Experiments and numerical simulation on soot formation in opposed-jet ethylene diffusion flames

An experimental and computational study is presented for soot formation in counterflow diffusion flames of ethylene and air. Experimentally, the soot extinction and scattering profiles are determined for four well-controlled flames subjected to different straining rates. Computationally, the experimental situations are simulated by combining the numerical formulation of the counterflow flame with a model of soot particle inception, coagulation, and growth, with the moment description of particle size distribution function. Numerical simulation yields satisfactory results when compared to the experimentally determined soot profiles. It is shown that the surface addition of acetylene is the dominant process of soot mass growth for the present counterflow diffusion flames, and that in order to predict the experimental soot growth, the soot surface radical sites must be conserved upon its reaction with acetylene. While the comparison between numerical calculation and experimental data is satisfactory, we have also identified uncertainties on which further work is needed within the framework of the soot model, particularly surface radical dynamics.