A Near-Field Investigation Into the Effects of Geometry and Compound Angle on the Flowfield of a Row of Film Cooling Holes

Abstract

The goal of this study was to determine the effects that hole geometry and compound angle have on the near-field downstream from a row of jets injected into a crossflow. Velocity and vorticity fields are presented in cross-sectional planes oriented perpendicular to the mainstream flow. Instantaneous field measurements were obtained using particle image velocimetry (PIV). Data were recorded at locations of 0, 1, 2, and 3.5 hole diameters downstream of injection for three different hole geometries inclined at 35° to the mainstream flow. These geometries consisted of a cylindrical hole, a 12° laterally-diffused hole, and a 15° forward-expanded hole with compound angles of 0°, 45°, 60°, and 90. Data are presented for a blowing ratio of 1.25 and density ratio of 1. The influences on jet penetration, coverage width, flow structure elevation, and flow structure separation for each configuration are discussed. Vorticity is presented in terms of field distribution and peak magnitudes. These studies show the degradation of the counter-rotating vortex pair into a singular, recirculating structure as the compound angle increases. Peak levels of vorticity are not encountered until between one and two diameters downstream of injection.