Research On The Non-linear Dynamic Characteristics Of Blades-rotor-bearings Coupling System

Rotating machinery is important basic equipment in the construction of national economy and national defense,which has been widely used in energy,power,aviation,aerospace and other fields.The stability of the rotating machinery will influence the development of the industry.With the development of the society,modern rotating machinery is moving toward high speed,overload,automation and complicate direction,and the resulting problems are more and more.Due to the complexity of rotating machinery running environment,the rotating machinery often loses stability and even destroies machine accidents,these accidents often cause incalculable economic losses and casualties and social harm,so the study of rotational stability is very necessary.The significance of this study is to establish a relatively refined dynamics model of continuum blades-rotor coupling system,then analyses the instability rule and stability under nonlinear support force,the influence of blade vibration on rotor-bearing system dynamic behaviour,the film instability rule of coupling system under different operation conditions and different parameters.So studying the instability rule and nonlinear dynamic characteristics of blades-rotor-bearing system is meaningful for the designing?solving the faults and improving the efficiency of rotating machinery.Firstly,based on the elasticity theory,a differential equation of forced oscillation of the blade-casing system with rub-impact excitation was deduced,and the steady analytic solution was derived.The analytic solution was verified with the FE(finite element)method.Then,using the FE and semi-analytical method,the comparison of dynamical response was investigated detailedly under different operation conditions and different parameters,and the analytical solution and semi-analytical solution were analytized.Secondly,on the basis of the rotating blade,the dynamic model of rotor-blades coupling system was established.And the rotating flexible shaft adapted the Timoshenko beam model,the rotating blades adapted cantilever Euler-Bernoulli beam model,which considered the rotation inertia effect of the section properties,spinning effect,and the gyroscopic effect.By solving the model,this paper analysed the inherent characteristics of rotor-blades coupling system.And the Campell of coupling system under different blade length and disk location were given.Last,this paper established analytic model of nonlinear bearing-rotor-blades coupling system by the Lagrange approch.And nonlinear bearing-rotor-blades coupling model was regard as the research object,the film instability rule,which easily happened in high speed,was studied under the support of nonlinear bearing.The film instability rule and nonlinear characteristics of coupling system under different operation conditions were investigated through three dimensional spectrum and bifurcation diagram,the response figure,spectrum diagram,phase diagram,the axis trajectory,Poincare section,analysed the influence of blades on film instability of nonlinear bearing-rotor system.In order to study the effect of the flexible blades on the oil film instability of rotor system,the dynamic model of rotor-bearings coupling system,which the blades were simplied to the disk,was established,and compared the dynamic characteristic of the model under nonlinear support force with the results of blades-rotor-bearings coupling system,and then researched the nonlinear characteristics in the effect of blade length and blade damping.