Upstream and Downstream Step Curvature Effects on Film Cooling Effectiveness and Flow Structures

Abstract

In this study, computational simulations were made using ANSYS CFX to predict the influence of upstream and downstream step curvature radii on the film cooling effectiveness. Five upstream steps and four downstream steps with different curvature radii were studied. The curvature radii of these steps of R = 1.64D, 2D, 3D, 4D, and 5D were used. The film cooling effectiveness (eta) of these steps was investigated and compared with experiment. The near-field flow phenomena such as the pressure coefficient and the jet trajectories were discussed. Results indicate that the step position in the upstream of a film hole has a higher effect on the film cooling effectiveness compared with the downstream position. The film cooling effectiveness increases in the case of the upstream curved steps at lower radii due to entrapping more coolant in the region upstream of a hole. The results show that the pressure difference has an important effect to draw the coolant in the upstream region of a film hole compared with the case without step.