reaction models of fundamental combustion properties1 reaction models of fundamental combustion...
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1
Reaction Models of Fundamental Combustion Properties
Hai Wang
University of Southern California
2009 Fuel Summit, USC
Baptiste Sirjean David Sheen Enoch Dames
2
3
• JetSurF 0.2 → JetSurF 1.0 • updated kinetic parameters
• uncertainty quantification
• lumped, simplified model (with C. K. Law & T.-F. Lu)
• JetSurF 1.1 – n-butyl-, n-propyl-, ethyl-and methyl-cyclohexanes and cyclohexane.
4
• JetSurF 1.0 – n-alkane (C1 to C12)http://melchior.usc.edu/JetSurF/JetSurF1.0
• Quantum tunneling in the isomerization of n-alkyl radical
• Model uncertainty quantification/propagation
• Lumped model of high-temperature n-alkane thermal cracking
• JetSurF 1.1 – n-butylcyclohexanehttp://melchior.usc.edu/JetSurF/JetSurF1.1
• Reaction kinetics of benzene + O(3P)in collaboration with C. Taatjes: photoionization mass spectrometry and master equation modeling
• Transport properties of long-chain moleculesin collaboration with A. Violi & J. Manion
5
Role of Tunneling in n-alkyl Radicals Isomerizations
• n-alkyl radical (C5 to C8) unimolecular decomposition
W.Tsang, J.A. Walker, J.A. Manion Proc. Combust. Inst. 31 (2007) 141
• H-transfer reactions: low A-factors & Ea from low temperaturedata (300 – 500K)
+ C2H5
+ C2H4
+ C3H6 + CH3
+ C3H7
6
Role of Tunneling in n-alkyl Radicals Isomerizations
W.Tsang, J.A. Walker, J.A. Manion Proc. Combust. Inst. 31 (2007) 141
Endrenyi and Le Roy (1966)
Watkins (1971)
• Tunneling must be considered to reconcile low and high temperature data
7
Tunneling in Reaction Rate Theory
• Transition State Theory: transmission coefficient κ(T)RTEaAeTTk /)()(
• Approximations:– One dimensional assumption:
0)]([82
2
2
2
sVE
hm
x
– Potential Energy Surface expressed as a function V(s)
• Wigner (1932): parabola function
• Skodje and Truhlar (1981): truncated parabola
• Eckart (1917) & Johnston and Heicklen (1966): « Eckart potential »
8
Computational Methods
• One dimensional tunneling transmission coefficient κ(T):- Wigner, Skodje & Truhlar, and Eckart (CSE-Online - Truong et al.)
• Multi-dimensional tunneling transmission coefficient κ(T):- Small Curvature Tunneling (SCT) - Large Curvature Tunneling (LCT) (Polyrate - Truhlar et al.)
Truong et al., http://therate.hec.utah.edu/
Hessian required for each points along the Minimum Energy Path
Computationally expensive
9
PES: n-heptyl radicals H-shifts
0.0
-3.2-2.9 -3.0
21.8
14.4
22.8
14.8
H H
HH
Ener
gy (k
cal/m
ol)
0.0
20.0
10.0
E (0K, ZPE scaled) - kcal/mol
CBS-QB3
10
100
101
102
103
400 800 1200 1600 2000
1-heptyl -> 2-heptyl
Wigner Skodge & Truhlar Eckart
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
100
101
102
103
104
400 800 1200 1600 2000
1-heptyl -> 3-heptyl
Wigner Skodje & Truhlar Eckart
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
100
101
102
103
104
105
106
400 800 1200 1600 2000
1-heptyl -> 4-heptyl
Wigner Skodje & Truhlar Eckart
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
100
101
102
103
104
105
106
400 800 1200 1600 2000
2-heptyl -> 3-heptyl
WignerSkodje & TruhlarEckart
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
One-Dimensional Tunneling
11
Multi- vs One-dimensional Tunneling
