Review of Buoyancy-Induced Flow in Rotating Cavities

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
J. Michael Owen ◽  
Christopher A. Long
Keyword(s):  
Thermal Stresses ◽  
Numerical Models ◽  
Three Dimensional ◽  
Solid Surfaces ◽  
Transient Temperature ◽  
Temperature Changes ◽  
Open Cavities ◽  
Induced Flow ◽  
Published Research ◽  
Buoyancy Induced Flow

Buoyancy-induced flow occurs in the cavity between two corotating compressor disks when the temperature of the disks and shroud is higher than that of the air in the cavity. Coriolis forces in the rotating fluid create cyclonic and anticyclonic circulations inside the cavity, and—as such flows are three-dimensional and unsteady—the heat transfer from the solid surfaces to the air is difficult either to compute or to measure. As these flows also tend to be unstable, one flow structure can change quasi-randomly to another. This makes it hard for designers of aeroengines to calculate the transient temperature changes, thermal stresses, and radial growth of the disks during engine accelerations and decelerations. This paper reviews published research on buoyancy-induced flow in closed rotating cavities and in open cavities with either an axial throughflow or a radial inflow of air. In particular, it includes references to experimental data that could be used to validate cfd codes and numerical models.

A Three-Dimensional Finite Difference Solution for the Thermal Stresses in Railcar Wheels

1969 ◽  
Vol 91 (3) ◽  
pp. 891-896 ◽  
Author(s):  
G. E. Novak ◽  
B. J. Eck
Keyword(s):  
Computer Program ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Transient Temperature ◽  
Shear Stresses ◽  
Radial Temperature ◽  
Closed Form Solutions ◽  
Brake Application ◽  
History Of ◽  
Thin Disks

A numerical solution is presented for both the transient temperature and three-dimensional stress distribution in a railcar wheel resulting from a simulated emergency brake application. A computer program has been written for generating thermoelastic solutions applicable to wheels of arbitrary contour with temperature variations in both axial and radial directions. The results include the effect of shear stresses caused by the axial-radial temperature gradients and the high degree of boundary irregularity associated with this type of problem. The program has been validated by computing thermoelastic solutions for thin disks and long cylinders; the computed values being in good agreement with the closed form solutions. Currently, the computer program is being extended to general stress solutions corresponding to the transient temperature distributions obtained by simulated drag brake applications. When this work is completed, it will be possible to synthesize the thermal history of a railcar wheel and investigate the effects of wheel geometry in relation to thermal fatigue.

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.

Three-Dimensional Thermal Analysis for Laser Assisted Milling of Silicon Nitride Ceramics Using FEA

2005 ◽  
Author(s):  
Xinwei Shen ◽  
W. J. Liu ◽  
Shuting Lei
Keyword(s):  
Silicon Nitride ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Transient Temperature ◽  
Operating Parameters ◽  
Beam Diameter ◽  
Transient Temperature Distribution ◽  
Failure Theory ◽  
Ceramic Machining ◽  
Laser Heat Source

Laser assisted machining (LAM) is one promising method for ceramic machining. In this paper, a three-dimensional heat transfer and thermal stress analysis is completed using commercial FEA software (ANSYS) to gain some insights on the thermal aspects for laser assisted milling. The transient temperature distribution was analyzed for a silicon nitride (Si3N4) ceramic workpiece undergoing a translating laser heat source which simulates the heating environment of the slot-milling operation with LAM. The effects of the operating parameters, such as laser power, laser beam diameter, laser preheat time and laser translating speed, were investigated. The thermal stresses induced from the steep temperature change and the effects of the operating parameters on thermal stresses were investigated. Additionally, the maximum-normal stress failure theory for brittle materials were employed to predict the possibility of cracking on ceramic workpiece due to thermal stresses.

Buoyancy-Induced Flow in a Heated Rotating Cavity

2004 ◽  
Vol 128 (1) ◽  
pp. 128-134 ◽  
Author(s):  
J. Michael Owen ◽  
Jonathan Powell
Keyword(s):  
Laser Doppler Anemometry ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Velocity Measurements ◽  
Turbine Engine ◽  
Rotating Cavity ◽  
Heated Disk ◽  
Induced Flow ◽  
Cooling Air ◽  
Buoyancy Induced Flow

Experimental measurements were made in a rotating-cavity rig with an axial throughflow of cooling air at the center of the cavity, simulating the conditions that occur between corotating compressor disks of a gas-turbine engine. One of the disks in the rig was heated, and the other rotating surfaces were quasi-adiabatic; the temperature difference between the heated disk and the cooling air was between 40 and 100°C. Tests were conducted for axial Reynolds numbers, Rez, of the cooling air between 1.4×103 and 5×104, and for rotational Reynolds numbers, Reϕ, between 4×105 and 3.2×106. Velocity measurements inside the rotating cavity were made using laser Doppler anemometry, and temperatures and heat flux measurements on the heated disk were made using thermocouples and fluxmeters. The velocity measurements were consistent with a three-dimensional, unsteady, buoyancy-induced flow in which there was a multicell structure comprising one, two, or three pairs of cyclonic and anticyclonic vortices. The core of fluid between the boundary layers on the disks rotated at a slower speed than the disks, as found by other experimenters. At the smaller values of Rez, the radial distribution and magnitude of the local Nusselt numbers, Nu, were consistent with buoyancy-induced flow. At the larger values of Rez, the distribution of Nu changed, and its magnitude increased, suggesting the dominance of the axial throughflow.

scholarly journals 3D Buoyancy-Induced Flow and Entropy Generation of Nanofluid-Filled Open Cavities Having Adiabatic Diamond Shaped Obstacles

Entropy ◽  
2016 ◽  
Vol 18 (6) ◽  
pp. 232 ◽  
Author(s):  
Lioua Kolsi ◽  
Omid Mahian ◽  
Hakan Öztop ◽  
Walid Aich ◽  
Mohamed Borjini ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Open Cavities ◽  
Induced Flow ◽  
Buoyancy Induced Flow
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