Operating characteristics and propagation of back-pressure waves in a multi-tube two-phase valveless air-breathing pulse detonation combustor

•Successful and stable operation of two-phase multi-tube air-breathing pulse detonation engine was performed.•Two firing patterns were carried out: all tubes firing simultaneously, and all tubes firing sequentially.•The detailed propagation of back-pressure waves was quantitatively discussed.•Tube-to-tube interactions were quantitatively evaluated.