Research On Simulation Analysis Of Dynamic Characteristics And Bearing Lubrication Performance Of High Speed And Heavy Duty Diesel Engine Crankshaft

As the increasing of requirement to higher speed and higher strength of heavy duty diesel engine, people have to consider more and more factors in the process of study and design of diesel engine. As a key component, the crankshaft’s strength, stiffness and friction lubrication performance of friction pair, even the coupling behavior between them, have effects on the diesel engine reliability that cannot be ignored. In this thesis, overall and comprehensive researches and analysis of high speed and heavy duty diesel engine crankshaft from the multiple disciplines perspective was conducted, mainly by means of the simulation analysis combined with the test, explored the modeling method and accuracy of the multibody system dynamic simulation model which contained nonlinear link elements, and researched the influence of the dynamic characteristics of crankshaft, the deformation coordination and bearing lubrication performance during the crankshaft working process considering all kinds of nonlinear factors. The main research contents were as follows.Based on dynamic substructure modal polycondensation theory and modal superposition method, the transient dynamic analysis was carried out on the crankshaft. Take the modal contribution factors as the evaluation criterion for crankshaft dynamic substructure condensation model, in this thesis discussed the mode selection strategy and analyzed the modal truncation convergence. The crankshaft multibody system dynamic simulation modal was established that contained parts dynamic substructure condensation modals and nonlinear link elements. The basic theory of elasto-hydro-dynamic lubrication was studied, as well as the influence mechanism of temperature and shape error of bearing lubrication was researched.The accuracy of simulation model was validated by the crankshaft torsional vibration test. Considering the oil film pressure, or rigid shaft neck hypothesis, the free end of the crankshaft torsional vibration, axial vibration, bending vibration and the change rule of each journal center orbit was studied, respectively. The influence law of journal elastic deformation on the bearing lubrication performance was studied.To the actual nonlinear influence factors existing in the working process of the crankshaft, dynamic characteristic and the change regularity of bearing lubrication performance were both studied. In this thesis the main factors researched including the oil supply pressure, different structure and size of oil groove, oil temperature, surface roughness, one cylinder off firing, and the shape error; the main crankshaft dynamic characteristics researched including the crankshaft torsional vibration, the free end shaft vibration, the bending vibration, and the performance which influenced the crankshaft and body connection pair place deformation coordinate, such as axis trajectory, journal tilt angle and the bearing clearance, etc; the main bearing lubrication performances researched including the oil pressure, the minimum oil film thickness, coarse contact pressure and ration, friction power loss and lubricant oil charge rate, oil inflow and oil outflow, etc.At last the crankshaft multidisciplinary simulation analysis method were extracted and inducted, took an example to illustrate the subject between the meaning of coupling analysis of numerical simulation calculation.