Soot Surface Growth And Oxidation In Laminar Unsaturated-Hydrocarbon/Air Diffusion Flames


The structure and soot surface growth and oxidation properties of round laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved ethylene-, propylene-, propane- and benzene-acetylene-fueled diffusion flames burning in coflowing air at atmospheric pressure with the reactants at normal temperature. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical (H, OH, O) species concentrations, and gas velocities. The results show that fuel decomposition yields significant acetylene concentrations at fuel-rich conditions, that soot formation begins where significant concentrations of both acetylene and H-radical are present, and that soot formation ends when acetylene concen-trations become small even in the presence of significant concentrations of Hradical. Present measurements of soot surface growth rates in diffusion flames were consistent with earlier measurements in both acetylenefueled diffusion flames and in ethylene- and methane-fueled premixed flames, with results over this entire data base exhibiting encouraging agreement with existing Hydrogen- Abstraction/Carbon-Addition (HACA) soot surface growth mechanisms. It also was found that present surface oxidation rates in diffusion flames could be described reasonably well by the OH mechanism with a collision efficiency of 0.10, with no significant effect of fuel type, in good agreement with the classical premixed flame measurements of Neoh et al. (1980). Finally, direct rates of soot surface oxidation by O2 were small compared to soot surface oxidation by OH, based on estimated soot surface oxidation rates by O2 due to Nagle and Strickland-Constable (1960), because soot surface oxidation was completed near the flame sheet where maximum soot concentrations were generally smaller than 1% by volume for present test conditions. © by G.M. Faeth.

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40th AIAA Aerospace Sciences Meeting and Exhibit

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Article; Proceedings Paper

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84894361421 (Scopus)

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