Full-Coverage Discrete Hole Film Cooling: Investigation of the Effect of Variable Density Ratio

Abstract

Experimental results of the overall and adiabatic cooling effectiveness for full-coverage discrete hole film cooling are presented for a range of practical geometries. The results are reported for various hot gas mainstream-to-coolant temperature (density) ratios, in the realistic range of 1.0–3.2. The variation of this ratio was achieved by increasing the crossflow mainstream temperature, over the range 300–930 K. For combustor wall film cooling applications, the overall cooling effectiveness increased significantly with the number of holes per unit wall surface area, over the range of 4306–26910 m−2 and with the hole size, in the range of 1.0–2.2 mm, due to the improvement in film cooling. The effect of varying the mainstream-to-coolant temperature ratio, in the present range of 1.0–3.2, on the film cooling performance was shown to be small and no consistent trends were established for various configurations, for the coolant mass flow rates per unit wall surface area, less than 0.4 kg/sm2. At a higher value of 0.89 kg/sm2, an increase in the temperature ratio improved the film cooling performance slightly.