Overview of Research at the CEFRC on Chemical Kinetics ......Overview of Research at the CEFRC on...
Transcript of Overview of Research at the CEFRC on Chemical Kinetics ......Overview of Research at the CEFRC on...
Overview of Research at the CEFRC on
Chemical Kinetics and Reaction Mechanisms of Foundational Fuels
D. Davidson,1 F. L. Dryer,2 F. N. Egolfopoulos,3 N. Hansen,4
R. K. Hanson,1 Y. Ju,2 S. Klippenstein,5 C. K. Law,2 H. Wang,3
1Stanford University, 2Princeton University, 3University of Southern California,4Sandia National Laboratories, 5Argonne National Laboratory
Combustion Energy Frontier Research Center
2011 MACCCR Fuel Summit
Mechanism, parameters, uncertainties
Kinetics model Critical parameters
Reduced mechanism
Understanding, models
Sensitivities at relevant conditions
Thermo & kinetics parameters and methods
Kinetics parameters
Reactive flow measurements
Combustion Reaction Model Hierarchy and Foundational Chemistry
Products
H2O, CO2
H2, CO
C2H2, soot
(NOx)……H2 Oxidation
CO‐H2 Oxidation
CHxOy, C2‐4Hx OxidationCH4
Alcohols Bio‐Diesel
Critical reviewof literature kinetic data
Modelcompilation
“Tuning”
Validation
Publishmodel
Critical reviewof literature kinetic data
Modelcompilation
“Tuning”
Validation
Publishmodel
Critical reviewof literature kinetic data
Modelcompilation
“Tuning”
Validation
Publishmodel
Critical reviewof literature kinetic data
Modelcompilation
“Tuning”
Validation
Publishmodel
proliferation of models
Combustion Reaction Model Development ‐ The Problem of Model Proliferation
Combustion Reaction Model Development ‐ The Problem of Model Proliferation and Solution
While for large oxygenate and hydrocarbon fuels there
will be continued parallel efforts leading to competing
reaction kinetic models, kinetic knowledge for small
hydrocarbons has converged to a point that it is
feasible to advance a unified, collaborative reaction
model of H2/CO/C1‐4 combustion for use as kinetic
foundation for higher hydrocarbons and oxygenates.
CEFRC Working Hypothesis
CEFRC Foundational Fuel Chemistry
• The need to revisit and unify H2/CO/C1‐4chemistry – H2 combustion
• Other CEFRC activities on foundational fuel chemistry.
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 5 10 15 20 25 30Pressure (atm)
Mas
s bu
rnin
g ra
te (g
cm
-2 s
-1)
Burke et al. (2010)Li et al. (2007)O'Connaire et al. (2004)Saxena & Williams (2006)Davis et al. (2005)Konnov (2008)Sun et al. (2007)GRI-MECH 3.0 (1999)Hong et al. (2010)
H2/O2/Ar, φ=2.5Tf ~1600K
-2 -1 0 1 2
Sensitivity Coefficient
phi=2.5
phi=1.0
phi=0.3
H+OH+M=H2O+M
O+H2=H+OH HO2+OH=H2O+O2
HO2+H=H2+O2
H2+OH=H2O+H
HO2+H=OH+OH H+O2=O+OH
H+O2(+M)=HO2(+M)
H2/O2/He, Tf~1400K10 atm
Updating of the H2/O2 model motivated by difficulties in predicting flame behaviors at high pressures and low flame temperatures.
None of the kinetic models predict P dependence across all conditions.
Motivation
Data from M.P. Burke, M. Chaos, F.L. Dryer, Y. Ju, Combust. Flame 157 (2010) 618–631.
