Experimental Simulation of a Film Cooled Turbine Blade Leading Edge Including Thermal Barrier Coating Effects

Abstract

For this study a simulated film cooled turbine blade leading edge, constructed of a special high conductivity material, was used to determine the normalized “metal temperature” representative of actual engine conditions. The Biot number for the model was matched to that for operational engine conditions ensuring that the normalized wall temperature, i.e. the overall effectiveness, was matched to that for the engine. Measurements of overall effectiveness were made for models with and without TBC (thermal barrier coating) at various operating conditions. This was the first study to experimentally simulate TBC and the effects on overall effectiveness. Two models were used, one with a single row of holes along the stagnation line, and the second with three rows of holes straddling the stagnation line. Film cooling was operated using a density ratio of 1.5 and for range of blowing ratios from M = 0.5 to M = 3.0. Both models were tested using a range of angles of attack from 0.0 to ± 5.0 degrees. As expected, the TBC coated models had significantly higher external surface temperatures, but lower “metal temperatures.” These experimental results provide a unique database for evaluating numerical simulations of the effects of TBC on leading edge film cooling performance.