While turbine rim sealing flows are an important aspect of turbomachinery design, affecting turbine aerodynamic performance and turbine disk temperatures, the present understanding and predictive capability for such flows is limited. The aim of the present study is to clarify the flow physics involved in rim sealing flows and to provide high-quality experimental data for use in evaluation of computational fluid dynamics (CFD) models. The seal considered is similar to a chute seal previously investigated by other workers, and the study focuses on the inherent unsteadiness of rim seal flows, rather than unsteadiness imposed by the rotating blades. Unsteady pressure measurements from radially and circumferentially distributed transducers are presented for flow in a rotor–stator disk cavity and the rim seal without imposed external flow. The test matrix covered ranges in rotational Reynolds number, Re∅, and nondimensional flow rate, Cw, of 2.2–3.0 × 106 and 0–3.5 × 103, respectively. Distinct frequencies are identified in the cavity flow, and detailed analysis of the pressure data associates these with large-scale flow structures rotating about the axis. This confirms the occurrence of such structures as predicted in previously published CFD studies and provides new data for detailed assessment of CFD models.
This paper describes a new engine-parts facility at the University of Oxford for high technology-readiness-level research, new technology demonstration, and for engine component validation. The Engine Component AeroThermal (ECAT) facility has a modular working section which houses a full annulus of engine components. The facility is currently operated with high-pressure nozzle guide vanes from a large civil jet-engine. A high degree of engine similarity is achieved, with matched conditions of Mach number, Reynolds number, and coolant-to-mainstream pressure ratio. For combustor-turbine interaction studies, a combustor simulator module is used, which is capable of both rich-burn and lean-burn combined temperature, swirl and turbulence profiles. The facility is being used for aerothermal optimisation research (e.g., novel cooling systems, aerodynamic optimisation problems, capacity sensitivity studies), computational fluid dynamics validation (aerodynamic predictions, conjugate predictions), and for component validation to accelerate the engine design process. The three key measurement capabilities are: capacity characteristic evaluation to a precision of 0.02%; overall cooling (metal) effectiveness measurements (using a rainbow set of parts if required); and aerodynamic loss evaluation (with realistic cooling, trailing-edge flow etc.). Each of these three capabilities have been separately developed and optimised in other facilities at the University of Oxford in the last 10 years, to refine aspects of facility design, instrumentation design, experimental technique, and theoretical aspects of scaling and reduction of experimental data. The ECAT facility brings together these three research strands with a modular test vehicle for rapid high technology-readiness-level research, demonstration of new technologies, and for engine component validation. The purpose of this paper is to collect in one place — and put in context — the work that led to the development of the ECAT facility, to describe the facility, and to illustrate the accuracy and utility of the techniques by presenting typical data for each of the key measurements. The ECAT facility is a response to the changing requirements of experimental turbomachinery testing, and it is hoped this paper will be of interest to engine designers, researchers, and those involved in major facility developments in both research institutes and engine companies.
This article presents an experimental and computational study of the efficiency of an unshrouded transonic turbine. This research formed part of the EU Turbine Aero-Thermal External Flows II programme. The experiments were performed in the Oxford Turbine Research Facility (previously the Turbine Test Facility at QinetiQ, Farnborough). This facility is an engine scale, short duration, rotating transonic facility, in which M, Re, T gas =T wall , and N = ffiffiffiffiffiffiffi T 01 p are matched to engine conditions. For these experiments, the MT1 turbine stage was installed. Historically, turbine efficiency measurements are conducted in steady state adiabatic facilities. However, short-duration facilities allow simultaneous aerodynamic and heat transfer measurements with a significant reduction in cost. An efficiency measurement system was developed for this investigation, and this is briefly described. The system allows efficiency to be evaluated to bias and precision errors of approximately AE1.45 per cent and AE0.16 per cent, respectively, to 95 per cent confidence. The results of accurate area surveys of the turbine inlet and exit flows are presented and discussed. At the turbine exit, data were taken at two traverse planes, approximately 0.5 and 4.5 rotor axial chords downstream of the rotor. The turbine efficiency was experimentally evaluated based on the data at both planes, using a number of mixing models, which are discussed and compared. The experimental result of turbine efficiency is also compared to that estimated from a mean-line prediction. Full-stage steady and unsteady computational fluid dynamics of the experiment using the Rolls-Royce HYDRA code was conducted and is also presented. The predicted and measured rotor exit flow-fields are compared at both downstream traverse planes.
By enhancing the premixing of fuel and air prior to combustion, recently developed lean-burn combustor systems have led to reduced NOx and particulate emissions in gas turbines. Lean-burn combustor exit flows are typically characterized by nonuniformities in total temperature, or so-called hot-streaks, swirling velocity profiles, and high turbulence intensity. While these systems improve combustor performance, the exiting flow-field presents significant challenges to the aerothermal performance of the downstream turbine. This paper presents the commissioning of a new fully annular lean-burn combustor simulator for use in the Oxford Turbine Research Facility (OTRF), a transonic rotating facility capable of matching nondimensional engine conditions. The combustor simulator can deliver engine-representative turbine inlet conditions featuring swirl and hot-streaks either separately or simultaneously. To the best of our knowledge, this simulator is the first of its kind to be implemented in a rotating turbine test facility.The combustor simulator was experimentally commissioned in two stages. The first stage of commissioning experiments was conducted using a bespoke facility exhausting to atmospheric conditions (Hall and Povey, 2015, “Experimental Study of Non-Reacting Low NOx Combustor Simulator for Scaled Turbine Experiments,” ASME Paper No. GT2015-43530.) and included area surveys of the generated temperature and swirl profiles. The survey data confirmed that the simulator performed as designed, reproducing the key features of a lean-burn combustor. However, due to the hot and cold air mixing process occurring at lower Reynolds number in the facility, there was uncertainty concerning the degree to which the measured temperature profile represented that in OTRF. The second stage of commissioning experiments was conducted with the simulator installed in the OTRF. Measurements of the total temperature field at turbine inlet and of the high-pressure (HP) nozzle guide vane (NGV) loading distributions were obtained and compared to measurements with uniform inlet conditions. The experimental survey results were compared to unsteady numerical predictions of the simulator at both atmospheric and OTRF conditions. A high level of agreement was demonstrated, indicating that the Reynolds number effects associated with the change to OTRF conditions were small. Finally, data from the atmospheric test facility and the OTRF were combined with the numerical predictions to provide an inlet boundary condition for numerical simulation of the test turbine stage. The NGV loading measurements show good agreement with the numerical predictions, providing validation of the stage inlet boundary condition imposed. The successful commissioning of the simulator in the OTRF will enable future experimental studies of lean-burn combustor–turbine interaction.
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