Three-Dimensional Dynamic Model of TEHD Tilting-Pad Journal Bearing-Part I: Theoretical Modeling
Suh, Junho(Texas A&M University)
United States | Journal of Tribology
2015-10 | 바로가기
Cited by 45
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Journal of Tribology
Published: October 2015
Junho Suh, Alan Palazzolo
Department of Mechanical Engineering, Texas A&M University
This paper is focused on a new modeling method of three-dimensional (3D) thermo-elasto-hydro-dynamic (TEHD) cylindrical pivot tilting-pad journal bearing (TPJB). Varying viscosity Reynolds equation and 3D energy equation are coupled via lubricant temperature and viscosity relationship. Three-dimensional finite element method (FEM) is adopted for the analysis of: (1) heat conduction in shaft and bearing pad, (2) thermal deformation of shaft and pad, (3) flexible bearing pad dynamic behavior, and (4) heat conduction, convection, and viscous shearing in thin lubricant film. For the computational efficiency, modal coordinate transformation is utilized in the flexible pad dynamic model, and pad dynamic behavior is represented only by means of modal coordinate. Fluid film thickness is calculated by a newly developed node based method, where pad arbitrary thermal and elastic deformation and journal thermal expansion are taken into account simultaneously. The main goal of this research is to provide more accurate numerical TPJB model than developed before so that the designers of rotating machinery are able to understand the bearing dynamic behavior and avoid unpredicted problem by selection of physical parameters.
Dynamic equation of motion for flexible FE pad model was produced, where the pad dynamic behavior was presented by means of modal coordinate. To avoid a singular matrix problem and produce more realistic pad elastic deformation, nonlinear transient pad dynamic analysis is adopted. On the other hand, earlier studies have adopted additional constraints leading to unrealistic pad deformation, where static analysis of pad elastic deformation is performed.
For the computational efficiency, modal coordinate transformation is adopted in flexible pad dynamic analysis. Pad tilting motion, pivot translation motion, and elastic deformation can be expressed by means of modal displacement.
Nonlinear pivot stiffness model considering Hertzian contact theory is adopted for more accurate prediction of TPJB dynamic behavior.
Heat conduction equation of journal and bearing pad was presented by use of 3D FE model.
Thermal distortions of 3D shaft and pad were evaluated adopting FE analysis, and the 2D thermal expansion profile was considered in film thickness evaluation.
Due to the arbitrary pad elastic deformation, conventional film thickness formula cannot be used. So a new formula is developed to calculate the nodal film thickness profile of the flexible pad TPJB model.
Full dynamic coefficients were presented by means of journal translational motion and modal displacement of flexible FE pad, and synchronously reduced dynamic coefficient was presented.
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