Thermoelastohydrodynamic lubrication in thrust bearings
Brockett, Theodore Scott, Department of Engineering, University of Virginia
Barrett, Lloyd, Department of Mechanical and Aerospace Engineering, University of Virginia
Allaire, Paul E., Department of Mechanical and Aerospace Engineering, Un
Flack, Ronald, Department of Mechanical and Aerospace Engineering, University of Virginia
Mansfield, Lois, Engineering-Dean's Office, University of Virginia
Haj-Hariri, Hossein, Department of Mechanical and Aerospace Engineering, University of Virginia
The subject of this dissertation is the theoretical prediction of the operating characteristics of fixed-pad and tilting-pad incompressible fluid-film thrust bearings using new and improved models. The new models of interest include runner elastic deformation and detailed 3-D elastic deformation and conduction within the pad. The operating characteristics of concern for a given speed-load condition include the temperature distribution in the film and solids, the pressure distribution in the film, the elastic deformation in the solids due to thermal and mechanical loading, minimum film thickness, power losses from lubricant shearing, and oil flow requirements.
The governing equations for the pressure distribution in the film, temperature distribution in the film and solids, and the elastic deformation of the solids are solved simultaneously using the finite element method with linear, bi-linear, and tri-linear elements. The generalized Reynolds equation including the effects of cross-film viscosity variation, centrifugal inertia term, and cavitation is coupled to the three-dimensional energy equation in the film, three-dimensional conduction and elastic equations in the pad, and the axisymmetric conduction and elastic equations in the thrust runner. The Reynolds equation and film energy equation include the effects of turbulence using a zero-equation turbulence model.
The effects of the different physical models on the operating characteristics are studied for a style of bearing that has not appeared before in the literature - a parallel tapered-land bearing. The operating characteristics for this bearing style are studied as a function of the different models included in the analysis, as a function of load, and as a function of rotational speed. Isoviscous, adiabatic, fully three-dimensional thermal, and thermoelastohydrodynamic analyses are considered. A detailed thermoelastohydrodynamic analysis of a spherical-pivot tilting pad thrust bearing is also considered.
It is found that the centrifugal inertia term has little effect even at higher speeds for typical lubricating oils and loadings. The runner deformation can cause either an increase or a decrease in the maximum film temperature of fixed geometry bearings, depending on the speed and loading. A decrease in the maximum film temperature is at the expense of minimum film thickness, however. Mechanical deformation in typical fixed geometry bearings can be neglected but thermal deformation can have a significant effect on the maximum film temperature. The single thermoelastohydrodynamic analysis on a tilting pad bearing demonstrates the benefits of using a 3-D conduction-elastic model in the pad compared to the simpler models available.
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PHD (Doctor of Philosophy)
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