Hydraulic losses analysis and a loss-reduction cage structure for oil-jet lubricated high-speed ball bearings

In transmission systems, bearings play a critical role, and their hydraulic losses have a marked influence on overall efficiency and thermal behavior. This study investigates the variation patterns of hydraulic losses in ball bearings under oil-jet lubrication across different operating conditions. A test rig was established to measure bearing hydraulic losses, and a CFD model incorporating oil-air two-phase flow was developed and validated against measurement results. The CFD results show good consistency with the experimental measurements, yielding average discrepancies of 15% at an injection speed of 2.5 m/s and 18% at 10 m/s. The effects of injection velocity and oil temperature on bearing hydraulic losses were systematically analyzed. The results show that hydraulic losses positively correlate with rotational speed and injection velocity, while negatively correlating with oil temperature. For bearings where the cage is guided by the outer ring(OR), the cage contributes more than 85% of the total hydraulic losses, primarily due to the high shear stress in the narrow clearance between the cage and the OR land. To address this, a cage structure with reduced hydraulic losses was proposed. Compared with the original cage, the novel cage reduces bearing hydraulic losses by 59.7% at 70°C. This work underpins the theoretical analysis of hydraulic losses in rolling bearings and offers practical guidance for high-speed ball bearing cage structure optimization.