It is believed that the rotating instability phenomenon originating in the compressor tip region is due to leakage flow, which is closely associated with the blade tip clearance. In this work, we have studied the correlation between the dynamic characteristics of blade tip flow and the size of tip clearance for a single-stage low-speed compressor rotor, so as to unveil the mechanism of rotating instability. The full-passage numerical simulations were carried out to obtain the variations in frequency, circumferential mode, and spatial flow field associated with rotating instability. The results of spatial mode decomposition with open clearance show the number of predominate instability modes identified are 25 and 30, respectively. By diminishing the blade tip clearance, all these unstable modes greatly diminished. The formation and propagation of the tip leakage vortex were described in detail to show the development of rotating instability. Two flow field reduced-order methods, proper orthogonal decomposition and dynamic mode decomposition, were used to analyze the flow field, energy proportion, and stability of related modes under different tip clearances. The results show that the first several modes with strong stability account for a large proportion of energy and make a major contribution to flow unsteadiness. The energy proportion and stability of rotating instability decrease as the tip clearance becomes smaller. The blade-passing frequency and its multiples emerge as the main components of the flow field.

可以认为，起源于压缩机尖端区域的旋转不稳定性现象是由于泄漏流引起的，该泄漏流与叶片尖端间隙紧密相关。在这项工作中，我们研究了单级低速压缩机转子的叶尖流动动力学特性与叶尖间隙大小之间的相关性，从而揭示了旋转不稳定性的机理。进行了全通道数值模拟，以获得与旋转不稳定性相关的频率，圆周模式和空间流场的变化。具有开放间隙的空间模式分解的结果表明，识别出的主要不稳定模式分别为25和30。通过减小叶片尖端间隙，所有这些不稳定模式都会大大减少。详细描述了尖端泄漏涡的形成和传播，以显示旋转不稳定性的发展。两种流场降阶方法分别是适当的正交分解和动态模式分解，用于分析在不同尖端间隙下的流场，能量比例和相关模式的稳定性。结果表明，前几种具有很强稳定性的模式占了很大一部分能量，并且对流动的不稳定做出了很大的贡献。随着尖端间隙变小，能量比例和旋转不稳定性的稳定性降低。叶片通过频率及其倍数成为流场的主要组成部分。分别采用适当的正交分解和动态模式分解来分析流场，能量比例以及不同尖端间隙下相关模式的稳定性。结果表明，前几种具有很强稳定性的模式占了很大一部分能量，并且对流动的不稳定做出了很大的贡献。随着尖端间隙变小，能量比例和旋转不稳定性的稳定性降低。叶片通过频率及其倍数成为流场的主要组成部分。分别采用适当的正交分解和动态模式分解来分析流场，能量比例以及不同尖端间隙下相关模式的稳定性。结果表明，前几种具有很强稳定性的模式占了很大一部分能量，并且对流动的不稳定做出了很大的贡献。随着尖端间隙变小，能量比例和旋转不稳定性的稳定性降低。叶片通过频率及其倍数成为流场的主要组成部分。结果表明，前几种具有很强稳定性的模式占了很大一部分能量，并且对流动的不稳定做出了很大的贡献。随着尖端间隙变小，能量比例和旋转不稳定性的稳定性降低。叶片通过频率及其倍数成为流场的主要组成部分。结果表明，前几种具有很强稳定性的模式占了很大一部分能量，并且对流动的不稳定做出了很大的贡献。随着尖端间隙变小，能量比例和旋转不稳定性的稳定性降低。叶片通过频率及其倍数成为流场的主要组成部分。