Abstract: Aiming at the oil-film instability problem of the sliding bearing at a high speed, a single span rotor system with two discs is studied. Considering the gyroscopic coupling effect, a lumped mass model of the rotor system is established where the left and the right bearings are simulated by a spring-damping model and a no-linear oil-film force model of the short bearing, respectively. Considering the eccentricities of two discs in opposite phases, the oil-film instability rule and the complicated nonlinear dynamic characteristics of the rotor system are analyzed by the rotor orbit, time domain waveform, amplitude spectrum and spectrum cascade. Experiments are performed by using a test rig to verity the simulation results. Theoretical analysis and experimental results all show that the first two oil whip will occur simultaneously at higher rotating speeds, oil-film instability can excite the complicated combination frequency components of the first and second oil-whip frequencies and the energy can be transformed between the first oil whip and the second one.

Key words: Combination frequency, Dynamic characteristic, Oil-film instability, Rotor system