Table 6.1. H2/O2 Reaction Model Units are cm3-mol-sec-cal-K; k = A T n exp(-E a /RT)
A n E a Reference1 H+O2 = O+OH 1.04E+14 0.00 1.53E+04 * Hong et al. (2010)2 O+H2 = H+OH Duplicate 3.82E+12 0.00 7.95E+03 * Baulch et al. (2005)
Duplicate 8.79E+14 0.00 1.92E+043 H2+OH = H2O+H 2.16E+08 1.51 3.43E+03 Michael & Sutherland (1988)4 OH+OH = O+H2O 3.34E+04 2.42 -1.93E+03 * Baulch et al. (2005)5 H2+M = H+H+M 4.58E+19 -1.40 1.04E+05 Tsang et al. (1986)
ε H2 = 2.5, ε H2O = 12.0, ε CO = 1.9, ε CO2 = 3.8, ε Ar = 0.0, ε He = 0.0 Li et al. (2004)H2+Ar = H+H+Ar 5.84E+18 -1.10 1.04E+05 Tsang et al. (1986)H2+He = H+H+He 5.84E+18 -1.10 1.04E+05 Li et al. (2004)
6 O+O+M = O2+M 6.16E+15 -0.50 0.00E+00 Tsang et al. (1986)ε H2 = 2.5, ε H2O = 12.0, ε CO = 1.9, ε CO2 = 3.8, ε Ar = 0.0, ε He = 0.0 Li et al. (2004)O+O+Ar = O2+Ar 1.89E+13 0.00 -1.79E+03 Tsang et al. (1986)O+O+He = O2+He 1.89E+13 0.00 -1.79E+03 Li et al. (2004)
7 O+H+M = OH+M 4.71E+18 -1.00 0.00E+00 Tsang et al. (1986)ε H2 = 2.5, ε H2O = 12.0, ε CO = 1.9, ε CO2 = 3.8, ε Ar = 0.75, ε He = 0.75 Li et al. (2004)
8 H2O+M = H+OH+M 6.06E+27 -3.32 1.21E+05 * Srinivasan & Michael (2006)ε H2 = 3.0, ε H2O = 0.0, ε CO = 1.9, ε CO2 = 3.8, εO2 = 1.5, ε N2 = 2.0, ε He = 1.1 See textH2O+H2O = H+OH+H2O 1.01E+26 -2.44 1.20E+05 Srinivasan & Michael (2006)
9 H+O2 (+M) = HO2 (+M)a k ∞ 4.65E+12 0.44 0.00E+00 * Troe (2000)k 0 6.37E+20 -1.72 5.25E+02 Michael et al. (2002), M = N2
F c = 0.5, T*** = 1.0E-30, T* = 1.0E+30 * Fernandes et al. (2008)ε H2 = 2.0, ε H2O = 14.0, ε CO = 1.9, ε CO2 = 3.8, ε O2 = 0.78, εAr = 0.67, εHe = 0.8 * See textH+O2 (+M) = HO2 (+M)b k ∞ 4.65E+12 0.44 0.00E+00 * Troe (2000)
k 0 9.04E+19 -1.50 4.92E+02 Michael et al. (2002), M = Ar or HeF c = 0.5, T*** = 1.0E-30, T* = 1.0E+30 Fernandes et al. (2008)ε H2 = 3.0, ε H2O = 21.0, ε CO = 2.7, ε CO2 = 5.4, ε O2 = 1.1, ε He = 1.2, εN2 = 1.5 * See text
10 HO2+H = H2+O2 2.75E+06 2.09 -1.45E+03 * Michael et al. (2000) x 0.7511 HO2+H = OH+OH 7.08E+13 0.00 2.95E+02 Mueller et al. (1999)12 HO2+O = O2+OH 2.85E+10 1.00 -7.24E+02 * Fernandez-Ramos & Varandas (2002) x 0.613 HO2+OH = H2O+O2 2.89E+13 0.00 -4.97E+02 Keyser (1988)14 HO2+HO2 = H2O2+O2 Duplicate 4.20E+14 0.00 1.20E+04 Hippler et al. (1990)
HO2+HO2 = H2O2+O2 Duplicate 1.30E+11 0.00 -1.63E+0315 H2O2(+M) = OH+OH(+M) k ∞ 2.00E+12 0.90 4.87E+04 * Troe (2010)
k 0 2.49E+24 -2.30 4.87E+04 * Troe (2010)F c = 0.42, T*** = 1.0E-30, T* = 1.0E+30 * Troe (2010)ε H2O = 7.5, εH2O2 = 7.7, ε CO2 = 1.6, ε O2 = 1.2, εN2 = 1.5, εHe = 0.65 * Troe (2010)ε H2 = 3.7 , ε CO = 2.8 See text
16 H2O2+H = H2O+OH 2.41E+13 0.00 3.97E+03 Tsang et al. (1986)17 H2O2+H = HO2+H2 4.82E+13 0.00 7.95E+03 Tsang et al. (1986)18 H2O2+O = OH+HO2 9.55E+06 2.00 3.97E+03 Tsang et al. (1986)19 H2O2+OH = HO2+H2O Duplicate 1.74E+12 0.00 3.18E+02 * Hong et al. (2010)
Duplicate 7.59E+13 0.00 7.27E+03
Indicates that reaction parameters has been revised from that utilized in Li et al (2004)
Recommended for use in mixtures where N2 is prevalent diluent
Recommended for use in mixtures where Ar or He are the prevalent diluent(s).
