

2000 rpm / 2 bar bmep

2.4-L engine @ 9:1 CR

Page 8: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

8

Burn rate improvement with new ignition• MS system V2.1 results

in faster burn rates at high and low load– EGR tolerance improves– Emissions and FE

improve– Knock resistance

improves• Level of improvement

would be greater for engines with higher levels of bulk motion– MS V2.1 may be able to

tolerate higher levels of bulk motion than other systems

40

50

60

70

80

90

0 5 10 15 20 25405060708090

3500 rpm / 9.6 bar bmep

0-50

% M

FB D

urat

ion

[deg

]

EGR [Vol %]

0-50

% M

FB D

urat

ion

[deg

]

Stock System MS system V1.0 MS system V2.0 MS system V1.1 MS system V2.1

2000 rpm / 2 bar bmep

2.4-L engine @ 9:1 CR

Page 9: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

9

High Load Performance• Ignition challenges at high

load are different– Spark blow out /

suppression– EMI– Pre-ignition

• MS V2.1 improves EGR tolerance at high load and reduces knock tendency– 20% EGR suppresses

knock – Engine runs at or near

MBT timing• Burn rate improvement

significant• WOT fuel economy good

despite low CR

1500 2000 2500 3000 3500 40006

8

10

12

14

16 220

230

240

250

BM

EP [b

ar]

Engine Speed [rpm]

20% EGRPeak loads limited by turbocharger

Stock System MS system V1.0 MS System V1.1

MS System V2.0 MS System V2.1

BSF

C [g

/kW

h]

2.4-L engine @ 9:1 CR

Page 10: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

10

Improving ignition (non-igniter hardware)

• Many other parameters can be adjusted to improve ignition– Increase coolant temperature

• Hotter temperatures at compression• EGR mitigates knock

– Increase compression ratio• Higher compression temperatures• EGR reduces knock• Also improves efficiency

• Change composition of the intake charge– H2 supplementation has significant potential

• Only small amounts required for benefit (SAE paper 2007-01-0475)

Page 11: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

11

H2 Amount and the Effect on Engine Stability• Very small amount of H2

necessary to stabilize engine– < 1 mg of H2 stabilizes

engine at most test conditions (~ 5% of gasoline mass)

– Benefits of H2 addition rapidly fall off at levels > 0.2 % by volume

• At high CR and high load, knock limits the benefit until high H2 levels reached

• H2 appears to improve stability through increased burn rates and more complete combustion

0.0 0.2 0.4 0.6 0.8 1.00

2

4

6

8

10

CoV

of i

mep

[%]

Volume % H2

11:1 CR; 3.1 bar imep (22% EGR) 11:1 CR; 5.5 bar imep (28% EGR) 14:1 CR; 3.1 bar imep (32% EGR) 14:1 CR; 5.5 bar imep (26% EGR)

Results from SAE Paper 2007-01-0475

0.75-L engine

Page 12: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

12

The Influence of H2 on Turbulent Burn Rate• Effect of H2 seen in 10-

90% MFB duration and spark advance– Biggest impact seen

with initial H2 addition

• H2 improves apparent flame speeds– Larger flammability

limits– Higher laminar burning

velocities– Reduced quench

distances

0.0 0.2 0.4 0.6 0.8 1.020

30

40

50

60

70

80

90 Spark Advance [deg bTDC] 10-90% MFB Duration [deg]

H2 [vol %]

3.1 bar imep, 11:1 CR, 22% EGR

Results from SAE Paper 2007-01-0475

0.75-L engine

Page 13: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

13

The Influence of H2 on Emissions• HC emissions reduced

considerably– H2 addition promotes

post-flame consumption of HC

– Crevice emissions reduced due to shorter wall quench distances

– Flame propagation improved due to improved flammability limits

• NOx emissions increase– Hotter flame temperatures

due to faster flame speeds– Still significantly reduced

from no EGR case

0.0 0.2 0.4 0.6 0.8 1.040

60

80

100

120

140

160

Perc

ent c

hang

e (0

% H

2 = 1

00%

) ISHC ISNO

H2 [vol %]

