Nonlinear Vibration and Bifurcation Analysis for Rotor-Seal-Bearing Systems of Centrifugal Compressors

This paper presents the nonlinear coupling vibration and bifurcation of a high-speed centrifugal compressor with a labyrinth seal and two journal bearings. The rotor system is modeled as a Jeffcott rotor. The Muszynska’s model is used to express the seal force with multiple parameters. For the journal bearings, the model proposed by Zhang is adopted to express the excitation of unsteady oil-film force. The Runge-Kutta method is used to determine the vibration responses at the disc center and the two bearings. With parameters of rotation speed and pressure difference of the seal, bifurcation diagrams are presented to demonstrate the complexity in the rotor motions. Multiple periodic bifurcations are pointed out using two seal pressure differences. The intricate bifurcation behavior shows inherent interactions between forces of oil-film and seal, which reflect much more complicated rotor dynamics than the one with either of the excitations alone.