  The present work is aimed at examining the ability of different models in
predicting soot formation in Delft flame III, which is a non-premixed pilot
stabilized natural gas flame. The turbulence-chemistry interactions are modeled
using a laminar steady 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 modelled
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.
