Analysis Of Nonlinear Dynamic Behaviors On The Elastic Rotor System Supported By Gas Journal Bearings

The progress of science and technology has made the design of rotating machinery more high-speedly and efficiently.Simultaneously,higher requirements for dynamic characteristics,stability and reliability to the rotating machinery have been met with.With the development and application of the modern nonlinear dynamic theory,the research on rotor dynamics especially the behavior of high-speed rotor nonlinear dynamics takes a new visage after introducing the theory of modern nonlinear dynamics.Nowadays,it has been become one of the most popular research problems at home and abroad.Gas rotor beatings are new type bearings which make use of gas as moving lubricant.Comparing with other bearings, because there is only a little mucosity in gas,gas rotor beatings have so much virtues such as a bit of frition,no abrasion,no pollution,smooth operation,high rotate precision,precise maintenance of bearings and etc.These make gas rotor bearings more ascendant,more economical and more practical in high-speed rotating machines.Gas rotor beatings are more widely used in industries such as national defence,armory and dynamics.In this dissertation,researches are mainly objected to complicated dynamic behaviors of the systems of high-speed and elastic rotor supported by gas journal bearings through using nonlinear dynamics theories.The dissertation mainly contributes to the research:Firstly,the analytical formula of non-linear gas film force of the short journal beating is cited in this thesis.The dynamic model of elastic rotor supported by gas journal beating is established using the formula.The stability of the non-dimensional form - system is analysized by using the first Lyapunov method.Secondly,Based on the further non-dimensional form of the rotor system,the motion differential equation of the system is solved by using the Runge-kutta method.Seeing about the nonlinear dynamic characteristics along the change of rotating speed,eccentric quantum and a parameter,the diagrams of the system such as the phase diagrams,Poincare maps,spectrum analysis diagrams,bifurcation diagrams are plotted by methods of numerical simulations.The complex dynamic phenomena of periodic and chaotic motions are showed in the results.Thirdly,adding two displace-feedback terms to the system mentioned,the nonlinear dynamic characteristics are reseached on the weakly controlled system..The influence to dynamic characteristics is analysised.Results show that this control method can transform chaotic,quasi-periodic and multiple periodic motions into synchronous periodic motions.Finally,the primary work of this text has been concluded,and the problem existed and the development trend of future work have been pointed out.