UBC Theses and Dissertations
Journal bearing optimization and analysis using streamline upwind Petrov-Galerkin finite element method Zengeya, Miles
A three-dimensional finite element thermo-hydrodynamic lubrication model that couples the Reynolds and energy equations is developed. The model uses the streamline upwind Petrov-Galerkin (SUPG) method. Model results indicate that the peak temperature location in slider bearing is on the mid-plane well as when pressure boundary conditions are altered in such a way that the inlet/outlet pressure is higher than the side pressure. The adiabatic temperature profiles of an infinite and square sliders are compared. The wider slider shows a higher peak temperature. Side flow plays a major role in determining the value and position of the peak temperature. Model results also indicate peak side flow at a width-to-length ratio of 2. A method of optimizing leakage, the Flow Gradient Method, is proposed. The SUPG finite element method shows rapid convergence for slider and plain journal bearings and requires no special treatment for backflow in slider bearings or special boundary conditions for heat transfer in the rupture zone of journal bearings. A template for modeling thermo-hydrodynamic lubrication in journal bearings is presented. The model is validated using experimental and analytical data in the literature. Maximum deviation from measured temperatures is shown to be within 40 per cent. The model needs no special treatment of boundary conditions in the rupture zone and shows rapid and robust convergence which makes it quite suitable for use in design optimization models and in obtaining closed relations for critical parameters in the design of journal and slider bearings. Empirically derived simulation models for temperature increase; leakage; and power loss are proposed and validated using the developed finite element model and experimental results from literature. Predictions of temperature increase, leakage, and power loss are better than those obtained for available relations in the literature. The derived simulation models include five important design variables namely the radial clearance, length to diameter ration, fluid viscosity, supply pressure and groove position. The derived model is used to minimize a multi-objective function using weight/scaling factors and Pareto optimal fronts. The latter method is recommended as preferable, and Pareto diagrams are presented for common bearing speeds. Including the groove location in the optimization model is shown to have a significant effect on the results. The lower bound of groove location appears to result in preferred power loss/side leakage values. Significant power loss savings may be realized with appropriate groove location.
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