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This paper presents experimental investigations of the effects of the presence of an internal 90o bend and the design of the scheme exit on the film cooling performance of the louver scheme over a flat plate using the transient Thermochromic Liquid Chrystal (TLC) technique. The Louver scheme is a shaped scheme with an internal 90o bend, circular hole followed by a horizontal slot, which adds the impingement cooling benefits to the enhanced film cooling performance of shaped schemes. The louver film cooling scheme was manufactured in the present study with two different exit designs. The first is characterized with straight interfaces between the scheme and the test surface and the second has curved interface lines. Meanwhile, a third scheme was manufactured with the same exit shaped of the louver with curved interface lines, but without the internal 90o bend. The film cooling performance of the proposed designs was investigated at three different blowing ratios, 0.5, 1.0 and 1.5, a density ratio of 0.93, a Reynolds Number of 1.24E+5, based on the free stream velocity and the main duct hydraulic diameter, and a turbulence intensity of 8.5. The blowing ratio is calculated based on the base diameter of the louver scheme and the same coolant amount is supplied to all cases. The investigations showed that the scheme exit design has a significant effect on the resulting effectiveness as it affects the interaction nature between the main and the secondary streams. This was clear during the investigations through the enhanced effectiveness performance downstream the louver scheme with curved exit design, compared to the louver with straight exit. Also, adding a 90o internal bend to the shaped scheme design for impingement cooling purposes does not have a contribution on the scheme film cooling performance. Changing the film cooling scheme design did not affect the resulting heat transfer coefficient distribution significantly. This was attributed to the small change in the supplied coolant mass due to using the scheme base diameter for blowing ratio calculations.

Experimental Investigation of the Effect of Louver Scheme Internal Bend and Exit Shape on the Film Cooling Performance over a Flat Plate