Research and Advanced Engineering The Influence of Fuel Cetane Number on Catalyst Light-Off Operation in a Modern Diesel Engine 2nd CRC Advanced Fuel and Engine Efficiency Workshop Nov 3, 2016 Eric Kurtz, Ford Motor Company Diesel Combustion System Technical Expert
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Research and Advanced Engineering
1
The Influence of Fuel Cetane Number on Catalyst Light-Off Operation in a
Modern Diesel Engine
2nd CRC Advanced Fuel and Engine Efficiency Workshop Nov 3, 2016
Eric Kurtz, Ford Motor CompanyDiesel Combustion System Technical Expert
Research and Advanced EngineeringEmissions Challenge
Statistical comparison across pairwise data (calibrations) isolating difference between two fuels
Paired T-Test
0 inside CI = fuel has no effect (verify null hypothesis)0 outside CI = fuel has an effect
Null hypothesis: fuels have no effect
Research and Advanced Engineering
Effect on Legacy Fleet in a Catalyst Light-Off Mode
Comparison across identical calibrations (analysis of all data)• Little/no difference in exhaust T & H, noise, smoke• Higher NOx, but lower NOx + HC
12
Increased cetane would have minimal impact on legacy fleet A/T function, but may reduce NOx + HC during catalyst light-off operation.
Analysis of data from all 4 points together
Difference (high CN – Low CN)
X production calibration
paired t-test 95% conf. interval
-60
-40
-20
0
20
40
60
Abs
. or R
el. D
iffer
ence
[°C
or %
]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B] -3
-2
-1
0
1
2
3
Abs
. Diff
eren
ce [d
B]
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
NO
x &
N
Ox
&
NO
x &
N
Ox
&
NO
x &
Research and Advanced Engineering
Effect on Future Fleet in a Catalyst Light-Off Mode
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Analysis of data from all 4 points together
Difference (high CN – Low CN)
X production calibration
paired t-test 95% conf. interval
optimized calibration
Optimize calibration for the fuel• 30% higher exhaust temperature and enthalpy for faster cast light-off• Higher NOx, but lower NOx+HC and smoke
Potential to more quickly light-off catalysts while controlling emissions with higher cetane fuel, thus reducing TP emissions.
-60
-40
-20
0
20
40
60
Abs
. or R
el. D
iffer
ence
[°C
or %
]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B]
Exh
. Tem
p. [°
C]
Exh
. Ent
halp
y [%
]
NO
x [%
]
THC
[%]
NO
x &
TH
C [%
]
Sm
oke
[%]
Noi
se [d
B] -3
-2
-1
0
1
2
3
Abs
. Diff
eren
ce [d
B]
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
-3
-2
-1
0
1
2
3
NO
x &
N
Ox
&
NO
x &
N
Ox
&
NO
x &
Research and Advanced Engineering
-30 -15 0 15 30 45 60 75 90
0
10
20
30
40
Engine Postion [dATDC]
AH
HR
[J/d
eg]
Low Cetane @ Base Cal.High Cetane @ Base Cal.Fed Cert Fuel @ Base Cal
-30 -15 0 15 30 45 60 75 90
0
10
20
30
40
Engine Postion [CA ATDC]
AH
HR
[J/d
eg]
Low Cetane @ Base Cal.High Cetane @ Optimized Cal.Fed Cert Fuel @ Base Cal
Heat Release Analysis
14
1200 rpm, 8% load, 90°C
-30 -15 0 15 30 45 60 75 900
20
40
60
80
100
Engine Postion [dATDC]
MFB
[%]
-30 -15 0 15 30 45 60 75 900
20
40
60
80
100
Engine Postion [CA ATDC]
MFB
[%]
Heat Release Rate Mass Burn Fraction
-30 -15 0 15 30 45 60 75 900
1
2
Engine Postion [CA ATDC]
Inj.
Sig
nal [
-]
-30 -15 0 15 30 45 60 75 900
1
2
Engine Postion [CA ATDC]
Inj.
Sig
nal [
-]
Higher cetane fuel enabled significantly later combustion while
controlling emissions.
Research and Advanced EngineeringConclusions
• This study suggests that:– increasing cetane would have minimal impact on catalyst light-off
and may slightly reduce tailpipe emissions in legacy vehicles.– the relatively low cetane fuel in the US may limit the ability to light-
off catalysts while controlling for future emissions standards.– further study is warranted.
• To fully understand the effect of changing fuels specifications, fuels testing should include:– evaluation with production calibrations to define effects on today’s
vehicles.– optimization of the calibration for the new fuel to estimate the
impact on tomorrow’s vehicles.
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Research and Advanced Engineering
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