Potentials for Efficiency Improvement of Gas Engines · 4th CIMAC CASCADES, London, 20140314, S. Murakami Public 5 AVL Gas Engine Project - Example 1 5 1 50 ... PowerPoint Presentation

4th CIMAC CASCADES, London, 20140314, S. Murakami

Potentials for Efficiency Improvement of

Gas Engines

1

Dr. Shinsuke Murakami Development Engineer

Commercial and Large Engines

Engineering and Technology Powertrain Systems

4th CIMAC CASCADES, London, 20140314, S. Murakami Public

Content

2

Examples of AVL Gas Engine Projects for Efficiency Improvement

Potentials for Further Efficiency Improvement

Summary and Conclusion

“Fuel Efficiency – Are Improvements Possible?”


Example 1

High speed gas engine 1500 rpm

Open chamber combustion concept with pre-chamber spark plug

Targets

Efficiency increase by 2.7 % points

BMEP increase by 3.4 bar

THC 1200 mg/Nm3 at 3 % O2

NOx TA-Luft

Tasks

SCE testing (set-up and commissioning + 5.5 months testing)

CFD simulations for optimization of charge motion and piston bowl geometry

Results

All targets achieved

Efficiency increased by 2.8 % points

Examples of AVL Gas Engine Projects

3

4th CIMAC CASCADES, London, 20140314, S. Murakami Public 4

Summary of development steps

Reduction of dead volume

Optimization of Miller timing and BMEP increase

Swirl optimization

Optimization of combustion chamber geometry and compression ratio

Optimization of pre-chamber spark plug geometry

AVL Gas Engine Project - Example 1

Reduction of Dead Volume Miller Timing and BMEP

Effi

cie

ncy

[%

]

BMEP [bar]

1 bar

0.2 %pt

knock limit

base IVC

Effi

cie

ncy

[%

]

BMEP [bar]

1 bar

0.2 %pt knock limit

IVC 20° adv.

knock limit

base IVC



5

1

50

0.2

+ + +

CO

V P

max

[%

]TH

C [

pp

m]

Effi

cien

cy [

%]

-1.5 -1 -0.5 0 0.5 1 1.5

MN

at

kno

ck li

mit

[-]

Swirl Ratio [-]

Opt.

Swirl Optimization

SCE Test

5 different swirl ratio tested

constant BMEP / 1500 rpm

constant MFB50% location

constant NOx at TA-Luft

Conclusions

Too high swirl ratio deteriorates

knock margin significantly

Too low swirl ratio deteriorates

THC emission and COV

Swirl ratio optimized


CFD

Measurement

Piston A Piston C

Piston A

Piston B

Piston C

Piston D

Piston E


6

Optimization of Piston Bowl Geometry

Pre-optimization by CFD

SCE Test

4 bowl shapes tested

4 compression ratios tested



Conclusions

Piston contour to be matched

with the half-spherical flame

propagation

Minimize piston to head

clearance to enhance squish

flow effect

Piston bowl design and

compression ratio optimized



7

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

Base A B C D E F G H I

ΔEf

fici

ency

, ΔCO

V IM

EP [%

pt.]

Pre-chamber spark plug variants

Efficiency CoV IMEP

Measurement results

Velocity distribution

(AVL CFD resutls)

Residual gas distribution

(AVL CFD results)

Optimization of Pre-chamber Spark Plug

SCE Test accompanied by CFD

to understand the phenomena

10 variants tested

Volume

number of holes, diameter

hole direction



Conclusions

Pre-chamber optimized for

both efficiency and COV_IMEP


0.0

1.0

2.0

3.0

Dead volumereduction

Miller timingoptimization

BMEPincrease

Swirloptimization

Optimizationpiston bowlgeometry

OptimizationPre-chamber

spark plug

Effi

cie

ncy

Imp

rove

me

nt

[%p

t]

8



Optimization of Miller timing and BMEP increase

Swirl optimization

Optimization of combustion chamber geometry and compression ratio

Optimization of pre-chamber spark plug geometry

Summary of development results

Efficiency improvement

of 2.8 %pt. achieved.



Example 2

Medium Speed Gas Engine 750 rpm

Fuel-fed pre-chamber with spark ignition

Targets

Efficiency increase by 2 % points

COV_Pmax reduction from 5~6 % to 3 %

NOx TA-Luft

Tasks

SCE and MCE testing support

CFD simulations for optimization of piston bowl and pre-chamber geometries

Results

COV_Pmax significantly reduced

Efficiency increase by 2.1 % points

Examples of AVL Gas Engine Projects

9




Optimization of combustion stability

Optimization of Miller timing and compression ratio

Optimization of piston bowl geometry

Optimization of pre-chamber geometry


Optimization of combustion stability Miller Timing and Compression Ratio

Design PFP limit

Higher ave.

