动叶叶顶结构对1.5级涡轮气动性能影响的数值研究

Numerical Investigation About the Effect of Rotor Tip Geometries on the Aerodynamic Performance for a One-Half Stage Turbine

基于Lisa 1.5级涡轮,构造全围带、全周小翼及翼型围带动叶叶顶结构模型,并应用数值计算方法,分析不同动叶叶顶结构对涡轮气动性能的影响规律。结果表明,0.97%叶片高度叶顶间隙值下,全围带叶栅气动损失最小,翼型围带次之,2 mm全周小翼控制损失的能力并不明显。此规律与涡轮平面叶栅研究中所得的结论相同。间隙增至1.38%叶片高度值时,间隙泄漏损失与总损失呈现等比例增加,表明此1.5级涡轮中气动损失主要来自于泄漏流动。最后,基于"Scaling"方法,分析不同叶顶结构对涡轮整级机械效率的影响。结果发现,三种叶顶结构均使效率得以提升。这进一步为翼型围带等叶顶结构的实际应用提供理论依据。

Various rotor tip geometries including the full shroud, the double-side winglet, and the winglet-shroud are constructed for the Lisa one-half stage turbine. Their impacts on the turbine aerodynamic performance are investigated using numerical simulations. Results indicate that at the tip clearance being 0.97 percent of the blade span, the full shroud geometry has the smallest loss,followed by the winglet-shroud structure, while the winglet with a width of 2 mm has limited ability to lessen the loss. This conclusion is the same with that previously obtained for a linear turbine cascade. When the tip clearance is enlarged to 1.38 percent of the blade height, the increasing rates between the tip leakage loss and the total loss are almost identical, implying that the aerodynamic loss is primarily attributed to the tip leakage flow. In order to evaluate the effects of tip geometries on the mechanical efficiency for the turbine stage, a scaling method is finally applied. It is demonstrated that the efficiency is improved for all three tip arrangements. The results further provide theoretical basis for these tip structures to be employed in the practical application.