The Dynamics Analysis And Recognition Of Rotating Machinery System Caused By Looseness

Rotating machinery is the most widely-used mechanical equipment in various industrialfields. The rotor-bearing system, as a rotating machinery core part, usually presents suchcomplex nonsmooth dynamics characteristics as coupling, sudden, jumping in engineeringpractice. The rotor-bearing system is frequently a typical nonsmooth dynamics system asthere axist some nonlinear factors like the nonlinear oil-film forces，rub-impact force, looseclearance, nonlinear rigid in the system. In this thesis, considering the nonlinear and unsteadybearing oil-film force, the dynamical models with different constraint types of rotor-bearingsystem are set up. The influence on nonlinear dynamics responses characteristics ofrotor-bearing system caused by rotating speed, off-center, loose bearing quality, and the statorstiffness is analyzed using the method of non-linear dynamics theoretical analysis andnumerical simulation. These results have a practical significance to reveal the failuremechanism of the system and optimize the dynamical parameters of system.The stiffness Jeffcott rotor-bearing model with the nonlinear and unsteady oil-film force isstudied, and the flexible rotor-bearing model which has the physical nonlinear factors of axisis bringed into consideration, too. Adopting the nonlinear dynamics methods such asbifurcation diagrams, maximum Lyapunov exponent diagrams, Poincarémaps, phase planeportraits, trajectories of axis center and amplitude spectra diagrams of rotor motion, thebehavioral characteristics of systematic dynamics are analyzed. The result shows that thestability of the oil-film lost caused by overlarge eccentricity under the condition of low speed.The axis center track is the circular or elliptical when the eccentric mass is small, and the axiscenter track is the banana shape or8shape when the eccentricity mass of system is larger.The main components of frequency spectra are1/2times or a quarter times frequency ofradial vibration characteristic. The nonlinear stiffness of elastic axis has an effect ofstimulation and amplification on the nonlinear factors of system.Studying the mechanism about the fault of bearing pedestal looseness, a rotor-bearingsystem model which has the fault of support looseness and the nonlinear stiffness axis isestablished. The dynamical behavior of system under different parameters is analyzed by thenumerical simulasion. The conclusion manifests that the support stiffness of rotor-bearingsystem could be changed by the fault of looseness. The vibration amplitude of the system isbigger in the direction of looseness. Trajectories of axis center display no rules. The spectrumdiagram show higher-order frequency component such as3times,5times,7times. Increasing the quality of looseness support properly, to a certain extent, can restrain the chaos movementof the system response.Considering the unsteady and nonlinear oil-film force and impact-rubbing force, thedynamics model of rotor-bearing-cabin system which has the coupling fault of looseness andimpact-rubbing is established. Using piecewise linear the impact-rubbing force model, therotor and the cabin are considered as a unified model to build. The numerical analysis methodis used to research the complex dynamics response of the rotor system under the condition ofdifferent parameters. The trajectories of axis center displays "angle" shape and the higherharmonic components are abundant on the3-D waterfall spectrum when the local minorimpact-rubbing occur between rotor and stator. These phenomena show that the system breaksout slightly vibrate within the scope of the loosening clearance for border. When the wholeimpact-rubbing occur between rotor and stator, the trajectories of axis center is chaos and thelow frequency continuous spectrum amplitude is larger on the3-D waterfall spectrum. Thenthe vibration of rotor-bearing-cabin system is aggravating. Increasing the stator stiffness ofrotor-bearing-cabin system can restrain the impact-rubbing vibration of system when thespeed is high, though meanwhile the movement of rotor system is instability at a low speed ofsystem.