Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Jackson, Richard; Tang, Hongxiao; Scobie, James A.; Owen, J. Michael; Lock, Gary

doi:10.1115/1.4053392

Cited by 8 publications

(18 citation statements)

References 26 publications

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“…In the closed-cavity experiments of Jackson et al [4], the relative difference between the speed of the core and that of the discs was less than 1%. For simplicity, in all the equations derived below it is assumed that the difference between the angular speeds of the core and discs is negligible and consequently 𝑈 𝜙 = Ωr.…”

Section: Plume Temperaturesmentioning

confidence: 86%

Plume Model for Buoyancy-Induced Flow and Heat Transfer in Closed Rotating Cavities

Tang

Owen

2022

Journal of Turbomachinery

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The radial clearance between the rotating blades and stationary casing of a gas turbine compressor depends on the radial growth of the rotating discs, and this growth depends on the buoyancy-induced flow and heat transfer in the air-filled cavities between adjacent discs. A theoretical model has been developed to calculate the radial distribution of the temperature of the disc in a closed rotating cavity. The principal assumptions are that the convective heat transfer from the hot shroud to the cold hub of the cavity is via plumes of fluid in which the cold fluid moves radially outward, and the hot fluid inward, inside an inviscid quasi-axisymmetric core of rotating fluid. The core is surrounded by boundary layers on all rotating surfaces, with free-convection layers on the surfaces of the shroud and hub and laminar Ekman layers on the surface of the discs. In addition to the convection, heat is transferred by one-dimensional radial conduction in the rotating discs. Using the model, equations have been derived to calculate the radial distribution of temperature in the discs and fluid core. These equations reveal that the non-dimensional temperatures for the disc and core, θd and θc, are controlled by three independent non-dimensional parameters: ReΦ, βΔT and x, the rotational Reynolds number, the buoyancy parameter, and the compressibility parameter. The theoretical model predicts radial distributions of temperatures in the discs and fluid core that are in good agreement with the experimentally derived values in a companion paper.

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Section: Plume Temperaturesmentioning

confidence: 86%

Plume Model for Buoyancy-Induced Flow and Heat Transfer in Closed Rotating Cavities

Tang

Owen

2022

Journal of Turbomachinery

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“…Only one vortex pair was detected in the 19 experimental cases. Experiments in a closed rotating cavity of the Bath rig measured between three and four pairs, with the flow structures experiencing almost solid body rotation (Ωs/Ω > 0.99) [16]. This suggests that, along with the slip, the interaction of the throughflow with the cavity flow has a strong influence on the number of vortex pairs.…”

Section: Accepted Manuscript N O T C O P Y E D I T E Dmentioning

confidence: 97%

“…This paper presents an analysis of unsteady pressure measurements, collected on the rotating disc surface in the central cavity of the Bath Compressor-Cavity Rig over a range of the important non-dimensional parameters. This measurement technique has been successfully used in rotor-stator systems to identify large-scale rotating flow structures [14,15], and more recently, on the disc surface of a closed rotating cavity of the Bath rig [16]. This is the first time that unsteady pressures have been directly measured on the rotating surface of a heated rotating cavity, which is open to the cooling throughflow at the inner radius.…”

Section: Accepted Manuscript N O T C O P Y E D I T E Dmentioning

confidence: 99%

Unsteady Pressure Measurements in a Heated Rotating Cavity

Jackson

Tang

Scobie

et al. 2022

Journal of Engineering for Gas Turbines and Power

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The flow in the heated rotating cavity of an aero-engine compressor is driven by buoyancy forces, which result in pairs of cyclonic and anticyclonic vortices. The resultant cavity flow field is three-dimensional, unsteady and unstable, which makes it challenging to model the flow and heat transfer. In this paper, properties of the vortex structures are determined from novel unsteady pressure measurements collected on the rotating disc surface over a range of engine-representative parameters. These measurements are the first of their kind with practical significance to the engine designer and for validation of computational fluid dynamics. One cyclonic/anticyclonic vortex pair was detected over the experimental range, despite the measurement of harmonic modes in the frequency spectra at low Rossby numbers. It is shown that these modes were caused by unequal size vortices, with the cyclonic vortex the larger of the pair. The structures slipped relative to the discs at a speed typically around 10% to 15% of that of the rotor, but the speed of precession was often unsteady. The coherency, strength and slip of the vortex pair increased with the buoyancy parameter, due to the stronger buoyancy forces, but they were largely independent of the rotational Reynolds number.

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“…The calculated Nusselt numbers lay above those measured at Aachen but the exponent of the NuB-RaB correlation from the LES results (0.286) agreed well with the exponent corrected by Bohn and Gier [11] (0.297); a similar exponent was determined by Saini et al [12] using a compressible DNS solver. Jackson et al [13] presented radial distributions of disc temperature and heat flux using the Bath Compressor Cavity Rig in a closedcavity configuration. Unlike the Aachen rig (where the discs were quasi-adiabatic) there was significant heat transfer from the disc surfaces; shroud heat transfer correlations were not produced as there was no measurement or calculation of the core temperature.…”

Section: Heat Transfer and Flow Structure In A Closed Rotating Annulusmentioning

confidence: 99%

“…In terms of flow structure, both Pitz et al [9] and Gao et al [10] computed either four or five pairs of counter-rotating vortices over the range 10 7 < RaB < 10 9 for the Aachen rig. Jackson et al [13] used unsteady pressure sensors to detect either three or four vortex pairs in the rotating core; the number of pairs changed with Grashof number, with the fluid core slipping relative to the rotating discs by < 1% of the disc speed.…”

Section: Heat Transfer and Flow Structure In A Closed Rotating Annulusmentioning

confidence: 99%

Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors

Lock¹,

Jackson

Pernak

et al. 2022

Journal of Turbomachinery

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The radial growth of compressor discs is strongly influenced by conjugate heat transfer between conduction in the co-rotating discs and buoyancy-driven convection in the rotating fluid core between the discs. An accurate prediction of metal temperatures of these discs is an important issue in thermo-mechanical design. This paper presents an experimental study of the fluid dynamics and heat transfer in a closed rotating cavity, comparing results with theoretical models and introducing a new compressibility parameter χ . At large values of χ, where compressibility effects are significant, the air temperature approaches that of the shroud; such conditions suppress buoyancy effects and the flow in the rotating cavity becomes stratified. The experiments reveal that there is a critical value of χ where the convective heat flux to the shroud is zero. The radial distribution of disc temperature was that expected from pure conduction in a cylinder. A new heat transfer correlation based on measured shroud heat flux and the theoretical core temperature is presented. The unsteady flow characteristics in the cavity were also investigated, identifying coherent rotating structures across a range of experimental conditions. These cyclonic / anti-cyclonic vortex pairs generate the non-dimensional circumferential pressure difference necessary for the radial outflow (of cold fluid) and inflow (of hot fluid) through the rotating core. The experiments show the magnitude of these pressure variations can be correlated against Grashof number and that at high values of χ the structures do not exist.

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Measurement of Heat Transfer and Flow Structures in a Closed Rotating Cavity

Cited by 8 publications

References 26 publications

Plume Model for Buoyancy-Induced Flow and Heat Transfer in Closed Rotating Cavities

Plume Model for Buoyancy-Induced Flow and Heat Transfer in Closed Rotating Cavities

Unsteady Pressure Measurements in a Heated Rotating Cavity

Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors

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