Coupled Soot Formation and Radiation in a Laminar Diffusion Flame

Abstract

The effect of soot formation on a flamelet structure and radiation in a laminar methane flamelet is presented in this paper. A new kinetics mechanism, GRI-Mech2.1, for methane combustion is used. TDMA computer code is used to solve the coupled mass conservation, momentum, energy, species, and soot transport equations to determine the properties of the flamelet. The flamelet structure and soot concentration profiles are presented over the entire range of mixture fraction. The soot enhancement by preheating is examined. Effects of soot formation and gaseous species on flame radiation are also investigated. The calculations show that the methane/air flamelet is a light sooting flame, and that the soot formation does not have a profound effect on flame radiation and flamelet structure. It is shown that preheating the combustion air can lead to a great enhancement in soot formation but not in flame radiation. While the soot formation contributes to larger Planck mean absorption coefficient for emission, the emission lowers the flame temperature. These opposing effects dampen the effectiveness of soot formation on flame radiation enhancement in methane/air flames.