100
101
102
400 800 1200 1600 2000
1-heptyl -> 3-heptyl
Wigner EckartSCT
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
100
101
102
103
400 800 1200 1600 2000
1-heptyl -> 4-heptyl
Wigner EckartSCT
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
Eckart good approximation for 300 < T < 2000 K
Wigner good for this system with T > 800 K
12
Small Curvature Tunneling
100
101
102
103
300 400 500 600 700 800 900 1000
1-heptyl -> 2-heptyl (7)1-heptyl -> 3-heptyl (6)1-heptyl -> 4-heptyl (5)2-heptyl -> 3-heptyl (5)
Tran
sfer
t Coe
ffici
ent, (
T)
Temperature, T (K)
In agreement with experiments
13
Sensitivity Analysis of Eckart κ(T): Variation of Imaginary Frequency
100
101
102
103
104
200 400 600 800 1000 1200
1-heptyl -> 4-heptyl
Eckart Eckart 90% imaginary frequencyEckart 110% of imaginary frequency
Tran
smis
sion
Coe
ffici
ent, (
T)
Temperature, T (K)
Uncertainty Propagation
David A. Sheen and Hai Wang
15
JetSurF (Version 0.2) Release date: September 08, 2008
Main page JetSurF 0.2 Download Performance How to Cite
20
30
40
50
60
70
0.6 0.8 1.0 1.2 1.4 1.6
Lam
inar
Fla
me
Spee
d, c
m/s
Equivalence Ratio,
n-Dodecane-Air (p = 1 atm, Tu = 403 K)
Data taken from X.Q. You, F.N. Egolfopoulos, H. Wang, “Detailed and Simplified Kinetic Models of n‐Dodecane Oxidation: The Role of Fuel Cracking in Aliphatic Hydrocarbon Combustion,” Proc. Combust. Inst. doi:10.1016/j.proci.2008.06.041 (2009). Symbols: experimental data taken with the counterflow twin‐flame technique with nonlinear extrapolation through detailed numerical simulations. Line: JetSurF (v0.2 prediction).
16
Kinetic Parameter Uncertainties
Baulch, et al. (2005)
~50%
H + O2 ↔ OH + O (R1)
• Logarithmic sensitivity coefficient= 0.24 (ethylene-air, = 1, p = 1 atm)
•±5% (±4 cm/s) uncertainty in predicted flame speed due to R1 alone
• Key question (Sheen et al. 2009): How do we propagate uncertainties in rate constants in combustion simulations?
• Uncertainty factor ~1.25
17
Propagation of Uncertainty
0
1 1...i ij ij
m m m
i j j kj k j
kk
x x
nominal value
1st order coefficients2nd order coefficients
basis random variable
Data structure that describes a chemical model + associated uncertainty
,0 , ,1 1
N N N
r r r i i r ij i ji i j i
a x b x x
x
Predictions of a chemical model (e.g. laminar flame speed)+ associated uncertainty
0, ,
1 1
ˆˆ,m m m
r r r i i r ij i ji i j i
x ξ x
Represents some physics model,e.g. PREMIX
1-atm C2H4-air mixtures
20
40
60
80
0.5 1.0 1.5 2.0
Egolfopoulos & Law (1990)Faeth & co-workers (1998)Law & co-workers (2005)La
min
ar F
lam
e Sp
eed,
su0 (
cm/s
)
Equivalence Ratio,
Sheen et al. (2009)
18
19
JetSurF (Version 1.0) Release date: September 15, 2009
Main page JetSurF 1.0 download Performance How to cite Symbols: Data from S.S. Vasu, D.F. Davidson, Z. Hong, V. Vasudevan, R.K. Hanson, “n‐Dodecane Oxidation at High Pressures: Measurements of Ignition Delay Times and OH Concentration Time Histories,” Proc. Combust. Inst. 32 (2009) 173‐180. Onset of OH emission. Lines: Nominal prediction with JetSurF v1.0. Blue symbols: Uncertainty in JetSurF v1.0 predictions using Monte Carlo simulation. The nominal predictions do not represent the mean of statistical uncertainties because the uncertainty calculations used an unoptimized H2/CO sub model.
