A parametric and computational aerothermal investigation of squealer tip geometry in an axial turbine: A parametric approach suitable for future advanced tip carving optimizations

A parametric computational study has been conducted in order to investigate the effect of a squealer geometry in axial flow gas turbines. Although the present investigation deals with the conventional squealer tip design, the main goal of the parametric approach is to obtain significant time savings in the computational analysis of future tip mitigation schemes. At this preliminary stage, both width and height of the conventional squealer tip have been introduced as design parameters. Computational Fluid Dynamics (CFD) analysis has been conducted for a linear turbine cascade arrangement. Computations have been performed for a single blade passage considering periodicity in the tangential direction with no relative motion between blade and the casing. In order to generate the mesh, an effective parametric grid generation has been performed using a multizone structured mesh. Numerical solutions have been obtained by solving the 3D, incompressible, steady and turbulent form of the Reynolds-Averaged Navier-Stokes (RANS) equations using the general purpose solver ANSYS CFX. Two equation turbulence model, Shear Stress Transport (SST) has been used. Sixteen different squealer tip geometries were modeled parametrically and their performance has been compared in terms of both aerodynamic loss and heat transfer to blade tip. In addition to significant time savings for the squealer tip modeling and gridding, the specific parametric approach paves the way for aerothermal optimization of advanced squealer geometries such as optimized tip carving based geometries. Results obtained in this study are going to be used for the aerothermal optimization of the squealer blade tip geometry.