Adiabatic Effectiveness Measurements and Predictions of Leakage Flows Along a Blade Endwall

Abstract

Traditional cooling schemes have been developed to cool turbine blades using high-pressure compressor air that bypasses the combustor. This high-pressure forces cooling air into the hot main gas path through seal slots. While parasitic leakages can provide a cooling benefit, they also represent aerodynamic losses. The results from the combined experimental and computational studies reported in this paper address the cooling benefit from leakage flows that occur along the platform of a first stage turbine blade. A scaled-up, blade geometry with an upstream slot, a mid-passage slot, and a downstream slot was tested in a linear cascade placed in a low-speed wind tunnel. Results show that the leakage flow through the mid-passage gap provides only a small cooling benefit to the platform. There is little to no benefit to the blade platform that results by increasing the coolant flow through the mid-passage gap. Unlike the mid-passage gap, leakage flow from the upstream slot provides good cooling to the platform surface, particularly in certain regions of the platform. Relatively good agreement was observed between the computational and experimental results, although computations overpredicted the cooling.