Low Temperature Heat Release Behavior of Conventional and Alternative … · 2014-03-10 · Low...
Transcript of Low Temperature Heat Release Behavior of Conventional and Alternative … · 2014-03-10 · Low...
Low Temperature Heat Release BehaviorLow Temperature Heat Release Behavior of Conventional and Alternative Fuels in aof Conventional and Alternative Fuels in a
Motored EngineMotored Engine
James P. Szybist* and AndrJames P. Szybist* and Andréé L. BoehmanL. BoehmanPenn State UniversityPenn State University
*Now at Oak Ridge National Laboratory*Now at Oak Ridge National Laboratory
2006 DEER Conference2006 DEER Conference
Are the growing interests in alternative diesel fuelsAre the growing interests in alternative diesel fuels and advanced combustion techniques compatible?and advanced combustion techniques compatible?
National Biodiesel Board (nbb.org)
Biodiesel productionBiodiesel production
CoalCoal--derived FT programs in PA and MTderived FT programs in PA and MT
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.00 0.20 0.40 0.60 0.80 1.00 1.20
NOx Emissions (g/mi)
PM E
mis
sion
s (g
/mi)
0
0.01
0.02
0.03
0.04
0.05
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
NOx Emissions (g/km)
PM E
mis
sion
s (g
/km
)
U.S. Tier 2 2004+
Bin 8
Bin 5
Euro 4 2005
Euro 3
2000 U.S. Tier 1 1994-2003
Reduced emission standardsReduced emission standards
Advanced combustion techniquesAdvanced combustion techniques
Reproduced from Ryan
Tier 2 emission standards
Are advanced combustion techniques sensitive toAre advanced combustion techniques sensitive to fuel composition?fuel composition?
…it is almost certain that future, advanced combustion engine technologies will show a greater [performance and
emissions] sensitivity to [fuel-property] variations… (section 4.7.1 of the FreedomCAR Multi-Year Program Plan)
•• Lack of direct control of combustion timingLack of direct control of combustion timing– No spark initiation in most cases – Limited control with fuel injection timing (combustion strategy
dependent) – Combustion is kinetically initiated
•• Traditional fuel ignition properties may not be sufficientTraditional fuel ignition properties may not be sufficient indicators of advanced combustion performanceindicators of advanced combustion performance– Influence of “physical” vs. “chemical” cetane number
Low temperature heat releaseLow temperature heat release
Reproduced from Christensen et al.
Gasoline HCCIGasoline HCCI
Reproduced from Christensen et al.
Diesel HCCIDiesel HCCI
With increasing temperature at constant pressure Non-Explosive → Explosive → Non-Explosive → Explosive
Reproduced from Glassman, 1996
•• What is formedWhat is formed during LTHR?during LTHR?
•• Alternative fuelAlternative fuel differences?differences?
Experimental platform and fuel matrixExperimental platform and fuel matrixGDI Injector
Main Air HeaterHeating Tape
Vacuum Pump
FTIR
Ice Bath Up to 260˚ C
Φ=0.25 to 2.0
Compression
In-house combustion analysis system
Variable Compression
Ratio CFR Engine
Exhaust
-
246
280
-
T90 (°C)
22449.5methyl decanoate (biodiesel surrogate)
-65.5FT diesel-light cut
-39.4#2 diesel-light cut
9852.6n-heptane
BP (°C)DCNFuel
Ratio=4.0-13.75
