Numerical prediction of turbulent sooting diffusion flames

Soot formation is an important but poorly understood subject. Although significant advances have been made in the last few years, soot formation models for numerical calculation still present recognized shortcomings. Different soot formation models are compared in the calculation of a propane turbulent diffusion flame and the influence of soot agglomeration and refractive index on soot volume fraction values inferred from extinction measurements are investigated. The time-averaged equations governing conservation of mass and momentum are closed by the k-epsilon eddy viscosity/diffusivity model and combustion is modeled using the laminar flamelet approach. Soot prediction involves the solution of transport equations for soot particle number density and soot mass fraction. The uncertainties of soot volume fractions obtained from extinction measurements due to agglomeration and the value of the complex refractive index were studied. Results using Rayleigh approximation were compared with predictions using the model presented by Iskander et al. for scattering and extinction of light by an ensemble of spherical particles.