Lubricant levitation in high-speed bearings: An experimental approach

Lubricant flow in rolling element bearings is quite complex due to the motion of balls, cage, and inner and outer races. This phenomenon is further complicated at high speeds. This study aims to experimentally investigate the phenomenon of lubricant condition on bearing surfaces under high-speed (HS) conditions. The primary tests were conducted using a dedicated test rig with a high-speed rotating ball and inner race and outer race setups. At high speeds, lubricant levitated from the surface of the ball and inner and outer race. Lubricant levitation was found to be governed by three factors: surface speed, lubricant properties, and surface finish. A high-speed camera was used to capture the lubricant levitation at various surface speeds ranging from 3.8 to 27.9 m/s. The experimental results revealed that as the speed increases, the aerodynamic Leidenfrost effect becomes significant, which inhibits lubricant adhesion to the bearing surfaces. The influence of lubricant properties was investigated by testing adhesion with lubricants of varying viscosities, while the effect of surface finish was examined by comparing coatings with different wettability characteristics. The observations from this investigation provide fundamental insight into the critical parameters influencing lubricant levitation, adhesion, and, consequently, the lubrication condition in high-speed tribology applications.