Analysis and Control of Unsteady Three-Dimensional Vortical Flow Structure in Complex Flow Fields

采用实验流体力学（EFD）和计算流体力学（CFD）方法研究了轴流压气机转子旋转失速起始的瞬态流动现象。采用时间插值的同步场测量方法，对套管壁面压力的瞬时分布进行了实验研究。通过非定常N-S流场模拟，得到了非定常三维分离涡结构。为了解释失速起始时的非定常流动现象，利用临界点理论识别了失速起始时的涡结构和分离拓扑，在小间隙轴流压气机转子中，泄漏涡很弱，对流场的影响很小。在旋转失速起始阶段，前缘分离起主导作用，导致短尺度旋转失速。短尺度失速是部分跨度型失速，只占据部分环形空间。它的细胞结构由龙卷风-l ...更多信息 连接叶片吸力面和机匣壁边界层的分离涡。在短尺度失速单元中占主导地位的龙卷风状分离涡具有较大的阻塞作用。当分离涡增长并向相邻叶片的压力面移动时，它增加了相邻叶片的冲角，从而在相邻叶片上产生新的前缘分离。在小间隙情况下，失速演变取决于定转子间隙。而在大间隙情况下，三种间隙的失速演变规律差别不大。从失速点附近的压力场和速度场的测量结果来看，对于三种不同的间隙，在大间隙的情况下，叶尖泄漏涡都发生了破裂。转子出口处的轴向速度分布支持了这一点。从失速前的压力场迹线中，我们可以发现类似旋转不稳定性的独特流动现象。叶尖涡对失速起始起着非常重要的作用。少

A transient flow phenomenon of rotating stall inception in axial flow compressor rotors has been investigated by experimental fluid dynamics(EFD) and computational fluid dynamics(CFD). Instantaneous distributions of the casing wall pressure were obtained experimentally by 'Synchronous Field Measurement' using time interpolation. Unsteady three-dimensional separated and vortical Flow structure was captured by unsteady Navier-Stokes flow simulation. To elucidate the unsteady flow phenomenon at the stall inception, vortex structures and separation topology were identified by the critical point theory.In the axial compressor rotor with small tip clearance, the tip leakage vortex is so weak as to have little influence on the flow field. The leading edge separation dominates the rotating stall inception, which results in the short length-scale rotating stall. A short length-scale stall is of the part-span type occupying only a part of the annulus. Its cell structure consists of the tornado-l … More ike separation vortex linking the blade suction surface and casing wall boundary layers. The tornado-like separation vortex dominating the short length-scale stall cells has a large blockage effect. As the separation vortex grows and moves toward the pressure surface of the neighboring blade, it increases the incidence of the neighboring blade, thus bringing about a new leading edge separation on the neighboring blade. In the case of small clearance, the stall evolution depends on the stator-rotor gap. However, in the case of large clearance, there is little difference of the stall evolution among three gaps. From the measurement of the pressure and velocity field near the stall point, it seems that breakdown of tip leakage vortex occurs in the case of large clearance for three different gaps. It is supported from the axial velocity distribution at the rotor exit. From the pressure field traces just before the stall, we can find the distinctive flow phenomenon like rotating instability. The tip vortex plays a very important role for stall inception. Less