Experimental study on dynamic behavior of ball bearing cage in cryogenic environments, Part II: Effects of cage mass imbalance

We studied the dynamic behavior of a ball bearing cage submersed in a cryogenic fluid and rotating at high speed as a function of the mass imbalance of the cage under various rotational speeds and light load conditions. The results include the whirling motions and distribution of whirling frequencies of the cage, the ball bearing torque, and the wear loss of the ball bearing elements for varying rotational speeds and mass imbalance conditions. The whirling motion of the cage tended to increase with the increase of the mass imbalance, and the influence of the mass imbalance was apparent with the increase of inner race speed. For all mass imbalance conditions, the whirling amplitude decreased with the increase of the inner race speed owing to the influence of the hydraulic force of liquid nitrogen. In addition, the standard deviation of the whirling frequency of the cage increased with the increase of the inner race speed. In particular, when the inner race rotational speed was 11,000 rpm, the standard deviation tended to increase markedly with increasing mass imbalance. The wear loss of the cage increased with the increase of the mass imbalance, and the wear loss at the bottom part of the cage increased owing to an abnormal motion caused by intermittent collision of the cage. The experimental results obtained under various mass imbalance conditions are consistent with existing interpretive literature and demonstrate the importance of the mass imbalance of the cage.