Institute for Internal Combustion Engines & Thermodynamics
G r a z U n i v e r s i t y o f T e c h n o l o g y
Application of Low Pressure Direct Injection and Semi-Direct Injection to a
Small Capacity Two-Stroke Engine
Franz Winkler
Roland Oswald
Oliver Schögl
Roland Kirchberger
Andreas Ebner
2SAE 2008-32-0059
JSAE 20084759
Benchmark4
Engine & vehicle
development
3
Combustion system
development
2
Introduction1
Conclusion5
Structure
3SAE 2008-32-0059
JSAE 20084759
Benchmark4
Engine & vehicle
development
3
Combustion system
development
2
Introduction1
Conclusion5
Introduction
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New European emission legislation EURO III < 50 cm³:
including cold start emission (weighting factor of 30% (50%))
catalyst durability (up to 10000km)
Introduction
Motivation
European emission cycle ECE R 47
0
10
20
30
40
50
60
0 112 224 336 448 560 672 784 896
time [sec]
veh
icle
sp
eed
[km
/h]
.
warm up phase hot phase
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Introduction
The Engine
Basic engine data
Capacity: 50 cm³ 2-stroke engine
Bore: 40 mm
Stroke: 39.2 mm
Compression ratio: 11.68
Power: 3.7 kW
Torque: 5 Nm
…
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Introduction
The Engine
Basic engine data
Port configuration
Loop scavenged
5 transfer ports
Reed valve
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Introduction
The strategyDirect injection mode
Fuel injection duringscavenge process
Homogenization in the cylinder
Figure 1
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Introduction
The strategyDirect injection mode
Fuel injection duringscavenge process
Homogenization in the cylinder
Stratified mode
Fuel injection trough the window of the piston
Figure 2Figure 2
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Introduction
The strategyDirect injection mode
Fuel injection duringscavenge process
Homogenization in the cylinder
Stratified mode
Fuel injection trough the window of the piston
Stratified scavenging troughthe boost port
Homogenization in the cylinder
Figure 2
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Introduction
The strategyDirect injection mode
low HCs
low BSFC
Stratified mode
low BSFC
max. Power @ high rpm
crankcase cooling
stability at idle and part load
lower HCs than carburettor
Figure 3
SPC SPO
EPC EPO
BDC
TDC
stratified
direct injection
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Introduction1
Benchmark4
Engine & vehicle
development
3
Combustion system
development
2
Conclusion5
Combustion system development
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Combustion System Development
Spray Quality and Fuel PressureTwo different spray types
400 kPA two holes 700 kPA three holes
Figure 4
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5000
10000
15000
20000
25000
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [U/min]
HC
[p
pm
]
carburetted
700 kPa direct injection
400 kPa direct injection
Figure 5
Combustion System Development
Spray Quality and Fuel Pressure
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Combustion System Development
Spray Quality and Fuel Pressure400 kPA injector
visualization 6000 rpm WOT simulation
Figure 6
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Combustion System Development
Spray Quality and Fuel Pressure700 kPA injector
visualization 6000 rpm WOT simulation
Figure 6
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Thermodynamic analysis
Combustion System Development
Figure 7
24.7 26.1 26.0 26.8
2.5
2.6 2.0 3.0 2.1
4.0
4.5 4.8 4.5 4.4
0.9
1.0 0.81.8 2.1
19.1
15.6 14.814.1 14.1
20.8
0.0
10.0
20.0
30.0
40.0
50.0
ext. mix.
