Nonlinear dynamics of a magnetically supported rigid rotor in auxiliary bearings

Abstract

The dynamics of a rigid rotor supported by load-sharing between magnetic and auxiliary bearings are investigated for a range of realistic design and operating parameters. Numerical results indicate that the system's response is mainly influenced by the magnitude of the rotor imbalance. For relatively large imbalance magnitudes, non-synchronous vibrations were found to dominate the system's response over a substantial range of the operating speed. The magnitudes of the stiffness ratio and Coulomb sliding friction coefficient were found to have almost negligible effect on the system's response for relatively large imbalance levels. For relatively small imbalance levels, however, the variation of these parameters' magnitudes were found to be effective in reducing the system's response amplitude and decreasing or totally eliminating the range of operating speed where non-synchronous vibrations occurred in the system's response. Non-synchronous vibrations of period-2, -3, -4, -5, -6, -11 and chaos, which were observed in the system's response, are not desirable as they cause fluctuating stresses in the main components of the system, which may eventually lead to their failure due to fatigue.