LEADING EDGE FILM COOLING HEAT TRANSFER INCLUDING THE EFFECT OF MAINSTREAM TURBULENCE

Abstract

The effect of injection hole geometry on leading edge heat transfer coefficient and film cooling effectiveness under high mainstream turbulence condition was experimentally studied for flow across a blunt body with a semi-cylinder leading edge and a flat afterbody. The incident mainstream Reynolds number based on the leading edge diameter was 100 000. Tests were conducted for Tu = 0.75% and Tu = 9.67%. Both the spanwise and streamwise distributions of heat transfer coefficient and film effectiveness in the leading edge and flat sidewall regions were obtained for blowing ratios of B = 0.4, 0.8 and 1.2 through injection rows located at ±15° and ±40° for two injection geometries: (a) circular film holes spaced four hole diameters (4-d) apart (4.3 cm), and (b) spanwise film slots spaced three slot lengths (3-ℓ) apart (4.2 cm). Both holes and slots were inclined at 30° and 90° to the surface in the spanwise and streamwise directions, respectively. The results show that the leading edge heat transfer coefficient increases and the film effectiveness decreases at the high mainstream turbulence level for both injection geometries studied, but this high mainstream turbulence effect is reduced at higher blowing ratios. The leading edge heat transfer with film cooling for the two rows of film slots is comparable with the two rows of film holes. The lowest leading edge heat transfer with film cooling occurs at an intermediate blowing ratio of B = 0.8.