旋转对气膜冷却覆盖区域的影响

Rotation effects on the film covering area

气膜冷却是应用于航空发动机上的冷却技术,旋转是影响气膜与主流掺混区域的重要因素.在旋转气膜外换热实验台上进行的平板气膜冷却实验对此问题进行了研究.与静止叶片相比,气膜出流在旋转叶片表面会发生展向偏离.在压力面,转速增加,气膜出流先向低旋转半径方向偏转,后向高旋转半径方向偏转;在吸力面,气膜出流向高旋转半径方向偏转.动量流量比固定,当密度比增加时,压力面气膜出流轨迹向低旋转半径方向偏转加剧;吸力面气膜出流轨迹向高旋转半径方向的偏转也增大.

Experimental research was conducted to investigate the rotation effect on the film covering area, which is important to comprehend the mixing process of the coolant flow and the hot gas over the high pressure turbine blades. A simple flat surface with a 30° inclined film hole was positioned parallel to the hot main stream and different rotation orientations were selected to simulate the blade pressure or sides. Liquid crystal was used to supply the temperature field information over the blade surface and the average adiabatic effective- ness of the area adjacent to the film hole was selected to measure the cooling effect. Rotating speed varied in 0, 300, 500, 800 and 1000 r/min. It was found that the film trajectory could bend under the rotation condition. With the increase of the rotating speed, on the pressure side the film trajectory inclines centripetally firstly and centrifugally at last. On the suction side, the film trajectory bends centrifugally. As the momentum flux ratio kept constant, the increase of the density ratio could lead the film trajectory to incline more centripetally on the pressure side. But on the suction side, the trajectory bends more centripetally.