ON THE STRUCTURE OF NONSOOTING COUNTERFLOW ETHYLENE AND ACETYLENE DIFFUSION FLAMES

The structures of ethylene/oxygen/nitrogen and acetylene/oxygen/nitrog en diffusion flames in the counterflow configuration were investigated experimentally and computationally. The temperature and major species concentration profiles were measured with spontaneous Raman scatterin g. The experimental situations were computationally simulated with det ailed reaction mechanisms and transport properties. The kinetic mechan ism was based on GRI-Mech, with modifications to predict more closely the adiabatic flame speeds of ethylene/air and acetylene/air mixtures, and with additional description of higher hydrocarbon formation and o xidation up to C-6 species. The numerical predictions were found to be in reasonably good agreement with the experiment. Both experimental a nd computational results indicate that acetylene is the major intermed iate species in the ethylene flame, having a significant influence on the heat release, overall fuel destruction, and molecular mass growth. The reaction pathways leading to benzene formation in these flames we re examined computationally, with the goal of achieving a better under standing of soot nucleation in diffusion flames. Copyright (C) 1996 by The Combustion Institute