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为研究连续超声速射流对撞诱导激波聚焦的机理,在喷口间距为70mm,不同入射压力的条件下进行了自由射流对撞、二维凹面腔内的射流对撞及三维凹面腔内的射流对撞诱导激波聚焦实验。通过对比自由射流对撞辐射啸声频谱和凹面腔内射流对撞中凹面腔底部的动态压力频谱,结合纹影照片对连续超声速射流对撞诱导激波聚焦的机理进行了研究。结果表明,沿射流对撞面两侧的椭球形激波阵面的高频拉锯式振荡是连续射流对撞诱导激波聚焦的本质。当两侧的波阵面同时到达凹面腔底部发生碰撞时,激波聚焦得以完成;在一定的入射压力范围内,由于射流对撞面不稳定,两侧椭球形激波阵面不能同时到达两喷口中间的对称面,因此在自由射流对撞的辐射噪声频谱上共存两种模式的啸声。在凹面腔内的射流对撞中,凹面腔底部的压力脉动频谱上也同时存在两个频率十分接近的峰值;随着入射压力的进一步提高,两侧的椭球形激波阵面经过一段时间的协调同步后同时到达喷口中间的对称面,辐射噪声和压力脉动频谱中双频率值共存的现象消失,并统一为单一值。
In order to study the mechanism of shock focusing induced by continuous supersonic jet collisions, free jet collisions, jet collisions in two-dimensional concave cavities, and jet pairs in three-dimensional concave cavities were performed at a nozzle spacing of 70 mm under different incident pressures Collision induced shock focusing experiment. The mechanism of shock focusing induced by continuous supersonic jet collisions was studied by comparing the dynamic pressure spectrum of the concave cavity at the bottom of the concave cavity with the spectrum of the free-jet collision howling and the concavity of the concave cavity. The results show that the high-frequency saw-tooth oscillation of the ellipsoidal shockwaves along the jet colliding surface is the essence of the shock focusing induced by continuous jet collisions. When both sides of the wavefront arrive at the same time the bottom of the concave cavity collides, the shock focusing can be completed; in a certain range of incident pressure, due to the jet collision surface instability, both sides of the ellipsoidal shock wave front can not reach the two The middle of the nozzle symmetry plane, so in the free jet collide with the radiation noise spectrum coexistence of two modes of howling. In the jet collision in the concave cavity, there are two peaks at the same time in the pressure pulsation spectrum at the bottom of the concave cavity. With the further increase of the incident pressure, the elliptical shock wave fronts on both sides of the concave wave cavity undergo a period of After the coordination and synchronization reach the symmetrical plane at the middle of the spout, the coexistence of the two frequencies in the radiated noise and the pressure pulsation spectrum disappears and is unified into a single value.