Scaling Film Cooling Performance from Ambient to Near Engine Temperatures

Robert W. Ashby


The present study examines the importance of various nondimensional parameters in scaling film cooling performance. Overall effectiveness measurements were obtained at engine representative conditions and then at matching near ambient conditions for matched free stream and coolant Reynolds numbers. A representative turbine airfoil leading edge model constructed of Hastelloy was used for both temperature regimes. While relatively good agreement was obtained for overall effectiveness magnitude for some cases, observed trends within the flow field did not agree well. Engine representative cases exhibited strong downward trends in overall effectiveness with axial position while near ambient cases displayed relatively flat profiles. This trend disagreement was attributed to less than ideal agreement in flow parameters such as free stream, coolant, and internal channel Reynolds numbers. Analysis of data obtained from each temperature regime revealed trends inconsistent with published results, suggesting possible time dependent effects in the experimental rig. Adiabatic effectiveness data was obtained using the Pressure Sensitive Paint method with carbon dioxide, argon, nitrogen, and helium as coolant gases. Analysis of preliminary results revealed expected trends with blowing ratio and density ratio for carbon dioxide, argon, and nitrogen injection.