Investigation of rim seal exchange and coolant re-ingestion in rotor stator cavities using gas concentration techniques

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Understanding the effectiveness of cooling flows when making life predictions for rotating components subject to the main gas path temperatures is crucial. A test facility has been developed at the University of Sussex incorporating a two stage turbine designed to support a European funded research project with the objective of enhancing the understanding of interactions between main annulus gas paths and secondary air systems. This thesis describes the specific contribution of the author to the research conducted at the test facility. Non-invasive gas seeding and concentration measurement techniques together with hot geometry displacement measurements have been developed to meet three distinct objectives: to determine inter-stage seal flows between rotor disc cavities; to provide data to quantify rim seal exchange flows between rotor stator cavities and the main annulus gas path for both bulk ingestion and egress conditions; and, to provide data to quantify the re-ingestion of cooling air egressed into the main annulus gas path. Detailed knowledge of these flows is vital to understanding the flow structures within rotor stator cavities and to optimise coolant delivery methods. Experimental results are presented for a number of cooling flow supply geometries and flow rates. The gas concentration measurement techniques developed and the results obtained are compared to traditional measurements as well as numerical simulations carried out by research project partners. This work develops the measurement techniques of rotor stator cavity flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process.