TY - JOUR
T1 - Kinetics of plasma assisted pyrolysis and oxidation of ethylene. Part 2
T2 - Kinetic modeling studies
AU - Tsolas, Nicholas
AU - Yetter, Richard A.
AU - Adamovich, Igor V.
N1 - Funding Information:
This work is sponsored by the AFOSR MURI “Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion” (AFOSR Grant no. FA9550-09-0602). N. Tsolas would like to thank Dr. Kuninori Togai for his helpful suggestions and discussions in numerically modeling PAC.
Publisher Copyright:
© 2016 The Combustion Institute
PY - 2017/2/1
Y1 - 2017/2/1
N2 - The kinetics of plasma-assisted pyrolysis and oxidation of ethylene have been numerically investigated. Combining plasma chemistry processes including electron-impact reactions, and reactions of electronically excited species with a comprehensive combustion mechanism, a plasma-assisted kinetic mechanism of ethylene pyrolysis and oxidation has been constructed. To test the accuracy of the constructed mechanism, numerical results were compared to experimental data obtained in a plasma flow reactor, performed under highly diluted conditions in argon at a pressure of 1 atm for temperatures ranging from 520 K to 1250 K. Comparison of plasma-assisted pyrolysis results indicates little discrepancy between the model and experiments. Direct collisional quenching of electronically excited argon by ethylene is responsible for the low temperature enhancement of fuel consumption seen in the plasma-assisted pyrolysis experiments. Hydrocarbon radicals generally undergo addition and recombination reactions to yield several C3 and C4 hydrocarbon intermediates. As temperature increases, the plasma effects diminish and the reaction is overtaken by thermal pyrolysis. Comparison of experimental and modeling results for plasma-assisted oxidation of ethylene demonstrated relatively good agreement for most major and minor species. However, poor agreement was found for ethylene and acetaldehyde for T < 750 K. In the oxidation system, collisional quenching of excited argon by O2 to generate the O-atom radical pool complemented the plasma-specific fuel dissociation reactions. The plasma was found to have different effects on the oxidation kinetics at different temperatures. At low temperatures, R+O2 type chemistry (R being a hydrocarbon radical) facilitates the formation of oxygenated species to enhance oxidation by way of formaldehyde. At intermediate temperatures, the formation of hydrocarbon and alcohol intermediates slows the oxidation process relative to the low temperatures. Finally, at high temperatures, plasma chemical reactions are unable to compete against the high temperature chain-branching reactions of the neutral chemistry that dominate and control the overall oxidation process.
AB - The kinetics of plasma-assisted pyrolysis and oxidation of ethylene have been numerically investigated. Combining plasma chemistry processes including electron-impact reactions, and reactions of electronically excited species with a comprehensive combustion mechanism, a plasma-assisted kinetic mechanism of ethylene pyrolysis and oxidation has been constructed. To test the accuracy of the constructed mechanism, numerical results were compared to experimental data obtained in a plasma flow reactor, performed under highly diluted conditions in argon at a pressure of 1 atm for temperatures ranging from 520 K to 1250 K. Comparison of plasma-assisted pyrolysis results indicates little discrepancy between the model and experiments. Direct collisional quenching of electronically excited argon by ethylene is responsible for the low temperature enhancement of fuel consumption seen in the plasma-assisted pyrolysis experiments. Hydrocarbon radicals generally undergo addition and recombination reactions to yield several C3 and C4 hydrocarbon intermediates. As temperature increases, the plasma effects diminish and the reaction is overtaken by thermal pyrolysis. Comparison of experimental and modeling results for plasma-assisted oxidation of ethylene demonstrated relatively good agreement for most major and minor species. However, poor agreement was found for ethylene and acetaldehyde for T < 750 K. In the oxidation system, collisional quenching of excited argon by O2 to generate the O-atom radical pool complemented the plasma-specific fuel dissociation reactions. The plasma was found to have different effects on the oxidation kinetics at different temperatures. At low temperatures, R+O2 type chemistry (R being a hydrocarbon radical) facilitates the formation of oxygenated species to enhance oxidation by way of formaldehyde. At intermediate temperatures, the formation of hydrocarbon and alcohol intermediates slows the oxidation process relative to the low temperatures. Finally, at high temperatures, plasma chemical reactions are unable to compete against the high temperature chain-branching reactions of the neutral chemistry that dominate and control the overall oxidation process.
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U2 - 10.1016/j.combustflame.2016.10.023
DO - 10.1016/j.combustflame.2016.10.023
M3 - Article
AN - SCOPUS:85002954132
SN - 0010-2180
VL - 176
SP - 462
EP - 478
JO - Combustion and Flame
JF - Combustion and Flame
ER -