101
102
103
104
0.70 0.80 0.90 1.00 1.10 1.20
0.565%n-C12H26-20.89%O2-78.55%N2= 0.5, p5 = 20atm
Igni
tion
Del
ay,
s
1000 K / T
101
102
103
104
0.7 0.8 0.9 1.0 1.1 1.2
1.123%n-C12H26-20.77%O2-78.1%N2= 1, p5 = 20atm
Igni
tion
Del
ay,
s
1000 K / T
20
20
40
60
80
0.5 1.0 1.5 2.0
Egolfopoulos & Law (1990)Faeth & co-workers (1998)Law & co-workers (2005)La
min
ar F
lam
e Sp
eed,
su0 (
cm/s
)
Equivalence Ratio,
Method of Uncertainty Minimization (MUM-PCE)
obs obs obs,0r r r r ξ
2* obs, ,2obs1 1 1
1 ˆˆminM M M M
r ir r i r ijr i i j ir
α
α
0
20obs
,00 *2obs1
minM r r
r r
x
xx
nominal value
uncertainty
0, ,
1 1
ˆˆ,m m m
r r r i i r ij i ji i j i
x ξ x 0
1i i
m
i jj
jx x
1-atm C2H4-air mixtures
20
40
60
80
0.5 1.0 1.5 2.0
Egolfopoulos & Law (1990)Faeth & co-workers (1998)Law & co-workers (2005)La
min
ar F
lam
e Sp
eed,
su0 (
cm/s
)
Equivalence Ratio,
“best” model
least-squares minimization
model + uncertainty
prediction + uncertainty
2* * obs, ,2,... obs1 1 1
1 ˆˆ,... min ...M M M M
r ir r i r ijr i i j ir
α β
α β
0
1 1...i ij ij
m m m
i j j kj k j
kk
x x
Sheen, et al. (2009)
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite How to Cite JetSurF 1.1: B. Sirjean, E. Dames, D. A. Sheen, F. N. Egolfopoulos, H. Wang, D. F. Davidson, R. K. Hanson, H. Pitsch, C. T. Bowman, C. K. Law, W. Tsang, N. P. Cernansky, D. L. Miller, A. Violi, R. P. Lindstedt, A high‐temperature chemical kinetic model of n‐alkane, cyclohexane, and methyl‐, ethyl‐, n‐propyl and n‐butyl‐cyclohexane oxidation at high temperatures, JetSurF version 1.1, September 15, 2009 (http://melchior.usc.edu/JetSurF/JetSurF1.1). Note: Detailed reaction model development is inherently a work in progress. The current release is for the purpose of discussion and evaluation. Although the model predicts a large body of experimental data, it should be used with caution. The release is meant to be used for modeling the pyrolysis and oxidation of n‐alkane (up to n‐dodecane) at high temperatures only.
22
Detailed Kinetic Model for High-Temperature Oxidation of Cycloalkanes
• Butyl-cyclohexane, methylcyclohexane, and cyclohexane
• All C6 cyclic alkanes from cyclohexane to butylcyclohexane
Shock Tube Laminar Flame Speed
Flow Reactor/Perfectly Stirred Reactor
Cyclohexane
Methylcyclohexane
Ethylcyclohexane
Propylcyclohexane
Butylcyclohexane
Dagaut and co-workers (2000), Sirjean et al. (2007), Westbrook and co-worker (2007) Curran and co-worker (2006)
Dagaut and co-worker (2001)
Detailed Chemical Kinetic Models
23
High-Temperature Combustion Chemistry of Cycloalkanes (I)
• Initial C-C bond fission
+ CH3
+ C2H5
+ C3H7
+ C4H9
HH
NoBack rate constant from nC3H7 + iC3H7 = C6H14 [1]
Alkyl group (Ct-Cs)
NoRing opening of c-C6H12 [2]Cyclic structure (Cs-Cs)
NoRing opening of c-C6H12 [2]Ea lowered by 1 kcal/mol
(BDEn-hexane – BDE 2-methylpentane)Cyclic structure (Ct-Cs)
NoBack rate constant from
2 C2H5 = n-C4H10Alkyl group (Cs-Cs)
NoBack rate constant from
CH3 + C2H5 = C3H8Alkyl group (Cp-Cs)
Pressure fall-of
Source and Method of Rate EstimationC-C bond fission
NoBack rate constant from nC3H7 + iC3H7 = C6H14 [1]
Alkyl group (Ct-Cs)
NoRing opening of c-C6H12 [2]Cyclic structure (Cs-Cs)
NoRing opening of c-C6H12 [2]Ea lowered by 1 kcal/mol
(BDEn-hexane – BDE 2-methylpentane)Cyclic structure (Ct-Cs)
NoBack rate constant from
2 C2H5 = n-C4H10Alkyl group (Cs-Cs)
NoBack rate constant from
