An experimental investigation of effusion film cooling has been completed for cylindrical, simple angle holes (θ = 20°), using a steady state, pressure sensitive paint (PSP) technique. The surface effectiveness measurements were obtained in a low speed wind tunnel where the average blowing ratio (M) was varied from 0.5 to 6. For all cases, the coolant–to–mainstream density ratio was fixed at DR = 1.0. The test surface was manufactured using direct metal laser sintering (DMLS), and was made to replicate full coverage film cooling typically seen for combustor cooling applications. The plate contained 10 staggered rows of film cooling holes, with P/D = 9.8 and S/D = 8.5. At blowing ratios greater than M = 1.0, the downstream film cooling effectiveness is greatly improved by the protection provided from the high momentum jets in the upstream rows. Within the latter-half of the matrix, the effectiveness measured on the surface gradually increased with each passing row. The combination of the holes made a substantial impact downstream, and the effect continued to grow all the way through the end of the plate. With the accumulation of the coolant above the surface, the coolant liftoff was mitigated and enhanced protection was observed on the surface. The DMLS manufacturing technique created surface and hole interior roughness. The hole interior roughness reduced the lateral average film cooling effectiveness by at least 50% when compared to previous investigations.

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