Study On Three-dimensional Coupling Vibration Characteristics Of Crankshaft Of High Power Diesel Engine

Crankshaft is one of the most important parts in diesel engine.Its vibration characteristics directly affect the reliability and service life of diesel engine.The high speed and high burst pressure of the high power diesel engine make the crankshaft vibration worse and affect the working performance of the diesel engine.Therefore,it is of great engineering significance and practical value to study the vibration characteristics of crankshaft to improve the working performance of high power diesel engine.In this paper,a high-power 12-cylinder diesel engine is studi.Firstly,the three-dimensional solid model of crankshaft and bearing seat is established in the three-dimensional solid software SolidWorks,and then the finite element mesh division is carried out in HyperMesh combined with mesh generation technology.Finally,based on the reduction theory and multi-body dynamics theory,the structure of crankshaft and bearing seat is reduced in AVL-EXCITE multi-body dynamics simulation software,and the vibration simulation model of crankshaft system of high-power diesel engine is established.Based on the calculation results,the torsional vibration,bending vibration and longitudinal vibration of diesel engine crankshaft are studied.Combined with the natural vibration frequency of the crankshaft,the three-dimensional coupling vibration analysis is carried out.In order to solve the problem of large torsional angular displacement of crankshaft,torsional shock absorber is matched.The results show that:1.The vertical force at the large end of the connecting rod reaches the maximum in turn with the ignition sequence,and the lateral force alternates with the positive and negative forces.The angular velocity between the free end of the crankshaft and the end of the flywheel reaches the maximum,and the angular acceleration tends to zero.2.The torsion angle displacement of the crankshaft is changed alternately,and themaximum torsional angle of the free end is 1.5 °.The bending vibration of the crankshaft is weaker than that of the torsional vibration and the longitudinal vibration.The amplitude of the longitudinal vibration decreases gradually from the free end to the fourth spindle neck and from the flywheel end to the fourth spindle neck.It shows the complexity of longitudinal vibration of crankshaft.The torsional vibration,bending vibration and longitudinal vibration of the crankshaft all affect each other.When the excitation frequency is close to the natural frequency of any one of the vibrations,in addition to the larger vibration,the other two kinds of vibration are also affected by different degrees.When the excitation frequency is close to the natural frequency of the first order torsional vibration,the three dimensional coupling vibration of the crankshaft is the strongest.3.In order to solve the problem of large torsional angular displacement of crankshaft,the torsional angular displacement of crankshaft torsional shock absorber has been matched.The torsional angular displacement of crankshaft free end has been reduced from 1.5 °to 0.7 °,and the torsional angular displacement has been obviously improved.The results provide a reference for high power diesel engine strengthening and crankshaft design.