Design And Research Of 12V240H Diesel Engine Medium Convex Variable Elliptic Composite Piston

As an important part of diesel engine,the piston’s normal and stable work is related to the whole diesel engine.This paper aims to design a new type of medium convex variable elliptic combined piston which can meet the daily work of 12V240 H diesel engine.Firstly,the finite element model is constructed,and then the relevant simulation is carried out.Through the simulation analysis,the temperature,deformation and stress distribution of the designed new medium convex variable elliptic piston assembly in real working conditions are obtained.According to results obtained,the piston skirt size is improved to make it close to the standard circle with a diameter of 240 mm after deformation in the real working process,which provides reference for subsequent researchers.The main contents of this paper are as follows:(1)The cooling form,piston head and piston skirt structure,eccentric circle and ellipse parameters of the piston skirt,skirt section design,longitudinal profile and corresponding medium convex variable ellipse parameters of the new medium convex variable ellipse piston are determined,and 20 height ellipse parameters are determined.The material and properties of the new piston are determined by comparison.(2)The finite element model of middle convex variable elliptic piston group was established by using 3D software according to the relevant parameters,and model was assembled.The model was preprocessed,including material assignment and mesh division.(3)The finite element model of piston group was simulated by thermal-mechanical coupling,and three kinds of distribution cloud diagrams of temperature field,stress field and deformation were obtained.The piston skirt was optimized,the part of the bottom of the piston skirt upward 31mm—87.3mm was selected as the optimize plane,and the direction of the piston pin axis was specified as Z direction,and the direction perpendicular to its axis was X direction.After 11 times of optimization,the optimal size was finally determined,that is,before the deformation,the size of the X direction was 240.38 mm,and the size of the Z direction was 239.62 mm.After deformation,the X direction size is 239.997 mm,and the Z direction size is 240.003 mm,which meet the design goal.(4)Will improve after the piston assembly strength check,mainly on the strength of the piston head,check the strength of the ring groove ring shore,the piston skirt than pressure,piston cooling cavity area is calculated,the piston skirt stress simulation,determine the security requirement of the piston head and skirt,and check the related safety coefficient.Finally,the design of the convex variable elliptic piston meets the design requirements.