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TECHNICAL PAPERS: Gas Turbines: CFD Modeling and Simulation

# Buoyancy-Induced Flow in Open Rotating Cavities

[+] Author and Article Information
J. Michael Owen

University of Bath, Bath, BA2 7AY, UK

Volvo Aero Corporation, 46181 Trollhättan, Sweden

J. Eng. Gas Turbines Power 129(4), 893-900 (Jan 11, 2007) (8 pages) doi:10.1115/1.2719260 History: Received June 19, 2006; Revised January 11, 2007

## Abstract

Buoyancy-induced flow can occur in the cavity between the co-rotating compressor disks in gas-turbine engines, where the Rayleigh numbers can be in excess of $1012$. In most cases the cavity is open at the center, and an axial throughflow of cooling air can interact with the buoyancy-induced flow between the disks. Such flows can be modeled, computationally and experimentally, by a simple rotating cavity with an axial flow of air. This paper describes work conducted as part of ICAS-GT, a major European research project. Experimental measurements of velocity, temperature, and heat transfer were obtained on a purpose-built experimental rig, and these results have been reported in an earlier paper. In addition, 3D unsteady CFD computations were carried out using a commercial code (Fluent) and a RNG $k‐ε$ turbulence model. The computed velocity vectors and contours of temperature reveal a flow structure in which, as seen by previous experimenters, “radial arms” transport cold air from the center to the periphery of the cavity, and regions of cyclonic and anticyclonic circulation are formed on either side of each arm. The computed radial distribution of the tangential velocity agrees reasonably well with the measurements in two of the three cases considered here. In the third case, the computations significantly overpredict the measurements; the reason for this is not understood. The computed and measured values of Nu for the heated disk show qualitatively similar radial distributions, with high values near the center and the periphery. In two of the cases, the quantitative agreement is reasonably good; in the third case, the computations significantly underpredict the measured values.

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## Figures

Figure 1

Simplified diagram of high-pressure compressor rotor with axial throughflow

Figure 2

Rayleigh-Bénard vortices in a closed rotating cavity

Figure 3

Rotating cavity with axial throughflow of cooling air

Figure 4

Schematic of flow structure in a heated rotating cavity with an axial throughflow of cooling air

Figure 5

Schematic of Bath rotating-cavity rig

Figure 6

Geometry and grid of CFD model

Figure 7

Radial distribution of ΔT (K) for heated disk

Figure 8

Computed contours of ΔTc (K) in mid-axial plane for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303)

Figure 9

Computed contours of ΔTc (K) in mid-axial plane for experiment 5 (Reϕ∕106=1.57, Rez∕104=0.164)

Figure 10

Computed velocity vectors in mid-axial plane for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303)

Figure 11

Computed velocity vectors in mid-axial plane for experiemt 5 (Reϕ∕106=1.57, Rez∕104=0.164)

Figure 12

Computed contours of Nusselt number for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303)

Figure 13

Computed contours of Nusselt number for experiment 5 (Reϕ∕106=1.57, Rez∕104=0.164)

Figure 14

Computed time-sequence of contours of ΔTc in mid-axial plane for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303). Time in ms.

Figure 15

Computed time-sequence of contours of ΔTc in mid-axial plane for experiment 5 (Reϕ∕106=1.57, Rez∕104=0.164). Time in ms.

Figure 16

Computed and measured radial distributions of Vϕ∕Ωr in mid-axial plane for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303), experiment 5 (Reϕ∕106=1.57, Rez∕104=0.164), and experiment 6 (Reϕ∕106=1.63, Rez∕104=0.173)

Figure 17

Computed and measured radial distributions of Nu for experiment 2 (Reϕ∕106=0.43, Rez∕104=0.303), experiment 5 (Reϕ∕106=1.57, Rez∕104=0.164), and experiment 6 (Reϕ∕106=1.63, Rez∕104=0.173)

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