中文摘要：

可调喷嘴涡轮通过调节喷嘴环的转角。改变涡轮的流通面积，使涡轮的流量特性和效率特性发生变化，从而使涡轮与发动机在较宽广的工况范围内保持良好的匹配。叶轮冲角发生变化时，对叶轮效率影响很大。运用三维数值模拟技术。对JK90S可调喷嘴涡轮叶轮冲角进行了数值计算和流场分析，研究叶轮冲角变化对叶轮效率的影响。结果表明，在不同的油门和不同的发动机转速下，叶轮的最佳效率对应的叶轮入口冲角不同。在发动机100％油门开度时。叶轮的最佳效率冲角约为-45°;在发动机50％油门开度时。叶轮的最佳效率冲角约为-35°。小于最佳效率冲角时，叶轮效率迅速下降；大于最佳效率冲角时，在一个较宽广的冲角范围内叶轮能维持较高效率。随着发动机转速的提高．叶轮高效区的冲角范围逐渐变窄。

英文摘要：

Variable Nozzle Turbine （VNT） could change the flow area by adjusting the angle of nozzle blade and the mass flow rate and efficiency characteristic to match turbine and engine well in a extensive operating range. By the use of 3D numeric simulation technique, the numerical calculation and flow field analysis on incidence of impeller of JK90S variable nozzle turbine were carried out. As for impeller incidence, the incidence corresponding to best efficiency is different under different throttling and engine speed. At 100% throttling of engine, the incidence of best efficiency is about -45°; at 50% throttling of engine, the incidence is about -35°. The efficiency of impeller decreases rapidly when the incidence is less than optimum; when incidence is larger than best efficiency incidence, it could maintain high impeller efficiency daring an extensive range. With the engine speed increases, the incidence range that corresponding to high efficiency of impeller eventually reduces.