Film Cooling of Cylindrical Hole With a Downstream Short Crescent Shaped Block

Abstract

This paper presents a method to improve the filmcooling effectiveness of cylindrical holes. A short crescentshaped block is placed at the downstream of a cylindrical cooling hole. The block shape is defined by a number of geometric parameters including block height, length and width, etc. The single row hole on a flat plate with inclination angle of 30 deg, pitch ratio of 3, and lengthdiameter ratio of 6.25 was chosen as the baseline test case. Filmcooling effectiveness for the cylindrical hole with or without the downstream short crescentshaped block was measured by using the pressure sensitive paint (PSP) technique. The density ratio of coolant (argon) to mainstream air is 1.38. The blowing ratios vary from 0.5 to 1.25. The results showed that the lateral averaged cooling effectiveness is increased remarkably when the downstream block is present. The downstream short block allows the main body of the coolant jet to pass over the block top and to form a new downwash vortex pair, which increases the coolant spread in the lateral direction. The effects of each geometrical parameter of the block on the filmcooling effectiveness were studied in detail.