A Research On Valve-train Dynamic Performance Of Marine Diesel Engine

Along with the continuous improvement of modern science and technology, energy crisis and environmental pollution problems are becoming more and more serious, as well as the importance of energy conservation and environmental protection is becoming more and more prominent, therefore increasingly strict emission regulations has been proposed in all countries of the world. Internal combustion engine toward the inevitable development of the direction of high power density, low emission, low noise and high reliability, corresponding to the requirement of performance figures of valve train is becoming more and more improved.The valve train controls the intake and exhaust stroke, and then influences the power,economy and emission characteristics of internal combustion engine.Based on the sufficient research on the basis of domestic and foreign development status of valve train, and study on the evaluation figures of valve train and the dynamics multi-rigid-body and rigid-flexible-body model. Set up dynamics simulation model of a certain type of a middle-speed marine diesel combine with the valve train dynamics calculation theory and in terms of professional valve train software AVL Excite Timing Drive.With the finite element software Workbench and 3D software UG as the auxiliary, calculate the quality and stiffness parameters, established on the basis of the multiple degree of freedom model of kinematics and dynamics model of valve train. In this paper, setting up the intake and exhaust part model firstly, and then beginning the kinematics and dynamics simulation.Setting up the dynamic model of the single cylinder, and compared its dynamic results with intake and exhaust system dynamics results. Finally, analysis influence of crankshaft speed,valve clearance, valve spring stiffness and preload, cam contour on dynamic performance of valve train. The research work includes:(1) Study on domestic and foreign technology development about valve train, summarize the abnormal phenomenon of valve train, and ensure whether or when the abnormal phenomenon occurred. Transmission dynamics calculation theory-single degree and multi degree of freedom model.(2) Combine with software UG set up solid model,get the quality and inertia of the parts,and then calculate the equivalent quality for later work. ANSYS Workbench analysis deformation of the parts can be used to calculate the equivalent stiffness. Input the equivalent mass and stiffness to the AVL Excite TD model, choose the recommend value of the software,and then establish the kinematics and dynamic model of intake and exhaust system, and the dynamic model of single-cylinder of valve train, define working condition and simulation control parameters to begin dynamic calculation.(3) Finally taking the exhaust system as an example, contrast and analysis the variables of crankshaft speed, valve clearance, spring stiffness, spring preload and cam contour influence the dynamic characteristics of valve for reference to other scholars and later work.