Integration of Cooling Holes Into a Turbine Vane Made Using Additive Manufacturing

Abstract

Additive manufacturing (AM) has emerged as a method to prototype novel designs for turbine airfoil cooling with complex internal and film cooling geometries. Creating engine scale features with AM comes with challenges that impact flow and heat transfer, which consequently affect the overall performance of the component. While AM has proven to be faster and more cost-effective than traditional casting methods, the scalability of AM requires further investigation. The purpose of this study was to integrate various film-cooling hole geometries identified through large-scale models and true-scale simple coupons into a true-scale turbine vane to assess overall cooling effectiveness. The National Experimental Turbine (NExT) vane was additively manufactured with a singular cooling passage feeding two rows of film-cooling holes: a row of baseline 7-7-7 holes; and a row of holes containing both parametrically optimized 15-15-1 holes and modified adjoint optimized cross flow holes. The internal passage was designed to have a section with ribs and a section without ribs to assess how internal features impact the cooling holes' performance. The vane was tested in the Steady Thermal Aero Research Turbine (START) rig over a range of film cooling blowing ratios. A combination of computed tomography scanning and non-contact infrared thermal imaging measurements were used to evaluate how as-built geometries impacted the overall cooling effectiveness on the NExT vane for each hole group. The 15-15-1 film-cooling holes with no internal ribs were shown to be the most effective in lowering surface temperatures relative to the other cooling hole configurations. Also, the 15-15-1 holes with no internal ribs to affect the cooling flow entrance to the hole were the least affected by blowing ratio changes. The 7-7-7 hole was found to have a negative impact on the vane because the downstream surface was warmed by a separating internal channel wall.