Research On Some Problem Of Nonlinear Dynamical Behaviors Of A Finite Journal Bearing-Rotor System

Rotating machinery has a very important position in machinery, power, communication, aerospace, space technology and so on. And it is also one of main equipment of pillar industries in national economy. Along with the development of production and the progress of science and technology, research on some problem of nonlinear dynamical behaviors of a rotor system has evolved to be a top point in related fields nowadays. In this thesis, the analytical formula of the unsteady oil-film force of the finite journal bearing is obtained by variational approach. The nonlinear dynamical behaviors of the finite journal bearing-rotor are studied by using numerical simulations.The motion characteristics are analyzed by phase diagram, bifurcation diagram, Poincare maps and spectrum analysis. Results show that at a specific parameter combinations, complexed nonlinear dynamical phenomena appear with the variation of system parameter, which may serve as a reference to solve the problems in the practical engineering systems.Firstly, the analytical formula of the unsteady oil-film force of the finite journal bearing, is cited in this thesis. In addition, the methods for the research of the motion characteristics of system are introduced.Secondly, based on the theories above, the dynamical model of the finite journal bearing-rotor system is established, and the motion differential equation of the system is sovled by using the Runge-kutta method,and in the different length to diameter ratio,bifurcation diagram, as well as partial phase diagram, Poincare maps and spectrum analysis about dimentionless rotating speed, dimentionless mass eccentricity and synthetical parameter are obtained. Results show the various forms of periodic, qusi-periodic and chaotic motions.Thirdly, the motion characteristics of the finite journal bearing-rotor are investigated under the consideration of oil-film force, together with rub-impact, and its motion differential equation is solved by the Runge-Kutta method. In the end, bifurcation diagram, partial phase diagram and Poincare maps about every parameter concerned are plotted.Finally, the results we've obtained are summarized in the end of this thesis. Alsosome creativities as well as existing problems are pointed out.