Influence of Manufacturing Errors on the Unbalance Response of Aerodynamic Foil Bearings

The present work tackles the impact of manufacturing errors on the unbalance response of a Jeffcott rotor supported on aerodynamic foil bearings. The peculiarity of the model is the use of the Abaqus software for describing the dynamic response of the foil structure, for calculating the thin film pressures and for integrating the equations of motion of the rotor-bearing model. The numerical results show that the foil bearing without manufacturing errors and with a radial clearance of 31.8 µm is unstable for the tested operating conditions (30 krpm rotation speed, 10 N static load and G1 unbalance class). However, taking into account manufacturing errors may lead to a different result. Bump height manufacturing errors were added to the model. Five cases with random manufacturing errors but all with 10 µm standard deviation of the bump height were analyzed. In four cases, the unbalance response was a limit cycle dominated by the 0.5 Ω subsynchronous frequency. This result may explain the discrepancies between theoretical and experimental results reported up to now in the literature.