|
Release date: |
||||
|
||||
|
Download: Mechanism,
Thermochemical, and Transport Databases in
ChemKin format.
Release notes: JetSurF 1.0 consists
of 194 species and 1459 reactions. The
model describes the pyrolysis and oxidation kinetics of normal alkanes up to n-dodecane at high temperatures. JetSurF 1.0 is capable of reproducing a large number of data
sets, but it is “un-tuned” and work-in-progress. The development effort centers on achieving
consistent kinetic parameter assignment and predictions for a wide range of
hydrocarbon compounds. This effort is
reflected in the validation tests documented in the Performance
that we know page.
JetSurF 1.0 release features a
preliminary determination of the model uncertainty and its quantitative
impact on predicted combustion properties, as shown for a selected set of
validation tests.
Some Model Details The base model is USC-Mech II
(111 species, 784 reactions) that describes the oxidation of H2 and CO
and the high-temperature chemistry of C1-C4 hydrocarbons.
The base model considers the pressure dependence for unimolecular and bimolecular chemically activated
reactions, and was validated against experimental data ranging from laminar
flame speeds, ignition delay times behind shock waves, to species profiles in
flow reactors and burner stabilized flames. The base model is appended with a set of reactions (83
species and 675 reactions) to describe high-temperature pyrolysis and
oxidation of normal alkanes (CkH2k+2, 5 ≤
k ≤ 12). The bulk of work is discussed initially in [1]. The following class of major reactions of n-alkanes have been considered: |
|
Reaction type |
Source and Method
of Rate Estimation |
Pressure |
|
C-C bond fission in n-alkane |
Back rate constant from 2C2H5
→ n-C4H10
(k∞) |
No |
|
H-abstraction by H, O, OH, O2, and CH3 |
Cohen’s method using the rate constants of C3H8
+ X → n-C3H7 or i-C3H7 + HX (X = H, O, O2 & CH3). CxH2x+2 + OH → CxH2x+1 + H2O:
Sivaramakrishnan & Michael [2] |
N/A |
|
Mutual isomerization of alkyl radicals (1,4,
1,5 and 1,6 H-shift) |
Tsang,
Manion and co-workers. n-pentyl
[3], n-hexyl [4], n-heptyl [5], n-octyl [6]. Rate parameters for the CkH2k+1
(9≤ k ≤ 12) radicals
are equal to those of n-octyl [5]. |
Yes |
|
All possible C-C bond beta-scission in alkyl radicals |
See
above |
Yes |
|
C-C bond fission
reactions kinetic parameters for C5-C12 alkenes as well
as mutual isomerization and C-C bond b-scission of alkenyl radicals are based on the work
of Tsang and coworkers [7, 8] on 1-hexenyl and 1-pentenyl radicals. H-abstractions kinetic
parameters are based on those of similar reactions of C3 and C4
species in USC-Mech II. Thermochemical properties for C>4
alkane, alkyl and alkene species were estimated from the group additivity
method using group values consistent with those in USC-Mech II. Additionally, a 4-species, 12-step n-dodecane oxidation model is appended
to capture some of the low- to intermediate-temperature chemistry. The lumped model is an adaptation
of that proposed by Bikas and Peters [9]. The use of this model does not
offer the possibility to closely predict the low-temperature chemistry, but
it enables a better understanding of the impact of low- to
intermediate-temperature chemistry on n-dodecane
oxidation at high temperatures. Lennard-Jones
parameters for long-chain alkanes were estimated the correlations of corresponding
states of Tee et al. [10], as discussed in [11]. Method
of Uncertainty Propagation Uncertainty
factors for Arrhenius pre-factors in USC-Mech II are given in [12]. The pre-factors for all reactions not
included in USC Mech II are assumed to have an uncertainty factor of 3. Though this assignment may under- or
over-predict the true uncertainty in each rate constant, its effect on the
uncertainty values propagated into the prediction of a certain combustion
property is expected to be small. With
the exception of H-atom abstraction reactions, the large hydrocarbon
chemistry of n-alkanes usually
affects the combustion properties quite minimally. Currently, the uncertainty factors for the
H-abstraction reactions are estimated to be roughly a factor of 3. Active
rate parameters were determined using a screening procedure similar to those
discussed in [13-15]. Uncertainty in
the model predictions is estimated using the MUM-PCE method [12]. In all cases it is assumed that reaction
rate parameters have a log-uniform distribution about their nominal values.
It should be noted that USC-Mech II contains the H2/CO oxidation
model of Davis et al [15], and so the rate parameters in the H2/CO
submechanism were reset to their nominal values. For
laminar flame speeds and selected ignition delay times, a response surface is
developed for each prediction with respect to the active parameters as
described in [12] and the 2s uncertainty is determined as described in
[9]. An uncertainty band
for each combustion property set is then determined by combining the
uncertainties of each member of that set.
For ignition delay times and perfectly-stirred reactor species
profiles, the uncertainties are calculated by Monte Carlo sampling of the
rate parameter and temperature space, thereby generating the uncertainty band
as a cloud of points. |
|
1. You, X.,
Egolfopoulos, F. N., Wang, H Proc.
Combust. Inst. 32 (2009) 403-410. 2. R. Sivaramakrishnan, J. V.
Michael, J. Phys. Chem. A, 113
(2009) 5047-5060. 3. W.
Tsang, J. A. Walker, J. A. Manion, Proc. Combust.
Inst. 27 (1998)
pp.135-142. 4.
W. Tsang, J. A. Walker, J. A. Manion, Proc. Combust. Inst. 31
(2007) pp.141-148. 5.
W. Tsang, I.
A. Awan, W. S. McGivern, J. A. Manion, Soot precursor from real fuels: the
unimolecular reaction of fuel radicals.
In Combustion Generated Fine
Carbonaceous Particles (H. Bockhorn, A. D’Anna, A. F. Sarofim, H. Wang,
Eds.), Karlsruhe University Press, in press, 2008. 6.
W. Tsang, W. S. McGivern, J. A. Manion, Proc. Combust. Inst. 32 (2009) 131-138. 7.
W. Tsang, J.
Phys. Chem. A 110 (2006) 8501-8509. 8.
W. Tsang, “
PrIMe: A Database for the Pyrolysis of Heptane and Smaller Hydrocarbons
Fuels; Implications for Realistic Fuels.” Poster Paper, 32nd
International Symposium on Combustion, Montreal, Canada, August 3-8,
2008. 9. G. Bikas, N. Peters, Combust. Flame 126 (2001) 1456-1475. 10. L. S. Tee, 11. Holley, A. T., You, X., Dames,
E., Wang, H., Egolfopoulos, F. N. Proc. Combust. Inst. 32 (2009) 1157-1163. 12. D. A. Sheen, X. You, H. Wang, T.
Løvås, Proc.
Combust. Inst. 32 (2009) 535-542. 13. M. Frenklach, H. Wang, M. J.
Rabinowitz, Prog. Energ. Combust. Sci. 18 (1992) 47-73. 14. Z. W. Qin, V. V. Lissianski, H.
X. Yang, W. C. Gardiner, S. G. Davis, H. Wang, Proc. Combust. Inst. 28 (2000) 1663-1669. 15. S. G. Davis, A. V. Joshi, H.
Wang, F. N. Egolfopoulos, Proc.
Combust. Inst. 30 (2005) 1283-1292. |