Fundamental study on the innovative film cooling technologies to suppress the mixing process with adding swirling motion to the coolant

本文研究了一种新的气膜冷却方法，即通过圆形和定形气膜冷却孔的旋流冷却。用瞬时和同时的LIF和PIV方法测量了气膜冷却空气和主流的混合现象，用PSP测量了壁面气膜冷却效率。结果表明，在圆形气膜冷却孔的情况下，冷却剂的强烈旋转运动抑制了冷却剂射流对主流的穿透，使气膜冷却效率提高了100%。因此，壁面上的气膜冷却效率在较长的距离内保持在冷却孔后面较高的值。此外，肾脏涡旋结构消失。对于成形的气膜冷却孔，冷却剂射流在跨度方向上扩展较大。因此，下游的螺距平均气膜冷却效率比非旋流情况下高50%。

This study has been conducted to investigate a new film cooling method that utilizes swirling coolant flow through circular and shaped film cooling holes. The mixing phenomena with a film cooling air and a mainstream was measured by a instantaneous and simultaneous LIF and PIV methods, and the film cooling effectiveness on the wall was measured by PSP.It appeared from the results that, in the case of a circular film-cooling hole, the penetration of the coolant jet into the mainstream was suppressed by the strong swirling motion of the coolant and attained 100% heigher film cooling effectiveness. As a result, the film cooling effectiveness on the wall maintained a higher value behind the cooling hole over a long range. Additionally, the kidney vortex structure disappeared. For the shaped film cooling hole, the coolant jet spreads wider in the span-wise direction. Thus, the pitch-averaged film cooling effectiveness downstream was 50% higher than that in the non-swirling case.