Research On Optimization Of Diesel Engine Foot Vibration Caused By Main Shaft Load

With the implementation of the increasingly strict diesel engine noise regulations,the vibration and noise control of diesel engine is becoming more and more important.It is also a valuable research topic to carry out the optimization design of diesel engine aiming at low vibration.The main bearing force is the main vibration source of diesel engine.It is necessary to establish the vibration transmission path from the main bearing force to the vibration of the engine foot.It is necessary to optimize the structure from the vibration transmission path.The CY4102 BQ type diesel engine is taking as case study in this paper.Firstly,the accuracy of the finite element model of the whole engine is verified by modal experiment and ANSYS simulation.On the basis of modal analysis,the main vibration transfer path from the main bearing force to the machine foot response is obtained through the transfer path analysis.The correlation mode and frequency range of the main vibration transmission path are obtained by comparison.According to the modal results of the whole machine,the key structural characteristics affecting the vibration from the main bearing force to the machine foot are obtained.The sensitivity analysis is used to optimize the key structural features.The design variables,constraint conditions and optimization mathematical model are selected for the key structural areas obtained from the transfer path analysis.The most important structural characteristics affecting the vibration of the machine feet are obtained through sensitivity analysis.The structure optimization of the body structure is carried out.The whole machine mode,acceleration of the machine foot,fuselage intensity and radiation noise of the whole machine surface are compared before and after optimization.By comparison,it is found that all modes of the optimized whole machine are increased,and the acceleration level of the machine foot,the intensity of the fuselage and the radiation noise are all reduced.A test bench is designed and built to simulate the vibration of the machine foot caused by the main bearing force.The excitation force exerted by the exciter and the acceleration of the foot position are measured.The correctness of the optimization method and optimization model is verified by comparing with the simulation calculation.Based on the force measured by the test,it is loaded into the simulation calculation model,and the reasons for the decrease of acceleration and radiation sound pressure are obtained,which is consistent with the conclusion of sensitivity analysis,and further proves that the sensitivity analysis method based on transfer path analysis is correct and the optimization design scheme is effective.