Endwall loss in turbine cascades

Prior to the detailed design of components, turbomachinery engineers must guide a mean-line or throughflow design towards an optimum configuration. This process requires a combination of informed judgement and low-order correlations for the principle sources of loss. With these requirements in mind, this paper examines the impact of key design parameters on endwall loss in turbines, a problem which remains poorly understood. The paper presents a parametric study of linear cascades, which represent a simplified model of real-engine flow. The designs are nominally representative of the Low Pressure Turbine blades of an aero engine, with varying flow angles, blade thickness and suction surface lift styles. RANS calculations are performed for a single aspect ratio and constant inlet boundary layer thickness. The paper first examines the two-dimensional design space before studying endwall losses in detail. It is demonstrated that endwall loss can be decomposed into two components: one due to the dissipation associated with the endwall boundary layer; and another induced by the secondary flows. This secondary-flow-induced loss is found to scale with a measure of streamwise vorticity predicted by classical secondary flow theory.Rolls-Royce pl