Experimental investigation on film cooling performance of pressure side in annular cascades

Experimental investigations were conducted to study the film cooling performance in a low speed annular cascades using Thermochromic Liquid Crystal (TLC) technique. The test blade was placed in the second stage, where 18 blades were installed with chord length of 124.3 mm and height of 99 mm. A film hole with diameter of 4 mm, angled 28° to the tangential of the pressure surface in streamwise, was set in the middle span of the blade. The Reynolds number based on the outlet mainstream velocity and the blade chord length of the second stage varied from 1.52×10⁵ to 2.00×10⁵. All measurements were made with the blowing ratio varying from 0.3 to 3.0. Air and CO₂ worked as coolant to achieve the coolant-to-mainstream density ratio of 1.03 and 1.57. The results show that the film coverage and cooling effectiveness scale up with the blowing ratio. Higher density ratio can generate larger film cooling coverage and effectiveness. The higher the Reynolds number, the larger the film coverage and cooling effectiveness.