| The engine body is the bracket of the whole engine.It is the assembly base of crankconnecting rod mechanism,valve distribution mechanism,timing system and other main parts of the system.It contains liquid such as cooling water and lubricating oil.It is a complex coupling body.Considering the influence of cooling water on the vibration attenuation characteristics of engine block,there is little research in this field in China at present,and it has not been applied to engineering practice.In this paper,the modeling method of finite element model of bidirectional fluid-solid coupling vibration response of engine block and the testing method of vibration response experiment are studied.The influence of different flow states of cooling water on the vibration characteristics of engine block is studied,which has practical engineering guiding value.Firstly,the finite element model is created by meshing the three-dimensional geometric model of the engine block,and the finite element model is analyzed by free model.Then the free modal experiment is performed on the corresponding solid model.The experimental results are consistent with the simulation analysis.The modal frequencies are all within 5%,which verifies the correctness of the finite element model of the engine block.Then the free modal test of engine block with cooling water is carried out.Compared with the no-water state,the modal mode shape is consistent,the modal frequency changes little,and the modal damping ratio is greatly improved.The existence of cooling water significantly improves the modal damping ratio of engine body.Secondly,based on reciprocity principle,vibration response test is carried out to verify the feasibility of the experimental method of vibration response.Then,a two-way fluid-solid coupling vibration response finite element model of engine block is built.By comparing the frequency response function curve of vibration response experiment with the vibration acceleration curve of vibration response simulation analysis,the resonance frequency of engine body is close to that of constraint mode,and the change trend of amplitude is consistent,which verifies the validity of the finite element model of engine block vibration response.Then the amplitudes of the frequency response function of each part of the engine body and the amplitude of the frequency domain vibration acceleration of each part of the engine block analyzed by simulation are compared with those of the non-water state and the water-added static state respectively.Finally,the correlation and difference between the damping ratio of each frequency response function and the damping ratio of each transmission path are analyzed by experiment and simulation.Finally,based on the finite element model of bidirectional fluid-structure coupling vibration response,the variation of vibration attenuation characteristics of cooling water under different flow conditions and the influence of different excitation forces on the vibration attenuation characteristics of engine body are analyzed.The influence mechanism of cooling water on various parts of engine block and the effect of vibration reduction are also studied.Based on the above analysis and research,it provides a basis for the following optimization design of engine body. |
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