Effect of non-axisymmetric endwall curvature on film cooling performance in annular cascade: A combined experimental and numerical study

Enhancement of turbine endwall cooling is essential for improving efficiency and extending component service life in advanced gas turbines. In this study, the impact of non-axisymmetric endwall contouring on film cooling effectiveness was systematically evaluated using pressure-sensitive paint measurements in conjunction with numerical simulations. Three distinct cooling hole geometries—cylindrical, fan-shaped, and laid-back fan-shaped—were examined on contoured endwalls characterized by various local curvatures. The results indicate that non-axisymmetric contouring of the endwall markedly modifies secondary flow structures, suppresses the intensity of near-wall vortices, and facilitates improved coolant retention. Variations in endwall curvature not only alter the exit geometry of film holes but also yield substantial increases in outlet area, with maximum enhancements of 65.1 %, 50.4 %, and 45.2 % for the laid-back fan-shaped, fan-shaped, and cylindrical configurations, respectively. These geometric modifications result in a more uniform and stable distribution of the coolant film, particularly in downstream regions, leading to significant improvements in overall cooling effectiveness. Among the configurations investigated, the laid-back fan-shaped hole exhibited the highest film cooling performance, followed by the fan-shaped and cylindrical holes. The optimal arrangement provided up to a 12.3 % increase in area-averaged film cooling effectiveness compared to a conventional planar endwall under identical flow conditions. These findings demonstrate that the combined optimization of endwall shape and hole geometry can effectively reduce hot spot occurrence, thereby contributing to the development of more reliable and efficient turbine components.