Abstract: In order to analyze the transforms of flow instability mechanisms when the work conditions change in transonic axial compressor，the work laws of two secondary flow namely blade tip leakage and suction side boundary layer separation are discussed. Instability mechanisms of the compressor are concluded at off-design work conditions via analyzing key factors of triggering flow blockage. The study shows an increasing rotation speed multiply leakage mass flow and tense of leakage vortex. When the pressure gradient of main flow boosts at a certain rotation speed，leakage mass flow hits its maximum and drops while the tense of leakage vortex multiplies all the time. Boundary layer separation and its span wise underflow are caused by attack angle at low rotation speed while by interaction of shock wave and boundary layer at high rotation speed. Increasing pressure gradient in main flow enlarges the separation and underflow. Blockage of blade tip passage，which triggered instability of the compressor，is caused by breakdown of leakage vortex and span-wise underflow. The two key factors lead to two pieces of blockage zone，respectively，located in the front of pressure side and at the back of suction side. Breakdown of leakage vortex is the main reason which causes compressor instability with the corrected rotation speed range from 75% to 105%，while it is the span-wise underflow to cause the instability with corrected rotation speed less than 75% or greater than 105%.

Key words: Transonic compressor；Corrected rotation speed；Leakage vortex；Span-wise underflow；Instability mechanism

摘要： 为了分析工作条件改变时跨声速压气机的失速机制，讨论叶顶泄漏和附面层分离等二次流在触发流动堵塞中的作用规律，总结在非设计条件下的压气机失速机制。研究表明，当转速增大，叶顶泄漏流量增大，泄漏涡增强；在某一转速下，主流逆压梯度增大，泄漏流量先增大后减小，泄漏涡则一直增强。在低转速下，附面层的分离和潜流主要由气流攻角引起，高转速下主要由激波与附面层干涉引起，主流逆压梯度增大使分离和潜流增强。压气机失速的触发原因是叶顶通道堵塞，由泄漏涡破碎和径向潜流两个因素对应引起位于叶顶通道的压力面前缘和吸力面尾缘的两个堵塞区。在75% ~ 105%换算转速，泄漏涡破碎引起的压力面前缘的堵塞是压气机失速的主要触发因素；换算转速小于75%或大于105%时，径向潜流引起的压力面尾缘的堵塞是主要触发因素。

关键词: 跨声速压气机；换算转速；泄漏涡；径向潜流；失速机制