A Novel Suction Side Winglet Design Method for High Pressure Turbine Rotor Tips

Abstract

Winglet tips are promising candidates for future high pressure turbine rotors. Many studies found that the design of the suction side winglet is the key to the aerodynamic performance of a winglet tip, but there is no general agreement on the exact design method. In this paper, a novel suction side winglet design method will be introduced. The winglets are obtained based on the near tip flow field of the datum tip geometry. The suction side winglet aims to reduce the tip leakage flow particularly in the front part of the blade passage. It is found that on the casing endwall, the pressure increases in the area where the winglet is used. This reduces the tip leakage flow in the front part of the blade passage and the pitchwise pressure gradient on the endwall. As a result, the size of the tip leakage vortex reduces. A surprising observation is that the novel winglet tip design eliminates the scraping vortex and results in a further increasing of the efficiency. The tip leakage loss of the novel winglet tip is 23% lower than the datum cavity tip, with an increase of tip surface area by only 20%. The spanwise deflection of the winglet due to the centrifugal force is small. Numerical simulation shows that in a turbine stage, this winglet tip increases the turbine stage efficiency by 0.9% at a tip gap size of 1% span compared with a cavity tip.