Enhancement of Film Cooling Performance Using a Shaped Film Cooling Hole with Compound Angle Injection

The present study is conducted to investigate the local heat/mass transfer characteristics and local film cooling effectiveness around a conical-shaped film cooling hole with compound angle orientations. The cylindrical hole and two types of shaped hole with conically-enlarged hole exits are used to investigate the effect of film cooling hole geometry. One shaped hole (shaped hole #1) expands 4° in all directions from the middle of hole to the exit. The other shaped hole (shaped hole #2) has the tilted center-line by 4° between the conical and metering holes and is enlarged by 8° to downstream side. The hole area ratios of the exit to the inlet are 2.55 and 2.48, respectively. The film cooling jet is ejected through the single hole, which is inclined at 30° to the surface based on the metering hole. The lateral injection angle is changed from 0° to 90°, and the blowing rates from 0.5 to 2.0. The naphthalene sublimation technique is used to obtain local heat/mass transfer coefficients and adiabatic/impermeable wall film cooling effectiveness around the film cooling hole. For the shaped holes, the penetration of jet is reduced, and higher and more uniform cooling performance is obtained even at relatively high blowing rates because the conically expanded hole exit reduces momentum of the coolant and promotes the lateral spreading. The better cooling performance is obtained with shaped hole #1 due to the uniform diffusion of coolant in the film cooling hole.