An Updated Reaction Model for the High-Temperature Pyrolysis and Oxidation of Acetaldehyde R. M´evela,b,∗, K. Chatelainc,∗, G. Blanquartd , J.E. Shepherde a Center for Combustion Energy, Tsinghua University, Beijing 100084, China Department of Automotive Engineering, Tsinghua University, Beijing 100084, China c ENSTA-ParisTech, Paris-Saclay University, Palaiseau, France d Mechanical Engineering Department, California Institute of Technology, Pasadena, CA, USA e Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, CA, USA b
This supplemental material presents the complete preliminary evaluation of the Aramco 2.0 with respect to ignition delay-time and species profiles data. The corresponding preliminary sensitivity analyses are also presented.
∗
Corresponding author:
[email protected]
Preprint submitted to Elsevier
September 28, 2017
1. Preliminary kinetics modeling and analyses To make a preliminary assessment of the predictive capability of reference reaction models and determine important reactions for acetaldehyde pyrolysis and oxidation, Aramco 2.0 has been employed. The choice of this reaction model is motivated by the specific validation performed for acetaldehyde in Metcalfe et al. [1]. 1.1. Characteristic time of reaction Figure 1 presents a comparison between the experimental results (present data and data from [2–4]) and the predictions of Aramco 2.0. The reaction model tends to over-estimates (90 to 120% error) the characteristic time of reaction based on emission signals (see Figure 1 a) and b)). The characteristic time of reaction based on CO2 and O2 (see Figure 1 c) and d)) are better reproduced but still overall overestimated with mean errors of 42% and 31%, respectively.
Figure 2 presents sensitivity analyses performed under oxidative conditions. The analyses performed on temperature, CO2 *, CO2 , and O2 are consistent with each other and demonstrate the primary importance of acetaldehyde decomposition, CH3 CHO(+M)=CH3 +HCO(+M), the branching reaction H+O2 =OH+O, and CH3 CHO +H=CH3 CO+H2 . The later reaction acts as a sink of H atom which would be otherwise formed by the rapid decomposition of HCO. The sensitivity analyses also show the importance of methyl radicals chemistry. 1.2. IR and UV absorption and emission profiles In Figure 3, the absorption and emission profiles have been calculated according to the procedure described in Yasunaga et al. [4]. Briefly, the absorption/emission profiles were calculated by including the contributions of the relevant species in each case, considering the concentrations predicted by the reaction models and the absorption/emission “cross-section” for each species provided by Yasunaga et al.
In Figure 3 a) and b), the experimental [4] and simulated absorption profiles at 3.39 µm obtained under pyrolytic and oxidative conditions are displayed. This 2
104
Time to CO 2* peak (µs)
Time to OH* peak (µs)
Mix 6 Mix 7 Mix 8
103
102
103
102
Mix 1 Mix 2 Mix 3
6
6.5
7 10,000/T 5 (K -1)
7.5
101 6.5
8
7
7.5
8
10,000/T (K -1) 5
a) Present data
b) Data from Dagaut et al. [2]
104
10
Time to O2 consumption onset (µs)
Time to CO 2 onset (µs)
Mix 14 Mix 15 Mix 16
3
102
101 5.5
Mix 9 Mix 10 Mix 11
103
102
6
6.5 7 10,000/T 5 (K -1)
7.5
8
5.8
c) Data from Yasunaga et al. [4]
6
6.2
6.4 6.6 10,000/T 5 (K -1)
6.8
7
7.2
d) Data from Hidaka and Suga [3]
Figure 1: Comparison between the experimental (present study and [2–4]) and the predicted (Aramco 2.0) ignition delay-time for CH3 CHO-O2 -Ar mixtures.
