Influence of Geometrical Parameters and Reynolds Number on Flat Plate Film Cooling Effectiveness

In the present paper the influence of dimensional tolerances, imposed by the manufacturing process, and of coolant Reynolds number on flat plate film cooling through shaped holes is experimentally investigated. In this study different modifications to the diffusing section of a standard fan-shaped hole geometry have been experimentally examined in a flat plate simplified model over varied injection condition. Geometrical parameters of injection holes, such as the length of the cylindrical section, hole injection angle and diffuser angles, were varied and tested under variable coolant to mainstream blowing ratio M (1.0, 1.5 and 2.0) and coolant Reynolds number in the range from around 1000 up to about 20000. The dual-luminophore Pressure Sensitive Paint (PSP) technique was used for measuring the adiabatic film cooling effectiveness distribution. Carbone dioxide was used as coolant to always simulate a density ratio DR of 1.5. Local adiabatic film cooling effectiveness maps as well as laterally and area averaged adiabatic film cooling effectiveness values are presented and discussed in order to highlight the impact of the considered geometrical features over the tested operating conditions. Discharge coefficient results for the same testing conditions are also presented and discussed, allowing to fully characterize and compare the tested geometries.