Implementation of Wide Diffusion Angle V-Shaped Holes for Gas Turbine Cooling: Design Phase and Numerical Simulation

Abstract

This paper describes the design process carried out to develop a new hole geometry. This geometry is able to increase the cooling coverage effect on a turbine blade, in order to have a higher efficiency compared to the standard holes. The first step of the activity described is a CFD analysis of the performances of different hole geometries on a flat plate. Starting from the cylindrical holes the performances of several geometries have been compared. This study allowed the determination of the geometrical parameters mostly responsible of the film effectiveness increase. In this way a criterion able to optimize the hole geometry has been found. Keeping as constraint the same inlet section for all the geometries, the shape of the outlet section was modified in order to maximize the film coverage performances. An optimized hole geometry had been determined. This solution, called V-Shaped hole is characterized by a wide lateral expansion angle and a negligible laidback angle and it is able to increase the cooling effectiveness compared to cylindrical and shaped holes with typical expansion angles (lateral and laidback about 10°). Finally, a comparison with an experimental campaign has been performed to confirm the main results of the CFD analysis.