Micro-Vibration Analysis and Optimization of Aerostatic Bearing with Pocketed Orifice-Type Restrictor

For an aerostatic circular thrust bearing with a single pocketed orifice-type restrictor, the flow field in the bearing clearance is analyzed numerically, and the formation mechanism of the bearing micro-vibration is investigated. Through flow field analysis, the flow structures in the bearing clearance are discussed and classified. The formed vortex flow in flow field is analyzed, and the influence of the vortex flow on bearing dynamic stability related to micro-vibration is discussed. For each flow structure, the vortex flow always exists and induces the bearing micro-vibration. The Reynolds number is used to represent the degree of bearing micro-vibration and the rationality is verified. Based on the flow analysis results, the maximum Reynolds number in the bearing clearance flow field is taken as the optimization objective to reduce the micro-vibration amplitude, the approximate model for design optimization is established by using the radial basis functions method and the optimization methodology is illustrated. Several cases of optimization are carried out with different given bearing loads. Through optimization, the maximum Reynolds number is reduced greatly, which means the enhancement of the bearing dynamic stability. The optimization results show that in order to suppress the micro-vibration, the air supply pressure should be kept as small as possible, the small air pocket diameter and orifice diameter are also needed.