Building Block Experiments in Discrete Hole Film Cooling

This paper reports a series of building block experiments for discrete hole film cooling. Seven different configurations, including variations in injection wall curvature, mainstream pressure gradient, and boundary layer thickness are measured for a round film cooling hole, inclined 30 degrees at injection, and operated at a blowing ratio of unity. Full three dimensional, three component velocity fields and scalar coolant concentration fields are acquired using Magnetic Resonance Imaging (MRI) techniques. The results show the effect of varying the mainstream condition on the mean coolant concentration distribution and mean velocity field, including the counter-rotating vortex pair (CVP), a dominant feature of jet in crossflow type flows. The present study focuses on an analysis of the building block configurations only possible with full three dimensional velocity and concentration fields. Several scalar parameters including normalized perimeter, jet trajectory, maximum coolant concentration, and coolant concentration spread are extracted from the collected data and compared across the different configurations. The results indicate that the pressure gradient variations have the strongest effect on the calculated quantities, the boundary layer slightly less, and the curvature very little.