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Potential of CNG-Direct-Injection for Downsizing Engine Concepts Thomas Hofherr, MSc
Potential of CNG-Direct-Injection for Downsizing Engine Concepts
Thomas Hofherr, MSc
A3PS – ECO‐Mobility 2025plusTU Wien
09.11.2015 | Wien | Th. Hofherr| Folie 2
Content
□ Motivation
□ State of the Art - Natural gas engines
□ Engine – Modifications
□ Results
□ Conclusion
A3PS – ECO‐Mobility 2025plusTU Wien
09.11.2015 | Wien | Th. Hofherr| Folie 4
Motivation – Natural Gas Direct Injection
~130
17,2
31,7 34,9
54,8
95
14,2
35,9 36,5
73,5
0
20
40
60
80
100
120
140
octane number[RON]
stoichiometric airmass
[kgAir/kgFuel]
mixture heatingvalue x10 (mixtureaspirated) [MJ/m³]
mixture heatingvalue x10 (air
aspirated) [MJ/m³]
gCO2/MJ
Natural Gas
Gasolineknock resistance
-25%Port Fuel Injection (PFI)
DirectInjection (DI)
A3PS – ECO‐Mobility 2025plusTU Wien
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State of the Art – Natural Gas Engines
1000 2000 3000 4000 5000 6000 70000
20
40
60
80
100
Mot
ordr
ehm
omen
t [N
m]
Motordrehzahl [min-1]
Drehmoment 1,0L Benzin Drehmoment 1,0L CNG Leistung 1,0L Benzin Leistung 1,0L CNG
0
20
40
60
80
100
Mot
orle
istu
ng [k
W]
H.J. Neußer: Der neue Erdgasmotor von Volkswagen, MTZ 04/2013
Natural Aspirated Engine
□ Port Fuel Injection (PFI) – State of the Art– Displacement of air at WOT– Reduction of LowEnd Torque– Limited scavenging capabilities– Limited in catalyst heating strategies
New approach: CNG direct injection– No displacement of air at WOT– High scavenging capabilities– High LowEnd Torque– Postinjection for catalyst heating
A3PS – ECO‐Mobility 2025plusTU Wien
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Engine Modifications
Base Engine
Act. Engine
No. of cylinders 3
Valves per cylinder 4
Valve train DOHC I-VCP
Displacement 658 cm³
Compression ratio 8,8 13,6 12,0
Fuel RON 95 CNG
Mixture formation Gasoline DI CNG-DI
Charging Turbo
P., Hofmann et al: Der CULT Antrieb: Hocheffizienter CNG Motor mit Direkteinblasung, Wiener Motorensymposium 2013
A3PS – ECO‐Mobility 2025plusTU Wien
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Engine ModificationsIncreasing the compression ratio – Combustion chamber shape
Compressionratio ε [-]
Surface / Volume ratio [cm-1]
8,8 3,32+64%
13,6 5,43
ε=8.8 ε=13.6
Intake valveExhaust valve
DI‐Injector
A3PS – ECO‐Mobility 2025plusTU Wien
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24,5 25,3 26,4
7,412,0 10,6
4,1
9,1 7,6
0
10
20
30
40
50
60
70ef
ficie
ncy
[%]
residual losses
unburned losses
wall heat losses
efficiency (measured)
ηth=58,1%
ηth=64,8%ηth=63,0%
Increasing compression ratio – Effects
Operating point: n = 2000 min-1 BMEP= 4 bar
Compression ratio of 12 is the optimum for this engine
A3PS – ECO‐Mobility 2025plusTU Wien
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Operating Strategies for Direct Injection – WOTInjection Timing
□ In PFI engines A/F mixture is aspirated and air is displaced partially by fuel□ Direct injection engines aspirate pure air, fuel is injected after IVC
Injection after IVC gains 20% volumetric efficiency compared to intake-synchronous injection
T. Hofherr, F. Forsthuber: Potential of direct Injection forIncreasing the LowEnd Torque ofBoosted CNG Enginges, 8. Konferenz Gasfahrzeuge, Stuttgart 2013
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Operating Strategies for Direct Injection – WOTcombination
1000 2000 3000
68
101214161820
BMEP
[bar
]
1000 2000 30000
20
40
60
80
100
120 intake synchronious injection late injection late injection + scavenging
air m
ass
[kg/
h]
1000 2000 3000
1000120014001600180020002200
engine speed [rpm]
MAP
[mba
r]
1000 2000 3000
20
40
60
80
100
injection injection
+ scavenging
diff
in a
ir m
ass
[%]
engine speed [rpm]
1000 2000 3000
68
101214161820
BMEP
[bar
]
1000 2000 30000
20
40
60
80
100