CH3 + C2H5 = C3H8Alkyl group (Cp-Cs)
Pressure fall-of
Source and Method of Rate EstimationC-C bond fission
[1] Tsang, W., J. Phys. Chem. Ref. Data 1988, 17, 887[2] Tsang, W., International Symposium on Combustion, 2008, Montreal, Canada
24
High-Temperature Combustion Chemistry of Cycloalkanes (III)
• H-abstraction by H, O2, OH, O, CH3, HO2Cycloalkanes
N/AH, O2, CH3, HO2 : C3H8 + X = C3H7 + HXO : Cohen’s method OH : Michael et al. (cycloalkanes)
Cyclic structure (Secondary H)
N/AH, O2, OH, HO2, O, CH3 : i-C4H10 + X = t-C4H9 + HXOH : Michael et al. (cycloalkanes)
Cyclic structure (Tertiary H)
N/AH, O2, CH3, HO2 : C3H8 + X = C3H7 + HXO : Cohen’s method OH : Michael et al. (n-alkanes)
Alkyl group
Pressure fall-ofSource and Method of Rate EstimationH-abstraction
N/AH, O2, CH3, HO2 : C3H8 + X = C3H7 + HXO : Cohen’s method OH : Michael et al. (cycloalkanes)
Cyclic structure (Secondary H)
N/AH, O2, OH, HO2, O, CH3 : i-C4H10 + X = t-C4H9 + HXOH : Michael et al. (cycloalkanes)
Cyclic structure (Tertiary H)
N/AH, O2, CH3, HO2 : C3H8 + X = C3H7 + HXO : Cohen’s method OH : Michael et al. (n-alkanes)
Alkyl group
Pressure fall-ofSource and Method of Rate EstimationH-abstraction
25
High-Temperature Combustion Chemistry of Cycloalkanes (V)
• C-C bond beta-scission in cycloalkyl radicals Cycloalkyl radicals n-alkyl radicals
+ +
+
+
26
C-C bond beta-scission Source and Method of Rate Estimation
Pressure fall-of
Alkyl group (Cp-Cs)Analogous rate constant of alkyl
radical isomer Yes
Alkyl group (Cs-Cs)Analogous rate constant of alkyl
radical isomer Yes
Alkyl group (Ct-Cs)2-methyl-pent-4-yl radical
-scission [1]Yes
Cyclic structure (Ct-Cs)Ring opening of c-C6H11 [2]Ea lowered by 1 kcal/mol
(BDEn-hexane – BDE 2-methylpentane)Yes
Cyclic structure (Cs-Cs) Ring opening of c-C6H11 [2] Yes
• Rate constants:
High-Temperature Combustion Chemistry of Cycloalkanes (VI)
[1] McGivern, W.S., Awan, I.A., Tsang, W., Manion, J.A., J. Phys. Chem. A, 2008, 112,6908[2] Tsang, W., International Symposium on Combustion, 2008, Montreal, Canada
27
High-Temperature Combustion Chemistry of Cycloalkanes (VII)
• Mutual isomerization of cycloalkyl radicals Cycloalkyl radicals n-alkyl radicals
H
H
H
28
High-Temperature Combustion Chemistry of Cycloalkanes (VIII)
• B3LYP/6-311G(d,p) PES + TST Theory + Eckart Tunneling
0.0
-4.8 -4.2-4.3
-6.7
-3.8 -3.7-3.7
20.7 21.3
30.0
13.7 12.5
27.4
20.420.8
13.6
21.022.8
20.3
16.5
16.9
29
Additional Features of JetSurF 1.1
• Branched alkenes decomposition reactions:– Initial C-C bond fission– Retro-ene reactions– Chemically activated reactions with H (analogous to C3H6+H)
• Branched alkenyl radicals decomposition:– C-C bond fission reactions and mutual isomerization pressure
dependant rates:
Tsang and co-workers, n-alkyls (C5 to C8), branched alkyl (2-meythylpentyl) and alkenyl radicals (C4 to C6)
• 352 species and 2083 reactions
30
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite
Performance That We Know: Validation tests for the base model, including JetSurF version 1.0 and USC‐Mech II, can be found at their respective web sites. For n‐butylcyclohexane and its related fuel compounds, the current validation tests include
Laminar flame speeds
Cyclohexane‐, methylcyclohexane‐ and n‐butylcyclohexane‐air mixtures, p = 1 atm, Tu = 353 K. Egolfopoulos (2009)
Cyclohexane‐air mixtures, p = 1 atm, Tu = 298 K. Davis & Law (1998).