3.1 bar imep, 11:1 CR, 22% EGR

Results from SAE Paper 2007-01-0475

0.75-L engine

Page 14: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

14

The Influence of H2 on EGR Tolerance• H2 constant at 1% by

volume• EGR tolerance increased

significantly– Benefit largest at low load

• EGR tolerance lower without H2 at this load

• Engine still very knock limited at high loads and high CR

• No boost – WOT condition stops EGR sweep

• Best results in multi-cylinder engine found at 40-50% EGR

20 25 30 35 40 45 50 55 600

2

4

6

8

10

CoV

of I

MEP

[%]

EGR %

11:1 CR; 3.1 bar imep 14:1 CR; 3.1 bar imep 11:1 CR; 5.5 bar imep 14:1 CR; 5.5 bar imep

EGR Limited by WOT

Stability Limit

Results from SAE Paper 2007-01-0475

Page 15: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

15

Ignition Improvement Options• Advanced igniter and coil designs pay big

dividend– Best MS system yielded a 100%

improvement in EGR tolerance• Changing fuel composition also works well

– Small amounts of H2 can significantly improve performance

• Emissions and fuel consumption are reduced• Engine stability improves

– Low mass of H2 makes reformer technology more easily packaged and less energy consumptive

– Ethanol will improve knock tolerance• Other techniques are proving to have some

benefits– Increasing manifold temperatures works well– High CR and coolant temperatures also help

Page 16: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

16

Cooled EGR for Knock Reduction• Boosted gasoline engines

are knock limited above 12-14 bar bmep (or less)– Significant spark retard

required to prevent knock– Excess fuel required to

reduce exhaust temperatures• Cooled EGR can reduce

knock tendency – Restore optimal combustion

phasing– Allows stoichiometric

combustion• Enables aggressive

downsizing ( > 25%) for US market

0 5 10 15 20 25-30

-20

-10

0

10

20

30

40

240

250

260

270

280

290

300

3100 5 10 15 20 25

-15

-10

-5

0

5

10

15

20

240

250

260

270

280

290

300

310 Spark Advance CA 50% MFB BSFC [g/kWh]

Deg

rees

afte

r TD

C

EGR [%]

Desired location of CA 50% MFB for MBT

Low speed / high load conditions2.4-L engine @ 10.5:1 CR

Page 17: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

17

Cooled EGR for Reduced Exhaust Temperatures• All EGR conditions run at

φ = 1.0• EGR reduces high load

exhaust temperatures significantly– Cost savings potential in

• Turbine materials• Exhaust valve and seat

materials• Catalyst substrate• Warranty exposure

– Also has the potential to reduce under-hood temperatures

• Less load on heat exchangers

• Increased ability to run at high loads in drive cycle– Emssions compliance at

high load realized– Greater downsizing

potential

0 5 10 15 20

600

700

800

900

1000

1100 2000 rpm / 14 bar bmep 2000 rpm / 18 bar bmep 4000 rpm / 18 bar bmep 5500 rpm / 15 bar bmep

Pre-

Turb

ine

Tem

pera

ture

[deg

C]

EGR [%]1.6-L GDI engine (10.5:1 CR)

Page 18: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

18

Cooled EGR at High Speed / High Load

• Fuel consumption reduced by 5-20% due to elimination of enrichment (depending on engine power and enrichment levels)• Exhaust temperature reduced by ~100 deg C with EGR addition• Emissions reduced significantly

→ High load / WOT may now be a potential drive-cycle operating condition for a LD automotive application

0 5 10 15 20 25

700

720

740

760

780

800

220

225

230

235

240

245

Exha

ust T

empe

ratu

re [d

eg C

]

EGR [%]

Temperature @ Phi = 1.0 BSFC @ Phi =1.0 Temperature @ Phi = 1.05 BSFC @ Phi = 1.05

BSF

C [g

/kW

h]

BSCO BSNO BSHC0

10

20

30

40

50

BS

emis

sion

s [g

/kW

h]

6%

-65%

-77%

2.4-L engine @ 10.5:1 CR

Page 19: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

19

Cooled EGR at Low Speed / High Loads• At low speeds and high

loads, enrichment is not typically an issue– Despite high levels of

spark retard, exhaust temperatures are not excessive

– Poor efficiency is due solely to spark retard due to knock

• EGR addition reduces knock– Big change in BSFC– BSCO and BSNO are

reduced significantly0 5 10 15 20 25 30 35

0

5

10

15

210

220

230

240

250

EGR [%]

