自振空化射流冲击压力脉动特性实验研究

自振空化射流是利用瞬态流和水声学原理调制而成的一种新型射流,本文研究了自振空化射流在常压及围压下的压力脉动特性及其参数影响规律。研究结果表明,在实验条件下各种风琴管喷嘴的压力脉动存在最优喷距,无因次最优喷距都在8～14范围内,风琴管自振空化射流的冲击压力脉动峰值和脉动幅度分别比普通喷嘴高37%和24%;最大脉动幅度并不出现在射流轴心,而是偏离轴心一段径向距离;随着围压的增加,脉动峰值压力随着喷距的衰减速度明显加快,而脉动频率基本不随围压、压降和喷距的变化而变化,保持在1.38KHz左右。

Characteristic and Mechanism of Pressure Fluctuation Caused by Self-Induced Oscillation of Supersonic Impinging Jet

When the underexpanded supersonic jet impinges on the obstacle, it is well known that the self-induced flow os- cillation occurs. This oscillation depends on the pressure ratio in the flowfield, the position of an obstacle and is related with the noise problems of aeronautical and other industrial engineering. The characteristic and the mechanism of self-induced flow oscillation, have to be clarified to control various noise problems. But, it seems that the characteristics of the oscillated flowfield and the mechanism of an oscillation have to be more cleared to control the oscillation. This paper aims to clarify the effect of the pressure ratio and the obstacle position and the mechanism of self-induced flow oscillation by numerical analysis and experiment, when the underexpanded su- personic jet impinges on the cylindrical body. From the result of this study, it is clear that occurrence of the self-induced flow osciUation depends on the pressure balance in the flowfield.