The Pressure Distribution of Externally Pressurized Journal Gas Bearings

Abstract

The externally pressurized gas journal bearing performances (load capacity, stiffness and damping) are affected by clearance pressure distribution. The pressure distribution is determined by the restrictor losses which are dependent on the type of restrictor (orifices and inherently compensated), number of restrictors, radial clearance, supply pressure and shaft rotational speed. In this paper, the pressure distribution around the restrictor is measured and influence of the above conditions on the restrictor losses is investigated. Following conclusions are obtained : (1) By the use of orifice restrictor, bearing operational clearance can be made narrower than in the case of inherently compensated restrictor. (2) The pressure distribution in the upstream and downstream of the restrictor is unsymmetrical in proportion to the shaft rotational speed, and this tendency can be ignored when the bearing clearance is smaller than 40-50 μm. (3) In case of using orifice restrictor, loss of load capacity amounts to 10-20% of the value obtained in purely viscosity calculations.