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Research Papers: Porous Media

Numerical Investigations on the Heat Transfer Behavior of Brush Seals Using Combined Computational Fluid Dynamics and Finite Element Method

[+] Author and Article Information
Jun Li

e-mail: junli@mail.xjtu.edu.cn
Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 9, 2012; final manuscript received April 30, 2013; published online September 27, 2013. Assoc. Editor: Jose L. Lage.

J. Heat Transfer 135(12), 122601 (Sep 27, 2013) (10 pages) Paper No: HT-12-1427; doi: 10.1115/1.4024556 History: Received August 09, 2012; Revised April 30, 2013

Brush seals have been applied in more and more challenging high-temperature locations. The high speed bristle-rotor friction causes a considerable heat generation which accelerates the bristles wear. The frictional heat generation at bristle-rotor interface becomes another major concern in brush seal applications. This study presented detailed investigations on the heat transfer characteristics and contact mechanics of brush seals using a combined computational fluid dynamics (CFD) and finite element method (FEM) brush seal model. The CFD model of brush seal for mass and heat transfer employed Reynolds-averaged Navier–Stokes (RANS) solutions coupled with non-Darcian porous medium approach. The nonlinear contact model of brush seal was established using FEM with considerations of internal frictions (bristle to rotor, bristle to backing plate, and bristle to bristle) and aerodynamic loads on bristles. The numerical method involved iterations between CFD and FEM models to better evaluate the heat transfer behaviors of the brush seal with consideration of bristle deflections. The frictional heat generation was calculated from the product of bristle-rotor frictional force and sliding velocity. The bristle deflections and temperature distributions of the brush seal were predicted at various operational conditions using the iterative CFD and FEM brush seal model. The effects of pressure differential and rotational speed on the contact behavior, temperature distribution and bristle maximum temperature of brush seals were numerically investigated using the developed approach. The detailed pressure contours and streamline distributions of the brush seal were also illustrated.

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Figures

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Fig. 1

Brush seal heat transfer mechanisms model

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Fig. 2

Combined CFD and FEM model calculation procedure

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Fig. 3

Brush seal computational grid

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Fig. 4

Comparison of numerical results and experimental leakage

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Fig. 5

Bristle centerline positions in axial radial plane

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Fig. 6

Bristle-rotor normal contact force and frictional force versus pressure differential

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Fig. 7

Static pressure contour of brush seal

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Fig. 8

Streamline distribution in the fence height region

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Fig. 9

Temperature contours for various pressure differentials

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Fig. 10

Frictional heat for various pressure differentials and rotational speeds

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Fig. 11

Temperature contours for various rotational speeds

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Fig. 12

Bristles maximum temperature at various pressure differentials and rotational speeds

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Fig. 13

Radial temperature distribution at the middle of bristle pack versus pressure differential

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Fig. 14

Radial temperature distribution at the middle of bristle pack versus rotational speed

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