reaction models of combustion properties4 • version 1.0+1.1 →jetsurf 2.0 n‐butyl‐,...
TRANSCRIPT
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Reaction Models of Fundamental Combustion Properties
Hai Wang
Enoch Dames, David Sheen & Rei Tangko
University of Southern California
2010 Fuel Summit, Princeton
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H. Wang, E. Dames, B. Sirjean, D. A. Sheen, R. Tangko, A. Violi, J. Y. W. Lai, F. N. Egolfopoulos, D. F. Davidson, R. K. Hanson, C. T. Bowman, C. K. Law, W. Tsang, N. P. Cernansky, D. L. Miller, R. P. Lindstedt, A high‐temperature chemical kinetic model of n‐alkane (up to n‐dodecane), cyclohexane, and methyl‐, ethyl‐, n‐propyl and n‐butyl‐cyclohexane oxidation at high temperatures, JetSurF version 2.0, September 19, 2010 (http://melchior.usc.edu/JetSurF/JetSurF2.0).
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• Version 1.0+1.1 → JetSurF 2.0 n‐butyl‐, n‐propyl‐, ethyl‐ and methyl‐cyclohexanes and cyclohexane.
n‐pentane to n‐dodecane
Some branched chain HCs + aromatics
• Key Revisions from version 1.0+1.1• Low temperature chemistry of cyclohexane and
methylcyclohexane added• H‐abstraction rates from Violi• ……
• Validation test sets > 200 (documented online)http://melchior.use.edu/JetSurF
JetSurF Status
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Multispecies Time‐History DataDavidson, Hong, Pilla, Farooq, Cook & Hanson, Combustion and Flame (2010)
10 100 100010
100
1000
Mol
e Fr
actio
n [p
pm]
Time [s]
1494K, 2.15atm300ppm heptane, =1
H2O
CO2
OH
C2H4
Solid lines: experiments; dashed lines: JetSurF 1.0
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Multispecies Time Histories
Solid lines: experiments; dashed lines: JetSurF 1.0
10-6
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
Time (s)
OH
H2O
CO2
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
Time (s)
C2H4
nC7H16
300 ppm n-C7H16 - 3300 ppm O2 in Ar, T5 = 1365 K, p5 = 2.35 atm
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What can we learn from the multispecies time‐histories?
• The model is accurate, but is it precise?
•Given the ~±5% experimental accuracy, can the data be utilized to improve model precision?
• To what extent the data improve model precision?
Multispecies Time Histories
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Propagation of Uncertainty
0
1 1...i ij ij
m m m
i j j kj k j
kk
x x
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)
9
10-5
10-4
10-3
Mol
e Fr
actio
n
C2H4
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
OH
Time (s)
10-5
10-4
10-3H2O
10-5
10-4
10-3
10-5 10-4 10-3
CO2
Time (s)
300 ppm nC7H16 / 3300 ppm O2 / Ar (T5 = 1494 K, p5 = 2.15 atm)
Multispecies Time Histories(Model Uncertainties)
JetSurF 1.0 is quite accurate
10
10-5
10-4
10-3
Mol
e Fr
actio
n
C2H4
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
OH
Time (s)
10-5
10-4
10-3H2O
10-5
10-4
10-3
10-5 10-4 10-3
CO2
Time (s)
300 ppm nC7H16 / 3300 ppm O2 / Ar (T5 = 1494 K, p5 = 2.15 atm)
JetSurF 1.0 is quite accurate… but aren’t we lucky!
Multispecies Time Histories(Model Uncertainties)
11
300 ppm nC7H16 / 3300 ppm O2 / Ar (T5 = 1365 K, p5 = 2.35 atm)
Even less precise towards lower T5.
