Effect of Blockage Inside Holes on Film Cooling Performance on the Suction Side of a Turbine Guide Vane

Abstract

In order to study the effect of thermal barrier coating deposition inside the film holes of turbine guide vanes on film cooling performance, film effectiveness on the suction side is measured by infrared thermal imaging technology. Film effectiveness is obtained at blockage ratios of 0, 0.2, 0.5, and 0.8, and blowing ratios of 0.7, 1.05, and 1.4. Film effectiveness decreases and the spanwise inhomogeneity becomes evident with an increase of the blockage ratio. When blowing ratios increase from 0.7 to 1.4, the surface averaged film effectiveness decreases by 55–60% at a large blockage ratio of 0.8, 21–27% at the middle blockage ratio of 0.5 and by no more than 11% at a small blockage ratio of 0.2. The rounded corners formed by blockage enhance the adhesion of the film at the small blockage ratio of 0.2, thereby improving the film cooling performance near the hole exit. There is a maximum increase of 0.2 in film effectiveness within four hole diameters.

Keywords

• film effectiveness
• thermal barrier coating
• blockage ratio
• blowing ratio
• infrared measurement