Rotating Stall Inception Due to Breakdown of Tip Leakage Vortex in Compressor Rotors

本文通过非定常三维N-S流动数值模拟和实验测量，研究了轴流压气机转子近失速状态下叶尖泄漏涡破裂引起的非定常流动特性。模拟结果表明，近失速状态下，转子通道内叶尖泄漏涡发生螺旋型破裂。在破裂开始的下游，叶尖泄漏涡随着时间的推移剧烈地扭曲和转向，从而与相邻叶片的压力面相互作用。旋涡的运动及其与压力面的相互作用是周期性的。涡的破裂使叶尖泄漏涡的性质发生了显著变化，导致近失速状态下叶尖附近时均流场出现了异常现象：泄漏涡在转子下游没有卷起，与泄漏涡对应的机匣壁压槽消失，泄漏涡在叶尖附近大范围扩散，叶尖附近时均流场出现了明显的畸变。 ...更多信息 压力侧流体能量低，压力波动大。随着流量的减小，叶尖泄漏涡因破裂而产生的运动变得如此之大，以至于泄漏涡与吸力面以及压力面相互作用。采用RANS数值模拟方法研究了轴流压气机转子近失速工况下的非定常全通道流场。该模拟捕捉了旋转失速起始的性质。结果表明，失速单元是由一个从叶尖吸力面连接到机匣的龙卷风型分离涡组成的部分展型失速单元。叶尖泄漏涡的螺旋型破裂导致泄漏涡与相邻叶片前缘的相互作用，从而形成龙卷风型涡。少

The unsteady flow nature caused by the breakdown of the tip leakage vortex in an axial compressor rotor at near-stall conditions has been investigated by unsteady three-dimensional Navier-Stokes flow simulations and by experimental measurements. The simulations show that the spiral-type breakdown of the tip leakage vortex occurs inside the rotor passage at the near-stall conditions. Downstream of the breakdown onset, the tip leakage vortex twists and turns violently with time, thus interacting with the pressure surface of the adjacent blade. The motion of the vortex and its interaction with the pressure surface are cyclic. The vortex breakdown causes significant changes in the nature of the tip leakage vortex, which result in the anomalous phenomena in the time-averaged flow fields near the tip at the near-stall conditions: no rolling-up of the leakage vortex downstream of the rotor, disappearance of the casing wall pressure trough corresponding to the leakage vortex, large spread of t … More he low-energy fluid accumulating on the pressure side, and large pressure fluctuation on the pressure side. As the flow rate is decreased, the movement of the tip leakage vortex due to its breakdown becomes so large that the leakage vortex interacts with the suction surface as well as the pressure one. The interaction with the suction surface gives rise to the three-dimensional separation of the suction surface boundary layer.Unsteady full passage flow fields at a near-stall operating condition in the axial compressor rotor has been investigated by RANS simulation. The simulation has captured the nature of the rotating stall inception. It is found that the stall cell is part-span type and consists of a tornado-type separation vortex linking from blade suction surface near the tip to the casing. The spiral-type breakdown of the tip leakage vortex causes the interaction between the leakage vortex and the adjacent blade leading edge, thus resulting in the formation of the tornado-type vortex. Less