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 on low thermal conductivity full coverage 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°, which parametrically vary the inclination angle, 30° and 45°, and the spacing of the holes, 14.5 and 19.8 diameters. Local film cooling effectiveness is obtained throughout these largely spaced arrays over up to 23 rows for the 19.8 spacing array and 30 rows for the 14.5 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 builds and provides high effectiveness in the gaps between injection. At low blowing, each individual jet throughout the entire array can be seen in the effectiveness profiles. At higher blowing rates, the profile is far more uniform due to jets spreading as they reattach with the cooled wall. Laterally averaged values of effectiveness easily approach 0.3 in most cases with some, high blowing low spacing, even reaching 0.5.