Coupled Thermal And Mechanical Load Analysis In Diesel Engine Piston

Piston is one of the most important components of the engine, the piston work reliability and durability is directly related to engine performance. Because of poor working conditions, the piston withstand very high thermal load and mechanical load, and the heat load is primarily caused by hot gas, the high-temperature gas not only cause piston temperature relatively high, but also cause the piston flux density to rise relatively large. The piston mechanical load was mainly due to the outbreak of pressure, reciprocating inertia force, lateral force, friction and other mechanical loads in the process of motion. So it is very complicated to analyze the stress and strain when the piston is working.The finite element method is used to analyze the diesel engine piston temperature, the piston temperature distribution can be obtained from results, and the results of the temperature distribution along the axial is substituted into the multi-body dynamic method to analyze the piston contact force, the result showed temperature changed the angle that connecting rod axis deviating from the cylinder axis to influence the contact force. On this basis, the contact force infulenced on the stress distribution is also analyzed, the piston stress and deformation is calculated under the thermal load, mechanical load and two load coupled. The results showed that the contact force increase the stress on the piston skirt, ring groove, the root of piston pin seat, and in the process of coupling analyzing, the deformation caused by thermal load worked as the main factor in the working time. So it provided a theoretical basis to reduce the contact force in the piston stress and to have insight into different loads on the impact of stress and deformation.In order to study heat transfer boundary condition of piston top surface, CFD numerical analysis method is used to analyze combustion, the gas temperature distribution,velocity distribution, density distribution near the piston top surface under different crank angles. The results showed that the heat transfer coefficient, heat flux and density near the top surface of the piston have relation with gas velocity distribution, density. And biggest heat flux exited in the chamber throat, mainly caused by by the fluid velocity distribution during compression time, and during expansion time the bigger heat flux existed in chamber throat and the bottom of the combustion, it is mainly caused by ignition and turbulance.