10-6
10-5
10-4
10-3
Mol
e Fr
actio
nC2H4
10-6
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
OH
Time (s)
10-6
10-5
10-4
10-3H2O
10-6
10-5
10-4
10-3
10-5 10-4 10-3
CO2
Time (s)
Multispecies Time Histories(Model Uncertainties)
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Multispecies Time Histories
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
Time (s)
C2H4
H2O
OH
CO2
300 ppm nC7H16 / 3300 ppm O2 / ArT5 = 1494 K, p5 = 2.15 atm
300 ppm nC7H16 / 3300 ppm O2 / ArT5 = 1494 K, p5 = 2.15 atm
300 ppm nC7H16 / 3300 ppm O2 / ArT5 = 1365 K, p5 = 2.35 atm
10-6
10-5
10-4
10-3
10-4 10-3
Mol
e Fr
actio
n
Time (s)
300 ppm nC7H16 / 3300 ppm O2 / ArT5 = 1365 K, p5 = 2.35 atm
C2H4
H2O
OH CO2
Analyses of Experimental Uncertainties
Dashed lines: ±10K T5 uncertainty; dotted lines: ±20% uncertainty on species concentration
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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
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
Sheen, et al. (2009)
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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
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
0
20obs
,00 *2obs1
minM r r
r r
x
xx
0, ,
1 1
ˆˆ,m m m
r r r i i r ij i ji i j i
x ξ 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
Sheen, et al. (2009)
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10-5
10-4
10-3
Mol
e Fr
actio
n
C2H4
10-5
10-4
10-3
10-5 10-4 10-3
Mol
e Fr
actio
n
OH
Time (s)
10-5
10-4
10-3H2O
10-5
10-4
10-3
10-5 10-4 10-3
CO2
Time (s)
Model Precision Improved by the data
Multispecies Time Histories
300 ppm nC7H16 / 3300 ppm O2 / Ar (T5 = 1494 K, p5 = 2.15 atm)
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(a)
(b)
(a)
(b)
Impact on Flame Speed Predictions
Multispecies Time Histories
0.7 0.9 1.1 1.3 1.5
Equivalence Ratio,
Flam
e Sp
eed
(cm
/s)
n‐heptane‐air mixtures (p = 1 atm, T0 = 353 K)
unconstrained – prior model
constrained – posterior modelOH, H2O, CO2 ( = 1, T5 = 1365 * 1495 K)
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Multispecies Time HistoriesEffect of Experimental Uncertainties
n‐heptane‐air mixtures (p = 1 atm, T0 = 353 K)
1
2
3
4
0 5 10 15 20
1/(2 obs)
= 1.0
s (
cm/s
)uo
= 1.4
20% 10% 7% 5%
Uncertainty in Species Value, 2 obs
2
3
4
0 5 10 15 20
1/(2 obs)
20% 10% 7% 5%
Uncertainty in Species Value, 2 obs
CH3 (Series 2) only
OH (Series 1) only
All multi-species (Series 1 & 2)
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Multispecies Time HistoriesEffect of Experimental Uncertainties
(a)
(b)
(c)
(a)
(b)
(c)
0.7 0.9 1.1 1.3 1.5
Equivalence Ratio,
Flam
e Sp
eed
(cm
/s)
n‐heptane‐air mixtures (p = 1 atm, T0 = 353 K)
unconstrained – prior model
posterior model (±20%)
posterior model (±5% - hypothetical)
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(d)(d)
(a)
(b)
(a)
(b)
Model is Accurate, and (Looks) Precise (Too)with constrained joint parameter uncertainties
Equivalence Ratio,
Flam
e Sp
eed
(cm
/s)
n‐heptane‐air mixtures (p = 1 atm, T0 = 353 K)
unconstrained – prior model
2 sets of OH, H2O, CO2 profiles
2 sets of OH, H2O, CO2 profilesFlame speedIgnition delay
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102
103
104
Igni
tion
Del
ay,
(s) 0.4% nC7H16 / 4.4 % O2 / Ar (p5 = 1 atm)
102
103
104
0.60 0.65 0.70 0.75
1000 K/T
Igni
tion
Del
ay,
(s)
Open diamond: Smith et al. (2005); filled circles: Davidson et. al. (2010)
Model is Accurate, and (Looks) Precise (Too)with constrained joint parameter uncertainties
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Multispecies Global Multispecies+properties Global properties
Joint Parameter Uncertainties
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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
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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
24
25
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
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Cyclohexane Low‐Temperature Chemistry
Miller, Taatjes (2009)
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28
29
Cyclohexane Ring‐Opening Reaction
CH3
CH2
k (s–1) = 5×1016 exp[ –88 (kcal/mol) / RT] (Tsang 1978)
CH3
CH2
CH3
C:H
H2.C
C.H2
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Methylcyclohexane Ring‐Opening Reaction
CH3
CH2
CH3
CH3
CH3
CH3
CH3
CH3
• •
CH2
CH3
CH3
CH3
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Ring‐Opening Reactions
CBS‐QB3 energy
→ Ho = 89.8 kcal/mol
→ Ho = 79.0 kcal/mol
CH3
C:H
CH3CH3
CH3
••
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Ea = 71 kcal/mol
Ea = 88 kcal/mol
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Summary
• JetSurF 2.0 is available online (still needs work).
•Major improvement from version 1.1• Added low temperature of cyclohexane
• Unresolved problems
• Low‐temperature chemistry for n‐butylcyclohexane not yet implemented
• Kinetics of alkylated cyclohexane thermal decomposition (ring opening through the carbene mechanism) currently unavailble)