High-Efficiency Clean Combustion Design for …...High-Efficiency Clean Combustion Design for...
Transcript of High-Efficiency Clean Combustion Design for …...High-Efficiency Clean Combustion Design for...
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Design for Compression Ignition High-Efficiency Clean Combustion
Engines
Mike PotterRuss Durrett
General MotorsAugust 24, 2006
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Overview
U.S. Heavy Duty Emission Standards
U.S. Light Duty Emission Standards
0.10 19982004
2007 2010
0.08
0.05
PM (g
/hp-
hr)
Tier 2, Bin 10 (2007-2010)
Euro 3 (2000)
Euro 4 (2005)
Euro 5 Prop
T2 Bin 5
T2 Bin 8
PM (g
/mi)
0.01 0.04
0.00 0 0.2 1 2 3 4
NOX (g/hp-hr) 0.02
0.01
0 0 0.1 0.3 0.4 0.6 0.8
NOX (g/mi)August, 2006 2
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
Tflame 21% O215%
10% 8%
NOX production zone
soot production
zone
CO / UHC oxidation
limit
Tcharge
fuel – charge mixing line
ignition zone
• The φ vs. T diagram is commonly used in diesel combustion discussions.
• Combustion processes pass through a particular path in this space.
• Time is not represented in the figure.
Temperature (K) August, 2006 3
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot Tcharge effect production zone
CO / UHC oxidation
limit
Tcharge
- VVA - Tintake
fuel – charge mixing line
ignition zone
Fuel – charge mixing line (green): As the fuel and charge mix, the temperature and equivalence ratio of the mixture will follow this line. The location of the line changes with Tcharge.
Tflame
Temperature (K) August, 2006 4
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
CO / UHC oxidation
limit
Tcharge
fuel – charge mixing line
ignition zone
fuel cetane effect
Ignition zone (grey): This is the temperature range above which a diesel fuel / air mixture will ignite rapidly.
Tflame
Temperature (K) August, 2006 5
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T flame
Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
CO / UHC oxidation
limit
Tcharge
fuel – charge mixing line
ignition zone
flame temperature
Flame temperature lines (red): The adiabatic flame temperature of a fuel / charge mixture at the given equivalence ratio.
Temperature (K) August, 2006 6
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
CO / UHC oxidation
limit
Tcharge
fuel – charge mixing line
ignition zone
soot production
zone
Soot production zone (blue): This denotes the region where soot is formed in significant quantities.
Tflame
Temperature (K) August, 2006 7
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
soot production
zone
CO / UHC oxidation
limit
Tcharge
fuel – charge mixing line
ignition zone
NOX production zone
NOx production zone (cyan): This denotes the region where NOX is formed in significant quantities.
Tflame
Temperature (K) August, 2006 8
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Equivalence Ratio (φ) vs T Space – Navigating the Terrain
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
fuel – charge mixing line
ignition zone
CO / UHC oxidation
limit
CO / UHC oxidation limit (orange): Must complete combustion above this temperature in order to consume CO and unburned HC.
Tflame
Temperature (K) August, 2006 9
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Conventional Diesel Combustion Eq
uiva
lenc
e R
atio
(φ)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
ignition zone
A
fuel – charge mixing line
Fuel mixes with charge (A) until the ignition temperature is reached.
The path shows the trajectory of a fuel parcel undergoing a conventional diesel combustion event.
Tflame
CO / UHC oxidation
limit
Temperature (K) August, 2006 10
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Conventional Diesel Combustion Eq
uiva
lenc
e R
atio
(φ)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
ignition zone
A
fuel – charge mixing line
B C
premixed
The fuel first undergoes a rich premixed reaction (B-C) in which part of the fuel energy is released.
Tflame
CO / UHC oxidation
limit
Temperature (K) August, 2006 11
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Conventional Diesel Combustion Eq
uiva
lenc
e R
atio
(φ)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
ignition zone
A
fuel – charge mixing line
B C
premixed
D
diffusion
The remainder of the fuel energy is released as the rich products continue to mix with oxygen (C-D) in a diffusion flame.
Tflame
CO / UHC oxidation
limit
Temperature (K) August, 2006 12
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Conventional Diesel Combustion Eq
uiva
lenc
e R
atio
(φ)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
ignition zone
A
fuel – charge mixing line
B C
premixed
D
diffusion
E
The combustion products continue to mix throughout the chamber (D-E).
Tflame
CO / UHC oxidation
limit
Temperature (K) August, 2006 13
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New Combustion Modes (PCCI) – Reducing NOx and Soot
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
A
B C
D’ D E
ignition zone
soot
B’ C’
NOX reduction
reduction
fuel – charge mixing line Increased mixing (lower φ at ignition)
comes from longer ignition delay via reduction in Tcharge at injection.
Flame temperature reduction comes from reduced oxygenTflame concentration via EGR.
CO / UHC oxidation
limit
Temperature (K) August, 2006 14
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zone
Soot Reduction Through Low O2 Concentration
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
Tcharge
ignition zone
fuel – charge mixing line
A
B C
D
incomplete
E
Tflame
CO / UHC oxidation
limit
soot and NOX reduction
In this scenario, soot is never formed due to the low temperature during ignition and combustion.
Difficult to avoid
combustion products (CO / UHC).
Temperature (K) August, 2006 15
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1510%
8%
Ideal Combustion Process Eq
uiva
lenc
e R
atio
(φ)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
Tflame 21% O2%combustion
NOX production zone
soot production
zone
CO / UHC oxidation
limit
Tcharge
ignition zone
takes place here
fuel – charge mixing line
The ideal process will create the necessary conditions in which most of the energy release will take place in the region shown.
Temperature (K) August, 2006 16
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New Combustion Modes (PCCI) – Reducing NOx and Soot
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0 500 1000 1500 2000 2500 3000
21% O215% 10%
8%
NOX production zone
soot production
zone
Tcharge
A
B C
D’ D E
ignition zone
soot
B’ C’
NOX reduction
reduction
fuel – charge mixing line Improvements in the hardware
available have improved our ability to use PCCI modes and increased their applicable range of speed and load.
Tflame
CO / UHC oxidation
limit
Temperature (K) August, 2006 17
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End of Presentation
• BackUp Material
August, 2006 18
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Early vs. Late PCCI
• PCCI mode requires a longer ignition delay.
• How to lengthen the ignition delay: • Lower T at SOI • Lower [O2] at SOI
• In order to access lower temperature, the injection must move away from TDC: • Advance timing for early PCCI • Retard timing for late PCCI
• Compression ratio and charge temperature will also affect the injection range.
comp. ratio or ignition delay
too short
Late
PC
CI
Reg
ion
Ear
lyP
CC
IR
egio
n
temperature in cylinder
charge temp. variation
injection range
injection range
ignition temp.
TDC
August, 2006 19
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CO / UHCoxidation
limit
Some Practical Limitations
• Impossible to achieve temperatures higher than the flame temperature – operation in the high T – high φ region is precluded.
• The ignition process must pass through the region shown (need better words here!)
• End of combustion temperature must remain high enough to insure complete oxidation of CO and UHC compounds.
Equi
vale
nce
Rat
io (φ
)
6
5
4
3
2
1
0500 1000 1500 2000 2500 3000
T flame 21% O2
15% 10%
8%
NOx production zone
soot production
zone
fuel – charge mixing line
ignition zone
Tcharge
high T – high φ region must pass
this region
incomplete HC / CO oxidation
Temperature (K)
August, 2006 20