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A Comprehensive Kinetic Model of Ethylene and Acetylene Oxidation at High Temperatures

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A Comprehensive Kinetic Model of Ethylene and Acetylene Oxidation at High Temperatures A Progress Report on A Comprehensive Kinetic Model of Ethylene and Acetylene Oxidation at High Temperatures for Work carried out under a contract from the trustees of Princeton University as a part of a research program on Optimization of a Comprehensive Detailed Chemical Kinetic Model for Simulating High-Speed Propulsion An AFOSR New World Vista Program Submitted to Department of Mechanical and Aerospace Engineering Princeton University (Professor C. K. Law) Prepared by Hai Wang, Assistant Professor and Alexander Laskin, Postdoctoral Research Associate Department of Mechanical Engineering University of Delaware Newark, DE 19716 Table of Contents Table of Contents ..................................................................................ii List of Tables .......................................................................................iii List of Figures...................................................................................... iv 1. Introduction .....................................................................................1 2. Critical Survey of Literature Combustion Data..............................................2 2.1. Shock-Tube Ignition ................................................................2 2.2. Laminar Burning Velocity.......................................................... 4 2.3. Burner-Stabilized Flames ..........................................................5 3. Quantum Mechanical and RRKM calculations ..............................................5 3.1. Computational Methodologies..................................................... 5 3.2. C2H2 + O2 Reactions ...............................................................6 3.3. CH3CO System .....................................................................9 3.4. C3H4 and C3H5 Systems ..........................................................11 4. Detailed Kinetic Model .........................................................................11 4.1. H2/O2 Chemistry ....................................................................12 4.2. C1 Chemistry ........................................................................12 4.3. C2 Chemistry ........................................................................13 4.4. C3 and C4 Chemistry ...............................................................14 5. Simulation of Shock-Tube Experiments .....................................................15 5.1. Ethylene Oxidation in Shock Tubes...............................................15 5.2. Acetylene Oxidation in Shock Tubes .............................................16 5.3. Mechanisms of Acetylene and Ethylene Oxidation in Shock Tubes........... 17 6. Simulation of Laminar Burning Velocity ....................................................18 7. Simulation of Burner-Stabilized Flames .....................................................19 8. Summary ........................................................................................20 9. References .......................................................................................22 Appendix A. A Comprehensive and Detailed Kinetic Model of Ethylene and Acetylene Oxidation at High Temperatures .................................................................68 ii List of Tables Table 1. Shock-Tube Ignition Delay of Ethylene-Oxygen-Argon Mixtures.............. 27 Table 2. Shock-Tube Ignition Delay of Acetylene-Oxygen-Argon Mixtures. ...........28 Table 3. Laminar Premixed Flat Flames for Model Verification........................... 29 Table 4. RRKM Parameters for the Reaction of CH3CO. .................................30 iii List of Figures Figure 1. Literature shock-tube ignition data of ethylene-oxygen-argon mixtures. Symbols are experimental data, line is the correlation equation given in the panel. See Table 1 for reference sources and mixture conditions. .......................................31 Figure 2. Literature shock-tube ignition data of acetylene-oxygen-argon mixtures. Symbols are experimental data, line is the correlation equation given in the panel.. See Table 2 for reference sources and mixture conditions. .......................................32 Figure 3. Reaction pathways following molecular oxygen attack on the π bond in acetylene. The bracket denotes that the species is a rovibrationally excited adduct............ 