Row-of-Holes Film Cooling of Curved Walls at Low Injection Angles

Abstract

Film cooling effectiveness data are presented against a backdrop of ammonia-diazo flow visualizations for row-of-holes injection along a convex wall and a concave wall at angles of 15, 25, and 45 deg to the mainstream and at density ratios of approximately one and two. Injection angle effects vary with the rate of injection: At low blowing rates the injection angle is unimportant, at moderate blowing rates the shallower angles provide better effectiveness, and at high blowing rates a steeper injection angle sometimes provides better effectiveness. The condition of the local boundary layer, the severity of jet lift-off, and the strength of vortex interactions among the bound vortices of neighboring jets are key considerations in interpreting the data.