To investigate the static characteristics of aerostatic journal bearings with porous bushing, the flow model—in which the compressibility of lubricating gas is considered—is established based on the Reynolds lubrication equation, Darcy equation for porous material, and continuity equation. With the finite difference method, difference schemes for non-uniform grids, relaxation method, and virtual node method, the numerical method for the governing equations of compressible flow in porous journal bearings is proposed. The effects of nominal clearance of bearings and compressibility of gas on the static characteristics are analyzed. Under the same minimum film thickness and the same gas compressibility, as the nominal clearance widens, the load capacity, mass flow rate, and power consumption increase. Under the same minimum film thickness and the same nominal clearance, with the increase in gas polytropic index, the load capacity strengthens, while the mass flow rate and power consumption decline. This study could provide a reference for the design of porous journal bearings.

The side chamber flow has a fundamental influence on the performance and reliability of centrifugal pumps. However, the radial wall shear stress in the flow modelling of pump side chambers is arbitrarily neglected. The current work proposes a model for the radial wall shear stress, which is an extension of the previous paper (DOI: 10.1115/1.4047532). By using the power-law for the velocity boundary layer and the Blasius law for the wall shear stress, introducing the Ekman layer thickness expression, and deducing the Bödewadt layer thickness expression, the radial wall shear stress on the rotating and stationary disks is formulated and then integrated into the side chamber flow model. Besides, the entire flow field of the centrifugal pump is solved using the computational fluid dynamics (CFD) software ANSYS CFX. The radial wall shear stress calculated by the new side chamber flow model (NSCFM) is in the identical magnitude as CFD. Compared with pressure measurements, NSCFM makes better pressure predictions than CFD from the rear seal to the hub; however, in other areas, CFD results are closer to experimental data than NSCFM results. The flow prediction tools show that the volumetric efficiency and the shroud thrust increase with the increase in flow rate. NSCFM achieves a good compromise between calculation speed and desired accuracy.

Hydrodynamic journal bearings, coated with polytetrafluoroethylene (PTFE) and lubricated by water, have been widely used in ships and large-scale pumps, and the function is to maintain the stability of rotor system. However, slip velocity exists on the PTFE-coated surface, whose effect is still an open question. This study aims to investigate the static characteristics of water-lubricated hydrodynamic journal bearings under three-dimensional slip velocity boundary conditions. Firstly, under the non-slip boundary condition, the CFD (computational fluid dynamics) method with ANSYS Fluent is verified based on the Reynolds lubrication equation and the open literature. Then, a three-dimensional slip velocity equation that is based on the Navier slip velocity boundary condition is proposed and embedded into Fluent. Finally, the effects of slip length on the static characteristics are analyzed. Under the same eccentricity ratio, with the increase in slip length, the load capacity decreases due to the decrease of the pressure circumferential gradient, and the friction power decreases. Under the same eccentricity ratio and the same slip length, with the increase in the attitude angle, the load capacity and friction power increase. However, under the non-slip boundary condition, the effects of attitude angle on the load capacity and friction power are insignificant. This paper could provide a reference for studying slip velocity in the hydrodynamic journal bearing.