Investigation of lubricant flow in a planetary bearing cavity under stationary carrier condition

Planetary bearings are critical components in planetary transmission systems. As transmission systems evolve toward higher speeds, the lubrication of planetary bearings faces significant challenges. In this study, a specialized test rig was developed to visualize the oil flow in a planetary bearing cavity under a stationary carrier condition, a configuration featuring outer ring rotation and central oil supply. The experimental results reveal the oil flow patterns and distribution characteristics within the bearing cavity. Additionally, a dynamic-static fluid domain coupled numerical model was established to simulate the oil-air two-phase flow field in the rotating bearing domain. This model was used to analyze the variations in oil distribution inside the bearing cavity and the oil volume fraction(OVF) on component surfaces under different speeds. The research results indicate that the bearing cavity is fully filled with oil at low speeds. As the speed increases, the oil near the roller end faces on the inner ring side begins to decrease, and an arc-shaped oil film forms along the inner side of the cage. With further speed increase, this oil film expands radially outward. At 9000 r/min, only a small amount of oil remains distributed near the outer ring. Increasing the oil flow rate further enhances the OVF on these surfaces, which can alleviate oil starvation in the lubrication zone between the rollers and the inner ring under high-speed conditions. However, higher flow rates also lead to increased churning losses in the planetary bearing. The research results provide theoretical guidance for the lubrication design of planetary bearings in transmission systems.