n‐Propylcyclohexane‐air mixtures, p = 1 atm, Tu = 403 K. Dubois et al. (2008).
Ignition delay times behind reflected shock waves
n‐Butylcyclohexane‐oxygen‐argon, p5 = 1.5 atm. Davidson & Hanson (2009).
Cyclohexane‐oxygen‐argon mixtures, p5 = 1.5 and 3 atm. Davidson & Hanson (2009).
Cyclohexane‐oxygen‐nitrogen mixtures, p5 = 15 & 50 atm. Daley et al. (2008).
Cyclohexane‐oxygen‐nitrogen mixtures, p5 = 8 atm. Sirjean et al. (2007).
Methylcyclohexane‐oxygen‐argon mixtures, p5 = 1.5 and 3 atm. Davidson & Hanson (2009).
Methylcyclohexane‐oxygen‐nitrogen mixtures, p5 = 20 atm. Vasu et al. (2009).
31
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite
10
20
30
40
50
60
0.6 0.8 1.0 1.2 1.4 1.6
Lam
inar
Fla
me
Spee
d (c
m/s
)
Equivalence Ratio,
Cyclohexane-Air (p = 1 atm, T0 = 353 K)
10
20
30
40
50
60
0.6 0.8 1.0 1.2 1.4 1.6
Lam
inar
Fla
me
Spee
d (c
m/s
)
Equivalence Ratio,
Methylcyclohexane-Air (p = 1 atm, T0 = 353 K)
10
20
30
40
50
60
0.6 0.8 1.0 1.2 1.4 1.6
Lam
inar
Fla
me
Spee
d (c
m/s
)
Equivalence Ratio,
Butylcyclohexane-Air (p = 1 atm, T0 = 353 K)
10
20
30
40
50
60
70
0.6 0.8 1.0 1.2 1.4 1.6
Lam
inar
Fla
me
Spee
d (c
m/s
)
Equivalence Ratio,
n-Propylcyclohexane-air (p = 1 atm, T0 = 403 K)Flame Speed comparisons. Data are preliminary and not shown here
32
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data from D.F. Davidson, R.F. Hanson, “Cycloalkane Ignition Studies,” unpublished, June 29, 2009. Onset of OH emission. Lines: JetSurF v1.1 predictions
102
103
0.65 0.70 0.75 0.80
0.22% n-butylcyclohexane - 4% O2 in Ar = 0.83, p5 = 1.5 atm
Igni
tion
Del
ay (
s)
1000 K / T
102
103
0.67 0.70 0.72 0.75 0.77 0.80 0.82 0.85
0.234% n-butylcyclohexane - 4%O2 in Ar0.88p5 = 3 atm
Igni
tion
Del
ay (
s)
1000 K / T
102
103
0.65 0.70 0.75 0.80 0.85
0.119%n-butylcyclohexane - 4%O2 in Ar0.45p5 = 1.5 atm
Igni
tion
Del
ay (
s)
1000 K / T
Ignition delay comparisons. Data are preliminary and not shown here
33
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data from D.F. Davidson, R.F. Hanson, “Cycloalkane Ignition Studies,” unpublished, June 29, 2009. Onset of OH emission. Lines: JetSurF v1.1 predictions.
