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OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Fuel Chemistry and Cetane Effectson HCCI Performance,
Combustion, and Emissions
presentation for DEER 2005
Bruce G. Bunting, Craig Wildman, Jim Szybist, Sam Lewis, and John Storey
Oak Ridge National LaboratoryFuels, Engines, and Emissions Research Center
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Outline of talk
• Purpose of research• Engine and experimental procedure• Results• Conclusions• Future work• Acknowledgements
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Purpose of research
• To provide simple comparisons of the performance of diesel range fuels differing in properties and chemistry in HCCI combustion
– Current study covers commercial fuels• cetane range of 40 to 73• aromatics range of 0% to 33%• includes 100% biodiesel and Fischer-Tropsch fuels
– A second study covers diesel secondary reference fuels• 18 to 76 cetane• will be presented at SAE HCCI Symposium
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Example diesel fuel composition (GC/MS)
0
100000
200000
300000
400000
500000
600000
700000
5 10 15 20 25 30
Elution Time
Con
cent
ratio
n (a
.u.)
C25
C24
C22
C21C20
C19
C18
C17C16
C15
C14
C13
C12
C23
Mixture of Aromatics & Branched Alkenes and Alkanes
Sulfur Compound :4(1)dimethylethyl-2-methyl Benzenethiol
Polyaromatic
Distinct peaks are straight-chain saturated compounds; i.e., Alkanes. Broad HC envelop is composed of everything else; i.e., branched alkanes, alkenes, aromatics…Broad range of straight-chain alkanes.
C9C10
C11
Normal paraffins with a carbon number range of 8 to 25
Iso-paraffins, cyclo-paraffins, olefins, and aromatics
2004 #2 pump fuel45 cetane
33% aromatic67% paraffin
0% olefin
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
15 fuels evaluated
10 Commercial fuels• 2004 fuels• 2007 fuels
• 5 diesel secondary reference blends
• Cetane range • 41 to 73
• Aromatics range • 0 to 33%
Fuel Cetane Aromatics (%)
A (2007) 45.4 23.5B (#2 Cert) 47.9 30.5
C (2004) 47.9 15.7D (2007) 50.5 12.0E (2007) 50.5 26.4F (2007) 50.5 32.8G (2007) 50.5 29.9
H (B100D) 53.2 0I (California) 53.6 21.4
J (FT) 73.0 0.9K (37%T/63%U) 40.7 15.8L (46%T/54%U) 46.7 15.0M (54%T/46%U) 50.5 14.4N (63%T/37%U) 53.6 13.6O (72%T/28%U) 60.7 13.0
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Engine used for experiments
• Based on Hatz 1D50Z– Single cylinder, air cooled– 2 valve, naturally aspirated– 517 cc, 97 mm bore, 70 mm stroke– Selected modifications made to engine
• 10.5 C/R• Port fuel injection with heated atomizer• Intake air heater
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
- Standard tube fittings- 400 watt cartridge heater- Slight air purge- Operated at 375 deg.C- Mounted between air heaterand intake port
- Fuel controlled by laboratorymetering pump
- Provides very uniform fuel mixing
Heated atomizer
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Engine and test stand
MODIFIED PISTONWITH SPHERICAL
COMBUSTION BOWL
INTAKE AIR HEATER
ATOMIZINGINJECTOR
ENGINE
BELT DRIVE
INDUCTION MOTOR
METERING PUMP
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
IMEP vs. MFB50%
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
350 355 360 365 370 375
MFB50% (CAD)
IMEP
(bar
)
Experimental procedure• Intake temperature used to
alter combustion phasing• MFB50 correlates best to
block temperature and Φ• Combustion phasing
bounds established– Retarded timing limited
by COV IMEP of 10% – Advanced timing limited
by rate of pressure rise of 25 bar/deg
• Point of best efficiency used for all comparisons
Operating Conditions• 1800 RPM• Stock valve timing• ~3 bar net IMEP• 15 mL/min fuel flow• 0.3 < Φ < 0.46
dP/dCA limit COV limit
Best eff.
