单转子轴流压气机涡动力学失稳机理研究

Research on Stall Mechanism Based on Vorticity Dynamics

关键词:  轴流压气机  叶顶泄漏涡  二次泄漏涡  失速先兆  数值模拟  涡动力学

Key words:  Axial compressor  Tip leakage vortex  Secondary leakage vortex  Stall precursor  Numerical simulation  Vorticity dynamics

摘要:

为了研究单转子轴流压气机的涡动力学失稳机理，采用基于Shear Stress Transport(SST)湍流模型的尺度自适应雷诺平均/大涡(RANS/LES)混合模拟的方法对低速单转子轴流压气机进行了非定常数值模拟。研究结果表明:在设计转速3kr/min条件下，叶顶泄漏涡、二次泄漏涡以及诱导涡破碎引起的叶顶区域的堵塞是触发单转子轴流压气机内部流动失稳的主要因素。压气机由近堵塞工况点向小流量工况点逼近的过程中，叶顶泄漏涡轨迹与轴向的夹角由70°增加到76°，二次泄漏涡起始点位置前移加速叶顶泄漏涡向转子前缘移动。近失速工况点叶顶泄漏涡的轴向动量与主流的轴向动量之间存在一种平衡，叶顶泄漏涡稳定在转子前缘。压气机进一步节流主流的轴向动量减小，对叶顶泄漏涡轴向动量的抑制能力减弱，叶顶泄漏涡的位置不再稳定，诱发尖脉冲型失速先兆。

Abstract:

In order to study the stall mechanism based on the vorticity dynamics in a single-rotor axial compressor，unsteady numerical simulation was performed using a scale adaptive hybrid Reynolds-average Navier-Stokes/large eddy (RANS/LES) method based on shear stress transport(SST) turbulence model. The results show that the rotor tip blockage caused by the breakdown of tip leakage vortex，secondary leakage vortex and induced vortex is responsible for the internal flow instability of the axial compressor at the design speed of 3kr/min. The angle between the tip leakage vortex trajectory and the axial direction increases from 70° to 76° as the compressor runs toward the small mass flow condition from near chock condition. At the same time the starting point of secondary leakage vortex moves upstream，which accelerates the tip leakage vortex movement to rotor leading-edge. The axial momentum of tip leakage vortex is almost same as that of the mainstream and tip leakage vortex moves to rotor leading-edge at near-stall condition. As the compressor’s mass flow decreases，the axial momentum of mainstream reduces. The axial momentum of the tip leakage vortex can not be suppressed and tip leakage vortex spillages to leading-edge of the rotor. As a result，spike-type stall precursor is induced.