Leading Edge Film Cooling Heat Transfer Through One Row of Inclined Film Slots and Holes Including Mainstream Turbulence Effects

Abstract

The effects of film opening shape and mainstream turbulence on the leading edge heat transfer coefficient and film effectiveness were experimentally investigated. The experiments were performed using test models with a semi-cylindrical leading edge and a flat afterbody. A bar grid (Tu = 5.07 percent) and a passive grid (Tu = 9.67 percent) produced two levels of mainstream turbulence. Two separate cases of one-row injection through film slots or holes located only at ±15 deg or only at ±40 deg from the stagnation line were studied for three blowing ratios of 0.4, 0.8, and 1.2 at the Reynolds number (ReD) of 100,000. The slots in each row were spaced three cross-sectional slot lengths (P = 3l) apart, while the holes were spaced four holes diameters (P = 4d) apart. Both geometries had equal cross-sectional area and pitch. The results show that the leading edge heat transfer coefficient increases and the film effectiveness decreases with increasing blowing ratio; however, B = 0.8 provides the highest film effectiveness for the film hole with ±40 deg injection. The heat transfer coefficient increases and the film effectiveness decreases with increasing mainstream turbulence level. However, the mainstream turbulence effect on the film effectiveness is reduced as the blowing ratio is increased. Slot geometry provides better film cooling performance than the hole geometry for all test cases at the lowest blowing ratio of 0.4. However, at higher blowing ratios of 0.8 and 1.2, the reverse is true for ±40 deg injection at mainstream turbulence of 0.75 and 9.67 percent.