A Fundamental Study on the Friction Reduction Characteristics of Microbubbles in Journal Bearings: Mechanics and Visualization

Improving motor efficiency by reducing frictional losses in the journal bearings used in many rotating machines is critical for advancing sustainable mechanical systems, especially automobiles. This study investigates the application of microbubbles, which are known to reduce frictional drag in fluids. The incorporation of microbubbles into lubricants offers an environmentally friendly friction-reduction method that avoids chemical additives. In this work, microbubbles were generated within lubricating oil and applied to a journal bearing. Experimental measurements of friction torque during shaft rotation demonstrated that lubricating oil containing microbubbles yielded lower torque than oil without microbubbles. These results indicate that microbubbles effectively reduce friction in journal bearings. Furthermore, a transparent quartz glass bearing and acrylic shaft were used to directly observe the dynamics of microbubbles flowing within the journal bearing clearance to elucidate the underlying frictional torque reduction mechanism.