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CH3CHO+HCH3CO+H2
CH3CHO+HCH3CO+H2
Φ=0.5 Φ=1 Φ=1.5
CH3+H(+M)CH4(+M)
T=1250 K T=1550 K
CH3+CH3(+M)C2H6(+M) CH3+H(+M)CH4(+M)
CH3+HO2CH4+O2
CH3+HO2CH4+O2
CH2CHO(+M)CH3+CO(+M)
CH3CHO+OHCH3CO+H2O
CH4+OHCH3+H2O
H2+OHH+H2O
CH3+CH3(+M)C2H6(+M)
CH3CHO+HO2CH3CO+H2O2
CH3+O2CH2O+OH
CH3CHO+O2CH3CO+HO2
HCO+O2CO+HO2
CH3+O2CH2O+OH H2+OHH+H2O CH2CHO(+M)CH2CO+H(+M) CH2CHO(+M)CH2CO+H(+M)
HCO+MH+CO+M
CH3+HO2CH3O+OH
CH3+HO2CH3O+OH
CH3CHO(+M)CH3+HCO(+M)
CH3CHO(+M)CH3+HCO(+M)
O2+HO+OH
O2+HO+OH -1
-0.5
0
0.5
1
-1
Sensitivity coefficient on temperature
a) Sensitivity on temperature CH3CHO+HCH3CO+H2
0
0.5
1
b) Sensitivity on CO2 * O2+HO+OH
T=1300 K T=1600 K
CH3+HO2CH4+O2
-0.5
Sensitivity coefficient on CO2*
T=1500 K T=1700 K
CH3CHO(+M)CH3+HCO(+M)
CH3CHO(+M)CH4+CO(+M)
HCO+O2CO+HO2
HCO+MH+CO+M
C2H2+H(+M)C2H3(+M)
CH3+CH3(+M)C2H6(+M)
CH3+HO2CH3O+OH
CO+O2CO2+O CH4+HCH3+H2 HCO+HO2=>CO2+H+OH CH3+HO2CH4+O2 CH3CHO+O2CH3CO+HO2 CH3+CH3H+C2H5
CH3+O2CH2O+OH
C2H3+HC2H2+H2
HCO+O2CO+HO2
C2H6+HC2H5+H2
CH3+HO2CH3O+OH CH3CHO(+M)CH3+HCO(+M)
CH3+OCH2O+H
O2+HO+OH
CH3CHO+HCH3CO+H2 -1
-0.5
0
0.5
1
-1
Sensitivity coefficient on CO2
-0.5
0
0.5
1
Sensitivity coefficient on O2
c) Sensitivity on CO2
d) Sensitivity on O2
Figure 2: Sensitivity analyses during the oxidation of CH3 CHO performed with Aramco 2.0. In a): mixture 1-3; T5 =1450 K; P5 =300 kPa. In b): mixture 8; T5 =1325 and 1550 K; P5 =500 kPa. In c): mixture 15; T5 =1300 and 1600 K; P5 =200 kPa. In d): mixture 9; T5 =1500 and 1700 K; P5 =40 kPa.
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parameter is representative of the C—H bond consumption rate. Overall, the predictions of Aramco 2.0 qualitatively and quantitatively match the experimental profiles. In Figure 3 c) and d), the experimental and predicted emission profiles at 4.68 µm are shown. This wavelength corresponds to a strong absorption/emission band of carbon monoxide [5]. However, Yasunaga et al. report that for the mixtures studied, the emission due to ketene, CH2 CO, plays a major role in reproducing the experimental profiles. Whereas Aramco 2.0 captures the shape of the profiles, discrepancies are observed in terms of amplitude, especially under pyrolytic conditions. Figure 3 e) and f) present the experimental and simulated UV absorption profiles, around 200 nm. These profiles are representative of the absorption by CH3 radicals and CH2 CO. The Aramco mechanism does not capture the shape nor the amplitude of the profiles under pyrolytic conditions. Under oxidative conditions, the amplitude of the profile is captured but not the overall shape.
As a complement to the analyses shown in Figure 2 for oxidative conditions, Figure 4 presents sensitivity analyses performed under pyrolytic conditions for CH4 , CO, and CH2 O. These species have been selected due to their primary contribution to the IR and UV absorption and emission signals obtained by Yasunaga et al. [4]. These analyses confirm the important role of acetaldehyde decomposition and of the reactions of methyl radical, especially its recombination to form ethane. In addition, the importance of the H-abstraction reactions (by H and CH3 ) on the methyl group of acetaldehyde, and their competition with the H-abstraction reactions on the aldehyde group of CH3 CHO, are to be underlined. The IR and UV emission signals are also sensitive to the decomposition of CH2 CHO into CH2 CO and H.
