| In recent years,with the continuous popularization of automobiles,the cylinder score and burning lubricating oil of automobile engines have become important issues in automobile failures,and they have received widespread attention.However,the problem of engine cylinder score and burning lubricating oil are usually closely related to the design of the piston skirt.Therefore,it is necessary to conduct in-depth research on the basic theoretical issues related to the design of the piston skirt.From the piston development stage,the design of the piston skirt profile should be considered in order to reduce the engine failure.At present,regarding the design of the piston skirt structure,the academic and engineering circles cannot provide a clear theoretical basis.In the actual piston development process,whether the relevant parameters of the piston group surface structure can meet various engine operating conditions,the designer has not yet fully grasped it.Therefore,the modern finite element method is used to analyze the thermodynamics and deformation of the piston skirt structure,therefore a better design scheme of the skirt structure is obtained.The research results not only can reduce the complicated work in the forward development process,but also have practical engineering value in reducing the engine failure rate.It also has important positive significance for improving the core competitiveness of the enterprise and promoting China’s piston design and development.This dissertation starts with the basic concepts and theoretical basis of the piston design for gasoline engine,by combining with the actual failure shape of the skirt cylinder core,to find out the factors related to the cylinder score failure,and by using CAE to analyze and simulate the piston movement,which under the conditions of heat deformation to grasp the law of piston deformation,and then provide a basis for improving the piston design.The main contents and steps are as follows:1.Introducing the structure and shape of piston skirt surface,analyzing the main influencing factor of the piston,discussing the unreasonable design of piston thatcausing the failure of cylinder score,and analyze the design method of the piston skirt.2.Establish the finite element analysis 3D model of the piston,set up the theoretical basis for the steady temperature field and linear deformation field of the piston;establish the piston heat transfer,boundary loading force model,and define the thermal boundary conditions of the piston and loading.Based on the engine relative parameters provided by OEM and boundary condition set-up,calculate the piston thermal deformation rate by analyzing coupling deformation for thermal loading and static loading and then get the relative parameters for piston skirt face.3.Take a prototype of a certain automobile engine piston as example to verify the research results of this dissertation.Through the research in this dissertation optimize the design of the piston skirt profile basically,and find the place which is easy to have the cylinder score issue,which can benefit to reduce the cylinder score issue caused by unreasonable piston profile design. |
