零间隙压气机失稳机理的全通道数值模拟研究

Full-annulus Numerical Investigation of Stall Mechanisms in a Compressor Without Tip Clearance

为了探究零间隙压气机流动失稳机理,采用全通道非定常数值模拟方法研究了一台零间隙斜流压气机转子的失稳机理,数值模拟过程中在转子出口施加了随时间动态变化的背压模拟压气机转子节流,非定常数值计算结果表明零间隙斜流压气机转子仍然表现为典型突尖流动失稳特征。通过详细地分析斜流压气机转子节流过程中不同阀系数对应的压气机内部流场结构,结果表明:尽管零间隙斜流压气机无叶顶泄漏特征,但随着对压气机节流,转子叶片尾缘率先出现流动分离,进一步节流,尾缘流动分离表现为一方面在周向范围加剧,另一方面分离点逐渐向上游移动,造成通道严重堵塞,最终引发相邻叶片通道尾缘回流和叶片前缘流动溢出进而诱发叶片通道内部出现径向涡结构,从而形成压气机突尖失速先兆。

To investigate the stall mechanisms of compressor without tip clearance,a mixed-flow compressor rotor without tip clearance was studied using full-annulus unsteady simulations.A dynamical outlet pressure varying with time was given on compressor rotor outlet.The unsteady numerical calculative results showed that the compressor rotor has the characteristic of spike-stall.The fundamental flow mechanism was obtained by detailed analyzing flow-field in the process of throttling the compressor.The underlying mechanism is that there is no tip leakage flow but flow separation near rotor trailing edge.Further throttling the compressor rotor,for one thing,the flow separation circumferentially intensifies,for another,the flow separation point moves upward,which leads to serious blockage in the tip region.As a result,the radial vortex is induced by tip leakage flow and backflow stemming from the fluid in adjacent passages at the trailing edge results in rotor spike-stall.