Effects of Film Hole Shape and Turbulence Intensity on the Thermal Field Downstream of Single Row Film Holes

Zheng Zhang, Hui-ren Zhu, Wei-jiang Xu, Cun-liang Liu, Zhuang Wu
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Abstract

A nylon mesh coated with broadband thermochromic liquid crystal was set in different planes perpendicular to the mainstream direction at various locations downstream of the film hole. By the temperature visualization technique, the colorful non-dimensional temperature images on the nylon mesh of cylindrical hole, water-drop hole and dustpan shaped hole at different blowing ratios and turbulence at angle of 30° and 60° were visualized. The visualization experiment visually studied the effects of hole shape, hole inclination angle, blowing ratio and mainstream turbulence on the distribution of the film. The results show that stream-wise diffusion of water-drop hole reduces kidney vortex intensity, making higher attachment of the film of water-drop than that of cylindrical hole, consequently the lateral coverage range of water-drop hole film is wider than that of cylindrical hole film. The lateral diffusion of dustpan shaped hole further reduces the kidney vortex intensity. This obviously increases the film coverage and strengthens the adhesion of film of dustpan shaped hole. Increasing the inclination angle of the hole and the blowing ratio will increase the normal velocity of the jet and increase the thickness of the film. however, increasing inclination angle and blowing ratio will enhance kidney vortex intensity and decrease the film cooling effectiveness. The high turbulent intensity of mainstream will enhance the lateral diffusion of the film and enhance the mixing of the secondary flow and mainstream, so the continuity and uniformity of film are better. However, the intense mix of secondary flow and mainstream results in the non-dimensional temperature of the film drops sharply and the film coverage reduced accordingly.
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膜孔形状和湍流强度对单排膜孔下游热场的影响
在膜孔下游的不同位置,在垂直于主流方向的不同平面上设置了涂覆宽带热致变色液晶的尼龙网。采用温度可视化技术,在不同吹气比和湍流角度为30°和60°的情况下,在圆柱孔、水滴孔和簸箕形孔的尼龙网上显示了彩色无因次温度图像。可视化实验直观地研究了孔形、孔倾角、吹气比和主流湍流度对膜分布的影响。结果表明:水滴孔的流向扩散降低了肾涡强度,使水滴孔膜的附着程度高于柱孔膜,因此水滴孔膜的横向覆盖范围比柱孔膜大;箕状孔的横向扩散进一步降低了肾涡强度。这明显增加了膜的覆盖率,增强了簸箕形孔膜的附着力。增大孔倾角和吹气比会增大射流的法向速度,增大膜的厚度。增大倾角和吹气比会增大肾涡强度,降低气膜冷却效果。主流的高湍流强度会增强膜的横向扩散,增强二次流与主流的混合,因此膜的连续性和均匀性较好。然而,二次流与主流的强烈混合导致膜的无因次温度急剧下降,膜的覆盖率相应减小。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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