120 intake synchronious injection late injection late injection + scavenging
air m
ass
[kg/
h]
1000 2000 3000
1000120014001600180020002200
engine speed [rpm]
MAP
[mba
r]
1000 2000 3000
20
40
60
80
100
injection injection
+ scavenging
diff
in a
ir m
ass
[%]
engine speed [rpm]
1000 2000 3000
68
101214161820
BMEP
[bar
]
1000 2000 30000
20
40
60
80
100
120 intake synchronious injection late injection late injection + scavenging
air m
ass
[kg/
h]
1000 2000 3000
1000120014001600180020002200
engine speed [rpm]
MAP
[mba
r]
1000 2000 3000
20
40
60
80
100
injection injection
+ scavenging
diff
in a
ir m
ass
[%]
engine speed [rpm]
Late injection + scavenging double achievable torque
A3PS – ECO‐Mobility 2025plusTU Wien
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WOT – comparison different systems
1000 2000 3000 4000 5000
8
12
16
20
BMEP
[bar
] =8,8 Gasoline =8,8 CNG PFI =13,6 CNG DI =12,0 CNG DI
1000 2000 3000 4000 5000405060708090100
cylin
der p
eak
pres
sure
[bar
]
1000 2000 3000 4000 5000
0,7
0,8
0,9
1,0
engine speed [rpm]
A/F
ratio
[-]
1000 2000 3000 4000 5000
400
500
600
700
800
900
exha
ust t
empe
ratu
re [°
C]
engine speed [rpm]
1000 2000 3000 4000 5000
8
12
16
20
BMEP
[bar
] =8,8 Gasoline =8,8 CNG PFI =13,6 CNG DI =12,0 CNG DI
1000 2000 3000 4000 5000405060708090100
cylin
der p
eak
pres
sure
[bar
]
1000 2000 3000 4000 5000
0,7
0,8
0,9
1,0
engine speed [rpm]
A/F
ratio
[-]
1000 2000 3000 4000 5000
400
500
600
700
800
900
exha
ust t
empe
ratu
re [°
C]
engine speed [rpm]
1000 2000 3000 4000 5000
8
12
16
20
BMEP
[bar
] =8,8 Gasoline =8,8 CNG PFI =13,6 CNG DI =12,0 CNG DI
1000 2000 3000 4000 5000405060708090100
cylin
der p
eak
pres
sure
[bar
]
1000 2000 3000 4000 5000
0,7
0,8
0,9
1,0
engine speed [rpm]
A/F
ratio
[-]
1000 2000 3000 4000 5000
400
500
600
700
800
900
exha
ust t
empe
ratu
re [°
C]
engine speed [rpm]
1000 2000 3000 4000 5000
8
12
16
20
BMEP
[bar
] =8,8 Gasoline =8,8 CNG PFI =13,6 CNG DI =12,0 CNG DI
1000 2000 3000 4000 5000405060708090100
cylin
der p
eak
pres
sure
[bar
]
1000 2000 3000 4000 5000
0,7
0,8
0,9
1,0
engine speed [rpm]
A/F
ratio
[-]
1000 2000 3000 4000 5000
400
500
600
700
800
900
exha
ust t
empe
ratu
re [°
C]
engine speed [rpm]
Low End Torque of Gasoline can almost be achieved with CNG-DI @ high efficiency
A3PS – ECO‐Mobility 2025plusTU Wien
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Optimization – Results during the NEDC
0 200 400 600 800 10000
20406080
100120
velo
city
[km
/h]
time [s]
NEDC CO2-emissions =8,8 gasoline CO2-emissions =13,6 CNG CO2-emissions =12,0 CNG optimized
0 200 400 600 800 10000
20406080
100120
velo
city
[km
/h]
time [s]
NEDC CO2-emissions =8,8 gasoline CO2-emissions =13,6 CNG CO2-emissions =12,0 CNG optimized
0
20
40
60
80
100
-33%
CO
2 em
issi
ons
[%]
-29%
Good compromize between high compression ratio and combustionchamber shape has to be found
0 200 400 600 800 10000
20406080
100120
velo
city
[km
/h]
time [s]
NEDC CO2-emissions =8,8 gasoline CO2-emissions =13,6 CNG CO2-emissions =12,0 CNG
0
20
40
60
80
100
-8% from comb. process
-33%
CO
2 em
issi
ons
[%]
-29%
-25% from CH4
A3PS – ECO‐Mobility 2025plusTU Wien
09.11.2015 | Wien | Th. Hofherr| Folie 18
Conclusion
□ Development of an combustion process for CNG DI
□ CNG allows significant raise in compression ratio
□ Combustion chamber shape / wall heat losses / unburned losses limit the maximum compression ratio
□ With CNG-DI the LowEnd Torque of gasoline is almost achievable
□ Natural gas and optimized combustion process reach a reduction of CO2 emissions of 33%
![Potential of CNG-Direct-Injection for Downsizing Engine ...€¦ · -emissions =13,6 CNG CO 2-emissions =12,0 CNG optimized 0 20 40 60 80 100-33% CO 2 emissions [%]-29% Good compromize](https://static.documents.pub/doc/80x56/5f0bd1e07e708231d4325f2a/potential-of-cng-direct-injection-for-downsizing-engine-emissions-136-cng.jpg)
