partially premixed combustion, ppc – why all diesel engines
TRANSCRIPT
Partially Premixed Combustion, PPC – Why all diesel engines should be run on
gasoline
Bengt Johansson Lund University
First a little statement:
Dual fuel is not needed!
And 100.000 diesel cars per year are filled up with the wrong fuel in UK. Can we expect an average US car owner to
put two correct fuels in two tanks?
But I still think a single fuel is enough…
Scania diesel engine running on gasoline
4
0 2 4 6 8 10 12 1420
25
30
35
40
45
50
55
60
Gross IMEP [bar]
Gro
ss In
dic
ate
d E
ffic
ien
cy [%
]
Group 3, 1300 [rpm]
FR47333CVX
FR47334CVX
FR47336CVX
! ηi=57% 147 g/kWh (@43 MJ/kg heating value)
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
Background Combustion concepts
Spark Ignition (SI)
engine (Gasoline, Otto)
Compression Ignition
(CI) engine (Diesel)
Homogeneous Charge
Compression Ignition
(HCCI)
Partially premixed
combustion (PPC)
Diesel HCCI
Spark Assisted
Compression Ignition
(SACI)
Gasoline HCCI
+ High efficiency
+ Ultra low NOx
-Combustion control
-Power density
+ Clean with 3-way
Catalyst
- Poor low & part load
efficiency
+ High efficiency
- Emissions of NOx and
soot
+ Injection controlled
- Less emissions
advantage
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
Partially Premixed Combustion, PPC
9
-180 -160 -140 -120 -100 -80 -60 -40 -20
1000
2000
3000
4000
5000
6000Spridare 8x0.12x90 & 8x0.12x150, Iso-oktan, CR-tryck 750 bar, Duration 0,6 ms = 3.6 CAD
HC
[ppm
]
SOI [ATDC]-180 -160 -140 -120 -100 -80 -60 -40 -20
200
400
600
800
1000
1200
NO
x [
ppm
]
Def: region between truly homogeneous combustion, HCCI, and diffusion controlled combustion, diesel
HCCI
PPC
CI PCCI
SAE 2004-01-2990
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
2006-01-3412
Characterization of Partially Premixed
Combustion (PPC)
Christof Noehre, Magnus Andersson, Bengt Johansson and
Anders Hultqvist
PPC with Diesel Fuel!
Experimental setup
Displacement Volume 1951 cm³
Swirl Ratio (standard) 1.7
Swirl Ratio (if modified) 2.9
Fuel Swedish MK 1 Diesel, CN51
Injector holes 8
Injector hole diameter 0.18 mm
Spray umbrella angle 120
12
Specifications of single cylinder engine:
Compression ratios A=12.4:1; B=14.3:1; C=17.1:1
SAE 2006-01-3412
13
Load 8 bar IMEP
Abs. Inlet Pressure 2.5 bar
Engine Speed 1090 rpm
Swirl Ratio 1.7
Compression Ratio 12.4:1 (Low)
Inlet temp without
EGR 25 C
Inlet temp max
EGR 55 C
Emissions at 8 bar IMEP
SAE 2006-01-3412
14
1
4 5
3
Injection virtually finished before start of combustion
15
- One reason: insufficient ignition delay
Why is PPC not possible at highest
compression ratio?
Load 8 bar IMEP
Abs. Inlet Pressure 2.5 bar
Engine Speed 1090 rpm
Swirl Ratio 1.7
Effect of EGR and compression ratio at 8 bar IMEP
EGR sweep and compression ratio variation
Increased EGR
• PPC possible at 8 bar IMEP on compression ratios 12.4:1 and 14.3:1.
• Narrower operating range with increased compression ratio.
SAE 2006-01-3412
17
Effect of EGR and compression ratio at 12 bar IMEP
Load 12 bar IMEP
Abs. Inlet Pressure 3.0 bar
Engine Speed 1090 rpm
Swirl Ratio 1.7
• PPC only possible at 12 bar IMEP with lowest compression ratio (12.4:1).
