Nonlinear Dynamics Analysis And Experimental Study On Rotor System With Multi Faults

As the core component of the rotating machinery,the rotor system is worth being studied.Research on its nonlinear behavior and dynamic characteristics is of great significance to control the fault of rotor system.In this paper,the existence of crack,rub impact and oil film instability are studied from the theoretical simulation.Rotor system dynamics model of rigid support and oil film bearing support are established considering time-varying crack stiffness,rub-impact force and nonlinear oil-film force.The influence of parameter variation on the nonlinear behavior and dynamic characteristics of the system is discussed,and the interaction among crack,rub impact and oil film is analyzed.Corresponding to the theoretical simulation results,the experiment of multi fault rotor system supported by rigid bearing and sliding bearing is developed.Thus,some valuable conclusions are obtained,which provides an important reference for rotor system design and engineering application.The main achievements obtained in the thesis can be drawn up as follows.1.Taking the Jeffcott rotor with rigid support as the research object,the crack rotor,rub-impact rotor and the rotor model of both crack and rub-impact are developed.The Runge-Kutta method is applied to solve the problem.Based on this,the effect of crack depth,ratio of static and dynamic stiffness and imbalance on system dynamic response are studied.2.Taking the double disc rotor with oil film support as the research object,a dynamic model considering time-varying crack stiffness and nonlinear oil-film force is developed.Bifurcation behavior and dynamic response of the system are analyzed by bifurcation plot,frequency spectrum,Poincaré map and three-dimensional spectrum.The effect of crack and oil film instability is obtained.3.Taking the multi faults rotor with oil film support as the research object,a dynamic model of the crack rotor with rub-impact was established,where the time-varying crack stiffness,rub-impact force and nonlinear oil-firm force were taken into account.With the help of the bifurcation plot,the largest Lyapunov exponent(LLE)and Poincaré map,the influence of rotating speed,crack depth and stator stiffness on the response of the system is discussed.The interaction among crack,rubbing and oil film is analyzed in detail.4.Several fault experiments on rotor test rig were conducted,include experimental study on the normal rotor and the cracked rotor with rigid support before and after the addition of rub impact fault,and the normal rotor and the cracked rotor with oil film support.The results are validated to agree with the numerical conclusion.