Surging and Stall in a High-Pressure-Ratio 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声速。在本研究中，使用几个具有高频响应的压力传感器，在冲击波出现的圆叶栅之间的侧壁上，详细测量了压力的变化。为了提供设计低固体度圆形叶栅扩压器的基本数据，讨论了扩压器失速与喘振的关系，以及激波的结构和非定常。为了测量叶栅间或叶轮入口之间的流量，讨论了一种新的PIV系统的适用性。(1)利用小波变换对压力信号进行频率-时间分析，可以有效地了解失速发生的时间以及失速下降前频率的时间变化。此外，时变的功率谱或时变的均方根规则对失速分析也是有效的。(2)在进入失速前，在诱导轮处观察到所谓的旋转失速，失速单元的发展可以通过每一桨距压力波动均方根值的变化历史或通过小波变换对叶片通过频率分量的分析来表示。(3)即使在近喘振状态下，安装在叶栅扩压器相邻间叶上的两个压力信号在空间上和时间上都是独立的。而在失速初期，叶片前部无叶区压力波动具有较高的时空相关性。(4)将双脉冲yag -激光PIV系统应用于机匣内旋转盘诱导的流动，讨论了精度等问题。实验结果表明，采用直径为0.8 mm的DOP颗粒的PIV系统，可以测量扩压叶栅之间和（或）叶轮入口处的流量。少

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, In the present study, variations of pressure are measured in detail using several pressure sensors with high-frequency response mounted on the side wall between circular-cascade vanes where shock waves appear. To propose the primary data for designing of a low-solidity circular cascade diffuser, the relationship between a diffuser stall and a surging, and the structure and unsteadiness of shock waves are discussed. For measurement of the flow between cascade vanes or the impeller inlet, a new PIV system is discussed for its applicability.(1) The frequency-time analysis using a wavelet transform for pressure signals is effective sufficiently to under- stand the incipience time of stall as well as the time change in frequency till the falling in stall. Furthermore, the time- varying … More power spectra or the time-varying rms rules are also effective for the stall analysis.(2) Before the entry to stall, so called a rotating stall was observed at the inducer and the development of stall cell are shown by the history of rms value of pressure fluctuation every one-blade-pitch or by the analysis of blade- passing-frequency component of wavelet transform.(3) Two pressure signals, mounted on the next inter-vanes of cascade diffuser with each other were independent in space as well as in time even at near surge condition. At the beginning of stall, on the other hand, a high spatiotem- poral correlation in pressure fluctuation was observed at the front vaneless zone.(4) A double-pulse YAG-laser PIV system was applied to the flow induced by a rotating disk in a casing and the problems such as accuracy and so on were discussed. It was verified that the present PIV system with the DOP particles, 0.8 mm in diameters, is applicable for the measurement of flow between diffuser cascade vanes and/or at the impeller inlet. Less