DETAILED KINETIC MODELING OF C-1-C-3 ALKANE DIFFUSION FLAMES

A study of detailed chemical kinetics in coflow and counterflow diffus ion flames is presented. The chemistry of diffusion flames is of funda mental 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 propan e diffusion flames. The formation of benzene and intermediate hydrocar bons via C-3 and C-4 species has been given particular attention and t he relative importance of reaction channels has been assessed. The dev eloped mechanism considers singlet and triplet CH2, isomers of C3H4, C 3H5, C4H3, C4H5 and C4H6. Computational results show that benzene in m ethane-air diffusion flames is formed mainly via reactions involving p ropargyl radicals and that reaction paths via C-4 species are insignif icant. It is also shown that uncertainties in thermodynamic data may s ignificantly influence predictions and that the reaction of acetylene with the hydroxyl radical to produce ketene may be an important consum ption path for acetylene in diffusion flames. Quantitative agreement h as been achieved between computational results and experimental measur ements of major and minor species profiles, including benzene, in meth ane-air and propane-air flames. It is also shown that the mechanism co rrectly predicts laminar burning velocities for stoichiometric C-1-C-3 flames. Finally, results for a two-dimensional methane-air flame on a Wolfhard-Parker burner obtained with full detailed chemistry are pres ented along with flamelet computations and the accuracy of the latter are discussed.