Study On Dynamic Modelling Methods Of Ship Engine Room And Dynamic Optimization Using Component Mode Synthesis

Ship's engine room is always under the exciting force of the main engine and other power machinery as well as the propeller.If the excitation frequency meets the natural frequency of the structure,harmful resonance vibration would happen.In order to keep resonance from happening,it's necessary to have better knowledge of the dynamic characteristic of the structure during the design phase.However,modeling of the relative structures directly affects the recognition of integrate modes and local modes.Hence factors that would affect the result,including the simplification methods of the relative structures,equipment on the bottom plate,the size of the finite element and the engine base structure,are considered.By comparing the modal analysis and frequency response analysis results of all the calculation models,modeling methods of the engine room dynamic analysis are proposed and can be applied in subsequent ship design.In fact,it's fully coupled between the engine,engine mount and the double bottom,comprehensive analysis is needed to reach a reasonable accurate solution.A 3D FE model of the engine costs heavy workload and large amount of computation,and the coupled mass matrix and stiffness matrix of the system may be ill-condition matrix because of the enormous discrepancy of degree of freedom between the bottom and the engine.The component mode synthesis method is applied in the dynamic analysis process in MATLAB to solve these problems.Example solutions illustrated that this approach reduced the cost of computation effectively and retained the vibration information of the coupled system,and also increased efficiency in cases where only substructures were modified.At last,the component mode synthesis is applied in multi-objective dynamic optimization of the double bottom to testify it's serviceability.In corporation with the approximation model method,the method decreased the time cost of the surrogate model to half,which is helpful in increasing dynamic optimization efficiency.