Dynamic Characteristcs Of Multi-rotor System Under The Action Of Nonlinear Oil Film Force

The rotor system is widely used in the fields of power, aviation and aerospace because itis an important part of rotating machinery, therefore, the study of the vibration characteristicsof rotor-bearing system under the nonlinear oil-film forces is of great significance to the safeoperation and status monitoring. The nonlinear dynamic characteristics of multi-rotor bearingsystem with the fault of bearing misalignment is studied, such as the bifurcation phenomena,time responses, frequency spectra and the Poincare maps in this work. Then the experiment ofthe rotor-bearing system is carried out for validating the vibrations of the misaligned bearingsystem. Finally, the nonlinear dynamics of the bevel gear rotor system under the nonlinearoil-film force is investigated by using numerical method. The main conclusions of the workwere summarized as follows:1. The dynamic characteristics of the flexible rotor system based on the short bearingmodel was analyzed. The results show that the system with a slight bearing misalignmentperforms a synchronous periodic motion at lower speeds. As the speed increases, the perioddoubling bifurcation appears which repeated alternately in cycle period1,2and quasi-period.When the long bearing model is carried out, the system still presents synchronous period under alower speeds, that is, the affect of bearing misalignment is not obviously to the movement of thesystem. As the speed increases, however, the quasi-periodic motion occurs and finally the motionsof rotor system become period1.2. The affect of the nonlinear dynamic characteristics of the system with the rotorparameter variations is studied, and the dynamic behaviors of the system under the massasymmetry and bearing misalignment are mainly concerned. The results show that the perioddoubling bifurcation of the system with mass asymmetry is earlier than mass symmetricsystems with the speed increasing, and period8is appeared in its motion. In addition, as the speed increases, the influence of misalignment on the motion of the system is more obvious.3. The dynamic characteristics of the system with bearing misalignment is studied byusing experiment and compared to the ones by numerical method. The results show that thedynamic behaviors of the system are similar to the orbits, frequency spectra and so on. Itproves the presented dynamic model is available.4. The nonlinear dynamic characteristics of the rotor system trained by bevel gears isinvestigated after considering the effects of unbalanced mass and nonlinear oil film forces. Theresults indicate that the motion of the rotor system appears period1, namely, the unbalanceresponses are dominant. As the speed increases, the amplitude of the rotor increases rapidlyand encountered the bearing wall.