Vortex generating flow passage design for increased film-cooling effectiveness and surface coverage. [aircraft engine blade cooling]

The present study examines the fluid mechanics of the basic discrete hole film cooling process described herein as an inclined jet in crossflow and hypothesizes a cusp shaped coolant flow channel contour that increases the efficiency of the film cooling process. The design concept requires the channel to generate a counter rotating vortex pair secondary flow within the jet stream by virtue of flow passage geometry. The interaction of the vortex structures generated by both geometry and crossflow was examined in terms of film cooling effectiveness and surface coverage. Comparative data obtained with this new vortex generating coolant passage showed increases up to factors of four in both effectiveness and surface coverage over that obtained with a standard round cross section flow passage. A streakline flow visualization technique was used to support the concept of the counter rotating vortex pair generating capability of the flow passage design.