Effects of orientation angles on film cooling over a flat plate: Boundary layer temperature distributions and adiabatic film cooling effectiveness

Presented are experimental results describing the effects of orientation angle of film cooling holes on boundary layer temperature distributions and film cooling effectiveness. Film flow data were obtained from a row of five film cooling holes on a flat rest plate. The inclination angle of the hole was fixed at 35 deg and four orientation angles of 0, 30, 60, and 90 deg were investigated, The velocity ratios surveyed were 0.5, 1.0, and 2.0. The boundary layer temperature distributions were measured at three downstream locations using 1 mu m platinum wire. Detailed adiabatic film cooling effectiveness distributions were measured using thermochromic liquid crystal. Results show that the increased lateral momentum in the case of large orientation angle injection strongly affects boundary layer temperature distributions. Temperature distribution characteristics are, in general, explained in the context of the interactions between injectant and free-stream fluid and between injectants issuing from adjacent holes. The adiabatic film cooling effectiveness distributions are discussed in connection with the boundary layer temperature distributions. Spanwise-averaged effectiveness distributions and space-averaged effectiveness distributions are also presented with respect to the velocity ratios and the orientation angles.