• Soot emissions relatively high (compared to 8 bar IMEP).
SAE 2006-01-3412
18
The effect of EGR (and swirl) at 15 bar IMEP
Increased EGR Increased EGR
• Low soot/low NOx combustion possible. • Increased swirl lowers soot emissions, but
primarily before soot hump.
SAE 2006-01-3412
19
6
4 3
Gasoline instead of diesel fuel
Lic. Thesis by Henrik Nordgren 2005 and presented at DEER2005 20
Gasoline instead of diesel fuel
Lic. Thesis by Henrik Nordgren 2005 21
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
23
Gasoline tests in Scania D12
Bosch Common Rail
Prailmax 1600 [bar]
Orifices 8 [-]
Orifice Diameter 0.18 [mm]
Umbrella Angle 120 [deg]
Engine / Dyno Spec
BMEPmax 15 [bar]
Vd 1951 [cm3]
Swirl ratio 2.9 [-]
Dilution
Lambda 1.5
EGR 50 %
Fuel: Gasoline or Ethanol
SAE 2009-01-2668
24
Emissions – different fuels
2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
2.5
Gross IMEP [bar]
So
ot [F
SN
]
Ethanol
FR47330CVX
FR47331CVX
FR47333CVX
FR47334CVX
FR47335CVX
FR47336CVX
FR47338CVX
2 4 6 8 10 12 14 16 18 200
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Gross IMEP [bar]
NO
x [g
/kW
h]
Ethanol
FR47330CVX
FR47331CVX
FR47333CVX
FR47334CVX
FR47335CVX
FR47336CVX
FR47338CVX
2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
Gross IMEP [bar]
CO
[g
/kW
h]
Ethanol
FR47330CVX
FR47331CVX
FR47333CVX
FR47334CVX
FR47335CVX
FR47336CVX
FR47338CVX
2 4 6 8 10 12 14 16 18 200
1
2
3
4
5
6
7
8
9
10
Gross IMEP [bar]
HC
[g
/kW
h]
Ethanol
FR47330CVX
FR47331CVX
FR47333CVX
FR47334CVX
FR47335CVX
FR47336CVX
FR47338CVX
SAE 2010-01-0871
Energy flow in an IC engine
FuelMEP
QhrMEP
IMEPgross
lMEPnet
BMEP
QemisMEP
QlossMEP
QhtMEP
QexhMEP
PMEP
FMEP
Combustion efficiency
Thermodynamic efficiency
Gas exchange efficiency
Mechanical efficiency
Net Indicated efficiency
Brake efficiency
Gross Indicated efficiency
FuelMEP
QhrMEP
IMEPgross
lMEPnet
BMEP
QemisMEP
QlossMEP
QhtMEP
QexhMEP
PMEP
FMEP
Combustion efficiency
Thermodynamic efficiency
Gas exchange efficiency
Mechanical efficiency
Net Indicated efficiency
Brake efficiency
Gross Indicated efficiency
MechanicaleGasExchangmicThermodynaCombustionBrake***
25
26 26
Efficiencies 17.1:1
4 5 6 7 8 9 10 11 12 1350
55
60
65
70
75
80
85
90
95
100
Gross IMEP [bar]
[%] Combustion Efficiency
Thermal Efficiency
Gas Exchange Efficiency
Mechanical Efficiency
SAE 2009-01-2668
27 27
4 6 8 10 12 14 16 18 50
55
60
65
70
75
80
85
90
95
100
Gross IMEP [bar]
[%] Combustion Efficiency
Thermal Efficiency
Gas Exchange Efficiency
Mechanical Efficiency
Efficiencies 14.3:1
SAE 2010-01-0871
28 28
Experimental Apparatus, Scania D13
XPI Common Rail
Orifices 8 [-]
Orifice Diameter 0.19 [mm]
Umbrella Angle 148 [deg]
Engine / Dyno Spec
BMEPmax 25 [bar]
Vd 2124 [cm3]
Swirl ratio 2.095 [-]
Standard piston bowl, rc: 17.3:1 SAE 2010-01-2198
29 29 29
20 30 40 50 60 70 80 90 1000
5
10
15
20
25
RON [-]
IME
P g
ross [b
ar]
Stable operational load vs. fuel type
Tested Load Area
30
D13 Running on Diesel & Gasoline
5 10 15 20 25 3034
36
38
40
42
44
46
48
50
52
Gross IMEP [bar]
Bra
ke
Effic
ien
cy [%
]
D13 Gasoline
D13 Diesel
D13 Diesel was calibrated by Scania and the calibration was done to meet EU V legislation.
