DEVELOPMENT OF AN EXPERIMENTAL FACILITY TO STUDY EXTERNALLY INDUCED INGRESS IN TURBINE RIM SEALS

<p dir="ltr">State-of-the-art gas turbines operate at extreme turbine inlet temperatures to maximize thermal efficiency and specific work, which increases demands on sealing and cooling technologies. The stator-rotor cavity is the wheel-space between the stationary and the rotating disks of a turbine. A rim seal and a purge flow mitigate hot gas ingress from the mainstream annulus into the cavity. Appropriate sealing of the cavity is key to protecting the inner turbine disk from thermal damage. Additionally, the purge flow cools the blade roots and platform. There are two primary ingress types: externally induced and rotationally induced. Externally induced ingress is driven by circumferential variations in annulus pressure that create regions of ingress and egress at the seal lip. Rotationally induced ingress is driven by the rotating disk pumping effect, resulting in egress near the rotor disk and ingress near the stator disk. The priority of engine designers is to minimize the purge mass flow bled from the compressor to seal the cavity, which improves engine efficiency. Yet, accurate prediction of the minimum sealing flow still relies on costly experiments and high-fidelity simulations. The dissertation presents the development of experimental and numerical tools for the study of ingress in turbine rim seals. First, it presents a computational design strategy that combines two-dimensional Reynolds-averaged Navier-Stokes simulations of parametrized rim seal geometries with three-dimensional unsteady Reynolds-averaged Navier-Stokes simulations. The two-dimensional computations accelerate geometry screening, quantifying rim seal pressure drop and cavity heat transfer sensitivity to geometrical parameters. The three-dimensional computations serve to assess sealing effectiveness. The challenges of simulating turbine rim seal ingress and predicting minimum purge mass flow to seal the cavity are highlighted. Second, it presents the design, modeling, construction, and commissioning of PT3, a high-speed open-return continuous wind tunnel. The facility is modular with lightweight components for rapid multi-configuration testing campaigns. An auxiliary heated injection system with accurate temperature and mass flow control has also been developed for turbine rim seal studies. The performance and flow quality of the facility are characterized. A reduced-order model that predicts operating lines and component losses is implemented and validated. Third, it presents the design and aerothermal characterization of the Advanced Stationary Test Article for the Study of Externally Induced Ingress in Turbine Rim Seals (ASTER). It consists of a cylinder array in a linear test section that imposes a nonuniform pressure field upstream of an axial rim seal. Three-dimensional unsteady Reynolds-averaged Navier-Stokes simulations support the design of the test article. An extensive experimental campaign evaluates the effects of mainstream Mach number, purge mass flow, and rim seal clearance on temperature-based sealing effectiveness. The minimum purge mass flow required to seal the cavity for different configurations is computed, and the flow physics are studied, showing consistent behavior between experiments and computations. Thus, this dissertation provides a framework for the aerothermal characterization of ingress in turbine rim seals.</p>