FILM-COOLING FROM HOLES WITH COMPOUND ANGLE ORIENTATIONS .1. RESULTS DOWNSTREAM OF 2 STAGGERED ROWS OF HOLES WITH 3D SPANWISE SPACING

Experimental results are presented that describe the development and structure of flow downstream of two staggered rows of film-cooling holes with compound angle orientations. With this configuration, holes are spaced 3d apart in the spanwise direction, inclined at 35 deg with respect to the test surface when projected into the streamwise/normal plane, and inclined at 30 deg with respect to the test surface when projected into the spanwise/normal plane. Results are presented for an injectant to free-stream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.50. Comparisons are made with measurements from two other configurations to determine: (1) the effects of hole angle orientation for constant spanwise hole spacing, and (2) the effects of spanwise hole spacing when the hole angle orientation is maintained constant. Results from the first comparison show that the compound angle injection configuration provides significantly improved film-cooling protection compared to a simple angle configuration for the same spanwise hole spacing, normalized streamwise location x/d, and blowing ratio m, for x/d < 60. At x/d > 60, spanwise-averaged adiabatic effectiveness data downstream of the two configurations generally cover about the same range. Results from the second comparison show that spanwise-averaged effectiveness values are 25 to 40 percent higher when 3d span wise hole spacing is employed compared to 3.9d span wise hole spacing for the same m and x/d, for x/d < 40. At x/d > 40, differences between the two configurations range from 12 to 30 percent. Results from all configurations studied show that spanwise-averaged iso-energetic Stanton number ratios cover approximately the same range of values and show roughly the same trends, ranging between 1.0 and 1.25. In particular, St(f)/St(o) values increase with m at each x/d, and show little variation with x/d for each value of m tested.