Average improvement of 16.6% points @ high load!!!
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
Close to Stoichiometric Partially
Premixed Combustion
- the Benefit of Ethanol in
Comparison to Conventional Fuels
Mengqin Shen, Martin Tuner and Bengt Johansson Lund University
2013-01-0277
Experimental System, Scania D13
Engine Piston Model
33
Scania D13 engine
Fuel Properties
Fuel RON MON CN H/C O/C LHV [MJ/kg]
Stoichiometric A/F Ratio
MK 1 - - 54 1.83 0 43.15 14.49
Gasoline 69 66 - 1.98 0 43.80 14.68
99.5% Ethanol 108 89 - 3 0.5 26.64 9
34
0 1 2 3 4 5 6 752
53
54
55
56
57
CA50 [CAD ATDC]
Gro
ss Indic
ate
d E
ffic
iency[%
]
O
Gross indicated efficiency as a function of combustion phasing (gasoline fuel, IMEP gross 11bar, FuelMEP 20.5 bar, λ=1.85,EGR=38%).
Optimized Combustion phasing
1 1.2 1.4 1.6 1.82
2.5
3
3.5
4
4.5
5
5.5
6
CA
50 [C
AD
AT
DC
]
[-]
MK1
Gasoline
Ethanol
Combustion phasing (CA50) as a function of λ (Fuel MEP 20.5 bar).
35
PPC-RoHR-diesel
-20 -10 0 10 20
0
50
100
150
200
Crank Angle [CAD ATDC]
Ro
HR
/10
[J/C
AD
] / In
jecto
r C
urr
en
t
=1.74
=1.58
=1.16
=1.05
36
PPC-RoHR-gasoline
-20 -10 0 10 20
0
50
100
150
200
Crank Angle [CAD ATDC]
Ro
HR
/10
[J/C
AD
] / In
jecto
r C
urr
en
t
=1.74
=1.58
=1.16
=1.05
37
PPC-RoHR-ethanol
-20 -10 0 10 20
0
50
100
150
200
Crank Angle [CAD ATDC]
Ro
HR
/10
[J/C
AD
] / In
jecto
r C
urr
en
t
=1.74
=1.58
=1.16
=1.05
38
FuelMEP ~20.5 bar EGR~38%
PPC-Efficiency
1 1.2 1.4 1.6 1.897.5
98
98.5
99
99.5
100
[-]
Com
bustion E
ffic
iency [%
]
MK1
Gasoline
Ethanol
1 1.2 1.4 1.6 1.835
40
45
50
55
[-]
Gro
ss Indic
ate
d E
ffic
iency [%
]
MK1
Gasoline
Ethanol
6% 9% 18%
39
1 1.2 1.4 1.6 1.80
0.5
1
1.5
2
[-]
Com
bustion L
oss [%
]
MK1
Gasoline
Ethanol
Efficiency & Losses
1 1.2 1.4 1.6 1.810
12
14
16
18
20
22
[-]
Exhaust Loss [%
]
MK1
Gasoline
Ethanol
• Relative combustion loss is between 0.2% and 1.7% in all cases.
