TPIV Experimental Investigation of Film Coolant-to-Mainstream Interaction From Shaped Cooling Holes With Various Inlet Geometries
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AbstractIn this investigation, multiple sets of time-averaged Tomographic Particle Image Velocimetry (TPIV) measurements are completed for laid-back, fan-shaped film cooling holes with racetrack shaped inlets. Traditional 10-10-10, laid-back, fan-shaped holes are inclined 30 to the mainstream flow on a flat plate. The inlet cross-section varies from round (1:1) to horizontally elongated in a racetrack shape (2:1 and 4:1). The cross-sectional area and the outlet-to-inlet area ratio for all the geometries are held constant. The flat plate is installed in a low-speed wind tunnel with a mainstream turbulence intensity of Tu = 8% and an average velocity of 21.6m/s. The blowing ratios of the film jets range from M = 0.6 to M = 1.5 and the density ratio of the jet is DR = 1. The Reynolds Number of the cooling jet varies from 2600 to 8400. The results of the TPIV measurements are presented in velocity and vorticity iso-surface distributions volumetrically, as well as planar slices of velocity, vorticity, and Reynolds Stress distributions within the measurement volume. The characteristics of the flowfield are coupled with the detailed film cooling effectiveness distributions obtained from the pressure sensitive paint (PSP) technique. It can be noted from the results that the counter-rotating vortex pair (CRVP) generated by the 2:1 inlet is the closest to the surface and weakest in strength, likely caused by the minimum peak jet momentum of the three. The Reynolds stresses downstream of the 2:1 and 4:1 inlets are significantly lower than that downstream of the shaped hole with a round inlet. An inverse relation between volumetric turbulence accumulation, TA, and surface effectiveness, , can be correlated for the blowing ratios considered. The turbulence accumulation term can thus be used to evaluate the performance of a film cooling hole design with flowfield data.