102
103
0.65 0.70 0.75
0.381% methylcyclohexane - 4%O2 in Ar1p5 = 1.5 atm
Igni
tion
Del
ay (
s)
1000 K / T
102
103
0.65 0.70 0.75 0.80
0.381% methylcyclohexane - 4%O2 in Ar1p5 = 3 atm
Igni
tion
Del
ay (
s)
1000 K / T
102
103
0.65 0.70 0.75 0.80
0.191% methylcyclohexane - 4%O2 in Ar0.5p5 = 1.5 atm
Igni
tion
Del
ay (
s)
1000 K / T
Ignition delay comparisons. Data are preliminary and not shown here
34
35
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data S. Zeppieri, K. Brezinsky, I. Glassman, “Pyrolysis Studies of Methylcyclohexane and Oxidation Studies of Methylcyclohexane and Methylcyclohexane/Toluene Blends,” Combustion and Flame 108 (1997) 266‐286. Lines: JetSurF v1.1 predictions
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60 70 80
1815 ppm methylcyclohexane - 14660 ppm O2 T = 1160 K, p = 1 atm
MethylcyclohexaneCH4C2H4
Time (ms)
Mol
e Fr
actio
n (p
pm)
0
2000
4000
6000
8000
10000
12000
0 10 20 30 40 50 60 70 80
1815 ppm methylcyclohexane - 14660 ppm O2 T = 1160 K, p = 1 atm
CO
CO2
Time (ms)
Mol
e Fr
actio
n (p
pm)
0
200
400
600
800
0 20 40 60 80
1815 ppm methylcyclohexane - 14660 ppm O2 T = 1160 K, p = 1 atm
C3H61,3-C4H6Isoprene (CH2=C(CH3)-CH=CH2)
Mol
e Fr
actio
n (p
pm)
Time (ms)
0
50
100
150
200
250
300
350
0 20 40 60 80
C2H6Allene (aC3H4)
Mol
e Fr
actio
n (p
pm)
Time (ms)
1815 ppm methylcyclohexane - 14660 ppm O2 T = 1160 K, p = 1 atm
36
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data from S. M. Daley, A. M. Berkowitz, M. A. Oehlschlaeger, “A shock tube study of cyclopentane and cyclohexane ignition at elevated pressures,” International Journal of Chemical Kinetics, 40 (2008) 624‐634. Onset of OH* emission. Lines: JetSurF v1.1 predictions.
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00
0.5802% cyclohexane - 20.89%O2 in N2 0.25p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05
0.5802% cyclohexane - 20.89%O2 in N2 0.25p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.80 0.85 0.90 0.95 1.00 1.05 1.10
1.154% cyclohexane - 20.77%O2 in N2 0.5p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10
1.154% cyclohexane - 20.77%O2 in N2 0.5p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
37
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data from J. Vanderover, M. A. Oehlschlaeger, “Ignition Time Measurements for Methylcyclohexane and Ethylcyclohexane‐Air Mixtures at Elevated Pressures,” International Journal of Chemical Kinetics 41 (2009) 82‐91. Onset of OH emission. Lines: JetSurF v1.1 predictions
101
102
103
104
0.75 0.80 0.85 0.90 0.95
0.4977% methylcyclohexane - 20.90%O2 in N20.25p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05
0.4977% methylcyclohexane - 20.90%O2 in N20.25p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05
0.9905% methylcyclohexane - 20.80%O2 in N20.5p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
105
0.80 0.85 0.90 0.95 1.00 1.05 1.10
0.9905% methylcyclohexane - 20.80%O2 in N21p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
38
JetSurF (Version 1.1) Release date: September 15, 2009
Main page JetSurF 1.1 download Performance How to cite Symbols: Data from J. Vanderover, M. A. Oehlschlaeger, “Ignition Time Measurements for Methylcyclohexane and Ethylcyclohexane‐Air Mixtures at Elevated Pressures,” International Journal of Chemical Kinetics 41 (2009) 82‐91. Onset of OH emission. Lines: JetSurF v1.1 predictions
101
102
103
104
105
0.7 0.8 0.9 1.0 1.1
0.4358% ethylcyclohexane - 20.92%O2 in N20.25p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05
0.4358% ethylcyclohexane - 20.92%O2 in N20.25p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.75 0.80 0.85 0.90 0.95 1.00 1.05
0.8603% ethylcyclohexane - 20.83%O2 in N20.5p5 = 15 atm
Igni
tion
Del
ay (
s)
1000 K / T
101
102
103
104
0.85 0.90 0.95 1.00 1.05
0.8603% ethylcyclohexane - 20.83%O2 in N20.5p5 = 50 atm
Igni
tion
Del
ay (
s)
1000 K / T
39
JetSurF (Version 1.1) Release date: September 15, 2009
What we know about the problem at high pressure?
