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Research Papers: Hydrodynamic Lubrication

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part II: Dynamic Response

[+] Author and Article Information
Jongin Yang

Mem. ASME
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: jiyang@tamu.edu

Alan Palazzolo

James J. Cain Professor I
Fellow ASME
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: a-palazzolo@tamu.edu

Contributed by the Tribology Division of ASME for publication in the Journal of Tribology. Manuscript received October 26, 2018; final manuscript received March 27, 2019; published online April 30, 2019. Assoc. Editor: Stephen Boedo.

J. Tribol 141(6), 061703 (Apr 30, 2019) (16 pages) Paper No: TRIB-18-1448; doi: 10.1115/1.4043350 History: Received October 26, 2018; Accepted March 28, 2019

Part II presents a novel approach for predicting dynamic coefficients for a tilting pad journal bearing (TPJB) using computational fluid dynamics (CFD) and finite element method (FEM), including fully coupled elastic deflection, heat transfer, and fluid dynamics. Part I presented a similarly novel, high fidelity approach for TPJB static response prediction which is a prerequisite for the dynamic characteristic determination. The static response establishes the equilibrium operating point values for eccentricity, attitude angle, deflections, temperatures, pressures, etc. The stiffness and damping coefficients are obtained by perturbing the pad and journal motions about this operating point to determine changes in forces and moments. The stiffness and damping coefficients are presented in “synchronously reduced form” as required by American Petroleum Institute (API) vibration standards. Similar to Part I, an advanced three-dimensional thermal—Reynolds equation code validates the CFD code for the special case when flow Between Pad (BP) regions is ignored, and the CFD and Reynolds pad boundary conditions are made identical. The results show excellent agreement for this validation case. Similar to the static response case, the dynamic characteristics from the Reynolds model show large discrepancies compared with the CFD results, depending on the Reynolds mixing coefficient (MC). The discrepancies are a concern given the key role that stiffness and damping coefficients serve instability and response predictions in rotordynamics software. The uncertainty of the MC and its significant influence on static and dynamic response predictions emphasizes a need to utilize the CFD approach for TPJB simulation in critical machines.

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References

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Figures

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Fig. 1

Configuration of tilting pad journal bearing model: (a) overview and (b) exploded view

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Fig. 2

Flow diagram of CFD-based FSI TPJB modeling for dynamic performance prediction

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Fig. 3

TPJB perturbations for stiffness: (a) pivot displacement and pad angle of the jth pad and (b) x and y journal displacements

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Fig. 4

Illustration of film thickness parameters at the equilibrium condition

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Fig. 5

Calculation procedure for obtaining frequency reduced, TPJB stiffness, and damping coefficients

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Fig. 6

Nondimensional direct stiffness of “without mixing effect” model: (a) case A, (b) case B, and (c) case C effects

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Fig. 7

Nondimensional direct damping of “without mixing effect” model: (a) case A, (b) case B, and (c) case C effects

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Fig. 8

Log decrement of “without mixing effect” model: (a) case A, (b) case B, and (c) case C effects

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Fig. 9

Nondimensional direct stiffness (Kxx) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 10

Nondimensional direct stiffness (Kyy) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 11

Nondimensional cross-coupled stiffness (Kxy) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 12

Nondimensional cross-coupled stiffness (Kyx) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 13

Nondimensional direct damping (Cxx) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 14

Nondimensional direct damping (Cyy) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 15

Nondimensional cross-coupled damping (Cxy) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 16

Nondimensional cross-coupled damping (Cyx) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 17

Log decrement (x-direction) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

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Fig. 18

Log decrement (y-direction) of the “with mixing effect” model for (a) case A, (b) case B, and (c) case C

Tables

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