ON THE PHYSICS OF VORTEX FORMATION AT THE TIP OF A TURBINE BLADE

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.