• Less relative exhaust loss with lower λ . • More heat transfer in stoichiometric PPC due
to higher combustion temperature .High heat transfer loss is the main reason for low efficiency of diesel.
40
1 1.2 1.4 1.6 1.825
30
35
40
45
50
[-]
Heat T
ransfe
r Loss [%
]
MK1
Gasoline
Ethanol
PPC-Emissions
1 1.2 1.4 1.6 1.80
0.2
0.4
0.6
0.8
1
1.2
1.4
UH
C/N
Ox [g/k
Wh]
1 1.2 1.4 1.6 1.80
1
2
3
4
5
6
7
CO
[g/k
Wh]
[-]
CO[g/kWh]
NOx[g/kWh]
UHC[g/kWh]
UHC, CO and NOx emissions as a function of λ (FuelMEP 20.5 bar, EGR 38%, gasoline fuel).
1 1.2 1.4 1.6 1.8 20
2
4
6
8
10
[-]
Soot [F
SN
]
MK1
Gasoline
Ethanol
Soot emission as a function of λ (FuelMEP 20.5 bar, EGR 38%).
41
It is possible to operate PPC from lean conditions to close to stoichiometric conditions.
Gross indicated efficiency decreased for all the fuels in close to stoichiometric operation:
– Ethanol showed higher efficiency and less efficiency reduction than gasoline
and diesel fuel.
Pronounced soot emission increase for diesel and gasoline. Ethanol showed very low soot in all conditions.
Ethanol - Clean Stoichiometric PPC (with TWC).
Observations
42
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
PPC- LD
Comparison of Negative Valve Overlap (NVO) and Rebreathing Valve Strategies on a Gasoline
PPC Engine at Low Load and Idle Operating Conditions
44
SAE Paper 2013-01-0902
Patrick Borgqvist, Per Tunestål, Bengt Johansson Lund University
Introduction Partially Premixed Combustion – Light Duty Engine
20 30 40 50 60 70 80 90 1000
5
10
15
20
25
RON [-]
IME
P g
ross [b
ar]
PPC Operating Region from Heavy Duty Experiments [1]
•Goal: Increase attainable operating region
45
- Means to reduce minimum load: Injection strategies
- Advanced pilot strategies - Split main Trapping hot residuals - Temperature increase - Dilution - Stratification Glow plug
[1] Manente, V., et al. “An Advanced Internal Combustion Engine Concept for Low Emissions and High Efficiency from Idle to Max Load Using Gasoline Partially Premixed Combustion”, SAE 2010.01-2198
Experimental Setup – Volvo D5
Displacement 480 cm3 (1 cyl)
Number of
cylinders
5 (1 used)
Bore 81 mm
Stroke 93.2 mm
Compression
ratio
16.5:1
Valve timings Fully flexible
46
Nozzle Holes 5
Umbrella Angle 140 deg
Hole Size 0.159 mm
Fuel Injector Standard D5 piston
Engine
Fuel Specification
Fuel RON MON LHV [Mj/kg]
A/F stoich
Gasoline 87 81 43.50 14.60
47
20 30 40 50 60 70 80 90 1000
5
10
15
20
25
RON [-]
IME
P g
ross [b
ar]
Negative Valve Overlap (NVO)
48
-200 -100 0 100 200 300 400 5000
5
10
15
20
25
30
35
40
45
50
55
Crank Angle [CAD]
Pre
ssure
[bar]
/ V
alv
e L
ift [a
.u.]
NVO
Pressure
Intake Valve
Exhaust Valve
NVO
Trap hot residual gas to elevate the initial temperature of the fresh charge of the subsequent cycle Disadvantage Gas-exchange efficiency penalty
Rebreathing
49
-200 -100 0 100 200 300 400 5000
5
10
15
20
25
30
35
40
45
50
55
Crank Angle [CAD]
Pressure [bar]
Intake Valve [a.u.]
Exhaust Valve [a.u.]
