Radiation simulation of a microgravity diffusion flame

This study numerically investigates the effects of radiation from both the soot and gas phase species on the soot kinetics in a quasi-steady state microgravity spherical acetylene-air diffusion flame by coupling the soot and gas phase chemistry with radiative heat transfer processes. The gas phase reaction is modeled by two step chemical kinetics. The soot reaction mechanism includes nucleation, surface growth, oxidation and coagulation steps. The radiation from both soot and the gas phase are calculated by employing a spherical harmonics (P-1 approximation) model. The local Planck mean absorption coefficients of the computed species are specified in the computations. Unlike normal gravity acetylene-air steady state jet diffusion flames in which the radiation from soot dominates gas radiation effects, it is found that for a microgravity diffusion flame, except at very early times, the radiation from the gas products dominates soot radiation. In the microgravity flame configuration, it is noted that the radiation heat loss fraction (defined as the ratio of the radiation heat loss rate to the chemical heat release rate) increases up to 80% shortly after ignition.