LES of rotational effects on film cooling effectiveness and heat transfer coefficient in a gas turbine blade with one row of air film injection

The effects of rotation on film cooling effectiveness and heat transfer coefficient distributions on the suction and pressure surfaces of a gas turbine blade were numerically simulated using large eddy simulation method. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blowing ratio (BR) is 0.5 on both the suction and pressure sides and the inlet Reynolds number based on the axial chord is 3 × 105. The effects of turbine rotating conditions on the film cooling effectiveness and heat transfer coefficient distributions were investigated at four rotating speeds of 0 rpm, 125 rpm, 250 rpm, and 500 rpm. Air was injected through one row of film holes each on the pressure and suction surfaces. The commercial code STAR-CCM+ was used in the prediction. The results indicate that film cooling effectiveness increases with an increase in the rotating speed. Higher turbine rotating speeds show more local film cooling effectiveness spread on pressure surface. The film cooling effectiveness and Nusselt number distributions were presented along with the discussions on the influences of rotating speed. Results showed that the rotation promotes an earlier boundary layer transition and increases the transition length on the suction surface.