Development and Evaluation of Shaped Film Cooling Holes Designed for Additive Manufacturing

Film cooling remains a critical technology for cooling gas turbine components. In recent years, additive manufacturing (AM) has been used to develop novel film cooling hole designs which significantly increase the film cooling effectiveness. However, engine scale AM builds have imperfections and roughness that can have a noticeable effect on performance. In this study, 9-9-3 shaped film cooling holes were constructed at engine scale using metal AM, specifically direct laser metal sintering (DMLS). These “as built” geometries were characterized through computerized tomography (CT) scans to quantify deviations from holes with design intent, or “as-designed” holes. To evaluate the performance of the “as-built” holes compared to “as-designed” holes, both adiabatic and overall cooling effectiveness were measured experimentally for 5x scale models. The larger scale enabled the use of finite deposition modeling (FDM) to construct hole geometry that closely matched the “as-designed” holes and the CT scans of the “as-built” holes. Two versions of the 9-9-3 hole were studied, the 9-9-3 rounded inlet (RI) hole with rounding at the inlet, and the 9-9-3 rounded inlet and exit (RIE) hole with additional rounding at the hole inlet, and rounding at the hole exit. Results showed that the adiabatic effectiveness and overall cooling effectiveness for the “as-built” holes were similar to the performance of the “as-designed” film cooling holes for both hole geometries tested.