旋转状态下曲率对气膜冷却影响的分析

Analysis of Curvature Effects on the Film Cooling Under the Rotation Frame

作为广泛应用于航空发动机涡轮叶片上的气膜冷却技术,其效果会受到叶片表面曲率、旋转、密度比等因素的影响。在通过理论分析着重研究了旋转状态下曲面上的气膜出流后,给出了评价曲面气膜出流受旋转速度影响的无量纲量局部旋转数。并且对各种影响因素进行了分析。在凸表面上,小局部旋转数会导致气膜趋于脱离壁面;大局部旋转数会使气膜趋于吸附壁面;对于凹表面,局部旋转数的影响正好相反。当局部旋转数很小时,动量流量比成为影响气膜出流脱离壁面与否的重要因素。文中并且给出了数值验证。

A theoretical analysis was carried out to comprehend the mechanism of the rotation and curvature effects on the film cooling which is important in understanding the mixing process between the film coolant and the hot stream air over the high pressure turbine blade. Under the rotation frame, the effects of curvature on film cooling effectiveness can be explained by determining whether the injected fluid moves closer or further from the wall surface. And the trend of the jet trajectory can be determined by considering the balance of the forces on the injected fluid. By the deduction, the local rotational number is used to estimate the effects of ro ration. It was found that a small local rotational number results in that the jet move away from the curved wall on the convex wall. For a large local rotational number, a high cooling effectiveness could be obtained. On the concave wall, the effects of local rotational number are the reverse of those on the convex wall. The momen turn flux ratio is the key factor affecting the film departure or attachment at a small local rotational number.