The Updated Model
In Press, International Journal of Chemical Kinetics, (2011)
Experiments near 1000K: suggest very different behavior.:Hippler et al. 1995 (Troe):
minimum at 1200KKappel et al. 2002 (Troe):
minimum at 1000KNo theoretical work presently
supports the above behavior.Few mechanistic studies at
conditions near the valleys of these results to test their impact.
Data at low temperatures and above ~1200 K are consistent with the rate expression of Keyser (1988). Burke et al utilizes Keyser (1988).
However:
0.5 1 1.5 2 2.5 3 3.5 4
1013
1014
1000/T (K-1)k
(cm
3 mol
-1 s
-1)
Peeters and Mahnen (1973)DeMore (1979)Lii et al. (1980)Cox et al. (1981)Kurylo et al. (1981)Braun et al. (1982)DeMore (1982)Goodings & Hayhurst (1988)Keyser (1988)Hippler & Troe (1992)
Hippler et al. (1995)Kappel et al. (2002)Srinivasan et al. (2006)Hong et al. (2010)Keyser (1988)Sivaramakarishnan et al. (2007)Chaos & Dryer (2008) - HipplerChaos & Dryer (2008) - KappelRasmussen et al. (2008)
Example: HO2+OH=H2O+O2;
Uncertainties - Model Parameters
1.E+11
1.E+12
1.E+13
1.E+14
0.00 0.50 1.00 1.50 2.00 2.50 3.00
1000/T (K-1)
k (c
m3 m
ol-1
s-1
)
Hippler et al. 1995
Kappel et al. 2002
Particularly for T-P dependence of HO2consumption/formation rxns
For example, rate constants for HO2+HO2 = H2O2 + O2 (R14) from the only two high-T studies in the literature differ by a factor of 3 yields 20% differences in predicted flame speeds
Uncertainties - Model Parameters
Rate constant expressions for k14.
11
Uncertainties – Mechanism Assumptions
H+HO2
H2OO HOOH H2O+O(3P) H2+O2
(i)(ii)
(vii)(v)
(vi)(iii)
(iv-1)
(iv-2)H2O+O(1D)
OH+OH
H2O+O(3P)HO…OH
H+HO2
H2OO HOOH H2O+O(3P) H2+O2
(i)(ii)
(vii)(v)
(vi)(iii)
(iv-1)
(iv-2)H2O+O(1D)
OH+OH
H2O+O(3P)HO…OH
For example: H + HO2 = H2O + O
Included only in some kinetic models
Experimental data available only below 400K
Previous theoretical treatments yield different answers about its role at combustion temperatures. Inclusion of the reaction using previous rate constant estimates result in up to 30% differences in predicted flame speed
Present calculations (VRC-TST) suggest this reaction may be important.
Non-statistical approaches (not considered here) necessary for accurate treatment b/c of short HOOH lifetimes
H2/O2/He flames. Mixture effects simulated by 10% higher A-factor for H+O2+M=HO2+M (R9).
