Prediction Study Of Vibration And Noise Characteristics Of Diesel Engine Block Under Multiple Excitation Loads

With the development of industry,the problem of vibration and noise has been well known,and the harm caused by it cannot be ignored,while it is unavoidable for diesel engines.With the improvement of the diesel engine R & D standards,the vibration and noise problems have also raised higher requirements.The diesel engine has been upgraded and accelerated,resulting in a shortened research and development cycle.Traditional research and development design schemes have been gradually phased out.Research on the prediction of diesel engine vibration and noise has been put on the agenda.As the skeleton structure of the diesel engine,the study of the vibration and noise of the diesel engine block is largely the study of the entire diesel engine.This thesis conducts prediction and research on the vibration and noise of the diesel engine block.First,this paper establishes a simulation model of the diesel engine block,analyzes the relevant modal information of the diesel engine block in free and constraint conditions,understands the relevant natural frequency and mode of the body,studies the characteristics of the diesel engine block,and lays the foundation for the study of the vibration and noise of the body.The dynamic model of the crank mechanism is established.The dynamic analysis of the crank mechanism is conducted.The movement laws of the piston and the link are studied,and the force distribution at the piston pin and the main bearing is analyzed.The theoretical calculation is highly similar to the force distribution at the main bearing under the simulation model,which verifies the feasibility of the simulation model.Based on the comparison of the force at the main bearing under the full rigid model and the force at the main bearing when the crankshaft elastic deformation is considered,the overall force when the crankshaft is considered to be elastically deformed is larger than that without the deformation.The paper analyzes the degree of influence of the inertial force.Based on the analysis of the main excitation force of the diesel engine block,the surface vibration in the time domain of the diesel engine block is studied.Starting from the vibration response at the observation point on the surface of the diesel engine block,the paper analyzes the vibration distribution of each part of the diesel engine block.The diesel engine block is mainly dominated by lateral vibration.The lower part of diesel engine block vibration is more severe than the upper part.The lower part of diesel engine block moves outwards and inwards.The piston side thrust has a pulse effect on the part of diesel engine block.This chapter considers that the overall vibration of the diesel engine block under the condition of elastic deformation of the crankshaft is greater than that under the full rigid force source.The contribution of gas force to the surface vibration of the diesel engine block is the largest,and the overall vibration magnitudes under the two ignition sequences tend to be the same.The vibration signal of the diesel engine block is used as the excitation force of the diesel engine block’s radiated noise,and the distribution of the radiated noise at each end face near the diesel engine block is analyzed according to the frequency distribution of the sound pressure level at each reference point.The chapter analyzes the influence of the elastic deformation of the crankshaft on the external radiated noise of the diesel engine block.The intensity of the radiated noise at each reference point corresponding to the gas force is slightly greater than that under the full excitation force.The inertia force does not contribute much to the external radiated noise of the diesel engine block.In the two firing sequences,the corresponding external radiation noise is basically the same.The two firing sequences have little effect on the outward radiation noise of this model.The above prediction research provides a reference basis for vibration and noise reduction of diesel engines.