FILM EFFECTIVENESS OVER A FLAT SURFACE WITH AIR AND CO2 INJECTION THROUGH COMPOUND ANGLE HOLES USING A TRANSIENT LIQUID-CRYSTAL IMAGE METHOD

This paper presents detailed film effectiveness distributions over a f lat surface with one row of injection holes inclined streamwise at 35 deg for three blowing ratios (M = 0.5, 1.0, 2.0). Three compound angle s of 0, 45, and 90 deg with air (D.R. = 0.98) and CO2 (D. R. = 1.46) a s coolants are tested at an elevated free-stream turbulence condition (Tu approximate to 8.5 percent). A transient liquid crystal technique is used to measure local heat transfer coefficients and film effective ness, Detailed film effectiveness results are presented near and aroun d film injection holes, Compound angle injection provides higher film effectiveness than simple angle injection for both coolants. Higher de nsity injectant produces higher effectiveness for simple injection. Ho wever, lower density coolant produces higher effectiveness for a large compound angle of 90 deg. The detailed film effectiveness obtained us ing the transient liquid crystal technique, particularly in the near-h ole region, provided a better understanding of the film cooling proces s in gas turbine components.