This paper describes the experimental investigations of film cooling effectiveness on a highly loaded low-pressure turbine blade under steady and periodic unsteady wake induced flow condition. The cascade facility in Turbomachinery Performance and Flow Research Lab (TPFL) at Texas A&M University was used to simulate the periodic unsteady flow condition inside gas turbine engines. Moving wakes that are originated from upstream stator blades are simulated inside the cascade facility by moving rods in front of the blades. The flow coefficient is maintained at 0.8 and the incoming wakes have a reduced frequency of 3.18. There are a total of 617 holes on the blade, which are distributed along 13 different rows. 6 rows cover the suction side, 6 other rows cover the pressure side and one last row feeds the leading edge. Each row has a twin row on the other side of the blade with exact same number of holes and arrangement (except for leading edge). They both are connected to the same cavity. Coolant is injected from either sides of the blade through the 6 cavities to form a uniform distribution along the span of the blade. In order to study the film cooling effectiveness under periodic unsteady flow condition, the blade surfaces were covered with Pressure Sensitive Paint (PSP) and were excited with green light. Experiments were performed for Reynolds number of 150,000 and approximate blowing ratio of coolant was maintained at one, based on equal mass flux distribution, for all rows throughout the experiments. Experimental investigations were performed to determine the effect of flow separation, and pressure gradient on film-cooling effectiveness in the absence of wakes. Moreover, the effect of impinging wakes on the overall film coverage of blade surfaces was studied.

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