BSFC [g/kWh] BSCO [g/kwH] BSNO [g/kWh] BSHC [g/kWh]

2.4-L engine @ 9.5:1 CR

Page 20: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

20

Downsizing Potential• BMEP values based on a 3 L

engine (i.e. 11 bar bmep in a 3 L = 14 bar in the 2.4 L)

• Engine calibration will require a continuum of EGR temperatures for optimal performance

• Low speed, high BMEP operation enabled by knock reduction from EGR– Shift vehicle operation window– Diesel-like torque curve

• Future emissions standards will require compliance at high loads– Enrichment region will be

eliminated or very limited

Potential BSFC improvement due to downsizing

1 3 4 5 6 7 8

5

10

15

20

25 Hot EGR Cold EGR

% d

ecre

ase

in B

SFC

Test Point

Test Point Conditions1 4400 rpm / 11 bar bmep3 800 rpm / 7 bar bmep4 1500 rpm / 1 bar bmep5 1600 rpm / 2.4 bar bmep6 2000 rpm / 2 bar bmep7 2000 rpm / 5 bar bmep8 3500 rpm / 7.5 bar bmep

Downsizing Goal:Run FTP at > 10 bar bmepIdle @ 2-3 bar imep or more

10.5:1 CR

Page 21: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

21

Cooled EGR and High CR Operation

1500 2000 2500 3000 3500 40000

2

4

6

8

10

200

210

220

230

240

25035% BTE

BM

EP [b

ar]

Engine Speed [rpm]

39% BTE

BSFC

[g/kWh]

Peak load limited by NA operation

• Friction losses increased significantly– Problem worse at low loads

and high speeds• EGR reduces knock

tendency enough to get near full load– If external boost is applied,

10-11 bar is likely

2.4-L engine @ 14:1 CR

Full Load Curve

6 8 10 12 14 16 180

20

40

60

80

0

2

4

6

8

10

10-9

0% M

FBD

urat

ion

[deg

]

EGR %

10:1 CR 14:1 CR

CO

V im

ep [%

] • High CR helps with EGR

tolerance at low loads– Hotter temperatures

improve stability and flame speed

– Less internal residual

1500 rpm / 1 bar bmep

Page 22: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

22

When do we use hot EGR?

02468

20

25

30

5 10 15 20 2505

1015202530

BSCO [g/kWh]

BSHC [g/kWh]

BSNO [g/kWh]

EGR [%]

Incomplete combustion loss [kW]

Heat Lost to Exhaust [kW]

CoV imep [%]

2500 rpm / 6.7 bar bmepHEGR CEGR

• Hot / uncooled EGR is beneficial as long as knock does not occur– Higher MAT increases EGR

tolerance– Higher MAT helps charge

preparation • CO emissions reduced over

cooled EGR– Higher MAT promotes more

complete combustion– Pre-heating intake air increases

cycle efficiencies• NO emissions increase slightly

– Still below baseline / 0% EGR levels

• Substantial CO reductions– WHY?

• Exact cutoffs between when to use cooled or uncooled EGR TBD on engine-by-engine basis

2.4-L engine @ 9.0:1 CR

Page 23: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

23

CO reductions with EGR• CO emissions are lower with

EGR in almost all applications• With H-EGR, part of the

reduction in CO emissions may come from improved vaporization / charge preparation

• At high loads, MAT is controlled by aftercooler

– No temperature differences between EGR condition and baseline conditions

– CO emissions still decrease• Simulations using CEA code

indicate that lower temperatures due to dilution result in less CO emissions

– Occurs with several diluent types– Very strong temperature effect– Lower temperatures reduce

dissociation• Unanticipated benefit of EGR use

1900 2000 2100 2200 2300 24000

40

80

120

160

200

2200 2400 2600 2800 30000

10

20

30

40

50

T0 = 500 K T0 = 1000 KT0 = 1500 K

CO

2 / C

O ra

tio

Flame Temperature [K]

Diluent: N2 (10% by volume)T0 = 300 K

Flame Temperature [K]

