Film cooling effectiveness and heat transfer analysis of a hybrid scheme with different outlet configurations

摘要

In this paper, film cooling performance and flow-field analyses of hybrid schemes and circular film hole are investigated numerically. The hybrid scheme is designed to include two consecutive film hole shapes with interior bending. The film cooling performance of the hybrid scheme with outlet configurations of trapezoid, elliptical (with two compound angles of 0° and 90°), rectangle and square are analyzed and compared with cylindrical film hole at blowing ratio of 0.5 and 1 for 0.94 density ratio. The results conducted that the hybrid schemes reduce the downstream boundary layer as the injection flow spreads close to the downstream surface due to the interior bending. In addition, increasing the hybrid scheme exit area leads to reduce the secondary flow jet penetration into the mainstream because of momentum flux ratio reduction. Consequently, the centerline and spanwise film cooling effectivenesses enhance at low and high blowing ratios. Moreover, the hybrid square scheme provides the highest overall area-averaged film cooling effectiveness at high blowing ratio among other case studies. Furthermore, the hybrid square and trapezoid schemes yield less aerodynamic losses compared to other hybrid case studies. As a result, the hybrid scheme with large outlet area is able to protect the airfoil surface at less significant coolant flow rate and aerodynamic losses, thus it has capability to increase overall gas turbine efficiency with long-term gas turbine durability and reliability.