Features of the turbocharger’s rotor vibration in unstable region

Two-mass simplified model of a rotor system, which takes into account nonlinear reaction of liquid layer of plain bearings, is developed. The rotor is discretized to finite mass system where equivalent masses are calculated based on FE eigenvalue and eigenform estimation. Application of numerical integration of differential equations and spectral analysis helped to reveal the effect of bearings on the rotor stability and development of the amplitudes of the subharmonic component of rotor vibration under increasing of rotor speed. It is shown that the loose of stability occurs at speeds that exceed the critical eigenvalue three times. It is found that bearing damping (with possible fluctuations of temperature and operation time) has little effect on the stability region. The increase of the amplitude of the subharmonic component of rotor vibration to unacceptable values occurs on a relatively small speed range in the unstable region. For the considered rotor this range is from about 13450 rpm to 13900 rpm.