Structure Optimization And Fatigue Life Prediction Of Engine Piston Based On The Temperature Test And Thermal Mechanical Coupling Simulation

The research object of this topic was gasoline engine piston.To improve the power performance fuel economy and reduce emissions of engine,intake type of supercharging air intakewas instead by naturally aspirated.The original engine piston was installed in supercharged engine and then did reliability test.After test,there was a crack around the piston pin hole.In order to satisfy the performance requirements of supercharged gasoline engine,there was a need toimprove the structure of piston.During gasoline engine running,fuel combustion produced high temperature and high pressure that made heat load and mechanical load acting on head of piston.The top of the piston temperature was higher than piston skirt because that piston skirt was not directly contact with high temperature gas.Temperature was difference of piston's different parts that caused thermal stress.In the process of work,the piston top gas explosion pressure is enormous that produced mechanical stress.In addition,relative motion between piston and other contacting parts was caused periodic variational inertial force side pressure friction force and so on.Designing the piston need consider about thermal load and mechanical load to make sure piston's reliability and durability of use,and then made thermal mechanical coupling analysis.At home or abroad,people researched the projects of piston thermal coupling and fatigue life prediction.At present,people widely used the method of computational fluid dynamics theory and finite element analysis to study the heat transfer condition of piston,for piston fatigue was researched in two ways that were fatigue simulation software simulation and durability test on engine test bench.In this research project,based on heat transfer theory and nonlinear finite element analysis and used software to calculate the simulation analysis of piston,the overall model was set up including piston pin cylinder and connecting rod.Temperature testing experiment proved the accuracy of simulated temperature field.Imported the boundary conditions of thermal load and mechanical load,under the coupling field to calculate the piston stress of size and distribution.The calculation results showed that the improvement of piston structure was effective to decrease stress.The numerical value was reduced 129.63 MPa than before.The thermal stress and mechanical stress were decreased obviously.The piston structure improvement was reasonable and meet the demands of the turbo engine.The fatigue life prediction of piston was 1.49e7,the use of reliability and durability of the piston can meet the needs of turbocharged gasoline engine.