工业汽轮机高负荷末级静叶积叠规律研究

Study on Last Stage Guide Vane Stacking Strategies for Industrial Steam Turbine

以高负荷、大扩张角、小根径/顶径比、大展弦比的工业汽轮机末级叶片为研究对象,设计了直扭静叶、弯扭静叶、周偏直扭静叶3种积叠方案,采用三维CFD方法数值模拟了3种方案的内部流动,分析了压比、反动度、马赫数、静压系数、气流角、效率等参数的变化和内部流场。结果表明:周偏直扭方案的级效率最高,达到90.65%,比直扭方案和弯扭方案分别高0.93%、0.81%;正弯和周偏都能提高根部反动度,形成从根部指向流道中部的压力梯度,减小端壁附近的横向二次流动,降低二次流损失,同时降低了马赫数、减小了激波损失。

The last stage of industrial steam turbine with high load,large expansion angle,small hub:tip diameter ratio and large aspect ratio was studied.Three stacking strategies were designed:straight twist guide vane,lean and twist guide vane,and circumferentially offset straight twist guide vane.Three-dimensional CFD method was used to simulate the internal flow.Aerodynamic parameters such as pressure ratio,reaction degree,Mach number,static pressure coefficient,flow angle,efficiency and flow field were analyzed.The results show that the stage efficiency of the circumferentially offset straight twist strategy is up to 90.65%,which is 0.93%and 0.81%higher than that of the straight twist strategy and the lean twist strategy respectively.Both the lean twist and the circumferentially offset straight twist strategies can increase the root reaction degree resulting in pressure gradient from root to the medium which can reduce the lateral secondary flow near the end wall,reduce the secondary flow loss,and at the same time reduce the Mach number and shock loss.