Time-resolved film-cooling flows at high and low density ratios

Film-cooling is one of the most prevalent cooling technologies that is used for gas turbine airfoil surfaces. Numerous studies have been conducted to give the cooling effectiveness over ranges of velocity, density, mass flux, and momentum flux ratios. Few studies have reported flowfield measurements with even fewer of those providing time-resolved flowfields. This paper provides time-averaged and time-resolved particle image velocimetry data for a film-cooling flow at low and high density ratios. A generic film-cooling hole geometry with wide lateral spacing was used for this study, which was a 30° inclined round hole injecting along a flat plate with lateral spacing P/D = 6.7. The jet Reynolds number for flowfield testing varied from 2500 to 7000. The data indicate differences in the flowfield and turbulence characteristics for the same momentum flux ratios at the two density ratios. The time-resolved data indicate Kelvin-Helmholtz breakdown in the jet-to-freestream shear layer.