NUMERICAL INVESTIGATION ON FILM-COOLING CHARACTERISTICS FROM A ROW OF HOLES WITH RIDGE-SHAPED TABS

A three-dimensional numerical simulation was conducted to investigate the enhanced cooling performances caused by ridge-shaped tabs located at the upstream edge of film-cooling holes. Three covering ratios of ridge-shaped tabs on the film holes and four blowing ratios were considered in the present study. By comparison with cylindrical holes (a baseline case), the presence of ridge-shaped tabs in the nearby region of the primary film-cooling holes mitigates the primary vortices due to the mainstream/coolant-jet interaction and transfers the coolant-jet momentum flux mainly in the streamwise direction. The coolant-jet penetration along the vertical direction is suppressed and the peak velocity along the streamwise direction is augmented under the action of the ridge-shaped tabs, providing an increment in the film-cooling effectiveness and enhancement of the heat transfer coefficient over the baseline case. The ridge-shaped tabs provide enhancements in the cooling effectiveness but at the expense of a large pressure drop. From the present study, it is suggested that a ridge-shaped tab with a middle covering ratio is the best choice.