Presentation S. Murakami

Potentials for Efficiency Improvement of
Gas Engines
Dr. Shinsuke Murakami
Development Engineer
Commercial and Large Engines
Engineering and Technology Powertrain Systems
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Content
“Fuel Efficiency – Are Improvements Possible?”
 Examples of AVL Gas Engine Projects for Efficiency Improvement
 Potentials for Further Efficiency Improvement
 Summary and Conclusion
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Examples of AVL Gas Engine Projects
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
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 1
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
Reduction of Dead Volume
Miller Timing and BMEP
Efficiency [%]
0.2 %pt
knock limit
IVC 20° adv.
knock limit
base IVC
1 bar
BMEP [bar]
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 1
 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
THC [ppm]
 constant BMEP / 1500 rpm
COV Pmax [%]
 5 different swirl ratio tested
MN at knock limit [-]
 SCE Test
Efficiency [%]
Swirl Optimization
-1.5
0.2
50
1
5
-1
-0.5
0
Opt.
+ 0.5
+1
+ 1.5
Swirl Ratio [-]
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 1
Optimization of Piston Bowl Geometry
CFD
 Pre-optimization by CFD
 SCE Test
 4 bowl shapes tested
Piston A
Piston B
Piston C
Piston D
Piston E
 4 compression ratios tested
 constant BMEP / 1500 rpm
 constant NOx at TA-Luft
Conclusions
 Piston contour to be matched
with the half-spherical flame
propagation
Measurement
Piston C
Piston A
 Minimize piston to head
clearance to enhance squish
flow effect
 Piston bowl design and
compression ratio optimized
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 1
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
Velocity distribution
(AVL CFD resutls)
 constant BMEP / 1500 rpm
Conclusions
 Pre-chamber optimized for
both efficiency and COV_IMEP
ΔEfficiency, ΔCOV IMEP [%pt.]
 constant NOx at TA-Luft
0.4
Measurement results
Efficiency
CoV IMEP
0.2
0
-0.2
-0.4
-0.6
-0.8
Base
4th CIMAC CASCADES, London, 20140314, S. Murakami
Residual gas distribution
(AVL CFD results)
A
B
C
D
E
F
G
Pre-chamber spark plug variants
Public
H
I
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AVL Gas Engine Project - Example 1
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
Efficiency Improvement [%pt]
Summary of development results
3.0
2.0
Efficiency improvement
of 2.8 %pt. achieved.
1.0
0.0
Dead volume
reduction
Miller timing
optimization
4th CIMAC CASCADES, London, 20140314, S. Murakami
BMEP
increase
Swirl
optimization
Optimization
piston bowl
geometry
Optimization
Pre-chamber
spark plug
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Examples of AVL Gas Engine Projects
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
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 2
Summary of development steps
 Reduction of dead volume
 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
SCE test result | constant BMEP | same ave. PFP
SCE test result
constant BMEP
Design PFP limit
Higher ave.
PFP possible
0.2 %pt
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 2
Optimization of Combustion Stability
Uneven combustion in PC
• Plug location
• Mixture distribution
 Pre-optimization by CFD
 SCE Test
 MCE Test for confirmation
Base design
Optimized design
 Gas supply to pre-chamber
 Pre-chamber geometry
 constant BMEP / 750 rpm
 constant NOx at TA-Luft
Conclusions
 Even combustion in the prechamber to be targeted
 Significant improvement of
combustion stability confirmed
by MCE testing
4th CIMAC CASCADES, London, 20140314, S. Murakami
COV_Pmax [%]
 Flow separation at holes to be
avoided
8
MCE test results
6
4
2
0
Base
AVL design
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AVL Gas Engine Project - Example 2
Optimization of Piston Bowl Geometry
CFD
 Pre-optimization by CFD
 SCE Test
Optimum
Cone
Flat
 MCE Test for confirmation
 3 bowl shapes tested
 5 compression ratios tested
Optimized Design
 constant BMEP / 750 rpm
 constant NOx at TA-Luft
Measurement
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
4th CIMAC CASCADES, London, 20140314, S. Murakami
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AVL Gas Engine Project - Example 2
Summary of development steps
 Reduction of dead volume
 Optimization of combustion stability
 Optimization of Miller timing and compression ratio
 Optimization of piston bowl geometry
 Optimization of pre-chamber geometry
Efficiency Improvement [%pt]
Summary of development results
2.5
2.0
1.5
Efficiency improvement
of 2.1 %pt. achieved.
