Modeling a Porous Slider Bearing With An External Reservoir
The use of porous bearings is widespread throughout industry. In classical cases, the porous medium can be thought of as an external reservoir and so their use is ideal for applications where an external oil supply is undesirable, impractical, or too costly. In these cases, as the bearing moves and creates a pressure gradient, the fluid from inside the porous layer is drawn into the film, further enabling lubrication.
The purpose of this project is to mathematically investigate the effects of modifying a slider bearing to include a porous layer and a fluid reservoir. Using the Darcy model for flow inside a porous medium, we consider a porous slider bearing above an external reservoir. Order of magnitude analyses are performed to simplify the governing equations inside the bearing. Further analysis of the directional permeabilities allows for a modified Reynolds equation to obtain a solution for the pressures inside all three regions (lubricating film, porous medium, and reservoir) of the bearing. The moving slider bearing establishes a pressure profile that circulates fluid between the lubricating region and the reservoir. Simplifications are made to allow for a semi-analytical solution to be constructed that can be easily solved using a standard computational package such as Maple. It is shown that the fluid is circulated inside the bearing to allow for load-carrying capability as well as for no external oil supply and pump. Future work will examine different bearing geometries using the porous medium/reservoir concept, and the inclusion of heat transfer analyses to examine the feasibility of a self-contained bearing. In the latter case the heat transfer must be sufficient to cool the circulating fluid before it re-enters the lubricating film region.