A Novel Methodology to Test Metallic Sealing Rings for Variable Guide Vanes

Abstract Among the design features included in axial expanders to achieve improved performance and operational flexibility, Nozzle Guide Vanes (NGVs) are a common topic of research and development. In the last years these components, which were already characterized by an intrinsic complexity, have been challenged to achieve higher efficiency and durability performances. Therefore, deeper experimental campaigns addressing the mechanical behavior of these assemblies are being performed. The state-of-the-art test bench targets actual full-scale geometries by operating at high temperature and by recreating the actual load and NGV motion. This paper focuses on the validation of sealing solutions introduced to avoid leakages from the flow-path through the housing of the NGV stem. The proposed solution consists in the design of a novel customized bench addressing the sealing system performance and durability. After summarizing different sealing concepts to be tested and selecting the most promising one, the results of the performed experimental campaign are detailed. The bench is designed to accomplish continuous endurance testing of the contact pair between sealing ring, stem and external housing at high temperature targeting actual loading conditions. Details are given regarding the design of the bench components which allow testing of sealing rings different by size and manufacturing technology. From the test campaign is possible to conclude that the sealing capability of the selected solution show limited losses compatible with working conditions even in “worn” scenarios.