Abstract
An experimental study on the effect of surface roughness inside a fan-shaped film cooling hole on the film cooling performance was conducted. The inside roughness was modeled using a groove pattern and the test plate with film cooling hole was manufactured by an additive manufacturing technique. The film cooling effectiveness was measured using the pressure sensitive paint technique. Considered hole was a fan-shaped film cooling hole with the diameter of 4.5 mm, the forward expansion angle of 3.54 degrees, the lateral expansion angle of 12.64 degrees, and the injection angle of 30 degrees. The density r atio w as 1 .5 and t he b lowing r atio w as r anged from 0.5 to 2.0. T ests were conducted in a l ow s peed w ind tunnel, and the mainstream speed was 20 m/s and the turbulence intensity was measured to be 4 %. The experimental results showed that the best film cooling effectiveness was achieved when the groove pattern was not applied inside the film cooling hole. If the blowing ratio was 1.0 or higher, the closely distributed groove cases showed higher film cooling effectiveness near the hole exit. When the blowing ratio was 1.5 or less, the sparsely distributed grooves resulted in higher film cooling effectiveness in the downstream region.
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