Film Cooling Hole Shape Effects on Turbine Blade Heat Transfer – Part I: Computational Comparison to Experiment

Gas turbines generate highly unsteady flow fields, which are further complicated by cooling. Film cooling technology is dependent on experimental and computational research performed for simplified geometries, which can be difficult to translate to turbine domains. To help explain disconnects between flat plate experiments and turbine operation, this study performs computational research, grounded with experimental measurements, examining the film cooling performance of several different hole shapes on rotating turbine blades. Round, fan, and advanced anti-vortex hole geometries are incorporated into experimental hardware and computational models, and pressure and heat flux results form a basis for comparisons between computation and experiment as well as between the cooling geometries. Unsteady and Steady simulations are both evaluated, and results indicate significant model accuracy improvement from the inclusion of unsteady consideration. Shaped film cooling holes are observed to provide stronger film effectiveness traces on the blade. Both the fan and advanced shaped film cooling holes generate stronger cooling jet cores that remain close to the blade wall on the pressure surface, suction surface, and near the leading edge. Advanced shaped holes provide increased lateral spread and increased resistance to radial migration. The results of this study help identify benefits of using shaped film cooling on the turbine blade as well as the mechanisms generating the cooling benefits. This will help designers weigh the manufacturing costs of shaped film cooling holes as well as identify areas of the blade where shaped film cooling is needed and where it is not. Additionally, this study observes significant improvements in blade heat transfer predictions through unsteady treatment alone, indicating better computational agreement can be achieved by leveraging lower-cost RANS simulation tools.