Abstract
Film cooling is a key technology to improve the thermal performance of high-pressure turbines. The mixing of the cooling air and the main flow is inherently unsteady, but the unsteady flow physics of different cooling holes are seldom investigated. In the current study, the large-eddy simulation method is used to investigate inclined jets in crossflow via a cylindrical hole and a fan-shaped hole. The angle between the hole and the main flow is 35 deg, and the blowing ratio is 0.5, which are representative for film cooling. First, the results are analyzed in a traditional way using counter-rotational vortices based on the time-averaged results. Then, the instantaneous flowfield is presented. The mixing of the injected flow with the main flow is highly related to the unsteady coherent vortices. The results showed that the instantaneous flowfield can provide a better explanation of the distribution of film-cooling effectiveness than the time-averaged flowfield. The effects of instantaneous vortices on the temperature distribution for different cooling hole geometry are discussed in detail.
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