Suction side roughness effects on film cooling heat transfer on a turbine vane

An experimental study was conducted in a simulated three vane linear cascade to determine the effects of surface roughness and film cooling on the heat transfer coefficient distribution in the region downstream of the first row of suction side coolant holes. Suction side film cooling was operated in the range 0 = M = 1.4. The showerhead was tested at Msh = 1.6. In addition to the completely smooth condition, simulated airfoil roughness was used upstream of the coolant holes, downstream of the coolant holes, and both upstream and downstream of the coolant holes. Two levels of mainstream turbulence intensity were tested. The heat transfer measurements were conducted by application of a uniform heat flux in the region downstream of the coolant holes. The resulting surface temperature distributions were measured with infrared thermography. Because the upstream region was unheated, the influence of film cooling on the heat transfer coefficient was due to only to hydrodynamic effects and not thermal effects. The coolant to mainstream density ratio of the majority of the experiments was unity; however, a single experiment was conducted at a density ratio of DR = 1.6 to determine how the coolant to mainstream density ratio affects heat transfer. Net heat flux reduction calculations were performed by combining the heat transfer coefficient measurements of the present study with adiabatic effectiveness measurements of a separate study. In order to gain insight into the hydrodynamics that affect the heat transfer, boundary layer measurements were conducted using hot-wire anemometry