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2 T=1329 K, P=200 kPa T=1477 K, P=240 kPa T=1589 K, P=272 kPa
1.8
T=1393 K, P=224 kPa T=1494 K, P=252 kPa T=1560 K, P=272 kPa
1.8 Normalized absorption at 3.39 µm
Normalized absorption at 3.39 µm
2
1.6
1.4
1.2
1
1.6 1.4 1.2 1 0.8 0.6 0.4 0.2
0.8
0
100
200 300 Time (µs)
400
0
500
200 300 Time (µs)
400
500
a) CH3 CHO pyrolysis: mixture 19
b) CH3 CHO oxidation: mixture 17 18 Normalized IR emission at 4.68 µm
Normalized IR emission at 4.68 µm
100
12 11 10 9 8 7 6 5 4 3 T=1419 K, P=224 kPa T=1492 K, P=244 kPa
2 1
0
100
200 300 Time (µs)
400
14 12 10 8 6 4
0
100
200 300 Time (µs)
400
500
d) CH3 CHO oxidation: mixture 17 0.25
T=1327 K, P=200 kPa T=1587 K, P=271 kPa
0.5
T=1393 K, P=224 kPa T=1494 K, P=252 kPa T=1560 K, P=272 kPa
16
2 500
c) CH3 CHO pyrolysis: mixture 19
T=1544 K, P=230 kPa
0.2 UV absorption at 216 nm
UV absorption at 200 nm
0
0.4
0.3
0.2
0.1
0.05
0.1
0
0.15
0
100
200 300 Time (µs)
400
0
500
e) CH3 CHO pyrolysis: mixture 19
0
100
200 300 Time (µs)
400
500
f) CH3 CHO oxidation: mixture 14
Figure 3: Comparison between the experimental [4] and the predicted (Aramco 2.0) IR and UV absorption/emission profiles during the pyrolysis and oxidation of CH3 CHO.
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CH3+CH3(+M)C2H6(+M)
T=1329 K, P=200 kPa T=1477 K, P=240 kPa T=1589 K, P=272 kPa
CH3CHO+HCH2CHO+H2 C2H6+HC2H5+H2 HCO+CH3CH4+CO CH3+H(+M)CH4(+M) HCO+MH+CO+M CH3CHO+HCH3CO+H2 C2H6+CH3C2H5+CH4 CH4+HCH3+H2 CH3CHO(+M)CH3+HCO(+M) CH3CHO+CH3CH3CO+CH4 CH3CHO(+M)CH4+CO(+M) -1
-0.5
0
0.5
1
Sensitivity coefficient on CH4
a) Sensitivity on CH4 CH3+CH3(+M)C2H6(+M)
T=1419 K, P=224 kPa T=1492 K, P=244 kPa
CH3CHO+HCH2CHO+H2 CH2CHO(+M)CH2CO+H(+M) C2H6+HC2H5+H2 CH2CHO(+M)CH3+CO(+M) CH4+HCH3+H2 HCO+MH+CO+M CH3CHO+HCH3CO+H2 CH3CHO(+M)CH4+CO(+M) CH3CHO+CH3CH3CO+CH4 CH3CHO(+M)CH3+HCO(+M) -1
-0.5
0
0.5
1
Sensitivity coefficient on CO
b) Sensitivity on CO CH3CHO+HCH3CO+H2
T=1327 K, P=200 kPa T=1587 K, P=271 kPa
CH2CO+HCH3+CO CH2CHO(+M)CH3+CO(+M) CH3CO(+M)CH3+CO(+M) CH3CHO(+M)CH3+HCO(+M) CH3CO(+M)CH2CO+H(+M) C2H6+HC2H5+H2 CH3+CH3(+M)C2H6(+M) CH3CHO+CH3CH3CO+CH4 HCO+MH+CO+M CH2CHO(+M)CH2CO+H(+M) CH3CHO+HCH2CHO+H2 CH3CHO(+M)CH3+HCO(+M) -1
-0.5
0
0.5
1
Sensitivity coefficient on CH2CO
c) Sensitivity on CH2 CO Figure 4: Sensitivity analyses during the pyrolysis of CH3 CHO performed with Aramco 2.0. In a), b) and c): mixture 19.
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References [1] W. Metcalfe, S. Burke, S. Ahmed, C. H.J., International Journal of Chemical Kinetics 45 (2013) 638–675. [2] P. Dagaut, M. Reuillon, D. Voisin, M. Cathonnet, M. M. Guinness, J. Simmie, Combustion Science and Technology 107 (1995) 301–316. [3] Y. Hidaka, M. Suga, Journal of the Mass Spectrometry Society of Japan 35 (1987) 74–83. [4] K. Yasunaga, S. Kubo, H. Hoshikawa, T. Kamesawa, Y. Hidaka, International Journal of Chemical Kinetics 40 (2008) 73–102. [5] L. S. Rothman, A. Barbe, D. C. Benner, L. R. Brown, C. Camy-Peyret, M. R. Carleer, K. Chance, C. Clerbaux, V. Dana, V. M. Devi, A. Fayt, J. M. Flaud, R. R. Gamache, A. Goldman, D. Jacquemart, K. W. Jucks, W. J. Lafferty, J. Y. Mandin, S. T. Massie, V. Nemtchinov, D. A. Newnham, A. Perrin, C. P. Rinsland, J. Schroeder, K. M. Smith, M. A. H. Smith, K. Tang, R. A. Toth, J. Vander Auwera, P. Varanasi, K. Yoshino, Journal of Quantitative Spectroscopy and Radiative Transfer 82 (2003) 5–44.
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