| The present experimental study deals with trailing edge film cooling of a turbine airfoil. The experimental test setup consists of a generic scaled-up model simulating the flow and heat transfer situation on the pressure side cutback surface of the trailing edge of an airfoil. Main focus of this study is the influence of hot gas acceleration on adiabatic film cooling effectiveness. The tests are performed at a temperature ratio between main flow and coolant of 1.6, i.e. the ratios of density, velocity, blowing, and momentum are met at the same time. An infrared measurement technique is employed to monitor the temperature on the cut back surface. Flow acceleration typical for the rear part of an airfoil’s pressure surface is established by inclining the wall opposite to the film-cooled surface. Two different internal turbulator designs are considered, a double in-line rib array and a staggered pin fin arrangement. Blowing ratio is varied within a range of 0.2 < M < 1.25. The results show that the effect of main flow acceleration strongly depends on the internal turbulator design. In case of an internal rib array film cooling effectiveness decreases at high blowing ratios only. With pin fins as turbulators, a significant impact can be seen at low blowing ratios also. The turbulence level within the cooling film plays an important role. |
