Study On Dimension Reduction And Stability Of High-Dimensional Nonlinear Rotor Systems With Misalignemt-Rubbing Coupling Faults

The problem brought by development of rotor system with high-speed, high-power and heavy-load, etc is increasingly outstanding. The rotor vibration is increased and all sorts of failure rate is significantly rised. The established dynamics equations of rotor systems based on such issues are usually high dimensional and complicated. Existing nonlinear theory is difficult to deal with such problems. In this paper, the rotor systems of aero-engine are used as the study object. The researchment on dynamic characteristics and dimension reduction method of high dimensional complex rotor systems with single fault and coupling faults are conducted. Then, based on it, the influence of squeeze film damper(SFD) is considered which is used to study the effect on vibration reduction of fault rotor and its inhibiting effect on non-coordinated response caused by rotor faults.The rotor systems is reviewed which contains the research methods of nonlinear vibration system, dynamic characteristics and stability of fault rotor systems and dynamic characteristics of squeeze film damper firstly. The related theoretical knowledge of this paper is introduced. Based on it, the dynamics model of rotor-ball bearing-spline coupling system with misalignment-rubbing coupling faults is established. Dimension of rotor systems is reduced by two kinds of Galerkin method and numerical simulation is done. Diagram such as bifurcation, waterfall, etc are compared and analyzed. The results show that: The results obtained by NGM in dealing with misalignment fault rotor system and misalignment rubbing coupling faults rotor system coincide with the results of original system, while by SGM in some degree differs and even can't be applied; The NGM is applied to analyse the rotor systems with faults. It finds that although the dimension of rotor systems with faults is reduced by NGM, it doesn't change the dynamic characteristics of rotor systems with faults and the fault feature information is reserved. Further considering the effect of SFD. The influence of the squirrel elastic support on the system critical speed, the influence of parameter changes of SFD on damping effect of system and the influence of SFD on single rub fault and misalignment-rub coupling fault are studied. The results show that: With the increase of elastic squirrel-cage support stiffness, the critical speed of system is also improving; The clearance of SFD has great influence on its damping effect. In a certain range, with the decrease of clearance, the damping effect is continuously improved. But, when the clearance is too small, the SFD will produce storng nonlinearity which makes the system vibration increase; SFD has good inhibitory effect on non-coordinated response caused by single rub fault and misalignment-rub coupling fault. The stability of system is improved.This work suggests that it plays an important role on the safe and stable operation of aero-engine rotor systems to search effective dimensional reduction on high-dimensional nonlinear rotor systems with misalignment-rubbing coupling faults and study the coupling faults mechanism and dynamic characteristics. The results of this study have a referential value on design of aero-engine rotor systems.