Effects of turbine blade tip shape on total pressure loss and secondary flow of a linear turbine cascade

Abstract

Leakage flow through the turbine blade tip clearance causes a strong leakage vortex near the suction side of the blade. The leakage vortex induces aerodynamics losses and a high heat transfer coefficient on the suction side of the near blade tip region. In this study, the effects of blade tip shape on the secondary flow and total pressure loss in a turbine cascade have been investigated experimentally. A total of 11 tip shapes including plane, single or double squealer, dimpled, chamfered, and grooved tips were tested. Tip clearances of 1.5% and 2.3% of the blade span were tested. The Reynolds number, based on the blade chord and cascade exit velocity, was 2.48×105. The secondary flow and total pressure were measured by a five-hole probe at one-chord downstream from the blade trailing edge. The total pressure loss coefficient increased as the tip clearance increased, and the effect of tip shape on secondary flow and total pressure loss was significant. Among the tested tip shapes, the double squealer tip and the grooved along pressure side tip performed best and both tips showed smaller total pressure loss coefficients than that of the plane tip.