Soot Surface Reactions in High-Temperature Laminar Diffusion Flames

Abstract

The structure and the soot surface growth and surface oxidation properties of round laminar jet diffusion flames were studied experimentally. Measurements were made along the axes of acetylene/argon-fueled flames burning at atmospheric pressure in coflowing oxygen/argon mixtures to provide higher temperature soot-containing regions (2000‐2350 K) than were considered during earlier work. The measurements yielded soot surface growth and surface oxidation rates as well as the flame properties that are thought to control these rates. The present measurements of soot surface growth rates (corrected for soot surface oxidation) were consistent with earlier measurements in laminar premixed and diffusion flames having lower temperatures and exhibited good agreement with existing hydrogen-abstraction/carbon-addition soot surface growth rate mechanisms in the literature with steric factors of these mechanisms having values on the order of unity, as anticipated. Similarly, the present measurements of soot surface oxidation rates (corrected for soot surface growth) were consistent with earlier measurements in laminar premixed and diffusion flames having lower temperatures and exhibited good agreement with existing OH soot surface oxidation mechanisms in the literature, with a collision efficiency for OH of 0.13, in good agreement with past work, and supplemented to only a minor degree by direct soot surface oxidation by O2.