Dynamic Characteristics of a Tilting-Pad Bearing System for High Expansion Ratio Expander

Abstract

In this paper, the dynamic characteristics of a tilting pad bearing system, which contains a rigid rotor supported by two bearings with three pivoted pads each, was analyzed. Ten degrees of freedom were used to describe the system: two translations and two tilts for the shaft, and pitch of each shoe. The bearing forces in each pad were evaluated by solving the Reynolds equation with full account of geometrical and pressure transient terms. The forces are used in the dynamic equations for all degrees of freedom involved. The stiffness and damping coefficients is calculated directly from the time histroy of bearing loading capacity, shaft velocity and displacement by means of the least-mean-square method. The bearing stiffness is used to estimate the natural frequency and resonance frequency of the 1st and 2nd rigid mode. The transient response of shaft and pads to initial displacement and unbalance mass is obtained throungh numerical integration of the motion equations.