Detailed kinetic modeling of C1 — C3 alkane diffusion flames

A study of detailed chemical kinetics in coflow and counterflow diffusion flames is presented. The chemistry of diffusion flames is of fundamental importance from a practical as well as a mechanistic viewpoint. The present study uses systematic reaction path flux and sensitivity analyses to determine the crucial reaction paths in methane and propane diffusion flames. The formation of benzene and intermediate hydrocarbons via C3 and C4 species has been given particular attention and the relative importance of reaction channels has been assessed. The developed mechanism considers singlet and triplet CH2, isomers of C3H4, C3H5, C4H3,H5 and C4H6. Computational results show that benzene in methane — air diffusion flames is formed mainly via reactions involving propargyl radicals and that reaction paths via C4 species are insignificant. It is also shown that uncertainties in thermodynamic data may significantly influence predictions and that the reaction of acetylene with the hydroxyl radical to produce ketene may be an important consumption path for acetylene in diffusion flames. Quantitative agreement has been achieved between computational results and experimental measurements of major and minor species profiles, including benzene, in methane-air and propane-air flames. It is also shown that the mechanism correctly predicts laminar burning velocities for stoichiometric C1—C3 flames. Finally, results for a two-dimensional methane-air flame on a Wolfhard-Parker burner obtained with full detailed chemistry are presented along with flamelet computations and the accuracy of the latter are discussed.