Study On Nonlinear Dynamics Of Limiter-airbag-rotating Machinery System

The air-bag vibration isolation system is commonly carried out for suppressing the vibration of rotating machinery of a surface ship or submarine. However, when the ship is moving, it may produce a large shock displacement, which may make the air-bag have a greater deformation. In order to avoid this situation, usually an air-bag vibration isolation system with an elastic constraint is introduced. The air-bag contact with the stopper due to the large deformation and then some nonlinear dynamic phenomenon are presented. Therefore in the proposed study is carried out based on the theory of analytical mechanics and nonlinear dynamics, which is involved in the dynamics analysis of airbag-rotating machinery system, limiter-airbag-rotating machinery system and airbag-rotating machinery system with two sided limiters. Moreover, the parametric effects on dynamic characteristics are discussed, the research contents are summarized as follows:1. The nonlinear dynamic model of the air-bag vibration isolation system for rotating machinery is established by the Lagrange’s equation. Numerical integration method is used to analyze the nonlinear vibration behavior of the system and the parametric effects on dynamic characteristics are also discussed. The results show that there exists a quasi periodic motion at low speeds, and with increasing the rotating speed, the responses present a series of nonlinear phenomena such as periods 3,5,7, quasi periodic motion and the chaotic oscillations etc. Furthermore, some parameters such as mass ratio and clearance ratio of the system exert a significant influence on dynamics of system, which can cause a series of complex nonlinear characteristics, for example, bifurcation, jump phenomenon and chaotic motion.2. Nonlinear dynamic model of limiter-airbag-rotating machinery system is proposed, the nonlinear dynamic characteristic of the coupled system are analyzed. And the effect of the different rotate speed and clearance ratio of the system on the behavior of the limiter-airbag-rotating machinery system is mainly discussed. The numerical results show that the amplitude is smaller and the motion may become stable at low speed. As increasing rotational speed, the vibration of the system experienced a phenomenon similar to the characteristics of linear resonance. At high speed, the amplitude of system is reduced and the chaotic phenomenon appeared.3. The model of airbag-rotating machinery system with two sided limiters is presented, and its nonlinear dynamical behaviors of the coupling airbag-rotating machinery system with two sided limiters are mainly investigated. The numerical simulation on nonlinear dynamic characteristics of system with two sided limiters due to the nonlinear stiffness of the limiters is carried out, and the effect on nonlinear dynamic characteristics of system caused by two sided limiters is discussed using the numerical analysis method. The characteristic of bifurcation and chaos caused by the rotate speed are analyzed emphatically. And the numerical results reveal that the abundant nonlinear phenomena such as periodic motion, quasi-periodic motion and chaos are found out in the system.