Effects of Oxygen on Soot Formation in Methane Diffusion Flames

Abstract

The effect of small additions of oxygen to the fuel on formation of soot in methane-air diffusion flames was studied over a range of flow rates and of burner diameters. The flames studied were shorter than those of previous studies, purely blue or blue and yellow without soot escape. Heights of various distinctive features were measured, and composition and temperature profiles were obtained; the distinctive features include.onset and termination of visible emission of radiation and deposition of material on a quartz filament inserted into the flame. The results indicate negligible influences of oxygen addition and thereby suggest that ions from the primary mechanism CH+Orarr;CHO⁺+e^- are unimportant in soot formation in these flames. A simplified one-step kinetic model accounting for buoyancy and momentum was developed and employed to obtain estimates of overall rate parameters for flame attributes related to soot formation.