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TECHNICAL PAPERS: Gas Turbines: Heat Transfer

Flow Characteristics and Stability Analysis of Variable-Density Rotating Flows in Compressor-Disk Cavities

[+] Author and Article Information
Bruce V. Johnson

 Heat Transfer Research Services, Manchester, CT

J. D. Lin

 University of Connecticut, Storrs, CT

William A. Daniels, Roger Paolillo

 Pratt & Whitney, East Hartford, CT

J. Eng. Gas Turbines Power 128(1), 118-127 (Mar 01, 2004) (10 pages) doi:10.1115/1.1925648 History: Received October 01, 2003; Revised March 01, 2004

Previous heat transfer experiments showed that significant differences in the flow and heat transfer characteristics can occur in models of aircraft gas-turbine, high-compressor drums. Experiments with heated disks and colder flow show large-scale instabilities that cause mixing between the cooling flow and the flow in the trapped cavities. The general result of this mixing is relatively high heat flux on the disks. Other heat transfer experiments, simulating the aircraft take-off condition with cold disks and hotter coolant, show decreased heat transfer due to the stabilizing effects of positive radial density gradients. A stability analysis for inviscid, variable-density flow was developed to quantify the effects of axial velocity, tangential velocity, and density profiles in the bore region of the disk cavities on the stabilizing or destabilizing characteristics of the flow. The criteria from the stability analysis were used to evaluate the axial velocity and density profile conditions required to stabilize three tangential-velocity profiles, obtained from previous experiments and analyses. The results from the parametric study showed that for Rossby numbers, the ratio of axial velocity to disk bore velocity, less than 0.1, the flow can be stabilized with ratios of cavity density to coolant density of less than 1.1. However, for Rossby numbers greater than 1, the flow in the bore region is unlikely to be stabilized with a positive radial density gradient. For Rossby numbers between 0.1 and 1.0, the flow stability is a more complex relationship between the velocity and density profiles. Results from the analysis can be used to guide the correlation of experimental heat transfer data for design systems.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of high-pressure compressor: drum and low-pressure shaft rotate at different RPM

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Figure 2

Sketch of UTRC eleven-cavity compressor model: drum and shaft rotated at same RPM

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Figure 3

Multi-lobed instability in cavity adjacent to bleed cavity

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Figure 4

Sketch of heat transfer model. Injection location “B” used for data and results in Figs.  56

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Figure 5

Heat flux data from heating and cooling experiments at one disk location

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Figure 13

Effect of tangential velocity profile on variation of density ratio required for stability with Rossby number for density and axial velocity profiles with δρ=δU=1∕22*Ra. Results for positive Δρ are identical for the upper log-linear (13a) and lower log-log presentations (13b) of Δρ with Rossby number.

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Figure 14

Effects of density and axial velocity profile widths on variation of density ratio required for stability with Rossby number for tangential velocity Profile 2

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Figure 12

Effect of shear layer width on variation of density ratio required for stability with Rossby number for tangential velocity Profile 2

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Figure 11

Axial velocity ratio profiles used to determine stability of shear layer near bore radius of cavity

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Figure 10

Variation of Vb∕(ΩRb) with Rossby number for coolant injection location B; determined from radial pressure measurements and analysis with two turbulence models (Johnson (25)). Symbols: Black-Re=7×106; Gray-Re=4×106; Open and closed—different turbulence models

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Figure 9

Tangential velocity profiles used to determine stability of shear layer near bore radius of cavity. Symbols are calculated profiles from Johnson (25).

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Figure 8

Second stability criterion of compressible swirling flow in narrow gap between concentric cylinders

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Figure 7

First stability criterion of compressible swirling flow in narrow gab between concentric cylinders

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Figure 6

“Instantaneous” heat transfer coefficients deduced from the data of Fig. 5

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