Effects of chemical kinetic mechanism on the DNS results for reactive high speed mixing layers

The comparative performance of seven chemical kinetic mechanisms for hydrogen-air combustion in turbulent high speed mixing layers is investigated in this work, where the mixing layers are treated as a simplified model of the ramjet/scramjet engine combustor. This is obviously a very important undertaking since reactive simulation results are as good as the kinetic models used. The mechanisms we have chosen to investigate constitute those that have received a lot of attention, albeit independently, in the literature, and vary from three to 53 species; and one-step to 325 steps. Laminar opposed-jet (OJF) simulations were carried out and compared for all the mechanisms. This is important because, for the diffusion flame problem in mixing layers, the OJF results have direct relevance to the turbulent reaction case in the same configuration. The OJF results suggest that the kinetic models have significant effects on some of the calculated variables, the heat release being one of these. The simulation of mixing layers reported in this paper is based on the direct numerical simulation (DNS) approach, so that no assumptions are necessary regarding the turbulence scales or the statistics that are included in the calculations.