Computational Fluid Dynamics Study of Oil Lubrication in Ball and Roller Bearings

Lubrication plays a significant role in performance of rolling element bearings. It is essential for proper functioning of bearings to reduce friction and to help avoid failure of bearings. Computational fluid dynamics (CFD) is one of the design and simulation tools, which is mainly used to identify proper lubrication for bearings. This work summarizes the CFD simulation results of oil transport within deep groove ball bearing and concave roller bearing. The volume fraction of oil has been predicted around the contacts at both outer and inner rings, all components and the gaps between the cage and rollers for both bearings. Drag losses (both pressure and shear drag) and film thickness have also been predicted. Cage design plays a significant role in determining the lubrication and the internal fluid drag losses in a bearing. The influence of cage design on the lubrication and the drag is evaluated by employing a metallic cage and a polymer cage. The simulation results show that oil content inside the bearing is dependent on the bearing free volume and operating speed. At lower speeds, both cage designs give similar performance; however, at the higher speed, it is different. Compared to metallic cage, polymer cage functions better in oil bath lubrication by splashing the oil on raceways at higher rotation speed. A linear decrease in oil content is observed with increased volume of polymer cage for concave roller bearing. In all case, cage and rollers experience maximum oil drag. An improved polymer cage is developed with the help of CFD to provide more oil to the cage and other bearing components.