Effect of wear damage on aero-thermal performance of the film-cooled squealer tip in a turbine stage

Abstract

Effects of wear damage on the aerodynamic performance, heat transfer and film cooling effect in the squealer tip region of a gas turbine stage were investigated under engine condition. Two wear parameters, including the starting-location of wear ( sl) and wear depth ( wd), were introduced to describe the degree of wear damage. Three starting-locations of wear ( sl = 32% C ax, 58% C ax and 79% C ax) and three wear depths ( wd = 0.33 mm, 0.67 mm and 1.0 mm) were selected to compute the heat transfer coefficient and film cooling effectiveness on the squealer tip at four blowing ratios ( M = 0.25, 0.5, 0.75 and 1.0). The pressure loss and isentropic efficiency of the turbine stage were calculated to assess the aerodynamic performance degradation induced by the tip wear. The results indicate that the pressure loss in the blade passage near tip region is increased and the stage efficiency is decreased with the increase of wd. Compared to the original design case at M = 0.75, the pressure loss in the rotor blade passage is increased by 7.39% and the stage efficiency is decreased by 2.22% at most after wear. As wd increases, the area-averaged heat transfer coefficient on the cavity floor is increased and film cooling effectiveness is decreased. For the worn cases at M = 0.25, 0.5, 0.75 and 1, the area-averaged heat transfer coefficient on the cavity floor is increased respectively by 87.7%, 62.3%, 71.3% and 88.0% at most, and the area-averaged film cooling effectiveness is decreased respectively by 37.2%, 26.8%, 26.7% and 22.2% at most, as compared to the original design cases.