Study On Some Nonlinear Dynamics Problems Of Rotor System With Impact-rubbing

Rotating machinery is referred mainly as to turboengine, centrifugal compressor, ventilator,machine tool and equipments that the rotor system is main working body. Along with the progress of science and technology and development of modern industry, rotating machinery is now going towards the tendency of large scale and high speed, integration and automation, which greatly increases work productivity and accelerates the course of mankind civilization. A rotating machine system may vibrate violently due to nonlinear oil-force, impact-rubbing, cracking of the shaft, looseness of pedestal and many other reasons, great tragedy may occur if the vibration is violent enough, which can cause the machine to destroy and the operators to death. Therefore, stability, security and reliability of the large rotating machinery are significant and important in whole industry. And because almost dynamic problems of large rotating machinery takes on the character of nonlinearity, research on the fault dynamics of large rotating machinery becomes significant subject in nonlinear rotor dynamics. It signifies much to study the nonlinear dynamics of faulting rotor systems using modern nonlinear dynamics theory and rotor dynamics theory, which may help to find out the mechanism of the faults and then to prevent the faults.With the increase of machinery operating speed and the decrease of gap between stator and rotor, the rub-impact fault of a rotor system is of much interest. Therefore, it is of very necessary and important for early diagnosis of rotor fault to analyze the dynamical behavior of gap rotor. The rotor system of rotating machinery is taken as study object in this paper. After the purpose and significance of the study subject are expanded, research status and problems remained on the nonlinear rotor dynamics are summarized. Moreover, the general situation of bifurcation and chaos motion of nonlinear rotor system with rubbing fault are also studied. The dynamics character of the ideal rotor with the rub-impact movement, the rub-impact movement of rotor with nonlinear stiffness and the bifurcation and chaos motion of Asymmetrical rotor-bearing are deeply studied; The main works of the paper are as follows:(1) The rub-impact movement of the ideal rotor is under consideration based on the Poincare map in the paper. By means of the rigorous theoretical derivation, the existence of single impact period motion is demonstrated. Moreover, the stability of periodic motion is studied and the corresponding characteristic equation is derived. Applying the means of numerical simulate, it is verified that the conclusion is valid.