TECHNICAL PAPERS: Gas Turbines: Heat Transfer

Brush Seal Temperature Distribution Analysis

[+] Author and Article Information
Yahya Dogu1

Department of Mechanical Engineering,  Kirikkale University, Yahsihan, Kirikkale 71451, Turkeyydogu@kku.edu.tr

Mahmut F. Aksit

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


To whom correspondence should be addressed.

J. Eng. Gas Turbines Power 128(3), 599-609 (Sep 06, 2005) (11 pages) doi:10.1115/1.2135817 History: Received August 30, 2005; Revised September 06, 2005

Brush seals are designed to survive transient rotor rubs. Inherent brush seal flexibility reduces frictional heat generation. However, high surface speeds combined with thin rotor sections may result in local hot spots. Considering large surface area and accelerated oxidation rates, frictional heat at bristle tips is another major concern especially in challenging high-temperature applications. This study investigates temperature distribution in a brush seal as a function of frictional heat generation at bristle tips. The two-dimensional axisymmetric computational fluid dynamics (CFD) analysis includes the permeable bristle pack as a porous medium allowing fluid flow throughout the bristle matrix. In addition to effective flow resistance coefficients, isotropic effective thermal conductivity as a function of temperature is defined for the bristle pack. Employing a fin approach for a single bristle, a theoretical analysis has been developed after outlining the brush seal heat transfer mechanism. Theoretical and CFD analysis results are compared. To ensure coverage for various seal designs and operating conditions, several frictional heat input cases corresponding to different seal stiffness values have been studied. Frictional heat generation is outlined to introduce a practical heat flux input into the analysis model. Effect of seal stiffness on nominal bristle tip temperature has been evaluated. Analyses show a steep temperature rise close to bristle tips that diminishes further away. Heat flux conducted through the bristles dissipates into the flow by a strong convection at the fence-height region.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Schematic of brush seal heat transfer

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Figure 2

Schematic of brush seal heat partition mechanism

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Figure 3

Schematic of bristle heat transfer as an infinitely long fin

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Figure 4

Bristle layout for calculation of convective heat transfer coefficient

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Figure 5

Brush seal CFD model domain

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Figure 6

Typical brush seal dimensions used in CFD model

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Figure 8

Convective heat transfer coefficient versus mass flow rate∕pressure load

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Figure 10

Velocity vectors (in meters per second) for ΔP=70kPa, qf=100kW∕m2

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Figure 11

Temperature contours (in degrees Celsius)

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Figure 12

Radial temperature distribution at the middle of the bristle pack for various pressure loads and frictional heat generations: (a) ΔP=70kPa, (b) ΔP=200kPa, (c) ΔP=350kPa, and (d) ΔP=700kPa

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Figure 13

Maximum temperature for various pressure loads and frictional heat generations

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Figure 9

Pressure contours (in kilopascal) for ΔP=70kPa, qf=100kW∕m2




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