Mechanisms of Ethylene Flame Propagation Enhancement by O₂(a¹Δg)


T. Ombrello (U.S. Air Force Research Laboratory)
N. Popov (Moscow State University)

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Recently estimated and updated quenching rates of O2(a1Δg) by H and H2 have been added to a known and validated combustion mechanism to predict enhancement of C2H4 flame propagation in the presence of O2(a1Δg). The results of experiments that targeted the isolated enhancement of O2(a1Δg) on C2H4 flame propagation were used as a means to compare the effects of different chain-initiation, chain-branching, and quenching rates. The ratio of chain-branching to quenching rates of 0.25 to 0.33 for H+O2(a1Δg) was found to accurately predict the enhancement trends found in the C2H4 flame propagation experiments. The results suggest that flame propagation enhancement of hydrocarbon fuels may not be strongly dependent on the reactions of intermediate hydrocarbon fragments with O2(a1Δg) since the dominant pathways may solely lie with primary radicals such as H.