Minimum possible NVO
Second exhaust valve opening
Advantage: Improved gas-exchange efficiency Disadvantage: Lower temperature of re-inducted residual gases compared to trapped residuals???
Combustion stability
50
Similar improvement on combustion stability with Rebreathing compared to NVO
NVO [CAD]IM
EP
gro
ss [bar]
NVO: std IMEPnet [bar]
60 80 100 120 140 160 180 200 2201.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
0.15
0.2
0.25
0.3
0.35
0.4
Rebreathing [CAD]
IME
Pgro
ss [bar]
Rebreathing: std IMEPnet [bar]
0 20 40 60 80 1001.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
0.15
0.2
0.25
0.3
0.35
0.4
Unburned Hydrocarbons
51
Similar improvement in hydro-carbon emissions reduction with Rebreathing compared to NVO
NVO [CAD]IM
EP
gro
ss [bar]
NVO: Unburned Hydro-Carbon Emissions [ppm]
60 80 100 120 140 160 180 200 2201.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
100
150
200
250
300
350
400
450
500
Rebreathing [CAD]
IME
Pgro
ss [bar]
Rebreathing: Unburned Hydro-Carbon Emissions [ppm]
0 20 40 60 80 1001.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
100
150
200
250
300
350
400
450
500
Gas exchange Efficiency
52
Gas-exchange efficiency is significantly higher with the Rebreathing strategy compared to NVO
NVO [CAD]IM
EP
gro
ss [bar]
NVO: Gas-Exchange Efficiency [%]
60 80 100 120 140 160 180 200 2201.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
84
86
88
90
92
94
96
Rebreathing [CAD]
IME
Pgro
ss [bar]
Rebreathing: Gas-Exchange Efficiency [%]
0 20 40 60 80 1001.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
84
86
88
90
92
94
96
Net Indicated Efficiency
53
The net indicated efficiency is higher with the Rebreathing case. Note, shown against IMEPnet
NVO [CAD]IM
EP
net [b
ar]
NVO: Net Indicated Efficiency [%]
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
25
30
35
40
Rebreathing [CAD]
IME
Pnet [b
ar]
Rebreathing: Net Indicated Efficiency [%]
0 20 40 60 80 100
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
25
30
35
40
NVO Injection
54
-200 -100 0 100 200 300 400 5000
5
10
15
20
25
30
35
40
45
50
Crank Angle [CAD]
Pressure [bar]
Valve Lift [a.u.]
Fuel Indicator [a.u.]
NVO Injection
Glow plug: ON Engine speed: 800 rpm Fuel: 87 RON Gasoline
Idea: Fuel reformation to improve the main combustion event
Effect of NVO Injection Timing
55
-40 -30 -20 -10 0 10 20 30 40-5
0
5
10
15
20
25NVO: 220 CAD
Fuel DistributionNVO/Main: 50/50 %
Lambda: 1.08 - 1.42
Crank Angle (Gas-Exchange TDC) [CAD]
Rate
of H
eat R
ele
ase [J/C
AD
]
Effect of NVO-Pilot Injection Timing
-22 CAD
-15 CAD
-10 CAD
-5 CAD
0 CAD
-40 -30 -20 -10 0 10 20 30 40-5
0
5
10
15
20
25NVO: 220 CAD
Fuel DistributionNVO/Main: 50/50 %
Lambda: 1.08-1.42
Crank Angle [CAD]R
ate
of H
eat R
ele
ase [J/C
AD
]
Effect of NVO-Pilot Injection Timing
-22 CAD
-15 CAD
-10 CAD
-5 CAD
0 CAD
NVO Injection – Ignition Delay
56
NVO [CAD]
IME
Pgro
ss [bar]
Ignition Delay (CA10-SOI) [CAD] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
8
10
12
14
16
18
Significant effect on the ignition delay when NVO is sufficiently high, from 200 CAD NVO
NVO Injection – Combustion stability
57
NVO [CAD]
IME
Pgro
ss [bar]
std IMEPnet [bar] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
0.1
0.15
0.2
0.25
0.3
Significant improvement on combustion stability with NVO injection and a high setting of NVO
NVO Injection - HC
58
