Experimental Evaluation of Large Spacing Compound Angle Full Coverage Film Cooling Arrays: Heat Transfer Augmentation

Heat transfer augmentation values are obtained experimentally with the use of temperature sensitive paint on constant flux heaters attached to full coverage film cooled surfaces as a function of blowing ratio. The effects of blowing ratio, surface angle and hole spacing are observed by testing four full coverage arrays of round 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 heat transfer augmentation is obtained throughout these largely spaced arrays over 20 rows for the 19.8 spacing array and 30 rows for the 14.5 spacing array. The first five to six rows show low heat transfer enhancement between holes with peaks in augmentation occurring directly downstream of the hole. Heat transfer enhancement is seen to be close to unity at the leading edge of the arrays. Laterally averaged values of heat transfer augmentation increase every row, leveling out to values between 20 and 30% augmentation with peaks reaching the 40% mark.