| The valve train is one of the most important mechanisms of the diesel engine,which controlled the gas exchange process according to the order of the air cylinder.Whether the diesel engine have a superior dynamic performance,a remarkable economic character and a dependable work mostly depend on its valve train system.In other words,the valve train system have a great influence on the whole dynamic property of the diesel engine.With the development of the high speed and high power,a brilliant working performance has been requested and commanded in diesel engine.Even under high speed and heavy load,it can still work steadily and dependably.In this thesis,it focuses on the dynamic analysis of a certain marine diesel engine.The main works are as follows:Firstly,using the least square method fit the curve of the intake and exhaust cam profile to getting the cam lift calculation formula in using the MATLAB software.Then,the speed and acceleration of each could be got,laying the foundation for calculating the dynamic analysis.Secondly,the single degree mass-spring dynamic model of the valve train was established.Determine every parameter in the formula and make its calculation by using Runge-Kutta method with MATLAB.The valve dynamic character calculation results is analysed under the rated speed.Thirdly,multi-body dynamics of the valve train were discussed in this thesis.The multi-body dynamics model of the valve train was established in ADAMS,analyzing the valve movement,the contact stress and force between cam and tappet.Combining with the ANSYS,analyzing the contact collision between valve and valve base at the moment of valve take its seat as well as the thermal stress when gas explosion.Find out different rotating speed and cam base circle how to influence the calculation results.Finally,a new cam profile was designed and comparative dynamics analysis is made by using the multi-body dynamics model of the valve train with the tow cam profiles. |
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