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Cetane and aromatic range covered
0
5
10
15
20
25
30
35
40 45 50 55 60 65 70 75
Cetane number
% a
rom
atic
s
B100 FT
Olefins ranged from0.7 to 2.3%
Lower heating valuesof fuels were within ±2%except B100 and FT, which were lower
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Maximum IMEP
Max IMEP does not appear to depend in cetane or aromatics
B100 and FT were lowest
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
3.6
3.5
3.53.4
3.5
3.5
3.3
3.2
3.5
3.5
3.2
3.5 3.5
3.02.9
2.9 bar
3.0 bar
3.1 bar
3.2 bar
3.3 bar
3.4 bar
3.5 bar
3.6 bar
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
MBT combustion phasingCombustion phasing correlates with cetane number but
not with aromatics. Higher cetane requires earlier MFB50
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
365.5
364
368.6364.7
364
367.9
363
360.2
362.5
362.9
360.3
362.6 359.7
353.8352.5
353.0 CAD
357.0 CAD
361.0 CAD
365.0 CAD
369.0 CAD
50% MFB vs. Cetane
352.0
354.0
356.0
358.0
360.0
362.0
364.0
366.0
368.0
370.0
40 50 60 70
Cetane Number
MFB
50%
(CA
D)
Highest IMEP: SRFs Highest IMEP: All Data
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Maximum rate of pressure rise
Rate increases with aromatics
Cetane number appears to have little effect
B100 is highest and does not fit trend
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
4.5
5.5
3.75.2
9.4
5.0
6.2
7.6
6.5
5.6
6.2
4.6 5.6
4.810.4
3.5 bar/deg
4.5 bar/deg
5.5 bar/deg
6.5 bar/deg
7.5 bar/deg
8.5 bar/deg
9.5 bar/deg
10.5 bar/deg
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
NOx emissions
NOx is below 10ppm for all
Highest NOxoccurs at high aromatics and low cetane
B100 highest NOx
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
3.7
4.4
3.84.1
8.9
4.2
5.0
7.9
4.1
3.0
3.3
2.1 2.3
2.410.1
2.0 ppm
3.0 ppm
4.0 ppm
5.0 ppm
6.0 ppm
7.0 ppm
8.0 ppm
9.0 ppm
10.0 ppm
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
HC emissions
HC increase with aromatics
Analyzer and sample train were seriously contaminated by B100
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
1927
1735
17871411
2047
2256
2332
2348
2061
1726
2403
1661 1474
17272607
1400 ppm
1600 ppm
1800 ppm
2000 ppm
2200 ppm
2400 ppm
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
NOx corresponds to rate ofpressure rise for all data
NOx vs. Max Rate of Pressure Rise
0102030405060708090
0.0 5.0 10.0 15.0 20.0 25.0
dp/dCA (bar/deg)
NO
x (p
pm)
REGION OF RETARDEDAND OPTIMUM TIMING
TIMING ADVANCEDFROM OPTIMUM
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
LTHR % of totalLow temperature heat release magnitude increases with cetane, no aromatic effect
40 45 50 55 60 65 70 75Cetane Number
0
5
10
15
20
25
30
35
Aro
mat
ics
(%)
3.4
3.0
1.91.4
1.8
1.5
2.9
3.3
3.8
4.5
4.1
6.7 7.7
10.92.6
1 %
2 %
3 %
4 %
5 %
6 %
7 %
8 %
9 %
10 %
11 %
Cumulative Heat Release vs. Crank Angle
0
50
100
150
200
250
300
350
400
330 340 350 360 370 380 390
Crank Angle (deg)
Cum
ulat
ive
Hea
t Rel
ease
(J)
LTHR
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Summary of results at best timingVARIABLE HIGHER
CETANEHIGHER AROMATICS B100 FT
Max IMEP ---- ---- ↓ ↓Optimum MFB50 advances ---- Follows cetane
trendFollows cetane
trendMaximum rate of pressure rise ---- ↑ ↑ ----
CA10-90 ---- ---- ↓ Longer (LTHR>10%)
COV IMEP ---- ---- ---- ----NOX emissions ↓ ↑ ↑ Follows cetane and
aromatic trend
HC emissions ---- ↑ ↑ ↑CO emissions ---- ---- ↑ ----
LTHR rate ↑ ---- ↓ Follows cetanetrend
LTHR % of total HR ↑ ---- ↓ Follows cetane
trendLTHR-HTHR spacing ↓ ---- ↓ Follows cetane
trend
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Conclusions
• Diesel fuels of 41 to 73 cetane and 0 to 33% aromatics were successfully operated in an HCCI engine at 3.5 bar and 1800 rpm
• B100 operated but produced high HC emissions and did not fit other trends of the fuels
• Heated atomizer worked for port fuel injection of diesel fuel
• Much of fuel behavior can be explained by cetane number
• Aromatics did affect rate of pressure rise, NOx, and HC
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Future work
• Apply statistical analysis to data to further understand trends and significance
• Continue fuel studies– Oxygenate and bio-diesel blends– Cycloparaffin and aromatic study– Separate effects of intake temperature and fuel/air
ratio to gain better ability to control engine. We are also considering EGR, throttling, VVT, and pressure boosting in future builds
• Continue related work with gasoline range fuels and spark augmented HCCI
OAK RIDGE NATIONAL LABORATORYU. S. DEPARTMENT OF ENERGY
Acknowledgements
• The work is supported by DOE’s Office of FreedomCAR and Vehicles Technology under the Fuels Technologies Program
• Steve Goguen and Kevin Stork are DOE’s program managers for this research
• Others at ORNL who contributed to this project include Jimmy Wade, Jim Tassitano, and Eric Nafziger
• Fuel samples were analyzed by Southwest Research Institute
• FT fuel was supplied by NREL