Experiments of discharge coefficient of film cooling holes under adverse pressure gradient

To study the influence of geometries and aerodynamic parameters on discharge coefficient in the presence of the mainstream adverse pressure gradient, experiments were carried out in a scaled up low speed wind tunnel. The discharge coefficient of the expanded holes is compared with that of the cylindrical holes firstly and then the investigation is focused on the discharge coefficient of the expanded holes. The results show that the discharge coefficient of the expanded holes is larger than those of the cylindrical holes. Both the large plane angles and the small radial angles provide the greater discharge coefficient. Discharge coefficient increases when the momentum flux ratios increase, especially at the momentum flux ratios lower than 4. The high turbulence intensity produces the large discharge coefficient, especially at the low momentum flux ratios. Density ratios have weak influence on the discharge coefficient, except at the large inclination angles of the film cooling holes.