Nonlinear Dynamic Analysis Of Rotor System With Pedestal Looseness And Rub-impact Coupling Fault

Rotating machinery is one of the most widely used power machinery in modern industry and its crucial component is the rotor system.In reality,due to the effect of its working environment and nonlinear factors in the system,mechanical failures in rotor system have always occurred and caused lots of economic loss.Since loosening and rub-impact are two common fault forms in the rotor system,this paper analyses the nonlinear dynamics of the rotor system with looseness and rub-impact coupling fault.In this paper,the dynamic model of a single-disk rotor system with loosening and rub-impact coupling fault,a double-disks rotor system with rub-impact fault,and a double-disks rotor system with loosening and rub-impact coupling fault were established respectively.Taking the effect of nonlinear oil film force into consideration,the dynamic differential equations of the three kinds of rotor systems were set up by Lagrange method,then the relevant parameters were nondimensionalized,and the differential equations were reduced into the first-order differential equations.Based on the Runge-Kutta method,the differential equations were calculated through MATLAB.Selecting rotation speed as a variable parameter,the bifurcation diagrams of three rotor systems under the given parameters were drawn.The time history diagrams,the orbits diagrams,the phase diagrams and the Poincare maps of the rotor system at different rotation speeds were used to elaborate the periodic motion,quasi-periodic motion and chaos of the system.The way of entering and leaving chaos and the mechanism of instability were also revealed.The transformation and evolution of periodic motion,the quasi-periodic motion and chaos were studied.Taking eccentricity,stator stiffness and pedestal mass as the changing parameters,the bifurcation diagrams of rotor system under different parameters conditions were plotted respectively.The periodic stability,chaos characteristics of the rotor system and the effects of various parameters on the system were analyzed.The quasi periodic and doubling characteristics of the unstable system under different dynamic models were studied on the condition of the oil film whirling or the oil film oscillation.