| Piston as an important component of internal comb ustion engine, its design and manufacturing level restricts the further development of internal combustion engine. The piston skirt plays a guiding role in the process of the engine, and its structure has a significant effect on the secondary motion of the piston. Established the matrix to describe the overall radial stiffness of the piston, studied the influence of the weight reduction gallery on the radial stiffness of the piston. In this thesis, build the dynamic model by AVL GLIDE, boundary conditions for dynamic analysis was revised and validated by FEA, temp-plug test and stiffness test of piston, studied the effect of the stiffness of the piston skirt on the impact of the kinetic energy in the case of different cylinder clearance. Basing on the failure problems of piston top land and cylinder bore of a diesel engine after test, we establish the dynamic model by AVL GLIDE of the piston component and study the piston secondary motion in this paper. Then by comparing different piston pin offset, different profile of piston skirt and crown, we get an optimized design,and successfully solve the failure of piston and cylinder.The detailed content is as follows:(1) Established the matrix to describe the overall radial stiffness of the piston with stiffness test and FEA, the matrix is one boundary condition of dynamic analysis. The effects of weight reduction cavity and skirt structure adjustment on the stiffness of the skirt are studied. Calculation results show, weight reduction gallery does not significantly weaken the overall radial stiffness of the pist on, and different structural parameters of the skirt had different influence on the stiffness of the skirt.(2) The thermal and elastic deformation of piston and liner, the assembly deformation of the liner and the height, radius and density of the surfac e roughness peak of the piston skirt and the liner are generally considered in dynamic analysis. Boundary lubrication is introduced into analysis. Simulation model thus can come closer to real working condition than before.(3) Analyzed the effect of skirt stiffness change on the secondary motion, the stiffness of different skirt include: the size of the stiffness of the skirt, the different distribution of the stiffness of the skirt, the asymmetry of the stiffness of the skirt. It is found that the stiffness of the skirt has a direct effect on the motion of the piston, the stiffness of the piston skirt decreases will lead to increase the radial displacement and maximum tilting angle of the piston. But the piston skirt in different height direction stiffness change on the piston dynamics performance is different, should be analyzed according to the design of specific models. The asymmetric stiffness design of TS and ATS will make the peak kinetic energy increased by 13.7%, the maximum tilting angle of the pis ton is also increased.(4) Basing on the failure problems of piston top land and cylinder bore of a diesel engine after test, we establish the dynamic model of the piston component and study the piston secondary motion in this paper. Then by comparing diffe rent piston pin offset, different profile of piston skirt and crown, we get an optimized design, and successfully solve the failure of piston and cylinder. The study also showed that, in setting piston pin offset, not only to consider the impact of piston pin offset on engine performance index such as engine noise, friction loss and so on, but also the impact on contact between piston and cylinder must be considered. In addition, when the piston heat load increases or the amplitude of the piston secondary motion increasing, reduction of top land diameter should be appropriately increased, it is beneficial to preventing contact between top land and cylinder. Optimizing the motion of the piston, not only can improve the reliability of the engine, and there is a significant improvement in both the engine economy and the power of the engine. |
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