涡轮叶片带扰流柱尾缘通道冷气流动的数值分析

Numerical Investigation of Pin-Fin Influences on Cooling Air Flow Characteristics in Turbine Blade Trailing Edge Region

关键词:  扰流柱  旋转  数值分析  流动特性  压力损失

Key words:  Pin-fin  Rotation  Numerical investigation  Flow characteristics  Pressure loss

摘要:

在涡轮叶片尾缘通道中添加扰流柱可以改变尾缝内冷气流量的分配及流场均匀性，但同时会增加流阻，因此尾缘通道中扰流柱和尾缝的几何匹配对叶片的换热性能有较大影响。本文采用数值方法，以尾缘通道内无扰流柱模型M0为基准模型，对比分析在静止和三种旋转速度下带有三种不同扰流柱结构的尾缘内部流动。其中，M1添加单列扰流柱，数目13，直径D=2mm；M2与M3添加双列叉排扰流柱，数目分别为16和17，直径D=1.2mm，两模型仅在靠近尾缝1处扰流柱布局不同。数值结果揭示：（1）尾缘通道扰流柱可有效增加各尾缝冷气出流的均匀性，对1~3尾缝内的流动影响较大，小直径叉排扰流柱布置形式更优于大直径单排；（2）与M0相比，三组带扰流柱模型的通道压力损失稍有增加。其中，M2和M3基本相同，因对流场扰动较大，略高于M1；（3）随着旋转速度的增加，尾缝内压力损失逐渐降低，但四组模型尾缝内的流场结构没有明显改变。

Abstract:

Using pin-fin structure in turbine blade trailing edge helps to improve cooling air allocation and the uniformity of flow filed in the trailing edge slots of turbine blades. However， the added pin-fins inevitably increases the resistance to the fluid flow. Therefore， the geometry matching of pin-fin and trailing edge slots have obvious influence on heat transfer of turbine blade. With M0 as a reference model of a real turbine trailing edge with no pin-fins， this paper adopted the numerical method to compare the flow fields in the trailing edge of three models with different pin fin structures under both static and three rotating speeds. M1 has a single row of 13 pin-fins with a diameter of D=2mm. M2 and M3 have two staggered rows of pin-fins with a respective number of 16 and 17 and a diameter D=1.2mm. Only a slight difference in pin fin arrangement exists near Slot 1 between the two models. The results demonstrated that： （1） The pin-fin located in trailing passage can increase the uniformity of flow field， have a big influence on flow characteristic of #1~3 trailing slots， M2 and M3 with two staggered rows of pin-fins has a better results than M1 with a single row. （2） Compared to M0， the added pin fins in M1， M2 and M3 models cause a moderate increase in pressure losses. The pressure loss coefficients of M2 and M3 are of the same level， and are slightly higher than that of M1 due to higher disturbances to the flow. （3） Increasing blade rotating speed causes continual decrease of pressure loss coefficient， but the flow structure in the slots of all the four models is not evidently changed.