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A new turbine blade tip shape called triple squealer is proposed. This shape is based on the conventional double squealer, and the cavity on the tip surface is divided into two parts by using a third squealer along the blade camber line. The effect of the ratio of groove depth to span (GDS ratio) was investigated. The flat-tip case (baseline case) and doublesquealer case were calculated for comparison. In-house, unstructured, 3D, Navier-Stokes, finite volume, multiblock code with DES (Detached Eddy Simulation) as turbulence model was used to calculate the flow field around the tip. The computational results show that the reduction in the mass flow rate of the leakage flow for the triple squealer is 15.69% compared to the flat-tip case.

The vortical flow at the blade tip area of a turbine rotor has a great effect on the aerothermal performance of the blade tip of turbine rotor however its physics is not fully understood. The present paper is a numerical study to investigate the physics behind vortex formation at the blade tip area. The blade under investigation is a linear model of the tip section of the GE-E3 high-pressure turbine first stage rotor blade. Calculations were carried out for three tip geometries, namely, conventional double squealer, thick pressure side squealer and thick suction side squealer. The code used in this study is an in-house, unstructured, finite volume, multiblock, 3D, compressible, viscous solver. The turbulent viscosity was calculated using the Delayed Detached Eddy Simulation (DDES) model. Computational results show that the vortex formation depends on the vorticity imparted with the incoming flow. Therefore, the flow with high velocity gradient caused larger vortex than that with low velocity gradient. This result is valid for both the cavity vortex as well as the leakage vortex.

The present study aims to control the leakage flow and total pressure loss in high pressure turbines. A new tip shape is proposed. It is based on the triple squealer shape by adopting a new middle squealer, along the camber line, whose first and last thirds were removed. An unstructured, finite volume, multiblock, 3-D, compressible Reynolds-Averaged Navier-Stokes equations solver was used to compute the flow through a high pressure turbine cascade. The turbulent viscosity was calculated by the Delayed Detached Eddy Simulation (DDES) model which is based on the Spalart-Allmaras one equation turbulence model. The performance of the new shape is compared to that of flat tip, double and triple squealers. The results successfully demonstrate that the new shape has the least total pressure loss among them.