Research Papers: Gas Turbines: Structures and Dynamics

Evaluation of Flow Behavior for Clearance Brush Seals

[+] Author and Article Information
Yahya Dogu1

Department of Mechanical Engineering, Kirikkale University, Yahsihan, Kirikkale 71450, Turkeyydogu@kku.edu.tr

Mahmut F. Aksit

Faculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul 34956, Turkeyaksit@sabanciuniv.edu

Mehmet Demiroglu

Department of Mechanical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180mehmet@alum.rpi.edu

Osman Saim Dinc

 Calik Enerji A.S., Ak Plaza, Yasam Cad, No. 7, Sogutozu, Ankara 06510, Turkeysaim.dinc@calikenerji.com


Corresponding author.

J. Eng. Gas Turbines Power 130(1), 012507 (Jan 09, 2008) (9 pages) doi:10.1115/1.2770479 History: Received March 15, 2004; Revised July 15, 2007; Published January 09, 2008

The industrial applications of brush seals have been increasing due to their superior sealing performance. Advances in the understanding of seal behavior have been pushing the design limits to higher-pressure load, temperature, surface speed, and rotor excursion levels. The highest sealing performance can be achieved when the bristle pack maintains contact with the rotor surface. However, due to many design and operational constraints, most seals operate with some clearance. This operating clearance cannot be avoided due to rotor runouts, transient operating conditions, or excessive bristle wear. In some applications, a minimum initial clearance is required to ensure a certain amount of flow rate for component cooling or purge flow. Typically, brush seal failure occurs in the form of degraded sealing performance due to increasing seal clearance. The seal performance is mainly characterized by the flow field in close vicinity of the bristle pack, through the seal-rotor clearance, and within the bristle pack. This work investigates the flow field for a brush seal operating with some bristle-rotor clearance. A nonlinear form of the momentum transport equation for a porous medium of the bristle pack has been solved by employing the computational fluid dynamics analysis. The results are compared with prior experimental data. The flow field for the clearance seal is observed to have different characteristics compared to that for the contact seal. Outlined as well are the flow features influencing the bristle dynamics.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic of a brush seal

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Figure 2

Sample mesh view

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Figure 3

Leakage versus pressure ratio

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Figure 4

Variation of bristle blowdown with respect to pressure ratio for initial clearances of 0.27mm and 0.75mm

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Figure 5

Leakage percentages through clearance with respect to pressure ratio for various clearances

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Figure 6

Axial pressure distribution on the rotor surface

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Figure 7

Radial pressure distribution on the backing plate

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Figure 8

Velocity vectors around the fence height for contact and clearance (0.27mm) seals for Rp=1.5

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Figure 9

Contour plots around the fence height for contact and clearance (0.27mm) seals for Rp=1.5

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Figure 10

Pressure in the bristle pack for contact and clearance (0.27mm) seals for Rp=1.5

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Figure 11

Flow properties in the bristle pack for contact and clearance (0.27mm) seals for Rp=1.5




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