对某气动阀式脉冲爆震发动机(PDE)亚声速进气道进行了试验和数值仿真研究,分析了该进气道在冷流条件和点火条件下的流场结构和工作特性.结果表明,在冷流条件下,通道内整流锥上游的流动较顺畅,无可见分离存在.但在点火条件下,爆震波的干扰使得进气道出口的压强呈周期性振荡,其峰值压力达300 kPa以上.由于气动阀并没有起到有效的隔离作用,爆震波在进气道出口平面形成的压力扰动会逐渐向上游传播,并在2 ms内越过气动阀,导致进气道进口出现了高速整体倒流,其倒流时间占据了约半个周期,且瞬时倒流马赫数最大可达到0.8.本文还对冷流条件和点火条件下的进气道流场进行了数值模拟,仿真较好地模拟出了该进气道的试验条件,且进气道内流动与试验基本一致.非定常仿真结果进一步表明了该进气道在爆震高压扰动下会出现整体高速倒流的现象.由于进气道进口的瞬时倒流形成了较大的反向冲量,对爆震发动机的推力特性极为不利,故必须在下一步的研究中对气动阀进行改进.
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.
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