Performance Prediction of Journal Bearing with Partial Fluid Slip Region on Lubricated Surface

Abstract

Rotating machineries supported in journal bearings are stably operated at a rotational speed between the one where the minimum oil film thickness is ensured to prevent direct contact of journal and bearing surfaces and the one where self-excited vibration occurs, while avoiding the critical speed of the rotor-bearing system. When a rotating shaft is supported in a cylindrical journal bearing, which has the simplest structure among journal bearings, the upper operational speed will be approximately twice the critical speed. In the present report, focusing on a rotating shaft supported in the bearing with slip regions on part of the bearing surface, those speeds are numerically calculated by applying a hydrodynamic lubrication theory, then the effects of the slip region on the range of stable operation are evaluated. It is found that the range of the stable operation of rotating shaft can be significantly extended simply by creating slip regions on a part of the bearing surface, without replacing complicated journal bearings or employing stabilization method such as adjusting the amount of oil supplied.