Experimental and numerical investigation on propagation of back-pressure waves of a four-tube pulse detonation engine

In order to investigate the propagation characteristics of back-pressure waves in multi-tube pulse detonation engine, a series of experiments and numerical simulations were carried out. The propagation characteristics of back-pressure waves of four-tube pulse detonation combustors were measured when the combustors operated at two firing patterns: all tubes firing simultaneously and all tubes firing sequentially. Numerical simulations were carried out to investigate the flow characteristics in the air buffer chamber. The length of the air buffer chamber was varied and a splitter was installed in the air buffer chamber numerically to study their effects on the propagation of back-pressure waves. The experimental results show that a strong back-pressure wave was observed in the air buffer chamber when all tubes were fired simultaneously and the peak value was about 0.12 MPa. However, when all tubes were fired sequentially, the air buffer chamber experienced four times pressure oscillation in a single cycle and the amplitude was smaller than that when all tubes were fired simultaneously. The numerical results indicate that there was a reverse flow in the engine inlet when the back-pressure wave propagated into the air inlet. The velocity of reverse flow was smaller when the tubes were operated at sequential firing pattern. The amplitude of the back-pressure waves was reduced when the length of air buffer chamber increased. The velocity of reverse flow was also reduced. No reduction of amplitude of the back-pressure waves was observed when the splitter was installed in the air buffer chamber.