Film cooling in the presence of mainstream pressure gradients

Abstract

Film-cooling in the presence of mainstream pressure gradients typical of gas turbines has been studied experimentally on a flat plate This paper describes, measurements of the spanwise averaged effectiveness and heat transfer coefficient for an inclined slot and a single row of holes in the presence of favourable, zero and adverse pressure gradients. Acceleration parameters of K = 2.62 ×10 -6 and - 0.22 ×10 -6 were achieved at the point of injection where the freestream unit Reynolds number was held constant at Re/m = 2.7 ×107. The flow was accelerated to high Mach number and results are analysed using a superposition model of film-cooling which included the effects of viscous energy dissipation. The experimental results show the effects of pressure gradient differ between the geometries and a discussion of these results is included. The unblown turbulent boundary layer with pressure gradient were also studied. Experiments were performed using the Isentropic Light Piston Tunnel, a transient facility which enables conditions representative of those in the engine to be attained.