preparation
4 bar DI 7 bar DI 4 bar DI (piston
bowl)
7 bar DI (piston
bowl)
eff
icie
nc
y[%
]
losses due to real working gas
scavenge losses
losses due to heat release rate
wall heat losses
charge exchange losses
indicated efficiency
Figure 7
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Combustion System Development
5000
10000
15000
20000
25000
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [U/min]
HC
[ppm
]
carburetted
direct injection
stratified
Figure 8
Injection strategies
18SAE 2008-32-0059
JSAE 20084759
Benchmark4
Engine & vehicle
development
3
Combustion system
development
2
Introduction1
Conclusion5
Engine & vehicle development
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Engine & vehicle development
Engine development
Design
Cylinder
Cylinder head
Intake system
Exhaust system
…
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Engine & vehicle development
Engine development
Design
Prototyping
Cylinder
Cylinder head
Intake system
Exhaust system
…
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Engine & vehicle development
Engine development
Design
Prototyping
Engine test bench
Performance
Emissions
Durability
…
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Test bench results – Engine test bench
0
1
2
3
4
5
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [U/min]
po
we
r [k
W],
to
rqu
e [
Nm
]
0
100
200
300
400
500
BS
FC
[g
/kW
h]
Power
Torque
BSFC
Figure 9
Torque, Power and BSFC
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Figure 210
25
50
75
100
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [rpm]
BS
HC
[g
/kW
h] HC untreated
CO untreated
Figure 10
Untreated HC- & CO-Emissions
Test bench results – Engine test bench
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Test bench results – Engine test bench
Figure 19
Exhaust gas purification
0.00
0.25
0.50
0.75
1.00
1.25
1.50
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [U/min]
eq
uiv
ale
nce r
atios [
- ]
Equivalence ratio
Equivalence ratio (unburned exhaust gas)
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0
10
20
30
40
50
60
70
80
90
100
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500
engine speed [U/min]
co
nve
rsio
n r
atio
[%
]
Conversion ratio HC
Conversion ratio CO
Conversion ratio of HC and CO
Test bench results – Engine test bench
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0
25
50
75
100
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [rpm]
BS
HC
[g/k
Wh] HC untreated
CO untreated
Figure 10
Test bench results – Engine test bench
Figure 190
25
50
75
100
3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
engine speed [rpm]
BS
HC
[g/k
Wh]
HC untreated
HC after catalyst
CO untreated
CO after catalyst
Figure 10
HC- & CO-Emissions after catalyst
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Engine & vehicle development
Vehicle development
Design
Fuel system
Oil system
Cooling system
…
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Engine & vehicle development
Vehicle development
Design
Prototyping
4 prototype vehicles
2 different speed versions
45 km/h ECE R47 (<50 cm³)
+60 km/h ECE 40 (<150 cm³)
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Engine & vehicle development
Vehicle development
Design
Prototyping
Chassis dyno & on road development
Performance (CVT setting)
Cold start
Warm up strategy (emissions)
Transient calibration
Cold chamber & altitude
…
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Test bench results – Chassis test bench
0
10
20
30
40
50
60
0 112 224 336 448 560 672 784 896
time [sec]
ve
hic
le s
pe
ed
[k
m/h
] .
warm up phase hot phase
Test cycle ECE R47
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0
10
20
30
40
50
60
0 112 224 336 448 560 672 784 896
time [sec]
ve
hic
le s
pe
ed
[k
m/h
], H
C [
pp
m]
x1
0
0
1
2
3
4
5
6
ac
cu
mu
late
d H
C [
g]
target speed transient emissions accumulated emissions
warm up phase hot phase
Figure 12
Test bench results – Chassis test bench
HC-Emissions
Catalyst light-off for HC < 60sec
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0
10
20
30
40
50
60
0 112 224 336 448 560 672 784 896
time [sec]
ve
hic
le s
pe
ed
[k
m/h
], C
O [
pp
m]
x1
0
0
1
2
3
4
5
6
ac
cu
mu
late
d C
O [
g]
warm up phase hot phase
Figure 12
CO-Emissions
Test bench results – Chassis test bench
Catalyst light-off for CO < 30sec
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Test bench results – Chassis test bench
0
10
20
30
40
50
60
0 112 224 336 448 560 672 784 896
time [sec]
veh
icle
sp
eed
[km
/h],
NO
x [
pp
m]
0
0,5
1
1,5
2
2,5
3
accu
mu
late
d N
Ox [
g]
warm up phase hot phase
Figure 12
NOx-Emissions
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1
1.2
CO [g/km] 0.90
HC + NOx [g/km] 1.14
CO 0.44 43.8 CO 0.57 57.0
HC + NOx 0.50 41.3 HC + NOx 0.68 56.7
CO [g/km] 0.24
HC + Nox [g/km] 0.22x
Emission results ECE R 47 (mileage ~1000 km) limits:CO [g/km]:
HC + NOx [g/km]:
0.5
Emissions warm up
Emissions hot
weighting
factor
% of limit % of limit0.5Emissions
[g/km]
+
weighting
factor
Emissions
[g/km]x
+
0.7
x
x
0.3
Test bench results – Chassis test bench
ECE R 47 emission results
Figure 13
Procedure
ECE R47 after 1000 km
Results< 50 % < 60 %
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Test bench results – Chassis test bench
Test cycle ECE 40 <150 cm³
0
10
20
30
40
50
60
0 195 390 585 780 975 1170
time [sec]
ve
hic
le s
pe
ed
[k
m/h
]
EURO II measurment phase EURO II warm up phase (2003)
EURO III measurment phase
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HC-Emissions
Test bench results – Chassis test bench
0
20
40
60
80
0 195 390 585 780 975 1170
time [sec]
veh
icle
sp
eed
[km
/h],
HC
[p
pm
x10]
0
1
2
3
4
acc.
