Abstract

Film-cooling hole-geometry research needs a better understanding in the mechanism of film cooling effectiveness, which was recently shown to depend rather strongly on the counter-rotating vortex pair (CRVP); in this work, a mechanism of the film-cooling heat transfer is proposed. Its mainstream entrainment was aimed to be eliminated by developing a new scheme named comb scheme, which was intended to move CRVP away from mainstream-coolant interface, rather than suppressing CRVP itself. It is investigated experimentally and numerically in this work. The transient thermochromic liquid crystal technique was used in the experimental work, while the Reynolds-averaged Navier-Stokes equations coupled with a realizable κ-ε turbulence model was used to simulate the flow numerically. The results were assessed against open published results hence demonstrating the so called ‘ideal’ performance (film cooling effectiveness = 1) of the new scheme, but with practical structural integrity. The geometric parameter analysis showed that the visualized strong CRVP, where intensity is more than 20, is trapped in the blind slot, hence its impact on mainstream-coolant interface is dropped to approximately 3, and mainstream entrainment is eliminated. It confirms the success of the comb scheme in achieving the high performance of the film-cooling heat transfer mechanism.

摘要

薄膜冷却孔几何研究需要更好地了解薄膜冷却效果的机制，最近表明该机制相当强烈地依赖于反向旋转涡流对 (CRVP)；在这项工作中，提出了一种薄膜冷却传热的机制。它的主流夹带旨在通过开发一种名为梳子方案的新方案来消除，该方案旨在使 CRVP 远离主流冷却液界面，而不是抑制 CRVP 本身。在这项工作中对其进行了实验和数值研究。实验工作中使用了瞬态热致变色液晶技术，而雷诺平均 Navier-Stokes 方程与可实现的κ-ε湍流模型用于数值模拟流动。根据公开发表的结果对结果进行了评估，因此证明了新方案的所谓“理想”性能（薄膜冷却效率 = 1），但具有实际的结构完整性。几何参数分析表明，强度大于20的可视化强CRVP被困在盲槽中，因此其对主流-冷却液界面的影响降至3左右，主流夹带被消除。它证实了梳状方案在实现薄膜冷却传热机制的高性能方面的成功。