Fuels progressed from only LTHR at low CR toFuels progressed from only LTHR at low CR to LTHR and HTHR at higher CRLTHR and HTHR at higher CR
0.005 1200 0.004 1100
10000.003 900 0.002 800CR = 4.47 7000.001
6000 500 Exhaust ofExhaust of
-0.001 400300 320 340 360 380 400 LTHRLTHRCrank Angle
0.005 1200 productsproducts0.004 1100 1000
0.003 900 onlyonly0.002 800 0.001 CR = 5.70 700
6000 500
-0.001 400300 320 340 360 380 400LTHR Crank Angle
0.025 2500
0.02 2000 HTHR 0.015 CR = 6.52
1500 0.01
0.005 1000
0 500 300 320 340 360 380 400
Crank Angle 0.05 2500
0.04 CR = 7.04 2000
0.03 1500
0.02 10000.01
0 500 300 320 340 360 380 400
Crank Angle
Hea
t Rel
ease
(kJ/
deg)
Hea
t Rel
ease
(kJ/
deg)
Hea
t Rel
ease
(kJ/
deg)
Hea
t Rel
ease
(kJ/
deg) Tem
perature (K)
Temperature (K
) Tem
perature (K)
Temperature (K
)
LTHR magnitude is dependent on CN andLTHR magnitude is dependent on CN and equivalence ratioequivalence ratio
0
5
10
15
0.0 0.5 1.0 1.5 2.0
LTH
R (%
of t
otal
)
Equivalence ratio
○ #2 diesel-light cut ◊ FT diesel-light cut ■ methyl decanoate
CH3
O
O
CH3
methyl decanoate
•• LTHR magnitude trends with derivedLTHR magnitude trends with derived cetanecetane numbernumberFT diesel-light cut > methyl decanoate > #2 diesel-light cut
•• MethylMethyl decanoatedecanoate LTHR likely overLTHR likely over--predicts LTHR ofpredicts LTHR of biodieselbiodiesel– Aliphatic chain is responsible for LTHR, not methyl ester – Over 50% of soy-based biodiesel is comprised of species with multiple
unsaturations – Unsaturated species exhibit less LTHR than saturated species
FTIR analysis ofFTIR analysis of nn--heptaneheptane exhaust revealsexhaust reveals CO andCO and aldehydesaldehydes are formed by LTHRare formed by LTHR
n-heptane, Φ=0.254 2000
■ acetaldehyde ○ formaldehyde
CH
O and C
H O
(ppm)
2 2
4
3 1500
2 1000
1 500
0 0 4 5 6 7 8 9 10
Compression Ratio
CO
and
CO
(%)
2
◊ carbon monoxide ▲ carbon dioxide
0.0050.0.0104 0.0350.0.0040080.03 0.0.0.003006025
8000000101675000090147008012650000
Hea
t Rel
ease
HHea
t Rel
ease
eat R
elea
se(k
J/de
g((k
J/de
g)kJ
/deg
)
Temperature (K
)TTem
perature (K)
emperature (K
)
• LTHR but no HTHR• LTHR a
nd H
THRNo reaction at low CR 0.02 700.0.002 600 00010004• 0.0150.0010.0020.01 550006080Aldehyde and COAldehyde and CO 500••• 0.005 0 506045000
-0.001 00 400404000
300 320 340 36030300 340 3600 320 340 360 380 400440000320 380380No exhaust aldehydesconcentrations plateauconcentrations dropor CO
• Negligible CO2
Crank AngleCrCrank Angleank Angle
• CO2 increases
2,52,5 heptanedioneheptanedione identified inidentified in nn--heptaneheptaneexhaust condensateexhaust condensate
CH3
CH CH3
CH3 CH3
Hydrogen Abstraction
O2 Addition
CH3 CH3
O O
CH3
CH3O O
Six-Membered-Ring Transition State
CH3 CH CH3
O OH
O2 Addition
CH3 CH3
O OH
O O
CH3
CH3
O
OH
O O
CH3 CH3
O
O OH
CH3 CH3
O
O
+ OH
Internal Isomerization
Internal Isomerization
Dehydration
2,5-heptanedione
Hydroperoxy Radical
n-Heptane
Alkyl Radical
Hydroperoxide Radical
Six-Membered-Ring Transition State
Ketohydroperoxide
Additional Species Identified Butanal2,3 Butanedione
4-penten-2-one
2-pentanone
Butanoic acid
Pentanoic acid
2,5 hexanedione
2-pentanone, 5-(1,2-propadienyloxy)
Reaction scheme taken from Curran et al., 1998.
