Numerical Investigation of a Laser-Drilled Cooling Hole

Modern aeroengines utilized effusion cooling technology to further protect the components from degrading at the operating temperatures. Most studies did not address the influence of the manufacturing process used to form the cooling holes on the flow physics where percussion laser drilling was a common technique that produced irregularly shaped holes with roughened surfaces. The investigated as-drilled hole surface was statistically homogeneous, non-isotropic, and generally composed of gradually transitioning plateaus that had imperfections with an average height of 0.32 hole diameters. A conjugate heat transfer CFD study was completed on cylindrical, conical nozzle, and as-drilled holes, all yielding the same hole mass flow rates, with the realizable k-ε turbulence model at representative engine conditions. The cylindrical hole had higher film cooling effectiveness due to lower effluent velocity, and better in-hole heat transfer performance due to higher on-average in-hole flow velocities. The as-drilled hole had nominally better film cooling than the conical nozzle hole due to the higher in-hole turbulence production caused by the roughened surface texture. Ultimately, the hole area profile more significantly influenced the averaged metal temperature.