The investigations of slot film outflow used on the laminated cooling configuration

Abstract

The discrete film hole is the most common form of film cooling configurations in the turbine vane and blade. To enhance the film cooling effect, the improved hole, such as expanding-shape hole, is being used to replace the traditional cylindrical hole in the vane and blade cooling design. However the slot film outflow is been seen as the best form of film cooling when compared to the discrete holes. The slot film cooling configuration is usually used in the trailing edge of turbine vane and blade, but cannot be used in the mid-body of turbine vane and blade, with be drawback of lower mechanical strength. The present paper used the slot film outflow on the laminated cooling configuration. With the ribs in the laminated cooling configuration, the novel configuration can remarkably overcome the mechanical drawback of the simple slot film cooling, and can enhance the film cooling effect of the laminated cooling configuration. To investigate the cooling effect of laminated configuration with slot film outflow, four kinds of specimens are designed, including the traditional design with discrete film hole (baseline), the rearrangement design with discrete film hole (case A), the novel design with discrete slot (case B), and the novel design with continuous slot (case C). The Conjugate heat transfer (CHT) computations and the Pressure Sensitive Paint (PSP) test methods are used to assess the overall cooling performance (ηoverall) and the adiabatic film cooling effectiveness (ηfilm). The results show the two slot design cases (case B and case C) have higher film cooling effectiveness with more covered surface areas of film outflow, while performs lower flow resistance due to the lower flow velocity of the coolants in the slot. With the increase of Br, the film cooling effectiveness of two slot design cases (case B and case C) can keep increase, but the two hole design case (baseline and case A) cannot increase at area of Br > 0.55. At the blowing ratio near 0.96, for the baseline case, case A, case B, and case C, the area-averaged film cooling effectiveness is 0.26, 0.20, 0.68, and 0.50 respectively; and area-averaged the overall cooling effectiveness is 0.72, 0.81, 0.89, and 0.85 respectively; the flow frictions coefficients is 1.78, 2.15, 1.37, and 2.01 respectively.