Identification of Axial Air-Foil Bearings and Radial Air-Foil Bearings

Abstract

Air-foil bearings (AFBs) are self-acting hydrodynamic bearings, a shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid (usually air) pushes the foil away from the shaft so that there is no contact. The shaft and foil are divided by air's high pressure which is produced by the rotation which pulls gas into the bearing via viscosity effects. AFBs provide a means to eliminate the oil system leading to reduce weight and enhanced temperature capability. In the present work, structural characteristics (stiffness and damping) of axial AFBs are identified in the light of experimental results. Due to the initial high torque requirement of the AFB, the experimental setup using a single AFB is proposed instead of standard two-foil bearing setups. Experiments are carried out at maximum speed of 60,000 rpm. Sub-structuring approach is used for identification of the structural (stiffness and damping) characteristics of the AFB. The results have shown that the developed experimental procedure is able to identify the stiffness and damping characteristics of axial AFBs accurately.