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Research Papers: Gas Turbines: Structures and Dynamics

Theoretical and Experimental Investigation on Tip Forces and Temperature Distributions of the Brush Seal Coupled Aerodynamic Force

[+] Author and Article Information
Shouqing Huang

e-mail: hshouqing@163.com

Shuangfu Suo

Associate Professor
e-mail: sfsuo@mail.tsinghua.edu.cn
State Key Laboratory of Tribology,
Tsinghua University,
Beijing 100084, China

Yongjian Li

Lecturer
e-mail: liyongjian@tsinghua.edu.cn

Yuming Wang

Professor
State Key Laboratory of Tribology,
Tsinghua University,
Beijing 100084, China

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 28, 2013; final manuscript received November 15, 2013; published online January 9, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(5), 052502 (Jan 09, 2014) (12 pages) Paper No: GTP-13-1389; doi: 10.1115/1.4026074 History: Received October 28, 2013; Revised November 15, 2013

Based on a type of three-dimensional slice model of a brush seal combined with the commercial CFD software FLUENT, the study calculated the leakage flow of the brush seal. The aerodynamic forces applied on upstream and downstream bristles are analyzed and reduced to a smaller amount of point forces for analysis convenience. The frictional coefficient between the bristle material Haynes 25 and rotor material 1Cr14Mn14Ni are tested. Tip forces including normal reaction and frictional forces caused by aerodynamic forces are quantitatively investigated under conditions with and without frictions using the torque balance principle and nonlinear beam theory (by ANSYS simulations), respectively. Torques, frictional heats, and the temperature distributions of the rotor and bristle pack are studied further. Details and characteristics of the flow and temperature distributions inside the bristle pack are presented. In the experiments, besides traditional tests, such as leakage and torque tests, an infrared camera is employed to capture temperature distributions at the interface of the rotor, bristle pack and nearby zones under various pressure differentials and rotation speeds. The three-dimensional slice model is firstly verified by calculating the leakages, torques and temperature distributions of the brush seal and confirmed via experimentation. The influence of various frictional coefficients and pressure differentials on tip forces, torque and temperature distributions are also examined.

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Figures

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Fig. 1

Photograph of the brush seal test rig

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Fig. 2

Partial cross-sectional view of the test cavity

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Fig. 3

Typical dimensions of the test brush seal: (a) front view; (b) side view; and (c) partial enlarged view

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Fig. 4

Infrared camera setup (remove the test cavity cover)

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Fig. 5

Three-dimensional slice CFD model of the test seal

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Fig. 6

Cross section of the bristle pack (along axis direction)

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Fig. 7

The force analysis of the bristle

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Fig. 8

The ANSYS model for calculating the tip force

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Fig. 9

Iterative solution flow chart of bristle tip forces

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Fig. 10

The friction experiment of the bristle-rotor materials: (a) installation picture; and (b) picture after wear

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Fig. 11

Fiction coefficient at various speeds and radial forces

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Fig. 12

The slice model of brush seal for temperature analysis

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Fig. 13

Mesh of the air among bristles in the CFD model

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Fig. 14

Mesh details of bristles and adjacent zones in the temperature analysis model

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Fig. 15

Leakages under various pressure differentials

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Fig. 16

Pressure contours on a symmetric plane (ΔP = 0.2 MPa)

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Fig. 17

Velocity vectors on a symmetric plane (ΔP = 0.2 MPa)

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Fig. 18

Pressure contours and velocity vectors on a horizontal plane (0.7 mm from bristle tips, ΔP = 0.2 MPa)

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Fig. 19

Pressure contours between the bristle pack and backing ring (ΔP = 0.2 MPa)

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Fig. 20

Velocity vectors between the bristle pack and backing ring (ΔP = 0.2 MPa)

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Fig. 21

Axial bristle forces per unit length of various segments of bristles (m = 15, ΔP = 0.2 MPa)

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Fig. 22

Radial bristle forces per unit length of various segments of bristles (m = 15, ΔP = 0.2 MPa)

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Fig. 23

Normal reaction forces of various bristles caused by aerodynamic forces in the CFD model (ΔP = 0.2 MPa)

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Fig. 24

Frictional forces of various bristles caused by aerodynamic forces in the CFD model (ΔP = 0.2 MPa)

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Fig. 25

Test torques under various pressure differentials

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Fig. 26

Calculation and test torques under various pressure differentials (3000 rpm)

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Fig. 27

Influence of pressure differentials on heat fluxes of various rows of bristles (μ = 0.05, 3000 rpm)

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Fig. 28

A typical thermal image at the bristles-rotor interaction zone (3000 rpm, 0.2 MPa)

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Fig. 29

Temperature distributions on the symmetry boundary@3000 rpm, 0.2 MPa: (a) based on uniform heat fluxes; and (b) based on nonuniform heat fluxes

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Fig. 30

Temperature distributions on bristles surfaces @3000 rpm, 0.2 MPa: (a) based on uniform heat fluxes; and (b) based on nonuniform heat fluxes

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Fig. 31

The maximum tip temperature under various pressure differentials (3000 rpm)

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Fig. 32

The maximum tip temperature under various rotation speeds (ΔP = 0.2 MPa)

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