Dynamics of offset journal bearings — revisited

Abstract

‘Offset’ journal bearings provide an alternate design approach for problematic applications lacking both load reversal and adequate journal angular velocity. More than a quarter century has gone by since the first publication of a dynamic analysis for offset journal bearings (and the concept of such bearings is much older still). Since then it has been found that the ‘squeeze film’ support crucial to successful operation of these bearings can be extremely sensitive to refilling rate from cavitated film regions, requiring a mass-conservative cavitation analysis that was unavailable earlier. Additionally, the earlier analyses were based on semi-analytic approximate solutions to the Reynolds equation, rather than on later numerically exact full solutions. The present work addresses these shortcomings and attempts thereby to put the design of these unique bearings on a sounder and more reliable footing. Thus, the choice of ‘revisited’ over ‘reviewed’ in the title is a deliberate one. Rather than a simple review of previous work, the article is a revisit of the design analysis of offset journal bearings using modern methods not available to previous authors. Included are dimensional sample applications and non-dimensional parametric optimization studies showing an order of magnitudeimprovement in predicted cyclic minimum film thickness and a modest reduction in cyclic maximum film pressure.