The surfacse roughness effect on the hydrostatic thrust spherical bearings performance

The study deals with the surface roughness and the predominant centripetal inertia terms due to the shaft rotation of the externally pressurized thrust spherical bearings. The solutions are presented for the recessed clearance type of bearings, hemispherical and partial hemispherical seats, with capillary tube and orifice restrictors. Expressions for the pressure distribution, load carrying capacity, volume flow rate, frictional torque, friction factor, power losses and stiffness factor are obtained. The study shows the combined effects of the centripetal inertia and the surface roughness on the bearing performance. An optimum design based on the minimum power losses and the optimal restrictor dimensions is theoretically examined. The conventional four cases of this type of bearings, dependant on the eccentricity ratio in the previous studies, have been reduced to three cases only. In addition, a unified solution for this type of bearings is developed. Finally, a general solution for the hydrostatic thrust spherical bearings is produced where it could be applied to the, un-recessed and the recessed - hemispherical, partial hemispherical - clearance and fitted types of bearings. This general solution considers the fitted type of bearings as a special case of the clearance type. A comparison between the results calculated by the general solution and the private solution for both of the fitted type and the un-recessed clearance type of bearings is performed.