Investigation of ignition and flame stabilization characteristics in a flush-wall circular axisymmetric scramjet combustor equipped with a center flame holder

In order to reduce the difficulty of thermal protection and achieve flame stabilization in flush-wall circular axisymmetric scramjets, a new center flame holder was designed and tested. Simulations under 4 different conditions and experiments under 19 different fuel distribution strategies were carried out in order to investigate the ignition characteristic, flame stabilization mechanism and the performance of the configuration. In this paper, the Mach number at the entrance of the isolator was 2.8, with the stagnation state P_t = 1680kPa and T_t = 1680 K, simulating the cruise condition of Mach number 6. The experimental data was captured by pressure transducers along the axis and then compared to and explained by the numerical simulation results. By analysing the result of experiment and simulation, it can be concluded that during the process of ignition, the oxygen supplement after the strut can adjust the local equivalence ratio within the ignitor coverage region to around 1 and destroy the low-speed recirculation zone after the strut so that the formed local flame can propagate outward. After the ignition process, the flame can be stabilized even if the oxygen supplement is cut off when using the new centre flame holder. Combustion effect can lift the streamlines, reducing the angle between the shear layer and the mainstream by 80.9 % and 87.5 % at plane θ = 30° and θ = 60° respectively. The recirculation zone can be enlarged by combustion as the reattachment point shifts back about 0.76D compared to the unfueled condition so that the flame can be stabilized. Experiments under different fuel distribution strategies were carried out to verify the flame stabilization capability and investigate the performance of the configuration in the paper.