Numerical Analysis of Effects of Turbine Blade Tip Shape on Secondary Losses

TLDR: In this article, the effect of the tip shape of a turbine blade tip on the secondary flow and the associated aerodynamic properties was investigated using a finite volume-based CFD solver, ANSYS FLUENT.

Abstract: This paper deals with a study of the effect of some turbine blade tip shapes on the secondary flows and the associated aerodynamics. A conventional plain tip shape and a novel squealer tip shape are compared aerodynamically using numerical analysis. The simulations are done using a finite volume-based, general purpose CFD solver, ANSYS FLUENT. The investigation was carried out on a turbine blade cascade consisting of three blades, test blade being the central blade which was modelled. The cascade analysis was done to capture the secondary flows and associated losses. Two cases of tip clearance viz., 0 and 1.5 % of the blade span were considered in this study contributing to the effect of blade tip geometry. The vorticity magnitude at a selected downstream vertical plane was estimated to aerodynamically compare the tip shapes employed in this study. Due to tip clearance, local secondary flows are found to be generated at the blade tip region. Results obtained in this study further indicate that squealer blade tip reduces the secondary flow losses when compared to the conventional plain turbine blade tips. Reduction in secondary flow losses is expected to subdue the effect of heat loads on blade tips. This is perhaps the most prominent practical implication of this key result. The magnitude of vorticity at the blade tip region for squealer tip with 1.5 % tip clearance is 21.25 % less than that for plain tip at the blade tip region for the same tip clearance. This is possibly because of separation of flow and recirculation at the squealer rim which induces weak leakage flows.