Large-scale experimental study of the turbulent flow over an effusion cooling plate

Used in gas turbines, effusion cooling of the blades is an efficient way to alleviate the thermal and shear strain they sustain while increasing the temperature in the chamber. A large-scale low-velocity experiment is carried out in the 3 x 1.5 x 20m3 test section of our closed-loop 10x5 wind-tunnel facility – Department of Aeronautics, Imperial College London. The scaled-up effusion device consists of a coolant-supplied settling chamber located directly underneath a perforated thick plate replacing a portion of the floor of the wind-tunnel. The effusion plate is pierced by a staggered grid of inclined D=16mm-diameter holes with a pitch of 5D. This set-up is placed in a turbulent boundary layer, tripped and developing over 15meters. Three cases: a) no effusion, null flow rate coming out of the chamber; b) effusion without cooling, atmospheric air is supplied to the chamber; c) effusion cooling is supplied by a carbon dioxide cylinder; are investigated to let us identify independently the effects of holes-induced roughness (a), jet-injected momentum (b), and negative heat flux (c) on the flow dynamics. Hot-wire measurements provide velocity profiles at various locations throughout the effusion plate.