Experimental Evaluation of Large Spacing Compound Angle Full-Coverage Film Cooling Arrays: Adiabatic Film Cooling Effectiveness

Adiabatic film cooling effectiveness contours are obtained experimentally with the use of temperature sensitive paint (TSP) on low thermal conductivity film cooled surfaces. The effects of blowing ratio, surface angle, and hole spacing are observed by testing four full-coverage arrays composed of cylindrical staggered holes all compounded at 45 deg, which parametrically vary the inclination angles, 30 deg and 45 deg, and the spacing of the holes 14.5 and 19.8 times the diameter. Local film cooling effectiveness is obtained throughout these largely spaced arrays to 23 rows for the 19.8 diameter spacing array and 30 rows for the 14.5 diameter spacing array. The coolant takes several rows to merge and begin to interact with lateral holes at these large spacings; however, at downstream rows the film merges laterally and provides high effectiveness in the gaps between injections. At low blowing, each individual jet remains discrete throughout the array. At higher blowing rates, the profile is far more uniform due to jets spreading as they reattach with the wall. Laterally averaged values of effectiveness approach 0.3 in most cases with some high blowing low spacing, even reaching 0.5.