Leading-Edge Endwall Suction and Midspan Blowing to Reduce Turbomachinery Losses

Abstract

A turbine cascade flow control scheme was implemented to simultaneously mitigate secondary fiowfield losses using leading-edge endwall suction and spanwise profile losses using vortex generator jet blowing. A proof-of-concept study was performed with a faired cylinder protruding normal from a flat plate. The application of endwall leading-edge suction eliminated the horseshoe-vortex system from the symmetry plane and reduced the total pressure losses by ~20%. A similar control scheme was then implemented in a turbine cascade. The high-lift turbine blades were equipped with discrete vortex generator jets to maximize loading while maintaining a separation-free flow. At Re Cx = 25, 000, the wake total pressure losses were dominated by the profile losses (no vortex generator jets). Total pressure data showed that endwall suction eliminated the horseshoe-vortex system but had minimal impact on the wake total pressure losses at both Re Cx = 25, 000 and 50,000. Simultaneous application of vortex generator jets and leading-edge suction, with matching mass flow rates, reduced the wake losses by 68 % at low Re Cx· The horseshoevortex system was shown to play a secondary role to the passage vortex in total-pressure-loss generation near the endwall.