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GASON: A LEAN CNG COMBUSTION FOR HIGHEST ENGINE EFFICIENCIES ABOVE 43% UTILISING AN IGNITION CHAMBERM. Weißner, F. Beger, C. Klüting, G. Lucas, Volkswagen AGT. Hilfiker, Empa
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GasOn: Lean CNG Combustion with ignition chamberMotivation
CNG = eco-friendly / sustainable / cost effective mobility
Paper 18CO-0060 2
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GasOn: Lean CNG Combustion with ignition chamberMotivation
3
State of the art:
• bivalent system• stoichiometric burn (λ=1) with TWC
GasOn:
• monovalent system• lean burn (λ>>1) to reach CO2 levels of 20% below best in class
(2015)
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberMotivation
4
MOTIVATION Combustion Process
Monovalent CNG‐Combustion to exploit fuel advantages and reach maximum efficiency
Efficiency can be improved by using lean combustion for CNG with λ>>1 Target: λ=2Increased requirements for ignition system (mixture, pressure)Creating a suitable distribution of NG in the air locally and globally
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
5
Section view through cylinderhead
Detail: ignition chamberHardware: ignition chamber
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
6
Designs with different internal shapes
Ignition Chamber Designs
cylinderhead
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
7
Design 1
Check Valve
Design 4Design 3Design 2
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
8
Target: lowest CNG massflow (<1mg/stroke)
Dosing system to supply CNG into the ignition chamber
Dosing System
Overview gas supply system
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
9
Engine #1: spark plug Engine #2: ign. chamber
Reference Engine
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberEngine Design
10
Engine assy Engine on testrig Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberResults
11
GasOn operating point K (2000 rpm / 220 Nm)
NO
x [g
/kW
h]0
2
4
6
8
10
12
14
16
Lambda [-]0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1
power loss /turbocharger limit
reference engine w/o prechamber engine w. scavenged prechamber
brak
e en
gine
effi
cien
cy [
%]
36
37
38
39
40
41
42
43
44
Lambda [-]0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1
reference engine w/o prechamber engine w. scavenged prechamber
GasOn operating point K (2000 rpm / 220 Nm)
power loss /turbocharger limit
- 14% bmep
- 30% bmep
- 2% bmep
- 9% bmep
Engine Efficiency NOx‐Emission
Engine efficiency over lambda NOx-emission over lambda
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberResults
12
GasOn operating point K (2000 rpm / 220 Nm)
T af
ter t
urbi
ne [
°C]
250
300
350
400
450
500
550
600
650
Lambda [-]0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1
power loss /turbocharger limit
reference engine w/o prechamber engine w. scavenged prechamber
GasOn operating point K (2000 rpm / 220 Nm)
THC
[g/
kWh]
0
5
10
15
20
25
Lambda [-]0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1
power loss /turbocharger limit
reference engine w/o prechamber engine w. scavenged prechamber
HC Emission (Methane) Exhaust Gas Temperature
THC Emission over lambda Exhaust gas temperature over lambda
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberResults
13
Later ignition/ faster combustion
‐505101520253035404550
‐30 ‐25 ‐20 ‐15 ‐10 ‐5 0 5 10 15 20 25 30
heat re
lease rate [J/°CA
]
crank angle [°CA]
spark plug engine prechamber engine
TDC
ignition timing
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamberResults
14
engine efficiency / lambda sweep NEFZ/WLTC VW operating points A,E,F,Kfuel: CNG / catalyst: none / scavenged prechamber operation / SOI pc: 300°CA b. TDC
brak
e en
gine
effi
cien
cy [
%]
20
22
24
26
28
30
32
34
36
38
40
42
44
46
Lambda [-]0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2
max. efficiency: lambda = 1.7
OP A (1400rpm/50Nm) / PC7 OP E (1200rpm/30Nm) / PC7 OP F (1500rpm/100Nm) / PC7 OP K (2000rpm/220Nm) / PC7
OP A (1400rpm/50Nm) / PC10 OP E (1200rpm/30Nm) / PC10 OP F (1500rpm/100Nm) / PC10 OP K (2000rpm/220Nm) / PC10
OP A (1400rpm/50Nm) / PC-C1 (straight nozzles) OP E (1200rpm/30Nm) / PC-C1 (straight nozzles) OP F (1500rpm/100Nm) / PC-C1 (straight nozzles) OP K (2000rpm/220Nm) / PC-C1 (straight nozzles)
OP A (1400rpm/50Nm) / PC-D2 (bigger volume) OP E (1200rpm/30Nm) / PC-D2 (bigger volume) OP F (1500rpm/100Nm) / PC-D2 (bigger volume) OP K (2000rpm/220Nm) / PC-D2 (bigger volume)
OP F Ref. passive prechamber / PC7 OP F Ref. passive prechamber / PC10 OP F Ref. passive prechamber / PC-C1 (straight nozzles) OP F Ref. passive prechamber / PC-D2 (bigger volume)
Engine efficiency with lambda sweep in relevant operating points
Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamber
Conclusions• Ignition chamber combustion increases
lean limit• Downscaling from large bore engines to
2.0l engine successful• Engine efficiency of 44% already shown• Challenging aftertreatment system
15Paper 18CO-0060
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GasOn: Lean CNG Combustion with ignition chamber
Thank you
Michael WeißnerVolkswagen AGPostbox 011/17780; 38436 Wolfsburg+49 5361 [email protected]
16Paper 18CO-0060