Abstract: A subsonic inlet of a pulse detonation engine (PDE) with aerodynamic valve is experimentally and numerically studied to obtain its flow structure and performance characteristics in both cold flow and ignited conditions. Results indicate that without combustion, the air flows into the inlet smoothly and no flow separation is found upstream the cone. However, after ignition, a detonation-induced pressure with a peak value of over 300 kPa is imposed on the inlet exit and it is found to oscillate periodically. Furthermore, since the aerodynamic valve cannot baffle the detonation-induced pressure effectively, the violent backpressure perturbation propagates upstream and passes through the aerodynamic valve within 2 ms. A reverse flow can be repeatedly observed near the inlet entrance in one cycle. Nearly half of the cycle is occupied by the reverse flow and its instantaneous Mach number can reach a peak of 0.8. To approximate the real experiment, the inlet flow field is numerically simulated and good agreements are found between the numerical and experimental results. In particular, the unsteady numerical results demonstrate again that due to the high detonation-induced pressure, there is a reverse flow in the entire entrance of the inlet. As a result of the reverse flow, a large reversed impulse is generated near the inlet entrance which is unfavourable to the PDE engine thrust. Hence, further studies should be carried out to improve the design of the aerodynamic valve.

Key words: pulse detonation engine, aerodynamic valve, inlet, oscillatory backpressure, reverse flow