Non-linear models for Rotor-AMB system drop

The proposed investigation deals with the assessment of several models for the prediction of the dynamic behaviour of turbomachinery supported by Active Magnetic Bearing when drop events occur leading the rotor to drop onto its Touch-Down Bearings (TDBs), which are emergency rolling element bearings in series with a ribbon damper. The rotor exhibits a non-linear transient motion where the amount of damping provided by the ribbon damper is a key parameter for avoiding dangerous behaviours. The ribbon damper is modelled successively with the Masing, the generalized Dahl and the Kelvin-Voigt models. Usually, the TDB is modelled as a viscous damper, used here as reference for comparisons. The originality of this work lies in the new modellings of that ribbon, based on dry-friction theory, where parameters are benchmarked to experimental results. The three models presented are successively integrated in the TDB model followed by rotor drop simulations. Comparisons are done in terms of rotor drop dynamics and show that the transient responses predicted with the Masing and generalized Dahl models are similar.