원형홀 내부 거칠기 분포가 막냉각 효율에 미치는 영향

Abstract

Film cooling had been widely applied to hot parts in gas turbines or propulsion systems in order to protect the components from the hot combustion gas. Conventional film cooling hole has cylindrical shape and the surface roughness of the hole depends on the manufacturing process. In this study, the effect of roughness distribution inside a cylindrical film cooling hole on the film cooling performance was experimentally studied. The test plate with film cooling holes was made by the additive manufacturing process, and the film cooling effectiveness was measured using the pressure sensitive paint technique. The diameter of the hole was 5 mm, the hole length to diameter ratio(L/D) was 6, and injection angle was 30 degrees. The density ratio was 1.5 and the blowing ratio varied from 0.5 to 2.0. The mainstream velocity and turbulence intensity were 20 m/s and 11%, respectively. Results showed that the hole roughness had effect on the film cooling effectiveness near the hole exit, but the effect was diminished toward the downstream region. Also, the effect of hole roughness was not significant for lower blowing ratio cases.