Aerothermal Performance of Different Tips in Transonic Turbine Cascade with End-Wall Motion

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Aerothermal Performance of Different Tips in Transonic Turbine Cascade with End-Wall Motion

Zhou, Chao

Modern high-pressure axial turbines of aircraft engines are often transonic. This paper investigates and compares the aerothermal performance of the tip leakage flow of two widely used tips, a flat tip and a cavity tip, in a transonic turbine cascade. Numerical methods were first validated and then used to study different cases. Shock waves appear within the tip gap of a flat tip and have a large effect on the aerothermal performance. Unlike the flat tip, the flow physics within the tip gap of the cavity tip is significantly affected by the cavity vortices, and the effects of the shock waves are small. The impact of tip leakage flow physics on the loss mechanism and heat transfer are investigated. The effects of the relative motion between the blade tip and the casing are also investigated. A tangential viscous force is imposed by end-wall motion and changes the flow physics within the tip gap. Furthermore, a scrapping vortex is formed in the main flow passage due to relative end-wall motion. The scrapping vortex has a large effect on the flow pattern downstream of the cascade.