透平动叶顶部间隙流的端壁二次流结构研究

对不同动叶顶部间隙的Aachen一级半轴流透平内部流动进行了数值模拟，以二次速度矢量和周向平均气流角的分布为依据，分析了间隙流、间隙涡与动叶顶部通道涡掺混的方式及其对二次流结构的影响．结果表明：较大的间隙尺寸导致间隙涡较早产生；间隙涡在向下游发展的过程中强度减弱，但范围有所增加；较小的间隙或者在接近叶栅前缘区域，间隙流仅将通道涡整体推移，不破坏通道涡的完整性；间隙较大或在叶栅的高加载区域，间隙流将通道涡拆分成2个独立的涡区，并将这2个涡区分别向压力面和中叶展推移，而间隙涡本身则占据动叶顶部较大的区域．最后，给出了不同间隙下2种不同的端壁二次流结构．

Study on Tip Clearance Flow of Turbine Blade-Endwall Secondary Flow Structure

Numerical simulations on Aachen 1-1/2 axial-flow turbine stages with different tip clearances were performed. Based on the distributions of secondary velocity and averaged azimuthal flow angle, the form of mixing process of tip clearance vortex with passage vortex and its influences on secondary flow structure were studied. The results show that tip clearance vortex forms earlier under larger tip clearance, accompanied with decreased intension and increased size during its development downstream-wise. Moreover,under small tip clearance or in the location nearby leading edge, the passage vortex is only shifted by tip clearance flow while integrity being preserved. However, under larger tip clearance or in the high-loaded area, passage vortex is divided into two independent vortices which are shifted towards pressure side and mid-span, while tip vortex occupies a large tip area near endwall. In addition,two different endwall secondary flow structures were presented.