Research On Excitation Characteristics Of Gear System And Vibration And Noise Of Diesle Engine Caused By Excitation

Researchers in the field of low noise design of diesel engine have paid less attention to timing gear system noise,compared with that of mechanical noise(such as piston clicking noise),burning noise,and gas dynamic noise.Based on the four-stroke marine diesel timing gear system,this paper conducted the mechanism research and characteristic analysis of the stiffness excitation and error excitation,synthesized the internal dynamic excitation of timing gear system,identified the bearing characteristics of time gear system,and finally finished the machine vibration and radiation noise prediction.By parametric modeling technology,this paper set up a precise solid model of helical gear,used the contact element method to analyze the tooth meshing process,and got the change curves of the tooth contact force and contact elastic deformation with the driving gear angle.Comparing the curve with the Y.CAI stiffness calculation formula of helical gear,this paper proved that it is feasible that using the contact element method to solve the helical gear meshing stiffness problem,and then studied the gear parameters’ impaction on the gear meshing stiffness.In view of the bearing form of crankshaft and camshaft,this paper established a multibody dynamic model of rigid and flexible coupling of diesel engine and obtained the load change curves of the crankshaft main bearing,camshaft bearing,and gear shaft bearing.Based on the Hertzian contact theory and fluid lubrication theory,the bearing characteristics of varieties of bearings in the timing gear system were also obtained in this paper.The change curve of comprehensive meshing stiffness of gears with driving gear angle was finally made,taking the transmission gear coincidence into consideration.After synthesizing the stiffness excitation and error excitation,the internal dynamic excitation of gear was gained.The dynamic analysis model of timing gear system-bearing-machine coupling configuration was finally made,and the natural vibration characteristics of coupling system was also obtained.By using the finite element method,the internal dynamic excitation in the gear system in the frequency domain was loaded,and the dynamic vibration response of the coupled system was calculated.On this basis,this paper used the boundary element method to calculate the surface radiation noise of the coupling system.