The Application of Double Conical Journal Bearings in High Speed Centrifugal Pumps — Parts 1 and 2

Abstract

Conical bearings can in principle support a combination of radial and axial load. Their application to centrifugal pumps is considered, which allows the thrust bearing of the conventional arrangement to be dispensed with. It is shown that with low pressure oil lubrication, the axial load of this type of bearing is limited to the ratio (axial load/radial load)=Tan A, where A is the half angle of the cone. Methods of avoiding this limitation are considered. The feasibility of water lubricated inclined journal bearings for centrifugal pumps is analysed. A ‘Vee’ configuration double conical journal bearing is considered with a central high pressure feed from the pump outlet. Although the enhancement of viscosity due to turbulence is not as great as anticipated, the bearing is shown to have an adequate axial and radial load capacity. It is shown that flow compensation or restriction to each side of the bearing is necessary to maintain the escaped flow at an acceptable level. The limits of bearing operation are set by acceptable film thickness rather than excessive temperature rise. For this reason, the correct choice of bearing materials to run under thin film or no film conditions in the presence of dirt is probably more important than correct hydrodynamic design.