Probing flame chemistry with MBMS, theory, and modeling

Abstract

The program objective is to establish kinetics of combustion and molecular weight growth in C{sub 3} hydrocarbon flames as part of an ongoing study of flame chemistry. Specific reactions to be studies are (1) the oxidation reactions of O and OH with C{sub 3}'s and (2) the growth reactions of C{sub 3}H{sub 5} and C{sub 3}H{sub 3} with themselves and with unsaturated hydrocarbons. Our approach combines molecular-beam mass spectroscopy (MBMS) experiments which give concentrations of stable species and free radicals in low-pressure flat flames; theoretical predictions of rate constants by thermochemical kinetics, Biomedical Quantum-RRK, RRKM, and master- equation theory; and whole-flame modeling using full mechanisms of elementary reactions. Detailed MBMS flame data are the principal results of the first nine months of the grant. Spatial profiles of temperature, area expansion ratio, and mole fraction have been mapped in two low-pressure flat flames, one fuel-lean ({phi} = 0.229) and the other fuel-rich ({phi} = 1.64) in propene/oxygen/argon. Species identities and trends suggest certain chemical pathways, but reaction theory and flame modeling are beginning to provide specific, quantitative insights into oxidation and growth chemistry. 5 refs., 23 figs., 1 tab.