时序效应对高负荷低压涡轮边界层流动的影响研究

Research on the Effect of Clocking Effect on the Boundary Layer Flow of Highly-loaded Low-pressure Turbines

在多级涡轮内,时序效应和寂静效应会对涡轮内部的流动及气动效率产生重要影响。以两级高负荷低压涡轮为研究对象,采用高精度大涡模拟(LES)方法对该涡轮叶中截面的非定常流场进行了数值模拟,分析了5个不同静子时序位置下第二级静子的时均流场、时均性能和边界层流动非定常演化过程。结果表明:第一级静子的不同时序位置对第二级静子的总压损失产生明显影响,不同时序位置下总压损失的变化可达20%;不同时序位置下的流动差异主要归因于尾迹在通道中的输运过程,尾迹与边界层相互作用诱导边界层转捩发生变化;当第一级静子尾迹撞击第二级静子前缘时,第二级静子吸力面的分离区明显减小,第二级静子的总压损失达到最小值;相反地,当第一级静子尾迹在第二级静子通道中靠近吸力面侧约40%栅距位置时,一个转子通过周期内第二级静子吸力面后部出现多个分离泡,使得时均总压损失最大。

In multi-stage turbines,the clocking effect and calming effect would have significant impacts on the internal flow and aerodynamic efficiency.Taking a two-stage highly-loaded low-pressure turbine as the research object,and the high-precision large eddy simulation(LES)method was utilized to simulate the unsteady flow fields at the mid-section of the turbine blade.The time-averaged flow field,time-averaged aerodynamic performance and unsteady evolution of the boundary layer flow in the second-stage stator under five different stator clocking positions were analyzed.Results show that the different clocking positions of the first-stage stator have a significant impact on the total pressure loss of the second-stage stator,with changes in total pressure loss reaching up to 20%across different clocking positions.The differences in flows under different clocking positions are mainly attributed to the transport process of the wake in the blade rows,as well as changes in boundary layer transition induced by the interaction between the wake and boundary layer.When the wake of the first-stage stator hits the leading edge of the second-stage stator,the separation zone on the suction surface of the second-stage stator is significantly reduced,resulting in the minimum total pressure loss.Conversely,when the wake of the first-stage stator enters the blade passage from a position approximately 40%of the pitch distance from the suction side of the second-stage stator,multiple separation bubbles appear at the rear part of the suction side of the second-stage stator during a rotor passing period,leading to the maximum time-averaged total pressure loss.