일정 분사비와 분사각도에서 슬록출구 형상에 따른 막냉각

Abstract

슬롯출구 상류면을 높이거나 낮추었을 때 슬롯출구 하류면의 막냉각 특성을 밝히기 위하여, 분사비를 1로 하고 분사각도를 30" 로 유지하였을 때 유동장과 온도장을 수치해석방법을 이용하여 조사하였다. 슬롯출구 상류면의 상승 및 하강폭은 0.8d(d는 슬롯폭)에서 2d 사이이다. 해석결과에 의하면, Id-상승면의 경우가 가장 막냉각 성능이 우수한 것으로 판명되었다. 이는 Id-상승면이 다른 경우에 비하여 슬롯출구 직후의 속도구배가 감소하여 난류운동에너지 생성이 최소화되며 따라서 냉각제의 혼합이 억제되어 하류 멀리까지 표면을 저온으로 유지하기 때문이다.

Film cooling characteristics has been investigated numerically with the aid of FLUENT software for the sunk or the lifted upstream wal1 from the slot injection exit. In this study, with the fixed blowing ratio of 1 and the fixed coolant injection angle of 30˚, the downstream flow field and the downstream temperature field were examined in terms of velocity vector, turbulent kinetic energy, temperature contours, and downstream wall temperature. Upstream wall was sunk or lifted from 0.8d to 2d(d ＝ slot width). The result shows that the up-ld upstream wall has the best film cooling performance. This is due to the fact that the up-ld upstream wall configuration reduces mean velocity gradient just enough to minimize the turbulent kinetic energy production which promotes mixing between the mainstream and the coolant just off the slot exit.

Film cooling characteristics has been investigated numerically with the aid of FLUENT software for the sunk or the lifted upstream wal1 from the slot injection exit. In this study, with the fixed blowing ratio of 1 and the fixed coolant injection angle of 30˚, the downstream flow field and the downstream temperature field were examined in terms of velocity vector, turbulent kinetic energy, temperature contours, and downstream wall temperature. Upstream wall was sunk or lifted from 0.8d to 2d(d ＝ slot width). The result shows that the up-ld upstream wall has the best film cooling performance. This is due to the fact that the up-ld upstream wall configuration reduces mean velocity gradient just enough to minimize the turbulent kinetic energy production which promotes mixing between the mainstream and the coolant just off the slot exit.