33 Figure 4. Reaction energy diagram obtained at the G2(B3LYP) level of theory for acetylene oxidation by molecular oxygen via vinylidene as the intermediate. The energies are given in the units of kcal/mol. .........................................................34 Figure 5. Potential energy diagram of the CH3CO reactions. The energy values in parentheses are obtained at the G2(B3LYP) level of theory. ..................................35 Figure 6. Comparison of theoretical prediction and experimental data for the pressure fall-off of the rate coefficients of CH3CO → CH3 + CO............................... 36 Figure 7. Comparison of theoretical prediction and experimental data for the rate coefficient of CH2CO + H → CH3 + CO........................................................... 37 Figure 8. Comparison of experimental (symbols, Homer and Kistiakowsky, 1967) and computed (lines) ignition delay times behind reflected shock waves for the mixtures of (a) 0.5%C2H4-3%O2 (shock mixture 1, see Table 1) and (b) 0.5%C2H4-1%O2 (shock mixture 2, see Table 1) in argon. The computational ignition delay was determined as the time corresponding to [CO] + [CO2] equal to 10% of its final value. .................................................................................38 Figure 9. Comparison of experimental (symbols, Jachimowski 1977) and computed (lines) ignition delay times in incident shock waves for the mixtures of (a) 1%C2H4-6%O2, (b) 2%C2H4-6%O2, and (c) 3%C2H4-6%O2 in argon. Other shock conditions can found in Table 1. The computational ignition delay was determined as the laboratory time corresponding to maximum [O][CO]. .......................39 Figure 10. Comparison of experimental (symbols, Jachimowski 1977) and computed (lines) maximum [CO][O] in incident shock waves for the mixtures of (a) 1%C2H4-6%O2, (b) 2%C2H4-6%O2, and (c) 3%C2H4-6%O2 in argon. Other shock conditions can found in Table 1. .............................................................40 Figure 11. Comparison of experimental (symbols, Baker and Skinner, 1972) and computed (lines) ignition delay times behind reflected shock waves. The computational ignition was determined by the maximum pressure gradient. Shock mixtures (in argon): (3) 1%C2H4-3%O2, (4) 0.5%C2H4-3%O2, (5) 0.25%C2H4- 0.75%O2, (6) 2%C2H4-3%O2, (7) 1%C2H4-1.5%O2, (8) 1%C2H4-6%O2, (9) 0.25%C2H4-6%O2, (10) 0.5%C2H4-1.5%O2. The initial pressure for all but one shock mixtures is 3 atm. The pressure of mixture 5 is 12 atm................................... 41 iv Figure 12. Comparison of experimental (symbols, Kistiakowsky and Richards, 1962) and computed (lines) ignition delay times behind reflected shock waves. The computational ignition was determined by the maximum pressure gradient. Mixture compositions (in argon): (a) 0.57%C2H2-4.43%O2 (shock mixture 18), (b) 2.9%C2H2-2.1%O2 (shock mixture 19), and (c) 2%C2H2-3%O2 (shock mixture 20). See Table 2 for additional experimental conditions.......................................... 42 Figure 13. Comparison of experimental (symbols, Homer and Kistiakowsky, 1967) and computed (lines) ignition delay times behind reflected shock waves. The computational ignition delay was determined as the time corresponding to [CO] + [CO2] equal to 10% of its final value. Mixture compositions (in argon): (a) 0.5%C2H2-0.8%O2 (shock 21), and (b) 0.5%C2H2-1.0%O2-0.5%H2 (shock 22). See Table 2 for additional experimental conditions. ...............................................43 Figure 14. Comparison of experimental (symbols, Jachimowski, 1977) and computed (lines) ignition delay times in incident shock waves. The computational ignition delay was determined as the time corresponding to maximum [O][CO]. Mixture compositions (in argon): (a) 1%C2H2-3.75%O2 (shock mixture 23), and (b) 1%C2H2-1%C2H4-5.5%O2 (shock mixture 24). See Table 2 for additional experimental conditions. ..............................................................................44 Figure 15. Comparison of experimental (symbols, Jachimowski, 1977) and computed (lines) maximum [O][CO]. Mixture compositions (in argon): (a) 1%C2H2-3.75%O2 (shock mixture 23), and (b) 1%C2H2-1%C2H4-5.5%O2 (shock mixture 24). See Table 2 for additional experimental conditions. ......................45 Figure 16. Comparison of experimental (symbols, Hidaka et al., 1981) and computed (lines) ignition delay times behind reflected shock waves. The computational ignition delay was determined by the maximum pressure gradient. Mixture compositions (in argon): (a) 2%C2H2-2.5%O2 (shock mixture 25), (b) 1%C2H2-3.5%O2 (shock 26), and (c) 1%C2H2-2.5%O2 (shock mixture 27). An estimated value of 0.6 atm was used for pressure in the simulation. ............................46 Figure 17. Comparison of experimental (symbols, Hidaka et al. 1984) and computed (lines) maximum ignition delay times in incident shock waves. The experimental and computational ignition were determined by the maximum laser- Schlieren density gradient. Shock mixtures (in argon): (28) 0.5%C2H2-1.25%O2 and (29) 0.5%C2H2-5%O2. See Table 2 for additional experimental conditions. ............47 Figure 18. Comparison of experimental (symbols, Hwang et al. 1986)
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