Research On Friction Simulation Of Diesel Engine Pistoncylinder System Based On Thermodynamics

The piston-cylinder system is an important part of the automobile engine,and its working state directly affects the life and discharge performance of the internal combustion engine.The thermal load and mechanical load of the system during the working process have an important impact on the friction of the system.Therefore,the friction-based study of the piston-cylinder system is based on the thermal coupling state.Main tasks as follows:Firstly,the force of the simulated piston-cylinder system under mechanical load.the magnitude and distribution of mechanical loads on the piston,piston ring and cylinder are determined.The obtained mechanical load is applied as a boundary condition to the ABAQUS to study the force of the system under mechanical load.Among them,the piston ring will generate the set stress during the installation process,so it is necessary to check the strength of the piston ring assembly process.Secondly,thermal analysis of the piston-cylinder system.In this paper,the third type of boundary conditions are used to calculate the temperature and heat transfer coefficient of the near-wall fluid that exchanges heat with the top surface of the piston.The heat transfer coefficient is calculated by empirical or semi-empirical formula.The temperature is calculated according to the AVL-FIRE simulation.After the boundary conditions are obtained,the thermodynamic simulation of the system is carried out.The temperature,thermal stress and contact stress distribution of the simulation system and the friction stress.Thirdly,the force state of the simulation system under thermal coupling conditions.Analyze the distribution of stress,deformation and contact force and the magnitude of frictional stress in the coupled state,analyze the force situation and the location of the stress,and compare the force state of the system under mechanical load and thermal load.The force in the coupled state is even worse,and the friction and wear are more serious.Finally,improve the system structure and carry out rationalization verification.Improvements to the system structure from five aspects: improved piston thickness,improved piston ring groove height,improved piston pin fillet size,improved piston top surface shape,and improved cylinder thickness for improved thermal coupling of piston-cylinder systems The simulation analysis compares the results with the simulation results of the standard piston to verify the rationality of the structural improvement.The factors affecting the stress state of the piston are from large to small: the shape of the top surface of the piston,the fillet of the piston pin seat,the thickness of the piston and the height of the piston ring groove.