涡轮叶栅端壁区流动的实验研究

本文在大尺寸低速开式叶栅传热风洞中对一种高压涡轮导向叶栅中的流场进行了实验研究。采用五孔针对5个雷诺数下的叶栅端壁区三维流场进行了测量,并用线簇和小球浮动法对5个工况的流动进行了流场显示。实验结果表明:马蹄涡压力面分支在向吸力面运动的过程中,破坏了来流附面层的结构,在马蹄涡压力面分支之后,叶栅通道中产生了一个新的从压力面到吸力面的新附面层,新附面层的厚度小于来流附面层厚度;三维流动区约占叶栅通道的40%;雷诺数的增大将增强端壁区的三维流动。从流场显示图片可以观测叶片吸力面靠近端壁的角涡形成与发展,以及吸力面上的三角形区域;流场显示的通道涡大小与流场测量结果吻合。本文的实验结果有助于分析端壁表面和叶片表面换热特性的形成机理。 

EXPERIMENTAL INVESTIGATION OF ENDWALL FLOW IN A TURBINE CASCADE

The flow field of straight HP turbine cascade was investigated experimentally in a large-scale low-speed open-loop cascade heat transfer wind tunnel.Three-dimensional flow fields near the endwall of the cascade were measured by using five-hole probe at five different Re .Cotton thread and floating small ball are applied to visualization of the flow fields.The experimental results show that the pressure side leg of the horseshoe vortex destroys the structure of the incoming flow boundary layer,when it moves from Pressure Side (PS) to Suction Side (SS).Behind the pressure side leg,a new boundary layer is generated near the endwall in the cascade.The new boundary layer goes from PS to SS.However,its thickness is thinner than that in the incoming flow.The 3D-flow region occupies 40% flow passage of turbine cascade.The increase of Re intensifies 3D-flow near endwall.From the photos of flow visualization it can be seen that corner vortex is generated and developed near the suction surface of blade/endwall junction,and forms a triangle region on the suction surface.The size of visualized passage vortex is consistent with measurement result.