HC
[g
]
acc. HC-Emissions
HC-Emissons
Figure 15
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Test bench results – Chassis test bench
CO-Emissions
0
10
20
30
40
50
60
0 195 390 585 780 975 1170
time [sec]
veh
icle
sp
eed
[km
/h],
CO
[p
pm
x10]
0
1
2
3
4
5
acc.
CO
[g
]
CO-Emissons
acc. CO-Emissions
Figure 15
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Test bench results – Chassis test bench
NOx-Emissions
0
10
20
30
40
50
60
0 195 390 585 780 975 1170
time [sec]
veh
icle
sp
eed
[km
/h],
NO
x [
pp
mx10]
0
1
2
3
4
5
acc.
NO
x [
g]
NOx-Emissons
acc. NOx-Emissions
Figure 15
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Test bench results – Chassis test bench
ECE 40 emission results
Procedure
ECE 40 after 1000 km
Results
CO [g/km]: 2
HC [g/km]: 0.8
NOx [g/km]: 0.15
CO
HC
NOx
limits:
Emission results ECE 40 urban cycle
(mileage ~ 1000 km)
Emissions
warm up + hot phase
% of the Limit
15.46
77.06
69.55
0.31
0.62
0.10
Emissions [g/km]
Figure 14
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JSAE 20084759
Benchmark4
Engine & vehicle
development
3
Combustion system
development
2
Introduction1
Conclusion5
Benchmark
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JSAE 20084759
Benchmark
Figure 28
Benchmark
Procedure
Comparison of 3 different low emission concepts
ECE R47
Technologies
50 cm³ four-stroke, efi, 3-way-catalyst
50 cm³ two-stroke, air-assisted direct injection, oxidation catalyst
50 cm³ two-stroke, low-pressure direct injection, oxidation catalyst
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Benchmark
Figure 28
ASDI
LPDI
4T
=1
ASDI
LPDI
4T
=1
0,0
0,2
0,4
0,6
0,8
1,0
0,0 0,2 0,4 0,6 0,8 1,0 1,2
HC+ NOx [g/km]
CO
[g/k
m]
Euro II (since 2003) without coldstart
Euro III (from 20XX) including coldstart
Euro IV ?
Euro II - EURO III Benchmark
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Analysis of the 2-stroke
scavenge process
3
Assessment of mixture
preparation systems
2
Introduction1
CFD-Simulation of spray
and mixture preparation
4
Conclusion5
Conclusion
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Conclusion
It was demonstrated that with the introduced injection strategy the reduction of untreated HC emissions is ~ 40%
The reduction of scavenge losses lead to a ~ 25% lower fuel consumption
Very lean exhaust gas due to the stratification of the scavenge process increase the conversion ratio of HC and CO
The increased exhaust gas temperature shortens the cat light-off time leading to reduced cold start emissions
There is no need for specific technology development (standard two-stroke engine with standard injection components) therefore the development risk is comparatively low
Focusing costs and market acceptance, this strategy is a valuable alternative to existing DI-systems
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Thank you foryour attention
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