Investigation on the effect of the expansion angle in the strut-based supersonic combustor

Abstract

To avoid the thermal choking problem, scramjet usually adopts a wall-expansion scheme, which inevitably brings challenges to flame holding. The effect of expansion angle change on the flameout limit needs to be further studied in the strut-based supersonic combustor. In this paper, large eddy simulation is used to obtain the details of the combustion process, and more attention is paid to the flame stabilization and lift-off characteristics under different pressure gradients caused by shock waves and expansion angles. The agreement between the calculated results and the experimental data verifies the reliability of the adopted rhoReactingCentralFoam solver. Numerical results show that the establishment of the recirculation zone provides favorable conditions for the flame stabilization, and the reflected shock waves caused by the strut enhance the mixing with the mixing layer to assist combustion. Cases with different expansion angles reveal the susceptibility of the strut-based supersonic combustor to changes in the expansion angle. The height of the flame lift and the length of the recirculation zone move backward with the increase of the expansion angle. On this basis, it is confirmed that the setting of the expansion angle is limited, and in the case of the expansion angle of 4°, the reduction of the mixing efficiency in the reflow zone leads to flame extinction. The obtained conclusions provide support for the organization of combustion in the design of scramjet.