CO

2 / C

O ra

tio

N2 diluent CO2 diluent

25% dilution15% dilution

10% dilution

0% dilution

Page 24: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

24

The Path to Fuel Economy: High CR versus High Load?• Question: What is the most effective way to

improve drive cycle efficiencies?• High CR

– Offers theoretical advantages in thermodynamic cycle efficiency

– High load becomes difficult• BSFC penalty due to spark retard is high

– Low load performance usually improved– May be best for NA / low boost applications

14 16 18 20 22 24274

276

278

280

282

284

286

288

290

292

BSF

C [g

/kW

h]

Spark Advance [deg bTDC]

2800 rpm15 bar bmep0% EGRE50 Fuel2.0-L engine11:1 CR

MBT timing

0 2 4 6 8 10 12 14 16 18 2005

1015202530

Pumping losses [% of BMEP] Friction Losses [% of BMEP] Location of 50% MFB [deg]

BMEP [bar]

220240260280300320340360

BSF

C [g

/kW

h]

2000 rpm10%<EGR<20%

• High Load– Low CR (10<CR<12) with

radical downsizing– Allows MBT timing at very high

loads– Marginal efficiencies become

very high• Friction and pumping as a % of

fuel energy → 0– Reduces or eliminates low

BMEP operation

Page 25: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

25

Cooled EGR• Cooled EGR improves fuel economy

– Knock reduction leads to improved combustion phasing• Reduced fuel consumption• Reduced exhaust temperatures

– Diluent effect of EGR reduces exhaust temperatures• Reduces requirement for overfuelling• Engine becomes emission compliant over entire performance

map

• Cooled EGR helps with emissions– CO and NO emissions reduced with lower combustion

temperatures– Ability to run stoichiometric over full performance map

makes engine fully emissions compliant • Cooled EGR with moderate compression ratio enables

radical downsizing (> 40%)– Efficiency benefits of EGR + Boost outweigh the benefits of

very high compression ratio

Page 26: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

26

Alternative Fuels• HEDGE and ethanol

– EGR can further improve ethanol operation

• Further increase knock resistance• Reduce pumping losses• Hot EGR can increase MAT to

help with fuel preparation issues– Improved ignition system can

benefit ethanol operation • CS benefits• With or without EGR

• Limited HEDGE technology can enable more efficient flex-fuel vehicles– SwRI has applied for a patent

under the HEDGE program– Enable engine optimization for

E100 / E85 fuel – Protect for E0 operation with EGR

• Will also work for other alternative fuels

0

5

10

15

20

25

30

0 20 40 60 80 100

Ethanol Percetnage in Fuel

EGR

Per

cent

age

in E

ngin

e

Page 27: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

27

15.9 15.917.2

19.3

0.0

5.0

10.0

15.0

20.0

25.0

NO EGR EGR

Dilution Case

BM

EP

(bar

)

92RON

92RON+H2

100RON

E50

E85

BMEP Limit Comparison (CR=11:1, Ф=1 )

• Exceeded BMEP target with E50 and E85 without EGR

• Exceeded BMEP target with 100 RON + EGR

• BMEP target NOT met with 92 RON due to engine knock and combustion stability limits

• BMEP target was met with 92 RON + EGR + H2 (60% increase)

• EGR alone extended knock limit by ~20% for gasoline fuels

Kno

ck &

PTT

Kno

ck &

PTT

Kno

ck (

MB

T)

Kno

ck &

PTT

Pea

k C

ylin

der P

ress

ure

(MB

T)

Kno

ck &

CoV

IME

P

Max

MAP

& K

nock

& C

oV

Max

MA

P &

Kno

ck (M

BT)

Target From Baseline (CR=9:1)

EGR ~ 21%

2800RPM

Page 28: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

28

BTE Comparison (CR=11:1, Ф=1 )

• BTE for ethanol blends exceeded 38%

• 100 RON + EGR achieved target BMEP at 37.3% BTE

• 92 RON + EGR + H2achieved ~30% BTE

– Lower BTE due to retarded spark timing and losses due to reforming the fuel

• 92 RON + EGR operated at > 35%, but not at target BMEP

– Enrichment may be used to increase knock limited BMEP

29.6

37.338.3 39.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

NO EGR EGRDilution Case

BTE

(%)

92RON

92RON+H2

100RON

E50

E85

2800RPM

NOTE:

The amount of fuel required to make the H2 was accounted for in BTE and BSFC comparisons –

