Influence of Endwall Flow on Airfoil Suction Surface Midheight Boundary Layer Development in a Turbine Cascade

Abstract

This paper presents the results of an analysis to assess the influence of cascade passage endwall flow on the airfoil suction surface midheight boundary layer development in a turbine cascade. The effect of the endwall flow is interpreted as the generation of a crossflow and a crossflow velocity gradient in the airfoil boundary layer which results in an extra term in the mass conservation equation. This extra term is shown to infuence the boundary layer development along the midheight of the airfoil suction surface through an increase in the boundary layer thickness and consequently an increase in the midheight losses, and a decrease in the Reynolds shear stress, mixing length, skin friction, and Stanton number. An existing two-dimensional differential boundary layer prediction method, STAN-5, is modified to incorporate the above two effects.

Predictions of Endwall Losses and Secondary Flows in Axial Flow Turbine Cascades

“…The method from Ref. 30 was used in the present exercise to calculate the two-dimensional boundary layer integral parameters together with the mixing analysis developed by Stewart et al (Ref. 32) was used to obtain the profile losses for each set of data described below.…”