The design concept for hydrostatic bearings is the generation of a high-pressure
fluid film by using an external pump. The hydrostatic system of a journal bearing
is shown in Fig. 1-4. The fluid is fed from a pump into several recesses around the
bore of the bearing. From the recesses, the fluid flows out through a thin
clearance, h0, between the journal and bearing surfaces, at the lands outside
the recesses. Previous literature on hydrostatic bearings includes Opitz (1967),
Rowe (1989), Bassani and Picicigallo (1992), and Decker and Shapiro (1968).
The fluid film in the clearance separates the two surfaces of the journal and
the bearing and thus reduces significantly the friction and wear. At the same time,
the thin clearance at the land forms a resistance to the outlet flow from each
recess. This flow resistance is essential for maintaining high pressure in the
recess. The hydrodynamic load capacity that carries the external load is the
resultant force of the pressure around the bearing.
There is also a fluid film in a hydrodynamic bearing. However, unlike the
hydrodynamic bearing, where the pressure wave is generated by the hydrody-
namic action of the rotation of the journal, hydrostatic bearing pressure is
generated by an external pump.
There are certain designs of hydrodynamic bearings where the oil is also
supplied under pressure from an external oil pump. However, the difference is
that in hydrostatic bearings the design entails recesses, and the operation does not
depend on the rotation of the journal for generating the pressure wave that
Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.
supports the load. For example, the hydrodynamic journal bearing does not
generate hydrodynamic pressure and load capacity when the journal and sleeve
are stationary. In contrast, the hydrostatic bearing maintains pressure and load
capacity when it is stationary; this characteristic is important for preventing wear
during the bearing start-up. In fact most hydrostatic j