平板气膜冷却孔下游湍流场的试验研究

Experimental Study of the Turbulent Flow Downstream of Film Cooling Holes on a Flat Plate

利用二维粒子图像测速(PIV)技术,在吹风比为0.5和1.0、雷诺数为480时,对平板直冷却孔和弯曲冷却孔下游湍流场的流动结构进行了测量,得到了中心截面及射流下游4个流向横截面上的平均速度、涡量分布以及烟雾显示照片,并分析了弯曲冷却孔通道对下游涡结构沿流向演化过程的影响.结果表明:冷却孔射流具有较低的射流轨迹,可以增强气膜的贴附效果,有利于提高冷却效率;弯曲冷却孔能为气膜提供较强的横向动量,使其具有较高的横向扩展能力,从而改善气膜的侧向覆盖效果.

Turbulent flow structures downstream of the straight and curved cooling hole were measured by means of 2D PIV （Particle Image Velocimetry） at blowing ratios of 0.5 and 1, with a Reynolds number of 480, during which the mean velocity, vorticity fields and smoke visualizations were obtained on the central symmetry plane and four cross sections, while the influence of hole structure on development of downstream vorticity field analyzed along the flowing direction. Results show that compared with straight holes, the curved hole produces a lower jet trajectory, which helps to raise the adhesion force of cooling film to wall surface, and therefore improve the cooling efficiency; simultaneously, the curved hole provides stronger transverse momentum, which makes the curved jet transversely expand more and finally improves the transverse coverage of cooling film.