Lubricant Additives Effects on the Hydrodynamic Lubrication of Misaligned Conical-Cylindrical Bearings~©

摘要

Conical-cylindrical bearings are used in electro-hydraulic servo systems to improvernthe control accuracy, eliminate the static friction, and increase the normal loadrncarrying capacity. A non-Newtonian rheological model to investigate theoretically therneffects of lubricant additives on the performance of misaligned conical-cylindricalrnbearings is proposed in this study. In this model, the non-Newtonian behaviorrnresulting from blending the lubricant with polymer additives is simulated by Stokesrncouple stress fluid model. The formed boundary layer at the bearing surface isrndescribed through the use of a hypothetical porous medium layer that adheres to thernbearing surface. The Brinkman-extended Darcy equations are utilized to model thernflow in the porous region. A stress jump boundary condition is applied at the porousrnmedia/fluid film interface. The misalignment of the cylinder rod is also considered. Arnmodified form of the Reynolds equation is derived and solved numerically using arnfinite difference scheme. The effects of bearing geometry, and non-Newtonianrnbehavior of the lubricant on the steady-state performance characteristics such asrnpressure distribution, load carrying capacity, and coefficient of friction are presentedrnand discussed. The results showed that lubricant additives significantly increase thernload carrying capacity and reduce the coefficient of friction as compared to thernNewtonian lubricants. Furthermore, the misalignment of the piston rod has significantrneffects on the performance of conical-cylindrical bearings.