PFP possible

SCE test result | constant BMEP | same ave. PFP

0.2 %pt

SCE test result

constant BMEP



11

Optimization of Combustion Stability


SCE Test

MCE Test for confirmation

Gas supply to pre-chamber

Pre-chamber geometry



Conclusions

Even combustion in the pre-

chamber to be targeted

Flow separation at holes to be

avoided

Significant improvement of

combustion stability confirmed

by MCE testing

Uneven combustion in PC

• Plug location

• Mixture distribution

Base design Optimized design

0

2

4

6

8

Base AVL design

CO

V_P

max

[%

]MCE test results



12

Optimization of Piston Bowl Geometry


SCE Test

MCE Test for confirmation

3 bowl shapes tested

5 compression ratios tested



Conclusions

Piston bowl contour to be

matched with the flame

propagation from the flame jet

out of pre-chamber

Piston bowl to be optimized

together with pre-chamber

nozzle configuration

Measurement

CFD

Optimized Design

Optimum

Cone

Flat


0.0

0.5

1.0

1.5

2.0

2.5

Dead volumereduction

Optimization ofcombustion

stability

Miller timing andCR optimization

Optimization ofpiston bowlgeometry

Optimization ofpre-chamber

geometry

Effi

cie

ncy

Imp

rove

me

nt

[%p

t]

13



Summary of development results

Efficiency improvement

of 2.1 %pt. achieved.


Optimization of combustion stability

Optimization of Miller timing and compression ratio

Optimization of piston bowl geometry

Optimization of pre-chamber geometry


Content

14





30

35

40

45

50

55

60

4

6

8

10

12

14

16

18

20

22

24

1985 1990 1995 2000 2005 2010 2015

Ge

ne

rati

ng

Effi

cie

ncy

[%

]

BM

EP [

bar

]

Year

Pre-Chamber spark ignited Open Chamber spark ignited

Looking Back

15

Efficiency improvement coupled with BMEP increase.

Higher BMEP for higher efficiency?

30

35

40

45

50

55

60

4

6

8

10

12

14

16

18

20

22

24

1985 1990 1995 2000 2005 2010 2015

Ge

ne

rati

ng

Effi

cie

ncy

[%

]

BM

EP [

bar

]

Year

Pre-Chamber spark ignited Open Chamber spark ignited


16

18

20

22

24

26

28

30

480 490 500 510 520 530

BM

EP [

bar

]

Miller Timing [° ATDC]

Required Compressor Pressure Ratio

16

Key Technologies to achieve higher BMEP

Aggressive Miller timing and Two-Stage Turbocharging

Model-Based

Analysis

1500 min-1

Pre-chamber

Spark ignition

NOx TA-Luft

MN 80

const. ε of 12


45.5

45.75

46

46.25

43.75

44

44.25

44.5

44.75

45

45.25

45.5

45.75

44.5

44.75

45

45.25

45.5

45.75

46

46.25

46.5

46.75

BMEP – Miller – BTE Matrix at const. ε

17

BTE

16

18

20

22

24

26

28

30

480 490 500 510 520 530

BM

EP [

bar

]


Model-Based

Analysis

1500 min-1

Pre-chamber

Spark ignition

NOx TA-Luft

MN 80

const. ε of 12

The higher the BMEP, the higher the efficiency at constant ε.


45.0

45.5

46.0

46.5

21 22 23 24 25 26

Bra

ke T

he

rmal

Eff

icie

ncy

[%

]

BMEP [bar]

SCE Result | BMEP Variation with two different ε

18

knock limit

ε low

ε high

SCE Test

Results

1500 min-1

Pre-chamber

Spark ignition

NOx TA-Luft

MN80

The higher the BMEP the higher the knock limited efficiency.


1010.5

11

11.5

12

12.5

13

13.5

14

14.5

15

15.5

11

11.5

12

12.5

13

13.5

14

14.5

15

19

16

18

20

22

24

26

28

30

480 490 500 510 520 530

BM

EP [

bar

]


ε

BMEP – Miller – ε Matrix at Knock Limit

Model-Based

Analysis

1500 min-1

Pre-chamber

Spark ignition

NOx TA-Luft

MN 80

ε at knock limit

High BMEP with low ε or high ε with low BMEP?


45.2

45.4

45.6

45.8

46

46.2

46.3

44.8

45.2

45.2

45.4

45.4

45.6

45.8

46

46.2

46.3

44.8

45

45

45.2

45.2

45.3

45.3

BMEP – Miller – BTE Matrix at Knock Limit

20

16

18

20

22

24

26

28

30

480 490 500 510 520 530

BM

EP [

bar

]


BTE

Model-Based

Analysis

1500 min-1

Pre-chamber

Spark ignition

NOx TA-Luft

MN 80

ε at knock limit

Optimum BMEP Target for the highest efficiency 24 – 26 bar

Design PFP requirement of 250 bar


Content

21





Summary

22


were reviewed.

Incremental development will result in “Many a little makes a mickle.”

CFD Simulation and SCE Testing are effective for rapid development.

Key Enablers for the further efficiency improvement are;

High BMEP of 24 – 26 bar

Aggressive Miller Timing

Two-stage turbocharging

High PFP capability


Conclusion

23

“Fuel Efficiency – Are Improvements Possible?”

“Where there is a will, there is a way!”


Thank you for your attention!

Documents

Potentials for Efficiency Improvement of Gas Engines · 4th CIMAC CASCADES, London, 20140314, S. Murakami Public 5 AVL Gas Engine Project - Example 1 5 1 50 ... PowerPoint Presentation