Nonlinear Oscillations of High-Speed Rotor Systems in Semi-Floating Ring Bearings

Semi-floating ring bearings are preferred to be incorporated in high-speed rotor systems since they usually provide a better vibration and damping behavior than full-floating ring bearings. Nevertheless, such rotor bearing systems can show whirl/whip instabilities as well which lead to subsynchronous oscillations in addition to synchronous oscillations due to unbalance. Moreover, a critical bifurcation can take place into a regime of subsynchronous oscillations with extremely high amplitudes which resembles Total Instability known from investigations of full-floating ring bearings. To illustrate the various types of subsynchronous oscillations, different rotor models are investigated under the influence of semi-floating ring bearings. First, transient run-up simulations are performed to outline the nonlinear phenomena. Then, the stability and bifurcation behavior is analyzed in detail by using the methods of numerical continuation.