PIV Measurement of Shock Waves in a Transonic Centrifugal Compressor

在单级高压比离心式压缩机中，相对于叶轮和扩散器的速度通常超过音速。也就是说，冲击波的产生是不可避免的。本研究的目的是用双脉冲粒子图像测速仪(PIV)测量包括叶轮入口和扩散器叶片之间的激波在内的流动，并阐明激波强度与流量的关系。应用条件采样技术获得了旋转叶轮与静止叶片的相对位置，进而讨论了激波的瞬时结构。此外，还将讨论在失速或喘振情况下激波结构的时间变化。(1)建立了模拟叶轮叶片通道或扩散器间隙的小型风洞的PIV诊断程序。(2)设计了一台用于亚微米粒子探测的激光投影仪。(3)成功地在叶轮入口处进行了PIV测量，最大绝对速度约为92m/S。目前还没有足够的数据来讨论细节，但速度矢量图表明了冲击波的存在。(4)在激光薄片照明、粒子播种、激光脉冲间隔、激光脉冲间隔等方面积累了许多技术知识。叶轮叶片位置的确定技术等。(5)对叶栅扩张器叶片间的压力场进行了详细的测量。建立了包含动静相互作用激波的非定常压力场结构生成系统。

In a single-stage high-pressure-ratio centrifugal compressor, the velocity relative to the impeller and to the diffuser usually exceeds the velocity of sound. That is, generation of shock wave is unavoidable. The objectives of the present study are to measure the flow including the shock wave in the impeller inlet or between diffuser cascade vanes using a double-pulse Particle Image Velocimetry (PIV) and to clarify the relationship between the intensity of shock wave and the flow rate. A conditional sampling technique is applied to get a relative position between a rotating impeller and stationary vanes, and then an instantaneous structure of shock wave is discussed. Furthermore, a temporal change in shock wave structure will be discussed with stall or surging.(1) PIV diagnostics using a small wind-tunnel, simulating an impeller blade passage or a diffuser intervanes, was constructed. The minimum time interval of 1 μs and the maximum velocity of 55 m/s were established.(2) A laser light sheet projector was designed for sensing of submicron particles.(3) PIV measurement at the impeller inlet was succeeded, where the maximum absolute velocity was about 92 m/s. There is not enough data to discuss details yet, but a velocity vector map indicated the existence of a shock wave.(4) Many know-hows are accumulated on a laser-sheet lighting, a particle seeding, a laser pulse interval, a technique to determine the location of impeller blades and so on.(5) A detailed measurement of pressure field between cascade diffuser vanes was carried out. The system to create the structure of unsteady pressure field including shock waves due to rotor-stator interaction was constructed.