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音速。也就是说，激波的产生是不可避免的，在本研究中，使用安装在出现激波的圆形叶栅叶片之间的侧壁上的几个高频响应压力传感器详细地测量了压力的变化。为了给低稠度圆形叶栅扩散器的设计提供基础数据，讨论了扩散器失速与喘振的关系，以及激波的结构和不稳定性。为了测量叶栅间或叶轮进口之间的流动，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起始时间和失速下降前频率的时间变化。此外，时变…对于失速分析，更多的功率谱或时变的RMS规则也是有效的。(2)在进入失速之前，在诱导器处观察到了所谓的旋转失速，失速单元的发展通过每一叶距压力波动的均方根值的历史或通过对小波变换的叶片通过频率分量的分析来反映。(3)即使在接近喘振的情况下，安装在叶栅扩张器相邻叶片之间的两个压力信号在空间上和时间上都是独立的。在失速初期，前部无叶区的压力脉动具有较高的时空相关性。(4)将双脉冲激光PIV系统应用于机匣内旋转圆盘诱导流动的研究，讨论了系统的精度等问题。结果表明，直径为0.8 mm的DOP颗粒的PIV系统适用于扩张器叶片间和/或叶轮进口处的流动测量。较少

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