Application of Different Turbulence Models to Study the Effect of Local Anisotropy for a Non-Premixed Piloted Methane Flame

Abstract

Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications, especially for the steel and refractory industry. Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields. The performances of the realizable k-ɛ and the RSM turbulence model are compared. Detailed chemistry is included with the GRI-Mech 3.0 mechanism in combination with the laminar flamelet combustion model. The combustion system selected for this comparison is a piloted non-premixed methane flame surrounded by co-flowing air. The simulation results are compared with experimental data of the “Sandia Flame D” published by the international TNF workshops on turbulent flames. For simplification a lot of steady-state flame simulations are performed axisymmetrical in 2D. Simple RANS models do not account for the local anisotropy in turbulent flows. To consider this effect a 3D calculation and the application of the RSM turbulence model, which accounts for these anisotropy, is necessary. In axially symmetric 2D flame simulation the realizable k-ɛ and in 3D the RSM give unexpected similar results. But still the predicted turbulence and temperature field shows some differences to the experimental data. A modification of a single empirical model constant for the turbulence helped to get better results in both, 2D and 3D.