Aerothermal Optimization of Turbine Squealer Tip Geometries with Arbitrary Cooling Injection

The optimization of the turbine tip geometry remains vital to create more efficient and durable engines. Balancing the aerodynamic and thermal aspects, while maintaining mechanical integrity is key to reshape one of the most vulnerable parts of the entire engine. The increasing turbine gas temperatures, combined with the aerodynamically penalizing overtip leakage vortex, makes the design of the tip a truly multidisciplinary challenge. While many earlier efforts focused on uncooled geometries, or studied the aerothermal impact with a fixed cooling configuration, the current paper presents the outcome of a multi-objective optimization where both the squealer rim geometry and cooling injection pattern were allowed to vary simultaneously. This study seeks a further synergistic aerothermal benefit through combining a quasi-fully arbitrary cooling arrangement, with mutating squealer rim structures. Specifically, the current manuscript presents the results of over 330 cooled and uncooled squealer tip geometries. The turbine tip was automatically altered using a novel parametrization strategy, varying both the squealer rim structures as well as the size and location of the cooling holes. The aerodynamic and thermal characteristics of every design were evaluated through 3D CFD, adopting high-density hexahedral grids. A multi-objective differential evolution algorithm was used to obtain a Pareto front which maximizes the aerodynamic efficiency, while minimizing the overtip thermal loads. Eventually, a detailed investigation and robustness study was performed on a set of prime squealer geometries, to further investigate the aerodynamic flow topology, and the effect of various cooling injection schemes on the heat transfer patterns.