1.0
0.5
0.0
Dead volume
reduction
Optimization of
combustion
stability
4th CIMAC CASCADES, London, 20140314, S. Murakami
Miller timing and
CR optimization
Optimization of
piston bowl
geometry
Optimization of
pre-chamber
geometry
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Content
 Examples of AVL Gas Engine Projects for Efficiency Improvement
 Potentials for Further Efficiency Improvement
 Summary and Conclusion
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Looking Back
22
60
Pre-Chamber spark ignited
Open Chamber spark ignited
55
20
BMEP [bar]
18
50
16
14
45
12
40
10
8
35
Generating Efficiency [%]
24
6
4
1985
1990
1995
2000
2005
2010
30
2015
Year
 Efficiency improvement coupled with BMEP increase.
 Higher BMEP for higher efficiency?
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Required Compressor Pressure Ratio
30
 Model-Based
Analysis
28
 1500 min-1
BMEP [bar]
26
 Pre-chamber
 Spark ignition
24
 NOx TA-Luft
22
 MN 80
20
 const. ε of 12
18
16
480
490
500
510
520
530
Miller Timing [° ATDC]
 Key Technologies to achieve higher BMEP
 Aggressive Miller timing and Two-Stage Turbocharging
4th CIMAC CASCADES, London, 20140314, S. Murakami
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BMEP – Miller – BTE Matrix at const. ε
30
 Model-Based
Analysis
46.75
28
46.25
46.5
45.75
BMEP [bar]
26
24
45.5
 Spark ignition
BTE 46
45.25
45.75
45.75
22
 NOx TA-Luft
45
45.5
45.5
 MN 80
44.75
45.25
20
 const. ε of 12
44.5
45
18
 Pre-chamber
46.25
46
44.75
 1500 min-1
44.25
44.5
44
43.75
16
480
490
500
510
520
530
Miller Timing [° ATDC]
 The higher the BMEP, the higher the efficiency at constant ε.
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Brake Thermal Efficiency [%]
SCE Result | BMEP Variation with two different ε
46.5
knock limit
 SCE Test
Results
 1500 min-1
 Pre-chamber
46.0
 Spark ignition
ε high
 NOx TA-Luft
 MN80
45.5
ε low
45.0
21
22
23
24
25
26
BMEP [bar]
 The higher the BMEP
4th CIMAC CASCADES, London, 20140314, S. Murakami
the higher the knock limited efficiency.
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BMEP – Miller – ε Matrix at Knock Limit
30
28
11.5
12
26
BMEP [bar]
 Model-Based
Analysis
10
10.5
11
ε 13
24
 1500 min-1
11
11.5
12.5
12
13.5
22
13
14.5
 MN 80
13.5
20
 ε at knock limit
14
15
18
 Spark ignition
 NOx TA-Luft
12.5
14
 Pre-chamber
14.5
15.5 15
16
480
490
500
510
520
530
Miller Timing [° ATDC]
 High BMEP with low ε or high ε with low BMEP?
4th CIMAC CASCADES, London, 20140314, S. Murakami
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BMEP – Miller – BTE Matrix at Knock Limit
30
28
44.8
45.2
45.6
45.4
BMEP [bar]
26
 1500 min-1
BTE 46.2
45.8
45
46.3
24
 Pre-chamber
 Spark ignition
 NOx TA-Luft
 MN 80
20
45.3
46
46.2
45
45.4
45.4
45.2
45.2
480
 ε at knock limit
46.3
45.2
45.8
45.6
18
16
45.2
45.3
46
22
 Model-Based
Analysis
44.8
490
500
510
520
530
Miller Timing [° ATDC]
 Optimum BMEP Target for the highest efficiency  24 – 26 bar
 Design PFP requirement of 250 bar
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Content
 Examples of AVL Gas Engine Projects for Efficiency Improvement
 Potentials for Further Efficiency Improvement
 Summary and Conclusion
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Summary
 Examples of AVL Gas Engine Projects for Efficiency Improvement
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
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Conclusion
“Fuel Efficiency – Are Improvements Possible?”
“Where there is a will, there is a way!”
4th CIMAC CASCADES, London, 20140314, S. Murakami
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Thank you for your attention!
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