Effects of compound angle on film cooling effectiveness with different streamwise pressure gradient and convex curvature

Streamwise pressure gradient and surface curvature are two important characteristics of turbine flow and compound angle film cooling is an efficient way to improve cooling performance. Compound angle film cooling effectiveness with those two effects was investigated using PSP technology. The corresponding numerical studies were validated and carried out to investigate the physical mechanism of the interaction between the coolant jet and the main flow. Compound angle increases film cooling effectiveness for high blowing ratios in the near hole region, but the stronger interaction between the jet and the main flow makes the coolant dissipate faster. On the flat surface, the favorable pressure gradient leads to a maximum of 50% increase of film cooling effectiveness compared with the adverse pressure gradient case. On the convex surface, the cooling jet is pushed to the wall by the radial pressure gradient in the free stream which makes film cooling effectiveness 20-50% higher than the flat wall case. The compound angle film cooling performance under strong favorable pressure gradient for the convex surface is quite different from the flat wall case and thus streamwise pressure gradient and surface curvature should be taken into consideration in gas turbine film cooling design.