Effect of backward injection with combined hole on film colling performance

Abstract

This study investigates the film cooling performance and flow features of backward injection with combined hole. This concept is evaluated by comparison to forward injection with combined hole and other forms with both injections, forward and backward. The shapes are namely, cylindrical hole, conical hole and fan-shaped hole. The eight configurations are computed for three blowing ratios M=0.5, 1.0 and 1.5. The air coolant was injected through holes inclined at 35° and 155° for forward and backward injection respectively. The lateral averaged film cooling effectiveness and the distribution of adiabatic film cooling efficiency are studied using commercial software ANSYS- CFX. In addition, several velocity vectors and contours are presented for analyzing the thermal behavior. The results show that a uniform coverage is obtained by the backward injection which leads to best cooling. The maximum improvement of film cooling is obtained by backward injection with combined hole at M=1.5.