Nonlinear Dynamic Behavior Of Marine Rotor-Bearing System Coupled With Air-Bag And Floating-Raft

In order to reduce the power transmission between the mechanical power equipment and the hull, the vibration isolation device is usually installed between the mechanical power equipment and the foundation. First, the air bag-floating raft isolation is embedded into the marine rotating machinery rotor-bearing system, the multi-dimensional system coupled with air bag-floating raft is built, and then based on the theory of dynamics, the differential equations of system is derived. Finally, the nonlinear dynamic characteristics of system are mainly discussed. The main contents and contributions can be summarized as:(1) The mechanical modeling and nonlinear dynamics of rotor-bearing coupled air bag-floating raft system are discussed. First, the modeling of marine rotor-bearing system coupled with air-bag and floating-raft is built based on the short bearing theory, the nonlinear dynamics of system is analyzed adopted numeric method, such as, displacement response, frequency spectrum, rotor orbit, Poincaré maps and largest Lyapunov exponent. The research results indicate the steady state responses are the single period synchronous motion at lower speeds, with increasing the speed it reveals the complex nonlinear dynamic phenomena, such as period two, quasi-period and chaotic motion.(2) The nonlinear dynamic characteristics of the rotor-bearing system coupled with air bag –floating raft influenced by the parameter. Based on the long bearing theory, the dynamic steady response of system with the change of the rotating speed is studied, it can be found that the state of motion can be summarized period one→quasi period→chaoes→quasi period; On the other hand, the system is analyzed by parameters change, such as the lateral and longitudinal stiffness, mass ratio, eccentricity. etc. The research results can provide the parameter optimization and theoretical basis in the vibration and control of rotor-bearing system coupled with air bag-floating raft.(3) The dynamic model of rotor-bearing system is built under the base excitation, considering the coupling effect between the foundation and rotor-bearing, and the dynamic differential equation of rotor-bearing under the base excitation is derived, the dynamic characteristics of this system are mainly studied, and the dynamic bifurcation and steady response under the excitation amplitude and excitation frequency ratio is mainly analyzed. The numerical results indicate that the dynamic characteristic effects of system are mainly in the low frequency state, and the same time the orbit embodied in the low frequency motion becomes much more intricate, lead to the motion orbit of rotor is no longer a single circle or ellipse, but with the increase of rotational speed, the effect of base excitation will gradually decrease, the dynamic system will be dominated by five-period, and then the system will enter the quasi period and chaotic motion in high speed.