Flat Surface Film Cooling from Cylindrical Holes with Discrete Tabs

摘要

The effect of discrete delta-shaped tabs on film cooling performance from a row of cylindrical angled holes is investigated. The holes are inclined at 35 deg along the stream wise direction. Four tab locations are investigated: 1) tabs placed along the upstream edge of the hole covering 33% of the hole, 2) tabs placed along the upstream edge covering 11% of the hole, 3) tabs placed along the downstream edge of the hole, and 4) tabs placed along the lateral edges of the hole. They are compared to the baseline case without tabs. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and freestream turbulence intensity in the low-speed wind tunnel are 8.5 m/s and 6%, respectively, and the Reynolds number based on hole diameter is 6375. Three blowing ratios of 0.56, 1.13, and 1.7 are tested. Results show that the tab placed upstream of the hole covering 33% of the hole exit provides the highest film effectiveness compared to other tab locations studied. This is because the jet liftoff in the presence of the upstream tabs is reduced and there is greater lateral spreading of the jet.