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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

A Study of the Effects of Inlet Preswirl on the Dynamic Coefficients of a Straight-Bore Honeycomb Gas Damper Seal

[+] Author and Article Information
Tony B. Sprowl

 Lockheed Martin Aeronautics Company, Fort Worth, TX

Dara W. Childs

Leland T. Jordan Professor of Mechanical Engineering, Turbomachinery Laboratory, Texas A&M University, College Station, TX 77843

J. Eng. Gas Turbines Power 129(1), 220-229 (Mar 01, 2004) (10 pages) doi:10.1115/1.2227416 History: Received October 01, 2003; Revised March 01, 2004

Honeycomb seals are frequently used as replacements for labyrinth seals in high-pressure centrifugal compressors to enhance rotordynamic stability. A concern exists that this enhanced stability will be lost if the honeycomb cavities become clogged. Static and dynamic tests were conducted on a honeycomb and a smooth seal (representing the honeycomb seal with completely clogged cells) at the same constant clearances using air with a supply pressure of 70 bars. The test matrix included three speeds, three pressure ratios, and three inlet preswirl conditions. The results show increased leakage, decreased synchronous stiffness, and decreased dynamic stability for the smooth seal with preswirled flow. The results strongly support the use of swirl brakes at the entrance of a honeycomb seal if clogging is a concern. Comparisons between test results and predictions from a two-control-volume theory by Kleynhans and Childs showed excellent agreement in general.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Honeycomb annular seal

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Figure 2

Annular gas seal test stand

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Figure 3

Pitot tube location and preswirl rings

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Figure 4

k* versus excitation frequency for the HC seal at three levels of preswirl

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Figure 5

Keff* versus excitation frequency for the HC seal at three levels of preswirl

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Figure 6

Ceff* versus excitation frequency for the HC seal at three levels of preswirl

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Figure 7

k* for the HC seal at high preswirl and the smooth seals at medium preswirl

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Figure 8

Keff* for HC at high preswirl and a smooth seal at medium preswirl

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Figure 9

Ceff* for HC at high preswirl and the smooth seals at medium preswirl

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Figure 10

Experimental and theoretical k* versus excitation frequency for low/high preswirl (50% backpressure)

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Figure 11

HC tests and theoretical K* versus excitation frequency for low/high preswirl (50% backpressure)

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Figure 12

HC Ceff* predictions versus measurements for low/high preswirl (50% backpressure)

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Figure 13

Ceff* versus preswirl ratio for the smooth and HC seals at 80Hz excitation frequency, 20,200rpm, and 50% pressure ratio

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