Numerical study of neighboring edge flame interactions

A five-slot burner with contoured nozzle exits has been used to create lifted flames with multiple stoichiometric gradients below the flame structure. The resulting lifted flames have multiple partially-premixed flame stabilization points in close proximity. Previous work has shown that the interactions between these flames lead to a bifurcation in the flame stability whereby the overall flame structure is asymmetric. The interaction also affects the overall stability of the structure which has implications for the propagation and stabilization of lifted turbulent flames. The burner used for these studies allows for the creation of a range of stoichiometric gradients below each of the edge flames, while also allowing for the ability to control the distance between stabilization points of the flames. Numerical simulations are presented and compared to recent experimental results. For large fuel-air gradients the experimental edge flames showed very little interaction as both flames stabilized at similar liftoff heights and with similar flame shapes. As the composition gradient below the flames was decreased, the edge flames broadened leading to an interaction where a lift-off height difference between the two flames was observed. This bifurcation in edge flame stabilization is examined in this paper using a comparison of numerical simulations and further analysis of previously reported Rayleigh scattering and PLIF imaging to validate the predicted compositions upstream and within each flame.