Vibration Characteristic Analysis And Vibration Reduction Effect Research Of Marine Gearbox

Marine gearbox is one of the important parts of marine ship, its transmission performance is the key to the normal operation of marine ship. Because of its complicated structure, poor working condition, and high transmission power, vibration noise problem of marine gearbox is particularly prominent. Therefore, the research of gearbox vibration characteristics analysis and vibration reduction effect, have important theoretical guiding significance and engineering application value to improve the running stability of marine gearbox.This research work is supported by National Natural Science Foundation of China, it takes marine gearbox which is under astern condition as research object, and focuses on vibration and noise issues. Thermal elastic coupling modification analysis of gear, parameter identification of joints, internal excitation simulation, parameters influence analysis of gearbox vibration, and gear system vibration reduction effect simulation were carried out. The main research work in this paper can be summarized as follows:(1) Tooth surface convection heat transfer coefficient is obtained based on the improved friction heat spread by centrifugal ejection model, gear transverse surface convection heat transfer coefficient is deduced by the equivalent plate model, tooth surface heat flow is obtained based on Hertz contact theory and friction heat analysis. The shaft system bulk temperature and thermal-elastic coupling analysis is simulated, and then the meshing in and out interference quantity caused by thermal-elastic deformation of each gear pair is calculated. The gear pair modification value is obtained which then compared with Sigg formula calculation results.(2) Kinetic differential equation of the gear transmission system was established using lumped parameter method, with the combination of the frequency response function matrix obtained by experiment modal analysis, the stiffness and damping of bearing and gear pair were calculated; considering tooth surface manufacturing error and the time-varying meshing stiffness, kinetic differential equation of the gear transmission system was solved using Runge-Kutta method, the gear transmission error curve is calculated; comprehensively considering the gear tooth time-varying meshing stiffness, gear pair transmission error and meshing impact, the numerical simulation of gearbox internal dynamic excitation is carried out.(3) The gear-shaft-bearing-casing coupling finite element dynamic model is established, applying the gearbox internal dynamic excitation, dynamic responses of gearbox is calculated by modal superposition method; under similar center distance and transmission ratio, the gearbox vibration characteristics influence law which caused by the change of the helical gear geometry parameters, such as: number of teeth, modulus and the gear tooth profile modification were analyzed. It is concluded that increasing the number of teeth, reducing module can increase the contact ratio, tooth profile modification can avoid meshing impact, both of these are helpful to reduce the vibration of gearbox.(4) Marine gearbox with conical rubber vibration isolator finite element model is established using super elastic Mooney-Rivlin constitutive model to simulate nonlinear elastic properties of rubber. Through the simulation, change rule of dynamic response of gearbox and base before and after adding vibration isolator is analysed, and rubber material parameter's effect on gearbox vibration intensity and base structure noise is studied. The results show that base vibration value is reduced greatly, while gearbox vibration increased after vibration isolation.