scholarly journals LARGE EDDY SIMULATIONS OF HIGH ROSSBY NUMBER FLOW IN THE HIGH PRESSURE COMPRESSOR INTER-DISK CAVITY

2021 ◽  
pp. 1-22
Author(s):  
Deepak Saini ◽  
Richard Sandberg
Keyword(s):  
Rayleigh Number ◽  
Outer Region ◽  
Large Eddy Simulations ◽  
Rossby Number ◽  
Air Cooling ◽  
Large Eddy ◽  
Number Flow ◽  
Induced Flow ◽  
Inner Region ◽  
Buoyancy Induced Flow

Abstract The focus of the present study is to understand the effect of Rayleigh number on a high Rossby number flow in a high pres- sure compressor (HPC) inter-disk cavity. These cavities form between the compressor disks of a gas turbine engine, and they are an integral part of the internal air cooling system. We perform highly resolved large eddy simulations for two Rayleigh numbers of 0.76 × 108 and 1.54 × 108 at a fixed Rossby number of 4.5 by solving the compressible Navier–Stokes equations. The results show a flow structure dominated by a toroidal vortex in the inner region of the cavity. In the outer region, the flow is observed to move radially outwards by Ekman layers formed on the side disks and to move radially inwards through the central core region of the cavity. An enhancement in the intensity of the radial flares is observed in the outer region of the cavity for the high Rayleigh number case with no perceivable effect in the inner region. The near shroud region is mostly dominated by the centrifugal buoyancy-induced flow and the wall Nusselt number calculated at the shroud is in close agreement with centrifugal buoyancy-induced flow without an axial bore flow.

scholarly journals Large Eddy Simulations of High Rossby Number Flow in the High Pressure Compressor Inter-Disk Cavity

2020 ◽  
Author(s):  
Deepak Saini ◽  
Richard D. Sandberg
Keyword(s):  
Outer Region ◽  
Large Eddy Simulations ◽  
Rossby Number ◽  
High Pressure Compressor ◽  
Large Eddy ◽  
Number Flow ◽  
Induced Flow ◽  
Inner Region ◽  
Buoyancy Induced Flow ◽  
Pressure Compressor

Abstract The focus of the present study is to understand the effect of Rayleigh number on a high Rossby number flow in a high pressure compressor (HPC) inter-disk cavity. These cavities form between the compressor disks of a gas turbine engine, and they are an integral part of the internal air cooling system. We perform highly resolved large eddy simulations for two Rayleigh numbers of 0.76 × 108 and 1.54 × 108 at a fixed Rossby number of 4.5 by solving the compressible Navier–Stokes equations. The results show a flow structure dominated by a toroidal vortex in the inner region of the cavity. In the outer region, the flow is observed to move radially outwards by Ekman layers formed on the side disks and to move radially inwards through the central core region of the cavity. An enhancement in the intensity of the radial flares is observed in the outer region of the cavity for the high Rayleigh number case with no perceivable effect in the inner region. The near shroud region is mostly dominated by the centrifugal buoyancy-induced flow and the wall Nusselt number calculated at the shroud is in close agreement with centrifugal buoyancy-induced flow without an axial bore flow.

Measurement and Analysis of Buoyancy-Induced Heat Transfer in Aero-Engine Compressor Rotors

2020 ◽  
Author(s):  
Richard W. Jackson ◽  
Dario Luberti ◽  
Hui Tang ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Outer Region ◽  
Conjugate Problem ◽  
Radial Temperature ◽  
Nusselt Numbers ◽  
Induced Flow ◽  
Aero Engines ◽  
Inner Region ◽  
Buoyancy Induced Flow

Abstract The flow inside cavities between co-rotating compressor discs of aero-engines is driven by buoyancy, with Grashof numbers exceeding 1013. This phenomenon creates a conjugate problem: the Nusselt numbers depend on the radial temperature distribution of the discs, and the disc temperatures depend on the Nusselt numbers. Furthermore, Coriolis forces in the rotating fluid generate cyclonic and anti-cyclonic circulations inside the cavity. Such flows are three-dimensional, unsteady and unstable, and it is a challenge to compute and measure the heat transfer from the discs to the axial throughflow in the compressor. In this paper, Nusselt numbers are experimentally determined from measurements of steady-state temperatures on the surfaces of both discs in a rotating cavity of the Bath Compressor-Cavity Rig. The data are collected over a range of engine-representative parameters and are the first results from a new experimental facility specifically designed to investigate buoyancy-induced flow. The radial distributions of disc temperature were collected under carefully-controlled thermal boundary conditions appropriate for analysis using a Bayesian model combined with the equations for a circular fin. The Owen-Tang buoyancy model has been used to compare predicted radial distributions of disc temperatures and Nusselt numbers with some of the experimentally determined values, taking account of radiation between the interior surfaces of the cavity. The experiments show that the average Nusselt numbers on the disc increase as the buoyancy forces increase. At high rotational speeds the temperature rise in the core, created by compressibility effects in the air, attenuates the heat transfer and there is a critical rotational Reynolds number for which the Nusselt number is a maximum. In the cavity, there is an inner region dominated by forced convection and an outer region dominated by buoyancy-induced flow. The inner region is a mixing region, in which entrained cold throughflow encounters hot flow from the Ekman layers on the discs. Consequently, the Nusselt numbers on the downstream disc in the inner region tend to be higher than those on the upstream disc.

