Lubrication And Friction Analysis Of Diesel Engine Piston Skirt And Optimal Design

It is important for improving the diesel engine performance to control the friction and lubrication condition of the piston skirt. Although there were many researches worked at this problem, the main issues were not solved totally. In order to reduce friction and improve reliability of the piston, the workload of piston design is heavy in traditional way, such as developping lots of piston samples, finishing lots of tests one by one, and lots of experiences on piston design. Obviously the method couldn't meet the requirement of current piston design.In this thesis, the lubrication model which was combined with the secondary motion of piston, was established through the analysis of the pair of piston skirt and cylinder and was solved by using the FEA method. There are many parameters which influence on the lubrication performance of the piston skirt to optimize using this model. And the analysis of the simulation result could be the theoretical basis of the piston skirt design. In order to reduce the workload, the orthogonal test method was used on this optimization.Therefore, the following work was carried out:1. Establish the model of piston's secondary motion through analyzing the equilibrium condition of forces on the piston, and solve this mathematical model by Runge-Kutta method using Matlab;2. Establish the lubrication model of piston skirt and cylinder sleece system by average reynolds equation, compile the FEA program to this model by Matlab, embed the FEA program into the program which solve the piston's secondary motion, then obtain to calculate the piston skirtlubrication model in a whole working cycle.3. Solve the Lubrication condition and secondary motion of the origin piston by the program.4. With the orthogonal test method, use the program established to optimize parameters such as piston pin offset, fitting clearance, position of the max diameter, piston skirt length, ellipticity and curvature of piston skirt profile; choose the best matching scheme; and then calculate the scheme and verify that the optimization is effective.