端壁收缩对环形叶栅气动性能影响的数值研究

Numerical Study of the Effect of Endwall Contouring on the Aerodynamic Performance of an Annular Nozzle Cascade

采用数值计算软件Numeca模拟了汽轮机低展弦比端壁收缩喷嘴中气动性能和二次流涡系的发展,并与相同边界条件下的平直端壁喷嘴比较,得到了端壁收缩对流场性能的影响。结果表明:在端壁收缩喷嘴中,较大的进口面积使得马蹄涡发展较弱,顶部区域显著的后加载特性更进一步抑制了顶部通道涡的发展,因此通道涡尤其是上通道涡的尺度和损失均较小。同时,顶部收缩导致了顶部气流出气角增大和根部出气角减小,虽然变化幅度不大,但是气流角沿叶高的分布更加均匀,对下排叶栅内的流动更加有利。另外还计算了不同高度收缩比喷嘴流动,给出了高度收缩比对叶栅流动的影响。

The aerodynamic characteristics and secondary flow vortices development of a steam turbine low aspect ratio endwall contouring nozzle cascade are investigated by CFD commercial software Numeca; the effects of tip endwall contouring are evaluated in comparison with the plain endwall nozzle under same boundary conditions. The results show that in endwall contouring nozzle the larger inlet area results in weaker horse vortex, and aft - loaded characters due to endwall contouring restrain upper passage vortex from developing, as a result the scale and loss of passage vorties especially the upper passage vortex are less than those in plain endwall nozzle. Meanwhile, endwall contouring causes flow angle in upper half cascades increases and in lower half cascades decreases. Although the change is little the flow angle along blade height are more uniform, which will benefit the next row cascade flow. Furthermore, the flow field of nozzles with three different contraction ratios are compared and the effect of contraction ratio on aerodynamics performance is given.