The Gas-to-Liquid Interface of Spiral Groove Journal Bearings and its Effect on Stability

Abstract

A spiral groove journal bearing has two significant advantages, compared with a plain journal bearing. These are the self-sealing capabilities and the favorable stability properties of the bearing under no-load or light-load conditions. Under eccentric operating conditions the axial width of the liquid film in such a bearing varies in the circumferential direction. The shape of the gas-to-liquid interface and its effect on load capacity and stability are investigated both theoretically and experimentally. It appears that there is a considerable difference in the shape of the gas-to-liquid interface, depending on whether it is the housing or the shaft that has spiral grooves, or more generally, on whether the load vector is rotating with respect to the grooves or not. It has further been found that the free boundary has an unfavorable effect on the stability of unloaded spiral groove journal bearing. A deep groove in the circumferential direction, close to the gas-to-liquid interface, can practically cancel this unfavorable effect.