Nonlinearities in bath-gas mixture rule for unimolecular reactions found to reach ~10% 15% differences in predicted flame speeds
More generally: high-pressure, dilute flames might require consideration of many “negligible”processes
Uncertainties – Kinetic Processes
Summary Hydrogen Modeling
Present model adequately reproduces previous and new targets across a wide range of conditions with substantial improvements against recent high-pressure flame speed and shock tube speciation measurements
Uncertainties in both model parameters and underlying assumptions affect predictions of relevant combustion behavior (including rate constants for HO2 rxns, potential missing rxns, and bath-gas mixture rules).
CEFRC Foundational Fuel Chemistry
• The need to revisit and unify H2/CO/C1‐4chemistry.
• Other CEFRC activities on foundational fuel chemistry.
Ab initio & reaction rate theory predictions of elementary reaction rate constants
Klippenstein/ANL
Davidson & Hanson/Stanford
Ethylene Oxidation
Ethylene PyrolysisRate Determination: C2H4 → C2H2 + H2
1.0% C2H4/Ar1895 K, 2.6 atm
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70.0
0.1
0.2
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0.5
Wei et al. (2011) Marinov et al. Healy et al. Wang et al. Ranzi et al.
Time [ms]
C2H
4 M
ole
Frac
tion
[%]
0.5% C2H4/3% O2/Ar1221 K, 3.4 atm
0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
Wei et al. (2011) Best Fit (C2H4=C2H2+H2) JetSurF 2.0
Time [s]
C2H
4 M
ole
Frac
tion
[%]
Shock tube/laser absorption measurements:Ethylene time‐Histories
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Equivalence Ratio
Lam
inar
Fla
me
Spee
ds, c
m/s
1 atm
1 atm
2 atm
2 atm
4 atm
4 atm
10
15
20
25
30
35
40
45
0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
Laminar Flame Speeds, cm/s
Equivalence Ratio
n-Butane/Air, p=1 atm
Egolfopoulos/USC
Measurement and model validation: laminar flame speeds
Methane/Air
Symbols: experimental dataLines: USC‐Mech II predictions
Measurement and model validation: burner stabilized flames
Hansen/Sandia
10.5%i-C4H8/39.5%O2/Ar Flame
Measurement and model validation: burner stabilized flames
Hansen/SandiaYang/Sandia/USC
Relative Energy (kcal/mol)
CCSD(T)/6‐311G(d) // B3LYP/6‐311G(d)
+ CH3
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. mass burning rate)+ 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. a laminar flame
Sheen, et al. (2009 & 2011)
0 x x αξ ,0lnln
i ii
i
k kx
f
Knowledge (Uncertainty) Quantification by Polynomial Chaos Expansions
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. mass burning rate)+ associated uncertainty
0, ,
1 1
ˆˆ,m m m
r r r i i r ij i ji i j i
x ξ x
Sheen, et al. (2009 & 2011)
0 x x αξ
Knowledge (Uncertainty) Quantification by Polynomial Chaos Expansions
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 + associated uncertainty
0, ,
1 1
ˆˆ,m m m
r r r i i r ij i ji i j i
x ξ x
Physics model
0 x x αξ
k1
k2
h1
0
2 2obs,0 0 0,*
0 2 2obs1 1min
M Nr r n
r n nr
x
x
xx
1
0 0 0 02obs1
1 4n
T T T T T
rr
* * * *bx x b ax b b x a aa I
1/2 *α
Uncertainty Minimization by Polynomial Chaos Expansions
Considering no combustion experiments
Model constrained by knowledge prior to 2010
Model constrained by the latest knowledge
Uncertainty Minimization by Polynomial Chaos Expansions – Measured Progress!
The Future
•Detailed H2/CO/C1‐4 reaction model with well defined uncertainties
•Active design of experiments
•Two‐way knowledge propagation.
Kinetic expt./electronicstructure
calc.
Reaction rate theory
Review of literature kinetic data
ModelcompilationValidation
Sensitivityanalysis
Newexperiments
Response surfacedevelopment
Uncertainty minimization
A New Approach