Influence of purge flow injection angle on the aero-thermal performance of a rotor blade cascade

This paper is focused on the influence of stator-rotor purge flow injection angle on the aerodynamic and thermal performance of a rotor blade cascade. Tests were performed in a seven-blade cascade of a high-pressure gas turbine rotor at low Mach number (Ma2is=0.3) under different blowing conditions. A number of fins were installed inside the upstream slot to simulate the effect of rotation on the seal flow exiting the gap in a linear cascade environment. The resulting coolant flow is ejected with the correct angle in the tangential direction. Purge flow injection angle and blowing conditions were changed in order to identify the best configuration in terms of end wall thermal protection and secondary flows reduction. The 3D flow field was surveyed by traversing a 5-hole miniaturized pressure probe in a downstream plane. Secondary flow velocities, loss coefficient and vorticity distributions are presented for the most significant test conditions. Film cooling effectiveness distributions on the platform were obtained by Thermochromic Liquid Crystals technique. Results show that purge flow injection angle has an impact on secondary flows development and thus on the end wall thermal protection, especially at high injection rates. Passage vortex is enhanced by a negative injection angle, which simulates the real counter rotating purge flow direction.