Influence of High Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer

Abstract

The influence of high mainstream turbulence on leading edge film effectiveness and heat transfer coefficient was studied. High mainstream turbulence was produced by a passive grid and a jet grid. Experiments were performed using a blunt body with a semi-cylinder leading edge with a flat afterbody. The mainstream Reynolds number based on leading edge diameter was about 100,000. Spanwise and streamwise distributions of film effectiveness and heat transfer in the leading edge and on the flat sidewall were obtained for three blowing ratios, through rows of holes located at ±15° and ±40° from stagnation. The holes in each row were spaced three hole-diameters apart and were angled 30° and 90° to the surface in the spanwise and streamwise directions respectively. The results indicate that the film effectiveness decreases with increasing blowing ratio, but the reverse is true for the heat transfer coefficient. The leading edge film effectiveness for low blowing ratio (B = 0.4) is significantly reduced by high mainstream turbulence (Tu = 9.67% and 12.9%). The mainstream turbulence effect is diminished in the leading edge for higher blowing ratios (B = 0.8 and 1.2) but still exists on the flat sidewall region. Also, the leading edge heat transfer coefficient for blowing ratio of 0.8 increases with increasing mainstream turbulence; but the effect for other blowing ratios (B = 0.4 and 1.2) is not so systematic as for B = 0.8. Surface heat load is significantly reduced with leading edge film cooling.

Experimental investigations on showerhead cooling on a blunt body

“…Following this work, Ou et al [9] experimentally determined the effect of the film hole row location on the leading edge film cooling under high mainstream turbulence conditions (Tu = 9.67%). Two locations of film injection cooling holes, located only at ±15°or ±40°, were studied and compared to the four-row configuration reported by Mehendale and Han [8]. The results showed that the mainstream turbulence effect was more severe for the ±15°one-row injection than for the ±40°one-row injection.…”

“…Tests were performed using a blunt body with a cylindrical leading edge and a flat afterbody. Adopting the same leading edge model, Mehendale and Han [8] studied the effects of the blowing ratio (from G = 0.4 to 1.2) and the free-stream turbulence intensity (Tu = 0.75%, 9.67%, 12.9%) downstream of two staggered rows of holes located at ±15°and ±40°from the stagnation line. Following this work, Ou et al [9] experimentally determined the effect of the film hole row location on the leading edge film cooling under high mainstream turbulence conditions (Tu = 9.67%).…”

CFD Predictions of Heat Transfer Coefficient Augmentation on a Simulated Film Cooled Turbine Blade Leading Edge

“…Downstream of the cooling jets, the spanwise average of mass transfer was found to be increased by a factor of two over that without film cooling at a blowing ratio of M = 2, and the size of the elevated mass transfer region was observed to increase with the blowing ratio. Mehendale and Han (1992) On the stagnation line, the heat transfer coefficient was found to be increased by 80% for a blowing ratio M = 1.9. Downstream of the off-stagnation holes, the heat transfer coefficient was more than doubled.…”

Effects of High Intensity, Large-Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades

“…Oldfield (1992, 1996) and the previous work by Holmberg (1996) and Holmberg and Pestian (1996) are the exceptions. Giel, et al (2000) Low speed 0.11 18% Barringer, et al (2002) Low speed 0.43 18% Wang, et al (1998) Low speed -20% Thole, et al (1994) Low speed 0.11 13% Low speed -10% Boyle, et al (1998) Low speed -17% Schauer and Pestian (1996) Low speed -20% Radomsky and Thole (2000) Transonic <0.1 5% Holmberg (1996) Low speed -13% Mehendale and Han (1992) …”