Thermal performance improvement on winglet tip of a turbine stage under engine condition-part I: Winglet geometry modifications

Abstract

Heat transfer and film cooling effect on the winglet-squealer tip in the first stage of a gas turbine were numerically investigated under engine condition. To reveal the effect of P.S. (pressure side) winglet geometry on the tip thermal performance, seven different tip configurations (i.e. conventional squealer tip, no P.S. rim tip, three kinds of uniform cross-section winglet tip, and two kinds of distorted winglet tip) were selected to determine a proper design. The heat transfer and film cooling effect on the distorted winglet tip, conventional squealer tip and no P.S. rim tip were compared at two different cooling arrangements (i.e. only tip cooling and both tip and P.S. cooling). The results show that a proper design of distorted winglet geometry can effectively eliminate the high heat transfer areas and enhance the uniformity of thermal load on the cavity floor. Compared with the convention squealer tip, the thermal load on the distorted winglet tip is reduced by 16.45%. With vertical ejections from both tip and P.S. holes, the film cooling effectiveness on the distorted winglet tip is improved by 9.13% and 9.6% as compared with the convention squealer tip and no P.S. rim tip, respectively.