Analysis of Starved Journal Bearings Including Temperature and Cavitation Effects

Abstract

A method of analysis is described treating starvation in finite journal bearing pads. A variable-size finite difference mesh is used to represent the two-dimensional temperature and pressure fields. A combination of Newton-Raphson iteration, direct iteration, and column matrix methods are used to solve for the start-of-film and journal positions as well as the coupled two-dimensional energy and Reynolds equations. Neglecting the pressure gradients in the energy equation has negligible effect on the location of the shaft, although it may increase some of the bearing coefficients between 14 and 16 percent at highly starved conditions. The variation of the temperature and start-of-the-film position during the differentiation for the stiffness and damping coefficients is important, particularly at highly starved conditions. A parametric study, describes the performance of the bearing (journal position, flowrates and temperature rises, stiffness and damping coefficients, and torque) for different degrees of starvation. An optimum L/D ratio (between 0.6 and 1) is found such that the minimum film thickness is maximized. For highly starved conditions, the component of eccentricity ratio along the load direction is found to be a strong function of supplied lubricant flowrate and rather insensitive to load and L/D ratio. When the differentiation is done properly, this produces a relatively high value of Kxy .