The Oxford Probe is an open access five-hole probe designed for experimental aerodynamic measurements. The open access probe can be manufactured by the end user via additive manufacturing (metal or plastic). The probe geometry, drawings, calibration maps, and software are available under a creative commons license. The purpose is to widen access to aerodynamic measurement techniques in education and research environments. There are many situations in which the open access probe will allow results of comparable accuracy to a well-calibrated commercial probe. We discuss the applications and limitations of the probe, and compare the calibration maps for 16 probes manufactured in different materials and at different scales, but with the same geometrical design.

Nonuniform combustor outlet flows have been demonstrated to have significant impact on the first and second stage turbine aerothermal performance. Rich-burn combustors, which generally have pronounced temperature profiles and weak swirl profiles, primarily affect the heat load in the vane but both the heat load and aerodynamics of the rotor. Lean burn combustors, in contrast, generally have a strong swirl profile which has an additional significant impact on the vane aerodynamics which should be accounted for in the design process. There has been a move towards lean burn combustor designs to reduce NOx emissions. There is also increasing interest in fully integrated design proc esses which consider the impact of the combustor flow on the design of the high pressure vane and rotor aerodynamics and cooling. There are a number of current large research projects in scaled (low temperature and pressure) turbine facilities which aim to provide validation data and physical understanding to support this design philosophy. There is a small body of literature devoted to rich burn combustor simulator design but no open lit erature on the topic of lean burn simulator design. The particular problem is that in non reacting, highly swirling and diffusing flows, vortex instability in the form of a precessing vortex core or vortex breakdown is unlikely to be well matched to the reacting case. In reacting combustors the flow is stabilized by heat release, but in low temperature simula tors other methods for stabilizing the flow must be employed. Unsteady Reynoldsaveraged Navier-Stokes and large eddy simulation have shown promise in modeling swirling flows with unstable features. These design issues form the subject of this paper.

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.

The accurate estimation of the unsteady response (bandwidth) of pneumatic pressure probe-systems (probe, line and transducer volume) is a common practical problem encountered in the design of aerodynamic experiments. Understanding the bandwidth of the probe-system is necessary to ensure that unsteady flow features are accurately captured. Where traversing probes are used, the desired traverse speed and spatial gradients in the flow dictate the minimum probe-system bandwidth required to fully resolve the flow. Existing approaches for bandwidth estimation are either complex or inaccurate in implementation, so probes are often designed based on experience. Where probe-system bandwidth is characterized, it is often done experimentally, requiring careful experimental set-up and analysis. There is a need for a relatively simple but accurate model for estimation of probe-system bandwidth.A new model is presented for the accurate estimation of pressure probe bandwidth for simple probes commonly used in wind tunnel environments. Experimental validation is provided.

This paper presents the first experimental characterisation of a fully annular combustor simulator incorporating both swirl and temperature pattern. The simulator has been designed to non-dimensionally replicate the conditions of next-generation low NOx combustors, with high swirl and high near wall temperature gradients, making it suitable for use in fully scaled (correct Re, M, N/√T, TG/TW) turbine facilities, to investigate combustor turbine interaction effects. In reacting combustor flows with high swirl, combustion has a significant influence on vortex stability and therefore flow structure. In non-reacting simulators, with approximately isothermal flow, it is common to find instabilities that are not present in the equivalent reacting flow. Where this is the case, artificial methods must be used to stabilise the vortex core. It has previously been shown numerically and in simple experimental studies that a low-momentum axial jet at the vortex centre suppresses precession of the vortex core. This paper reports experimental data for highly swirling flows both with and without stabilizing jets. This investigation is the first of its type, and the results have implications for the design of simulators for next-generation scaled turbine experiments both in industry and academia.