Dynamic Excitation Simulation And Dynamic Performance Optimization Of Marine Gearbox

Marine gear transmission device is the key equipment of ship propulsion system, the performance of which directly determines the operation reliability of the ship. With the progress of equipment manufacturing technology, gear transmission is developing towards the direction of high speed, high power, high precision, light weight and low noise. The research about dynamic excitation simulation and dynamic performance optimization of gearbox has important theoretical significance and wide application prospect.The thesis is supported by National Natural Science Foundation of China and aims at a certain type of marine gearbox. The research includes meshing performance analysis, dynamic excitation simulation, vibration characteristics analysis, discrete optimization of transmission system, modal-response joint optimization. The main research work in this paper can be summarized as follows:① To comprehensively consider the bending and torsional deformation of shaft, the elastic displacement of bearing, the manufacturing and assembly error of tooth, the statics analysis model of gear transmission system is constructed in the software of Romax. Tooth surface load distribution of gear pairs and bearing stiffness are analyzed. The internal dynamic excitation caused by the time-varying mesh stiffness, transmission error and meshing impact and the external excitation caused by the torque fluctuation of marine diesel engine are simulated by analyzing the statics model.② The coupled multi-body dynamic finite element model of gear system is constructed in the software of ANSYS. The natural frequency and vibration mode are analyzed by using the block Lanczos. The dynamic response of gearbox is analyzed by using the mode superposition method and vibration displacement, vibration velocity and vibration acceleration are obtained.③ The dynamic performance single-objective optimization model of marine gearbox is established with the optimization object to avoid the specific frequency of the gear system or reduce the vibration acceleration, housing and shaft size as design variables, the volume of gearbox, Von Mises stress and displacement vector sum of housing as constraint conditions. Sensitivity analysis of the design variables is carried out by using gradient tool method. Zero-order and First-order optimization methods are used to the modal and response optimization.④ To realize the consistency of optimal design variables of the modal and response optimization, the two sub-objective functions of modal and response can be transformed into single objective function by using method of weigh-adding combination based on the multi-objective optimization design theory. The modal-response joint optimization model of marine gearbox is established to avoid the specific frequency of the gear system and reduce the vibration acceleration. The optimal design variables are determined through the sensitivity analysis. The optimal solution of design variables of marine gearbox are obtained through the analysis of optimization model.⑤ The dynamic model of gear transmission system is established by using the lumped parameter method. The analytic solution of the vibration response of each component can be obtained by using the harmonic balance method. The dynamic optimization model of transmission system of marine gearbox is established by taking the mass of all components and vibration acceleration as optimization object, the number of teeth, modulus and helical angle as design variables and gear strength and transmission ratio as constraint conditions. The mixed-discrete nonlinear optimization program based on the branch-bound algorithm is used to obtain the optimal solution of design variables of transmission system.