叶根负荷对低速压气机失稳过程影响实验研究

Experimental Study of Blade Hub Loading Effects on Instability Evolution in a Low-Speed Compressor

关键词:  叶根负荷  失稳过程  转化时间  低速压气机

Key words:  Blade hub loading  Instability evolution  Transition period  Low-speed compressor

摘要:

基于在一台单级低速轴流压气机上发现的增大叶尖负荷可以使其失稳先兆由模态波变为突尖波的现象，一种假设认为失速先兆的类型与压气机径向负荷分布有着密切的联系。对此，设计了一系列实验来验证叶根负荷大小对压气机失速先兆类型及其失稳发展过程的影响。通过在压气机进口安装特殊设计的叶根畸变屏，可以实现压气机工作在不同的径向负荷分布。均匀来流条件下压气机最终的失速是由模态波引起，在此基础上加装叶根畸变屏增大叶根负荷，压气机仍发生模态波型失速，但经过仔细分析数据后发现，由线性增长的模态波转化为最终大幅值旋转失速团的时间间隔却相较增大。在这段过程中，转子进口壁面压力信号显示叶尖区域不存在完整的周向传播扰动。与此同时，叶根处先兆信号幅值相较变大。进一步加大叶根负荷，叶根区域失速先兆的压力脉动变得更加剧烈，使得气流沿叶片径向的流动和掺混加剧，从而进一步延迟了先兆诱发失速团出现的时间。综上，通过研究表明:增大叶根负荷，压气机失稳过程发生改变，失速先兆诱发旋转失速团出现的时间延长；在叶根区域，失速先兆脉动信号随着叶根负荷的增大而愈发强烈；径向负荷分布是影响压气机失稳过程发生变化的重要因素。

Abstract:

Based on the previous results of a single-stage low-speed axial compressor showing that a stall inception can be changed from modal wave to spike with the blade tip loading increasing， a hypothesis is further proposed that the type of stall inceptions is related to the radial loading distributions. A series of experiments are designed to examine the effects of hub loading to the stall inception and its evolution. Well-designed hub distortion screen installed at the inlet of the compressor induces various radial distributions of blade loading for compressor operating. The uniform inflow situation， i.e. without screen， shows the modal type stall inception of the compressor’s final instability. With hub distortion screen， the hub loading is keeping to be increased， however， the compressor still shows modal type of stall inception. After detailed examining the data， it is found that the period between linear growth of modal wave and the formation of a large amplitude stall cell is growing longer. In that transition period， the tip pressure signal does not show any complete traveling disturbances in circumferential direction. Meanwhile， there are large disturbances formed in the hub region during this period. With further increasing the hub loading， the large amplitude disturbances in hub region appear stronger and stronger. It makes flow unstable in hub region and intensifies the flow mixing in radial direction and further lengthens the transition period between stall inception and final instability. At the same time， there are three main findings: (1)With hub loading increasing， the compressor instability evolution will be changed and the transition period between stall inception and final instability is prolonged. (2)The pressure fluctuations in the hub region become stronger as hub loading changing. (3)The radial load distributions do have significant effects on the compressor instability evolution.