O (ppm
)
Conventional diesel and FT fuels showConventional diesel and FT fuels show trends similar totrends similar to nn--heptaneheptane
15 1800
•• Partially oxidizedPartially oxidized 12.5 1500 2 2
4C
H O
andC
H
species are formed byspecies are formed by LTHR, consumed byLTHR, consumed by main combustion eventmain combustion event at higher CRat higher CR
•• High MW oxygenatedHigh MW oxygenated species identified inspecies identified in exhaust condensateexhaust condensate – C7 to C15 straight-chain
aldehydes – C9 to C12 straight-chain
2-ketones– C5 to C11 straight-chain C
O2 a
nd C
O (%
)C
O2 a
nd C
O (%
)
10 1200
7.5 900
5 600
2.5 300
0 0 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8
Compression Ratio ■ acetaldehyde ○ formaldehyde ◊ carbon monoxide ▲ carbon dioxide8 2400
2 2
4 C
H O
and C H
6 1800
4 1200
O (ppm
)
2 600
organic acids 0 0
4.4 4.6 4.8 5 5.2 5.4 Compression Ratio
DecarboxylationDecarboxylation of methylof methyl decanoatedecanoateproduces COproduces CO22 during LTHRduring LTHR
10 2000
7.5 1500
5 1000
2.5 500
0 0 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8
Compression Ratio
•• Comparable levels of CO and COComparable levels of CO and CO22 are formed by LTHRare formed by LTHR– Temperatures are insufficient to oxidize CO to CO2– CO2 is a product of decarboxylation
•• DecarboxylationDecarboxylation is undesirable from sootis undesirable from soot--suppression standpointsuppression standpoint– Under-utilization of fuel-bound oxygen to remove carbon from soot-precursor
reactions – Better oxygen utilization could be realized by oxygenates with ether functional
groups
CO
and
CO
(%)
2
CH
O and C
H O
(ppm)
2 2
4
LTHR reactions of aliphatic chain occurLTHR reactions of aliphatic chain occur prior toprior to decarboxylationdecarboxylation
29.50methyl decanoate
28.83 + 4 othersMethyl decenoate (isomers)
25.90Methyl nonanoate
22.12, 25.85Methyl nonenoate (isomers)
22.06Methyl octanoate
21.72Methyl octenoate
17.59Methyl heptenoate
17.45Methyl hexanoate
12.862-methyl butanoic acid methyl ester
Retention TimeMethyl esters
Methyl Decanoate
O
3
O
2 (3H) f ne-5ethyldihydroCH3
O O
4 ethyl ester
O C
O O O
5-mMethyl Decanoate
CH
urano3O CH
-oxopentanoic acid m
H3
ethoxycarbonylpentan-4-olide
OCH3
O
2 (3H) furanone-5ethyldihydroCH3O CH3
O O
4-oxopentanoic acid methyl ester
OCH3
O OO
5-methoxycarbonylpentan-4-olide
32.069-oxodecanoic acid methyl ester
30.032-oxodecanoic acid methyl ester
29.864-oxooctanoic acid methyl ester
25.446-oxoheptanoic acid methyl ester
20.905-oxohexanoic acid methyl ester
17.455-oxopentanoic acid methyl ester
16.454-oxopentanoic acid methyl ester
Retention TimeOxo-methyl ester
ConclusionsConclusions•• LTHR behavior of different fuels can be investigated in aLTHR behavior of different fuels can be investigated in a
motored enginemotored engine•• LTHR magnitude trends withLTHR magnitude trends with cetanecetane numbernumber•• The oxidation taking place during LTHR produces partiallyThe oxidation taking place during LTHR produces partially
oxidized species with only negligible amounts of COoxidized species with only negligible amounts of CO22– High concentrations of CO and aldehydes – 2,5-heptanedione, found in n-heptane exhaust condensate, can
be closely linked to LTHR mechanism •• If allowed to proceed through HTHR, partially oxidizedIf allowed to proceed through HTHR, partially oxidized
species largely converted to COspecies largely converted to CO22•• COCO22 produced during LTHR from methylproduced during LTHR from methyl decanoatedecanoate is ais a
product ofproduct of decarboxylationdecarboxylation– Decarboxylation is undesirable from a soot-suppression standpoint – LTHR reactions with aliphatic chain can occur before
decarboxylation, incorporating additional oxygen into themolecule
AcknowledgementsAcknowledgements
The authors wish to thank the Department ofThe authors wish to thank the Department of Energy for support under Contract No. DEEnergy for support under Contract No. DE--FC26FC26-01NT41098.01NT41098.
The authors also wish to thank Doug Smith, KirkThe authors also wish to thank Doug Smith, Kirk Miller, Etop Esen, Jim Rockwell, RafaelMiller, Etop Esen, Espinoza,Jim Rockwell, Rafael Espinoza, Keith Lawson and Ed Casey of ConocoPhillips forKeith Lawson and Ed Casey of ConocoPhillips for their support of this work.their support of this work.