A Preliminary Nonlinear Analysis of the Axial Transient Response of the Sector-Shaped Hydrodynamic Thrust Bearing-Rotor System

This paper describes a nonlinear model and analysis of the axial transient response of the sector-shaped hydrodynamic thrust bearing-rotor system in a turbo-expander under a suddenly applied step load. The model is comprised of a time-dependent Reynolds Equation for oil film forces, and a vibration equation for the axial shaft system. The time-dependent form of the Reynolds Equation is solved by a finite difference method with a successive over-relaxation scheme, and the vibration equation is solved by the fourth-order Runge-Kutta method and the Adams method. In addition, a linear analysis is attempted in order to evaluate its suitability for the situation under consideration. The result of the analysis has shown that the linear model is unsuited, while the nonlinear analysis appears reasonable. Two system parameters, the initial oil film thickness and the angle of the inclination of the tapered land in a thrust bearing, are shown to have significant impacts on the transient response under consideration, anal to be possibly optimized to achieve a minimum axial transient response.

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