HEAT TRANSFER COEFFICIENT AUGMENTATION FOR A SHAPED FILM COOLING HOLE AT A RANGE OF COMPOUND ANGLES

Shaped film cooling holes are used to efficiently deliver coolant to the surface of a gas turbine part to keep metal temperatures low. The ultimate goal of film cooling is to reduce le heat flux into a component, relative to a case with no coolant ejection. This reduction in heat flux is primarily achieved via a)lower driving temperature at the wall for convection, represented by the adiabatic effectiveness. Another important consideration, however, is how the disturbance to the flowfield and thermal field caused by the injection of coolant augments the heat transfer coefficient. The present study examines the spatially-resolved heat transfer coefficient augmentation for a shaped film cooling hole at a range of compound angles, using a constant heat flux foil and IR thermography. Results show that the heat transfer coefficient increases with compound angle and with flowing ratio. Due to the unique asymmetric flowfield of a compound angle hole, a significant amount of augmentation occurs to the side of the film cooling jet, where very little coolant present. This causes local regions of increased heat flux, which is counter to the goal of film cooling. Heat transfer results re compared with adiabatic effectiveness and flowfield measurements from a previous study.