不同冲角下有叶顶间隙的涡轮叶栅拓扑与旋涡结构

对具有叶顶间隙的直叶栅和正、反弯三套涡轮叶栅进行了实验测量，研究在较大间隙（0．036）下，气流冲角和叶片弯曲对叶顶泄漏流动的影响。根据壁面流动的墨迹显示，应用拓扑学原理，分析了叶片表面和上、下端壁的拓扑结构，指出当气流冲角由0°增至20°时，与零冲角下的同类叶栅相比较，鞍点的位置均移向上游，分离区的范围在沿流向和垂直流向的方向上扩大，上、下通道涡分离线向叶展中部爬升。在冲角为零以及20°的情况下，叶片正弯均消除了上通道涡，这一方面减少了壁面流场中奇点和分离线的数量，较大地降低了上通道涡与泄漏涡的相互作用损失，另一方面强化了端壁横流对泄漏流动的封堵作用，有利于降低相对漏气量。

Turbine cascade topology and vortex structure under different incidence angles with tip clearance

The experimental measurement was performed with three sets of conventional straight, positively curved and negatively curved turbine cascades with tip clearance, and the effect of flow incidence angle and blade bending on top leakage was studied under larger clearance of 0. 036. By means of the ink trace visualization of the wall flow and the topology theory, the to- pological structures of the blade surface, the upper and lower end-wall were analyzed. It is pointed out that, compared with the same cascade under zero incidence angle, the saddle points all move to the upstream, the scope of the separation expands along the flowing direction and the vertical flow direction, and the separation line of upper and lower passage vortex climbs to the mid-span of the blade when the flow incidence angle increases from zero to 20°. This paper points out that under the conditions of zero and 20° incidences, blade positively curving eliminates the upper passage vortex, which on the one hand deereases the numbers of the singular points and the separation line within the wall flow field, reduces the interaction loss between the passage vortex and the leakage vortex greatly, and on the other hand strengthens the blocking effect of the end wall cross flow on the leakage flow, thereby reducing the relative leakage.