Study of Flow Structures within Turbine Cascade with Large Tip Clearance

Flow visualizations on wall surface and numerical simulations within turbine cascade with large tip clearance were carried out.Based on the experiential results and with the aid of numerical simulations,detailed flow structures within a typical turbine cascade were discussed.The detailed information of the flow fields near the wall surface,in the tip clearance,and especially,around the trailing edge was shown in the present study.In the up-half-span region,the flow became very complex due to the existence of the tip clearance.There are interactions among those vortices such as leakage vortex, up passage vortex,shed vortices on the pressure and suction sides,and trailing edge vortices.In the low-half-span,the flow fields near the region formed by the trailing edge and the endwall were also very complex.There are 3 saddle points company with 6 separation lines and 2 nodal points represent the trailing edge vortices on the wall surface near those region.At the end of this paper,vortical structures of the turbine cascade were developed.