Experimental Study Of Gas Foil Thrust Bearing And Porous Aerostatic Bearing

Along with the continuously development of the technologies of turbo-machinery, precision manufacture and aerospace exploration, the speed of rotating machinery is becoming increasingl y higher. Traditional bearings can no longer work stably in the demanding operation conditions, such as high revolving speed, high precision and high temperature. Bearing technology has become a stumbling block in the way of the development of rotating mac hinery. Air bearing has shown overwhelming superiority when applied to the high speed, high precision, low friction supporting and other special supporting condition. According to its operating principle, air bearing can be classified into two types, aerodynamic bearing, aerostatic bearing. However, due to the difficulty of manufacture, non-thorough theoretic study and insufficient experimental investigation, air bearing was not put into application until recently. Therefore, in this dissertation, a compreh ensive test rig was developed in order to investigate two kinds of air bearing-gas foil thrust bearing and porous aerostatic bearing. Gas foil bearing is a kind of compliant-surface aerodynamic bearing, using ambient air as their working lubricant and supp orting medium. Aerostatic bearing utilize a thin film of pressurized air in the surface of the bearing to provide a zero-friction supporting. The main contents of this dissertation are shown as below.(1) A comprehensive test rig was developed to conduct relevant experimental study on gas foil thrust bearing and porous aerostatic bearing. This experimental facility contains four major parts, high-speed rotating section, loading section, air supply system and data acquisition system. In the high-speed rotating section, two porous aerostatic bearing s were used as the radial supporting of the rotor. Moreover, gas foil thrust bearings were used in this test rig as restriction in axial direction. In order to verify the design of the bearing-rotor system in the rotating system, rotor-dynamics analysis was conducted in software called XLrotor and the result of the analysis shows that it can be operated stably in the designed speed range.(2) Based on the manufacture process of gas foil journal bearing which was developed by our research group, a viable manufacture process of gas foil thrust bearing was developed in this dissertation. According to this process, five gas foil thrust bearing with different structures were made and then experiments about them were conducted. The major objective of these experiments is to study the relationship between rotating speed and stiffness of the bearings as well as the relationship between bearing structure and its stiffness. The test result demonstrates that the stiffness of the foil t hrust bearing increases with the operation speed.(3) In addition to the contents mentioned above, rotor dynamics experiment of the bearing-rotor system in the high-speed rotating section was conducted, aiming at investigating the porous aerostatic bearing’s influence on the performance of the rotor. Vibration test by knocking on the rotor was done to learn about the inherent frequency of the rotor. And the influence of air porous bearing on the performance of the rotor was studied by testing the vibration per formance of the bearing-rotor system under different air supplying pressure. It shows that the higher pressure of the supplying air can induce higher stiffness of bearing, which can suppress the sub-synchronous vibration of the rotor. Besides, the influence of the O-ring of the bearing is studied. The result shows that although the stiffness of the bearing is lower with O-rings but it can suppress sub-synchronous vibration of the rotor in high speed range by absorbing energy.