Effect of inlet-valve structures on thrust of air-breathing pulse detonation engines

Wenjuan Chen ^a, Wei Fan ^b, Feiteng Luo ^a,*, Gaohu Tang ^b, Yaosong Long ^a

a. School of Aerospace Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
         b. School of Power and Energy, Northwestern Polytechnical University, Xi’an, Shanxi, 710072, China

Abstract: Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines (APDEs) with self-designed inlets and valves structures. The present experimental research utilized a gasoline/air APDE (with 68 mm inner-diameter, 2050 mm length and maximum operating frequency not less than 40 Hz which was as a benchmark structure) at different operating frequencies, with freestream air inflow of 1.1 atm and 0 ℃. The theoretical equivalence ratio of gasoline/air was 1. Two kinds of inlets with centerbody or without were considered and combined with two kinds of self-designed valves (the elastic-valve and the convergent aero-valve) specially designed for comparative experiments. During the test, the inflow parameters, the pressure along the longitudinal direction inside the engine and the thrust force were measured for the APDE operating characteristic analysis, including the detonation combustion, the aerodynamic drag, the pressure/ flame reverse propagation and the thrust generation. The research results indicate that: The inlet centerbody does not increase drag but plays a positive effect on airflow stability and operation matching. The elastic-valve and the convergent aero-valve, though increase the inlet aerodynamic drag, have obvious effects on suppressing the detonation wave and pressure forward propagation, resulting in effective thrust increase. Effects of the convergent aero-valve are the best when the flow choked, while the effects of elastic-valve are better and continuously stable in a wider range of frequency. The maximum nondimensional thrust increases with the elastic-valve is reached about 1.12 at the frequency of 8-9 Hz, and about 0.97 with the convergent aero-valve at the frequency of 7 Hz. The maximum fuel specific impulse is 2514.6 s when using the convergent aero-valve. And this study provides technical reserve for the APDE optimization design.

Keywords: Air-breathing pulse detonation engine; Elastic-valve; Convergent aero-valve; Thrust augmentation; Pressure/flame reverse propagation

https://doi.org/10.1016/j.jppr.2021.11.002