FILM-COOLING FROM HOLES WITH COMPOUND ANGLE ORIENTATIONS .2. RESULTS DOWNSTREAM OF A SINGLE ROW OF HOLES WITH 6D SPANWISE SPACING

Experimental results are presented that describe the development and structure Of flow downstream of a single row of film-cooling holes with compound angle orientations. With this configuration, holes are spaced 6d 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 span wise/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 < 30 when m = 0.50 and for x/d < 60 when m = 1.0 and 1.5. 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 20 to 39 percent higher when 6d spanwise hole spacing is employed compared to 7.8d spanwise hole spacing for the same m and x/d, for x/d < 60. When plotted in etaBAR/m versus Xl/s coordinates, spanwise-averaged film effectiveness data measured downstream of one and two rows of holes from all injection configurations tested show a reasonable collapse. For m values between 1 and 3, spanwise-averaged iso-energetic Stanton number ratios measured just downstream of one row of holes are lower than results measured just downstream of two rows of holes, which evidences greater mixing and higher turbulence levels when the injectant emerges from two rows of holes.