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

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 inclination angles 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 expansion of water-drop hole reduces kidney vortex intensity, making the attachment characteristic of the film of water-drop hole is better than that of cylindrical hole, and then the lateral coverage range of water-drop hole film is wider than that of cylindrical hole film. The lateral expansion of dustpan shaped hole further reduces the kidney vortex intensity. This significantly increases the film coverage and strengthens the attachment characteristic 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 more intense mix of secondary flow and mainstream results in the non-dimensional temperature of the film drops sharply and the film coverage reduced.