Effect of High Free Stream Turbulence on Film Cooling Using Double Row of 30 Deg.Slant-Hole Injectors

摘要

In this study free stream turbulence levels from 7.3% to 17.8% are applied tofilm cooling over a flat plate with two rows of 30 deg slant holes using a wall jet as the main stream air supply and source of turbulence. Blowing ratios are varied from 0.25 to 2.0 and free stream velocities at injection range from 10 m/s to 85 m/s. A constant density ratio of 1.07 is kept throughout the experiment. Results show that for different magnitudes of blowing ratio free stream turbulence has a different influence on effectiveness. At the forward stations, where blow off was present at high blowing ratios, high free stream turbulence increased effectiveness. While at mid to aft stations for all blowing ratios high free stream turbulence decreased effectiveness. A correlation for effectiveness with a non-dimensional group of film cooling parameters is offered. The effectiveness correlated best 10 to 15 diameters after injection where blow off effects are no longer present, and before the very far downstream stations where uncertainties in the measurements were greater.