Rotordynamic Characteristic Of Rotor Bearing System For Ship With Vertical And Horizontal Swinging

The reliability and security of ship are important indicators to measure performance of ship, while the stability and reliability of rotor-bearing system of ship propulsion device can directly affect the navigation safety and reliability of ship, especially when the ship sailing in adverse sea condition it would become more prominent.If the ship suffered special condition such as adverse sea condition when it is sailing, stormy waves and other various disturbing factors could cause low frequency vertical and horizontal swing of ship, because the rotor-bearing system of ship propulsion device is fixed to the ship hull, the low frequency and large displacement vibration of the ship hull caused by the vertical and horizontal swing of ship would pass to the journal bearing through the foundation, and then pass to the rotor. Although the vibration frequency of the vertical and horizontal swing of ship is far below the speed of the rotor, these vibrations will have a great impact on the vibration characteristics of the rotor-bearing system of ship propulsion device through the oil film force the journal bearing, and then have a significant impact on the stability of the rotor-bearing system of ship propulsion device, ultimately, affect the reliability and safety of ship. Therefore, in order to improve the reliability and security of ship when it sailing in adverse sea condition, meanwhile, in order to overcome the shortage that ignoring the effect of ship swing when analyzing the dynamic behavior of the rotor-bearing system of ship propulsion device in the past, it is necessary to do further analysis and research for the dynamic behavior of the rotor-bearing system of ship propulsion device.Firstly, in this dissertation, introducing common used numerical integration method for solving the dynamic differential equation, and determining the numerical integration method which will use is Newmak method and the finite element model of the rotor which will use in this paper; and then giving the swing function model which is used to describe the vertical and horizontal swing of ship.Secondly, in this dissertation, respectively establishing the finite element models of the disk and elastic shaft which are established after considering the change of the gyroscopic torque when the ship is swinging.On this basis, obtaining the dynamic differential equation of the rotor-disk system which is established after considering the gyroscopic torque change when the support condition is rigid, and then using the Newmark method to solve the differential equation of the system. For the rigid support, comparatively analyzing how the swing amplitude and swing frequency of the ship vertical and horizontal swing affect the vibration characteristic of the system.Finally, in this dissertation, for the linear and nonlinear oil film force respectively establishing the dynamic model of the rotor-journal bearing system when the ship is vertical and horizontal swinging, and then using the Newmark method to solve the differential equation of the system. For the linear support condition, comparatively analyzing how the swing amplitude and swing frequency of the ship vertical and horizontal swing affect the vibration characteristic of the system, at the same time obtaining the frequency domain and time domain characteristics of the oil whirl and oil whip of the journal bearing-rotor system for different swing states; for different sway parameters and three different states of the ship: does not swing, vertical swing and horizontal swing, comparatively analyzing the stability of the journal bearing-rotor system.Thereinto, the rotor model which used in the finite element analysis is the Bently-RK4 rotor model, during analysis the rotor using Euler beam element model, the nonlinear oil film force of the journal bearing using the Capone nonlinear oil film force model, the disk is assumed to be lumped mass.