NVO [CAD]
IME
Pgro
ss [bar]
Unburned Hydro-Carbon Emissions [ppm] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
350
400
450
500
550
600
650
700
Significant reduction of unburned hydrocarbon emissions with NVO injection and a high setting of NVO
NVO Injection - NOx
59
NVO [CAD]
IME
Pgro
ss [bar]
NOx [ppm] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
20
40
60
80
100
120
High NOx emissions in the intermediate region between too low and too high NVO settings Low NOx emissions when engine load is low and NVO is sufficiently high
NVO Injection -Soot
60
NVO [CAD]
IME
Pgro
ss [bar]
soot [FSN] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Soot emissions are much higher when NVO injection is used
NVO Injection -Lambda
61
NVO [CAD]
IME
Pgro
ss [bar]
soot [FSN] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
NVO [CAD]
IME
Pgro
ss [bar]
Lambda [-] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
NVO [CAD]
IME
Pgro
ss [bar]
NOx [ppm] (NVO Injection)
60 80 100 120 140 160 180 200 220
1.6
1.8
2
2.2
2.4
2.6
20
40
60
80
100
120
Putting it all Together
62
1. NVO, single injection 2. NVO with NVO injection, 200 CAD NVO 3. NVO with NVO injection, 220 CAD NVO 4. Rebreathing, single injection
Comparison of different valve strategies and fuel injection strategies, with optimized settings, at low engine speed and load operating conditions
Putting it all Together
63
Highest combustion stability with the NVO injection strategy
1 1.5 2 2.5 3 3.50.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
IMEPgross [bar]
std
IM
EP
net [b
ar]
NVO, sing. inj.
NVO, NVO inj. 200 NVO
NVO, NVO inj. 220 NVO
Reb, sing. inj.
Putting it all Together
64
Soot emissions are significantly higher with the NVO injection strategy depending on NVO setting Higher NVO gives a lower global air-fuel ratio
1 1.5 2 2.5 3 3.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
IMEPgross [bar]
soot [F
SN
]
NVO, sing. inj.
NVO, NVO inj. 200 NVO
NVO, NVO inj. 220 NVO
Reb, sing. inj.
Putting it all Together
65
Net indicated efficiency is highest with the Rebreathing strategies
1 1.5 2 2.5 3 3.524
26
28
30
32
34
36
38
40
42
IMEPgross [bar]
Net In
dic
ate
d E
ffic
iency [%
]
NVO, sing. inj.
NVO, NVO inj. 200 NVO
NVO, NVO inj. 220 NVO
Reb, sing. inj.
Low Load Operating Strategy Summary
66
IMEPgross [bar]
2.0
NVO NVO injection
+ Lowest std of IMEP - soot emissions
Rebreathing
+ highest indicated efficiency - Low load limitation • Tradeoff between Nox and UHC emissions
3.0
Gradually replace hot residuals with EGR to suppress NOx emissions
2.5
Outline
• Combustion concepts
• PPC – background
• PPC with diesel fuel
• PPC with gasoline
• Low dilution PPC with ethanol
• Too low load with too high octane number
• Summary
Partially Premixed Combustion, PPC
• Compression Ignition should use gasoline not diesel
• PPC is the most efficient of all processes known (using one fuel)! – Combustion Efficiency >99.8%
– Thermodynamic Efficiency= 55-57%
– Gas exchange efficiency reasonable
– Mechanical efficiency high as load can be high
• Load range 1.5-26 (30) bar IMEP
• Low enough emissions – NOx, HC and CO below legal limits without catalytic aftertreatment
– PM low enough using ethanol and low with gasoline
68
The End
Thank you
69
Partially Premixed Combustion, PPC – Why all diesel engines should be run on
gasoline
Bengt Johansson Lund University