The Nonlinear Analysis On The Mechanism Giving Rise To The Oil Whip Instability Of Large High-Speed Rotor

The problems of the self—excited vibration as well as the motion stability emerging form nonlinear rotor—bearing system are of widspread and important realistic background in enginering, specially speaking of the large turbine—generators, the problem of oil film instability has not been solved well at home and abroad up to now, so the study on the mechanisms that give rise to instability has become a difficult point that needs solving urgently.Starting from the aspect of qualitative research, this thesis uses a rigid Jeffcott rotor system with short—bearing model as the object of study and makes use of center manifold theorem,averaging method, normal form theory, singularity theory, method of Takens' double-zero eighenvalue theory, fast Galerkin method as well as Floquet theory and so on to study some of its local dynamical behavior in the neghborhood of threshold and its global dynamical behavior in relatively wide parameter range. Through experiment with mechanical model,the dynamical behavior of self—excited vibration and the effects of varied factors on them are acquired, which prove parts of the conclusions of theoretical analysis.The work done in this thesis is divided into four sections.In the first section(the second chapter), in Cartesian coordinates, under the condition of short—bearing assuming and in consideration of the effect of turbulence, the formulas of nonlinear bearing oil film forces are derived from Reynolds equation;in the end,the object of the study in this thesis—the nondimensional motion differential equatons of the rigid Jeffcott rotor system with short—bearing model is acquired.In the second section(the third chapter), the threshold—the Hopf bifurcation point of the unperturbed(mass balance)system is acquired first. Then, mainly for the unbalanced rotor system, the bifurcation pattens, the bifurcation characteristics of the periodic, amplitude—modulated and phase—modulated vibrations, as well as the homoclinic and heteroclinic orbits in the neighborhood of the threshold for 1/2 subharmonic resonace are studied with the method of center manifiold theorem in combination with averaging method, singularity and Takens' double-zero eigenvalue theories. The regions of the structural parameters that control the stable...