Complete multicomponent versus mixture-averaged calculations of a laminar H2/N2 diffusion flame including heat transfer at the burner and Soret effects

The implementation of full multicomponent treatment of diffusion fluxes in the CFD solver for laminar reacting flows with detailed kinetic mechanisms laminarSMOKE++ is presented. The optimised 1+M multicomponent formulation (including Fick diffusion and Soret effects) derived from the Kinetic Theory of Gases, with a similar computational cost as mixture-averaged, is considered. Results are presented for a H2/N2 laminar coflow diffusion flame, where either heat transfer at the burner wall is included, either the wall is considered adiabatic. We observe that full multicomponent and mixture-averaged results are very similar when Soret effects are neglected. However, differences are observed when including thermodiffusion. In particular with heat transfer at the wall, large differences are observed whether thermodiffusion is neglected or included. In this case, the mixture-averaged approximation used for the thermal diffusion coefficients leads to significant differences in the results compared to the full multicomponent 1+M formulation.