An Axial Turbobrake

Journal of Engineering for Gas Turbines and Power

2014

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.

Section: Oxford Turbines Research Facilitymentioning

confidence: 99%

Design of a Nonreacting Combustor Simulator With Swirl and Temperature Distortion With Experimental Validation

Hall

Chana

Journal of Engineering for Gas Turbines and Power

2014

“…Steady conditions are achieved for approximately 500 ms, during which the experimental data is acquired. The torque developed in the turbine is opposed by a turbobrake [19], which is on the same shaft as the turbine and is driven by the turbine exit flow. Thus, approximately constant speed is maintained during the 500 ms test period.…”

Section: Oxford Turbine Research Facilitymentioning

confidence: 99%

A combustor-representative swirl simulator for a transonic turbine research facility

Qureshi

Proceedings of the Institution of Mechanical Engineers, Part G:

2011

Tighter aircraft emissions regulations have let to considerable improvement in gas turbine combustion in the past few decades. Modern combustors employ aggressive swirlers to increase mixing and to improve flame stability during the combustion process. The flow at combustor exit can therefore have high residual swirl. The impact of this swirl on the aerodynamic and heat transfer characteristics of the HP turbine stage has not yet received much attention.In order to investigate the effects of swirl on the HP turbine stage, an inlet swirl simulator has been designed and commissioned in an engine scale, short duration, rotating transonic turbine facility. The test facility simulates engine representative Mach number, Reynolds number, nondimensional speed and gas-to-wall temperature ratio at the turbine inlet. The target swirl profile at turbine stage inlet was based upon extreme exit swirl conditions for a modern low-NO x combustor with peak yaw and pitch angles over AE40 . A number of candidate swirler designs were considered during a pilot study that was conducted in a subsonic wind tunnel to achieve suitable swirler design. The swirl simulator was developed based upon the pilot study results, which achieved a good match to the target profile after commissioning in the facility. This article mainly deals with the design and development of the swirl generator. It presents the experimental and computational results of the pilot study, followed by the description of the installation and commissioning of the swirl simulator on the test facility. Novel instrumentation was required to survey the swirl profile, which is also described. A comparison of the measured and computational aerodynamic results with and without swirl, at 10 per cent and 90 per cent span of HP nozzle guide vane is also presented. The comparison highlights significant impact of swirl on the vane incidence angle, and therefore a considerable affect on the loading distribution of the vane.

“…For the experiments described in this paper, only the HP stage was installed. A novel feature of the facility is the aerodynamic turbobrake [6], which is on the same shaft as the turbine and is driven by the turbine exit-flow. At the design speed, the turbobrake power is matched with the turbine, and thus constant speed is maintained during a run.…”

Section: Description Of the Facilitymentioning

confidence: 99%

A hot-streak (combustor) simulator suited to aerodynamic performance measurements

Proceedings of the Institution of Mechanical Engineers, Part G:

Qureshi

2008

A new hot-streak (combustor) simulator has been designed and implemented in a turbine test facility at QinetiQ Farnborough (the QinetiQ Isentropic Light Piston Facility, ILPF) to study the impact of temperature distortion on high pressure (HP) turbine efficiency, aerodynamics, and heat transfer. The ILPF is an engine scale, short duration, rotating transonic turbine test facility, in which M , Re, T g /T w , and N / √ T are matched to engine conditions. The research forms part of the EU Turbine Aero-Thermal External Flows (TATEF II) programme.The hot-streak simulator is a second-generation design, in which cold gas is introduced into a hot mainstream though radial and circumferential slots upstream of the turbine stage. The simulator is rotatable, so the effect of clocking (relative circumferential position of hot streak and nozzle guide vane leading edge) can easily be investigated. An emphasis was placed on accurate measurement of turbine inlet enthalpy flux so that the impact of hot streaks on turbine efficiency could be investigated.The hot-streak simulator differs from all previous systems in that a pronounced radial and circumferential temperature profile has been generated, with a hot-streak to vane count of 1:1. The profile is very well matched (non-dimensionally) to the target profile, which is a combustor temperature profile measured in a modern operating engine at the most extreme point in the cycle. The most accurate area survey of a simulated temperature profile has been conducted to date, and this demonstrates that the simulator offers an exceptionally high degree of circumferential symmetry and run-to-run repeatability.The design and commissioning of the simulator is described, and the measured temperature profiles are compared with the target profile.