• Impurities: not likely
• Sensitivity towards the rate of H abstraction:
R-cC6H11 + HO2 → products
• No kinetic dead ends
• Missing appropriate FREE-RADICAL CHAIN INITIATION!
Non-equilibrium kinetics upon shock heating?Carbene + O2 → free radicals?
Simplified Chemical Kinetic Models for High-Temperature
Oxidation of C5 to C12 n-alkanes
B. Sirjean, E. Dames, D.A. Sheen, H. Wang
University of Southern California
41
Systematic Simplification of C5-C12 Detailed Model
n-CnH2n+2 with 12 ≥ n ≥ 5
H-abstraction: OH, H, CH3, O, O2, HO2Unimolecular initiation
Chain length ?
1,5 H-shift if ≥ C6
1-alkene simplified
USC Mech II
C0 – C4
Radical type?C5– C12
Primary
Secondary
C5-C6 1-alkenes C-C -scission
Alkyl ≥ C6
Lumped n-alkane C5 to C12 model:9 species & 193 reactions
+Detailed C0 to C4 model (USC Mech II)
111 species & 784 reactions
“Model II”120 species
977 reactions
42
Model Details and Validation
Model n-alkane cracking
H2/CO/C1-C4 based model
Number of species
Number of reactions
I detailed detailed 194 1459
II lumped detailed 120 977
III lumped skeletal 84 499
Standard ofpresentation
43
Validation: Pyrolysis of n-dodecane in a Jet-Stirred Reactor
O. Herbinet, P.M. Marquaire, F. Battin-Leclerc, R. Fournet, Anal. Appl. Pyrolysis 78 (2007) 419
0
20
40
60
80
100
850 900 950 1000 1050
Con
vers
ion,
%
Temperature, K
0
20
40
60
80
100
0 1 2 3 4 5
Con
vers
ion,
%
Residence time, s
873 K
973 K
44
Validation: Laminar Flame Speed
10
20
30
40
50
60
70
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8Equivalence Ratio,
n-Dodecane-air Tu = 403 K, P = 1 atmLa
min
ar F
lam
e Sp
eed
(cm
/s)
45
Validation: Ignition
101
102
103
104
101 102 103 104
Model IModel II
Sim
ulat
ed ig
nitio
n de
lays
, s
Experimental ignition delays, s
Set of experimental data:n-C5H12 (Φ = 1; 0.5 – P5 = 1.9; 1.7 atm)n-C6H14 (Φ = 1; 0.5 – P5 = 1.8; 1.7 atm)n-C7H16 (Φ = 2; 1; 0.5 – P5 = 1 atm)n-C8H18 (Φ = 1; 0.5 – P5 = 2 atm)n-C9H20 (Φ = 1; 0.5 – P5 = 2 atm)n-C10H22 (Φ = 1 – P5 = 1.2; 13 atm)n-C12H26 (Φ = 1; 0.5 – P5 = 20 atm)
S. S. Vasu, D. F. Davidson, Z. Hong, V. Vasudevan, R.K. Hanson, Proc. Combust. Inst. 32 (2009) 173D. F. Davidson, S. C. Ranganath, K.-Y. Lam, M. Liaw, Z. Hong, R. K. Hanson, "Ignition Delay Time Measurements of Normal Alkanes and Simple Oxygenates" Journal of Propulsion and Power, in press (2009)