Influence of wear damages on aerodynamic and heat transfer performance in squealer tip gap

Abstract

Numerical simulations were performed to investigate the effect of rim wear on aerodynamic and heat transfer performance in a squealer tip gap of gas turbine. Flow patterns, heat transfer coefficient distributions, and total pressure losses in tip gap regions were obtained at three starting-locations of wear (sl = 25%Cax, 50%Cax and 75%Cax. Cax: axial chord) and five wear-depths (wd = 1 mm, 2 mm, 3 mm, 4 mm and 5 mm). With the existing experimental data, numerical methods were carefully examined with respect to the turbulence model and mesh density. Results indicate that flow fields in squealer tip gap are significantly affected by the geometrical parameters of worn rims. As wd (wear depth) increases, high heat transfer area on cavity floor near leading edge is enlarged, whereas heat transfer coefficient on worn rims are decreased. The intensity of leakage vortex is increased significantly while the intensity of passage vortex is decreased, leading to increased total pressure loss in tip region. As sl (starting-location of wear) moves towards the leading edge, total pressure loss in cascade is increased, and area-averaged heat transfer coefficient on cavity floor is increased sharply. However, the area-averaged heat transfer coefficient on rims is decreased, significantly.