APPLICATION OF A COHERENT FLAME MODEL TO PREMIXED TURBULENT COMBUSTION IMPINGING ON A WALL

A coherent flame model is applied to analyse premixed turbulent flames stabilised in a stagnation flow impinging on a wall. Because flames w hich are well separated from the wall are investigated here, interacti on between the turbulent wrinkled flame and the wall is assumed to be insignificant. rn view of this assumption a mean reaction rate model w hich was previously used in a counterflow geometry is adopted to solve the present problem. Therefore, a model parameter, beta, describing a nnihilation between flame surfaces, is given the same value as that fo und in corresponding back-to-back premixed turbulent counterflow flame s. Non-reactive outer and reactive inner regions ih the flow are also found and described by a composite solution for these two regions, wit h an allowance for the displacement thickness of the thermal boundary layer next to the wall, Boundary layer analysis based on a modified (k ) over tilde-<(epsilon)over tilde> model is also adopted to resolve th e effect of the wall on the evolution of turbulent motion. The thermal boundary layer is found to be thick and slightly overlaps the flame b rush. However, the effective displacement thickness of the thermal bou ndary layer is found to be small in comparison with the separation bet ween the nozzle exit and the plate. The present solutions for the boun dary layer analysis are related to an equivalent non-reactive hot flow impinging on the wall. Thus, a limited amount of experimental data fr om stagnating cold hows can be used to compare predicted heat transfer rates. Generally the predictions give satisfactory agreement with exp eriments.