Numerical Investigation of Round-to-Slot Holes on Film-Cooling Performance in a Turbine Vane

Abstract

The numerical investigation of single row holes on suction surface and pressure surface of a scaled turbine guide vane is carried out. In particular, the effects of round-to-slot holes (RTSHs) on film cooling performance are illustrated. Four RTSHs with different exit-to-inlet area ratios are considered under different blowing ratios. The results show that RTSHs can suppress the normal penetration of cooling jet and broadening the lateral coverage of film layer. With the increase of slot aspect ratio, the anti-kidney vortices pair is generally strengthened, making the film cooling improvement more significantly. The film cooling improving effects of shaped holes on the pressure surface is better than that on the suction surface, particularly under high blowing ratios. A key factor affecting the bleed pressure of coolant flow is exit-inlet area ratio of RTSH. The equivalent-area RTSH achieves nearly the same discharge coefficient (Cd) as the cylindrical hole. Viewed from the comprehensive effects of the Cd and adiabatic film cooling effectiveness on shaped hole, the RTSH-3 with a slot aspect of 9 and an exit-inlet area ratio of 1.27 is suggested to be the most favorable film-hole geometry among the current shaped-holes, either on the pressure surface or on the suction surface.