The Influence of Real Gas Radiation On the Stability and Development of Benard Convection in a Two-Dimensional Layer

2021 ◽  
Author(s):  
Brent W. Webb ◽  
Vladimir Solovjov
Keyword(s):  
Rayleigh Number ◽  
Critical Rayleigh Number ◽  
Radiative Heating ◽  
Two Dimensional ◽  
Gas Temperature ◽  
Layer Depth ◽  
Real Gas ◽  
Gas Radiation ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Abstract The influence of real gas radiation on the thermal and hydrodynamic stability is investigated in a two-dimensional layer of radiatively participating H2O and/or CO2 heated from below. The non-gray radiation effects of the two species are treated rigorously using a global spectral approach, the Spectral Line Weighted-sum-of-gray-gases model. The phenomena are explored by solving the full coupled laminar equations of motion, energy, and radiative transfer from the low-Rayleigh number, pure conduction-radiation regime through the onset of buoyancy-induced flow to the developed Bénard convection regime. The evolution of the thermal, velocity, and radiative heating fields is studied, and the critical Rayleigh number is characterized as a function of species mole fraction, average layer gas temperature, layer depth, wall emissivity, and the total gas pressure. It is found that participating radiation in the medium has the effect of stabilizing the layer, delaying transition to buoyancy-induced flow. The development of buoyancy-induced flow and temperature, along with the radiative heating are presented. It is found that the critical Rayleigh number in the radiatively participating gas layer can be more than an order of magnitude higher than the classical convection-only scenario. The onset of instability is found to depend on the species mole fractions, average gas temperature in the layer, wall emissivity, layer depth, and total pressure. Generally, all other variables being the same, H2O has a greater stabilizing influence on the layer than CO2.

Large eddy simulations of thermal convection at high Rayleigh number

2000 ◽  
Vol 140 (1) ◽  
pp. 163-174 ◽  
Author(s):  
Noä Cantin ◽  
Alain P. Vincent ◽  
David A. Yuen
Keyword(s):  
Rayleigh Number ◽  
Thermal Convection ◽  
Large Eddy Simulations ◽  
Large Eddy

Large-Eddy Simulation of Buoyancy-Induced Flow in a Sealed Rotating Cavity

2018 ◽  
Author(s):  
Diogo B. Pitz ◽  
John W. Chew ◽  
Olaf Marxen
Keyword(s):  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Flow Structure ◽  
Flow Characteristics ◽  
Global Features ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Buoyancy-induced flows occur in the rotating cavities of gas turbine internal air systems, and are particularly challenging to model due to their inherent unsteadiness. While the global features of such flows are well documented, detailed analyses of the unsteady structure and turbulent quantities have not been reported. In this work we use a high-order numerical method to perform large-eddy simulation (LES) of buoyancy-induced flow in a sealed rotating cavity with either adiabatic or heated disks. New insight is given into long-standing questions regarding the flow characteristics and nature of the boundary layers. The analyses focus on showing time-averaged quantities, including temperature and velocity fluctuations, as well as on the effect of the centrifugal Rayleigh number on the flow structure. Using velocity and temperature data collected over several revolutions of the system, the shroud and disk boundary layers are analysed in detail. The instantaneous flow structure contains pairs of large, counter-rotating convection rolls, and it is shown that unsteady laminar Ekman boundary layers near the disks are driven by the interior flow structure. The shroud thermal boundary layer scales as approximately Ra−1/3, in agreement with observations for natural convection under gravity.

Phase Resolved Laser Diagnostic Measurements of a Downscaled, Fuel Staged Gas Turbine Combustor at Elevated Pressure and Comparison With LES Predictions

2006 ◽  
Author(s):  
Klaus Peter Geigle ◽  
Wolfgang Meier ◽  
Manfred Aigner ◽  
Chris Willert ◽  
Marc Jarius ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Combustion Process ◽  
Elevated Pressure ◽  
Large Eddy Simulations ◽  
Air Cooling ◽  
Gas Turbine Combustor ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Chemical Scheme ◽  
Pulsating Flames

A technical gas turbine combustor has been studied in detail with optical diagnostics for validation of Large-Eddy Simulations (LES). OH* chemiluminescence, OH laser-induced fluorescence (LIF) and particle image velocimetry (PIV) have been applied to stable and pulsating flames up to 8 bar. The combination of all results yielded a good insight into the combustion process with this type of burner and forms a data base which was used for the validation of complex numerical combustion simulations. Large-Eddy Simulations (LES) including radiation, convective cooling and air cooling were combined with a reduced chemical scheme that predicts NOx emissions. Good agreement of the calculated flame position and shape with experimental data was found.

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