Assumed an ideal fuel reformer

Page 29: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

29

Comparison to Baseline

02468

1012141618

BM

EP

(bar

)

E85E85+EGR100RON+EGR92RON+EGR+H292RON Cr=9:1

0.80

1.00

1.20

1.40

1.60

0 1000 2000 3000 4000 5000 6000 7000

Engine Speed (rpm)

Equ

ival

ence

Rat

io

• Baseline Data– CR=9:1– Turbocharged – WOT– To meet target BMEP

• Spark retard for knock• Ф > 1 due to PTT limit

• Test Data– CR=11:1– Supercharged – WOT– To meet target BMEP

• Spark retard for knock • Ф held to 1

Page 30: Cooled EGR and alternative fuels V1 - Mechanical Engineeringsae/Files/Cooled_EGR_and_alternative_fuels_V1.pdf · Cooled EGR and alternative fuels Solutions for improved fuel economy

30

Comparison to Baseline

• E85 + EGR was 9% higher than baseline even though the LHV of E85 was 25% lower than gasoline

• 92RON + EGR + H2 improved fuel consumption by 8%

• 100RON + EGR improved fuel consumption by 19%

• Fuel consumption difference between 100RON and E85 was proportional to difference in LHV

200220240260280300320340360380

0 1000 2000 3000 4000 5000 6000 7000

Engine Speed (rpm)

cBS

FC (g

/kW

-hr)

E85 E85+EGR100RON+EGR 92RON+EGR+H292RON Cr=9:1

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Result with Ethanol and EGR

• Test engine could operate as an E85 flex fuel engine with CR = 11:1– Premium required EGR to meet target load– Regular required EGR and H2 addition to meet target load

• EGR improved fuel consumption and emissions with ethanol blended fuels

• Increasing CR and employing EGR improved engine performance and emissions compared to base engine operating on gasoline– NOX and CO were significantly reduced – Full load fuel consumption with regular gasoline was estimated to be

8% lower with EGR and H2

– Full load fuel consumption was only 9% higher with E85 (EGR, CR=11:1) than base engine (No EGR, CR=9:1) despite 25% lower LHV

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Terry [email protected]

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EGR Systems

PM Traps

High EGR,NOx Aftertreatment

Turbocharging

Intercooling

High PressureInjection

ElectronicFuelInjection

U.S. Heavy-Duty On-Road –Emissions Regulations Increasingly Difficult to Meet

ImprovedCombustion &RetardedTiming

Emissions Regulation History and Technology Solutions

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Engine, Emissions and Vehicle Research DivisionSouthwest Research Institute

Engine, Emissions and Vehicle Research DivisionEngine, Emissions and Vehicle Research DivisionSouthwest Research InstituteSouthwest Research Institute

Emissions Regulation History and Technology Solutions

U.S. Light-DutyEmissions Regulations

Toughest Anywhere

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Include Fuel Economy and the Problem is Clear http://www.sanantoniogasprices.com/retail_price_chart.aspx

Fuel price is increasing and highly volatile

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CO2 Review

• Europe CO2 Regulations– Europe sets CO2 goals for near

future• 120 g/km maximum CO2

• U.S. Supreme Court ruling– U.S. EPA should consider CO2– Likely that CO2 regulation will

occur in U.S.– U.S. President reveals plan to

pursue CO2 reduction• Asks EPA and DOE to work together

for CO2 reduction

From SwRI Consulting Service Report:

Climate change awareness is intensifying in the US. The recent Supreme Court decision ordering the EPA to take action to reduce GHG emissions from vehicles lags state actions which are already moving ahead with their own low-carbon vehicle rules, potentially leading to a GHG policy “mess”. To avoid that, the US president ordered EPA, the Department of Transportation, the Department of Energy and the Department of Agriculture to propose and finalize new regulations by the end of next year that would respond to the Supreme Court order. As a starting point for such new regulation, the president proposed a 20% cut in gasoline consumption by 2017, which would force 35 billion gallons of renewable and other fuels into the US motor fuel pool by 2017. According to an environmental law specialist, the “mess” involves regulation, litigation, and Congress trying to figure out GHG legislation and how the transportation sector fits in. According to him, the ideal solution would be for Congress to take action, eliminating states from the equation. (WRFT 23-05-07)