Experimental Investigation of Effusion Film Cooling on a Cylindrical Leading Edge Model

Abstract

Effusion film cooling is effective for cooling high-temperature turbine blades because it requires less coolant and produces a more uniform temperature distribution than conventional film cooling. Effusion cooling for a cylindrical model representing the leading edge of a gas turbine blade was investigated. The experiment was performed in a low-speed wind tunnel at a Reynolds number of 100,000. Pressure-sensitive paint was used to measure the adiabatic film cooling effectiveness. Additive manufacturing was used to fabricate a porous structure on the test cylinder for effusion cooling. Both simple and compound angles were used for cooling injection. The effects of streamwise and spanwise hole spacings, turbulence intensities (1% and 8.7%), and blowing ratios (0.075, 0.15, 0.3, and 0.6) were studied at a fixed density ratio of 1. The effusion hole diameter was 0.1 cm, and the spanwise hole pitch-to-diameter ratio was either 2 or 4. Compared with conventional film cooing, effusion cooling achieved a higher cooling effectiveness and produced a better coolant coverage. Increasing the streamwise spacing noticeably reduced the cooling effectiveness for the simple-angle design due to film lift-off; the compound-angle designs thus achieved higher effectiveness. The simple-angle holes were more sensitive to changes in the mainstream turbulence intensity; increases in the turbulence intensity promoted the mixing of the coolant with the mainstream. Moreover, effusion cooling was more resistant to coolant lift-off at high blowing ratios.