Stability analysis of orthogonally displaced bearings

Abstract

Journal bearings operating at high speeds often exhibit vibrational instability. Circular bearings are known to be prone to vibrations and, in general, a non-circular bearing geometry enhances shaft stability. Among the several possible configurations of non-circular bearings, elliptical, offset, three-lobe and tilted three-lobe bearings have attracted attention. The present analysis is a theoretical prediction of stability for a hybrid two-lobe bearing obtained by displacing the lobe centres of an elliptical bearing. It has been found that an orthogonally displaced bearing is more stable than the hitherto known bearings and at the same time it is easier to manufacture. Numerical results have been presented for nine combinations of horizontal and vertical displacements of lobes and three L D ratios so that a suitable profile and L D ratio can be selected by a designer in a specific application.