Abstract: In order to evaluate the effects of uncertain nozzle vane hub and shroud clearances on the performance in a variable geometry radial turbine, firstly, the numerical results of turbine for fully open nozzle vanes condition were compared with experimental data , and then several steady numerical simulations were carried out for the turbine under partially open nozzle vanes condition to predict the differences on turbine performance induced by uncertain hub/shroud clearances.At last the unsteady computations were performed for the even clearance model and peak efficiency model to study the aerodynamic interaction between nozzle vanes and rotor. The results show that the turbine efficiency reaches up to the maximum when the clearance value near the shroud wall is roughly 5%~15% of total clearance value while the minimum efficiency appears when all the clearance is concentrated on the shroud side. The difference between maximum and minimum efficiency is almost 6%. The clearance leakage flow along with different clearance model alters inlet flow angle to downstream rotor, and changes the loss for the rotor suction surface separation vortex. Moreover, the hub and shroud uncertain clearances configuration of nozzle vanes can add the risk of rotor blade failure by means of changing the shock wave stood on the suction surface of nozzle vane, which leads to fluctuating load to the rotor blade. 

Key words: Variable geometry radial turbine; Clearance; Performance; Shock wave; Loading

摘要： 为了评估可调向心涡轮导流叶片叶顶及叶根间隙尺寸不确定性对涡轮级性能的影响,首先将喷嘴环叶片大开度模型的单通道定常数值结果与实验数据对比；然后以导流叶片小开度涡轮为研究对象,数值模拟导叶两端叶顶间隙尺寸多种分配模型三维流场,总结出导叶间隙不确定性与涡轮级性能之间相应变化规律；最后选取导叶两端间隙平均分配模型和最优涡轮性能下间隙分配模型开展多通道定常/非定常计算,用于分析间隙分配变化对转静干涉影响。研究结果表明:当导流叶片轮缘侧间隙尺寸占全部间隙尺寸5%～15%范围时,涡轮级效率较高；当导叶间隙全部集中在轮缘侧时,涡轮效率较低；最高、最低效率差别约为6%。间隙泄漏流变化将引起下游转子叶片进口气流角发生变化,进而改变转子叶片吸力面前缘分离涡损失大小。此外,导叶两端间隙分配变化可以改变嘴环叶片吸力面激波强度,并通过诱发交变载荷变化方式影响转子叶片可靠性。 

关键词: 可调向心涡轮;间隙;性能;激波;载荷 