Numerical Investigation of Soot Formation in Turbulent Diffusion Flame With Strong Turbulence–Chemistry Interaction

The present work is aimed at examining the ability of different models in predicting soot formation in “Delft flame III,” which is a nonpremixed pilot stabilized natural gas flame. The turbulence–chemistry interactions are modeled using a steady laminar flamelet model (SLFM). One-step and two-step models are used to describe the formation, growth, and oxidation of soot particles. One-step is an empirical model which solves the soot mass fraction equation. The two-step models are semi-empirical models, where the soot formation is modeled by solving the governing transport equations for the soot mass fraction and normalized radical nuclei concentration. The effect of radiative heat transfer due to gas and soot particulates is included using P1 approximation. The absorption coefficient of the mixture is modeled using the weighted sum of gray gases model (WSGGM). The turbulence–chemistry interaction effects on soot formation are studied using a single-variable probability density function (PDF) in terms of a normalized temperature or mixture fraction. The results shown in this work clearly elucidate the effect of radiation and turbulence–chemistry interaction on soot formation. The soot volume fraction decreases with the introduction of radiation interactions, which is consistence with the theoretical predictions. It has also been observed in the current work that the soot volume fraction is sensitive to the variable used in the PDF to incorporate the turbulence interactions.