Film-cooling performance of converged-inlet hole shapes

A converged-inlet shape for cylindrical film-cooling holes is proposed. The film-cooling performance was analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport model as a turbulence closure model. The numerical results of the film-cooling effectiveness for the cylindrical holes were validated with previous experimental data. Spatially averaged film-cooling effectiveness was used as a performance parameter, and a parametric study was performed for the converged-inlet shape with four geometric parameters: the streamwise and lateral expansion angles, injection angle, and the ratio of the length to the diameter of the cylindrical part of the holes. The computational results show that the converged-inlet shape resulted in about 46.5% improvement of the spatially film-cooling effectiveness compared to a cylindrical film-cooling hole. The film-cooling performance was sensitive to all four geometric parameters. And, the maximum spatially averaged film-cooling effectiveness occurred at an injection angle of 40°.