Design and Stress Analysis of Extraterrestrial ... - The Black Vault

(a)
(b)
Fig. 3.6. Dry-fri'ction bearings: a - with graphite
inserts; b - with inserts made of tungsten and titanium
carbides.
t
Slider-type bearings, in which the friction surfaces are
separated by a layer of liquid, are more promising for use in the
turbogenerator of extraterrestrial power plants. Two types of
these bearings, differing in the means of obtaining bearing power
in the liquid layer, are used today. The best known is the hydrodynamic
bearing, whose carrying capacity in thM carrying layer of
liquid is created during the rotation of the central shaft which
traps (because of viscosity) the lubricating liquid and drives it
into the wedge-shaped clearance between the center shaft and the
bearing insert (the housing).
II
During the rotation of the shaft, under the )ffect of the
difference in the hydrodynamic pressures of the lubricating liquid
in the clearance, the shaft comes up and the center line of the
shaft neck turns angle p in the direction of rotation (Fig. 3.7);
purely fluid friction is thus ensured. Figure 3.7 shows the typical
distribution of surplus hydrodynamic fluid pressure in the bearing
clearance. The resultant forces of the pressure during purely fluid
friction are equal in magnitude but reverse in direction to the
carrying capacity P of the bearing.
It should be noted that the necessary load-lifting capacity
* of such a bearing is obtained with fully defined rotational velocity
of the shaft (which should be lower th•a operating), a determined
clearance, and a determined viscosity of the lubricating liquid.
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