A Transient Study on the Development of Temperature Field and Soot under Reduced Gravity in a Methane Air Diffusion Flame

Abstract

The transient behavior of flame in terms of temperature development and soot formation has been investigated numerically with an in-house developed code at normal gravity, reduced gravity of 0.5 G, and 0.0001 G (microgravity) in a methane air co flow laminar diffusion flame. The intermediate data of the field variables have been recorded at suitable intervals of time from ignition to convergence. Enhanced soot volume due to more residence time at lower gravity increases the radiative heat loss causing shrinkage of high temperature borne zone. Both soot volume and soot number register a build up and then a decay till steady state. The corresponding periods increase with the reduction of gravity. At microgravity, both the soot volume and soot particle number reach the peak at the same time and also almost stabilize concomitantly, unlike in other two gravity levels. The peak value of soot volume fraction, under 0.5 G and microgravity at steady state, become as high as 3.5 and 7 times respectively of the values at normal gravity due to surface growth. The soot number density, however, increases only 1.2 and 1.35 times respectively. The relatively lower factor of increase of soot number density is due to coagulation.