Soot surface growth in laminar hydrocarbon/air diffusion flames

The structure and soot surface growth properties of round, laminar, jet diffusion flames were studied experimentally. Measurements were made along the axes of ethylene-, propylene-, propane-, and acetylene-benzene-fueled flames burning in coflowing air at atmospheric pressure with the reactants at normal temperature. The measurements included soot structure, soot concentrations, soot temperatures, major gas species concentrations, some radial species (H, OH, and 0) concentrations, and gas velocities. The results suggested that soot surface growth involved decomposition of the original fuel to form acetylene and H, which were the main reactants for soot surface growth, and that the main effect of the parent fuel on soot surface growth involved its yield of acetylene and H for present test conditions. Measurements of soot surface growth rates (corrected for soot surface oxidation) in laminar jet diffusion flames were consistent with earlier measurements of soot surface growth rates in laminar premixed flames and exhibited good agreement with existing hydrogen-abstraction/carbon-addition soot surface growth mechanisms in the literature with steric factors in these mechanisms having values on the order of unity, as anticipated.