Thermal Fatigue Analysis And Structural Optimization Of A Vehicle's Three-way Catalytic Converter

China is currently the largest automobile production and marketing country in the world.With the continuous improvement of the national emission standard,the position of the three-way catalytic converter is closer to the exhaust hot end in order to make the automotive catalysts reach the working temperature soon.The thermal load of the three-way catalytic converter is heavier,and the problem of thermal fatigue is becoming more and more prominent.A vehicle's three-way catalytic converter is in the design verification phase.During the engine thermal shock test,there are phenomena of air leakage and cracking at the intake pipe of the three-way catalytic converter,which leads to the thermal shock test of the three-way catalytic converter failed.The three-way catalytic converter cannot meet the design requirement.In view of the above-mentioned issue,this thesis establishes a thermal-fluid-solid coupling analysis model of the three-way catalytic converter based on ANSYS Workbench software.Through the simulation analysis,the cause of the three-way catalytic converter cracking is found.The structure of the three–way catalyst converter is optimized and the thermal fatigue strength of the three-way catalytic converter is improved.Finally,the three–way catalytic converter passed the thermal shock test and met the requirement.The main contents of this thesis are as follows:1.The failure parts of three-way catalytic converter are analyzed.Through the analysis of the material and the inspection of the weld bead in the cracked area,it is determined that the cracking is caused by thermal fatigue.Therefore,the thermal fatigue analysis scheme for the three-way catalytic converter is proposed.The technical roadmap for the thermal-fluid-solid coupling analysis of the three-way catalytic converter is designed.2.The thermal-fluid-solid coupling simulation model of the three-way catalytic converter is established on the ANSYS Workbench software platform.The fluid field of the three-way catalytic converter is analyzed and simulated and the temperature and the pressure distributions in the three-way catalytic converter are obtained.The thermal load calculated by the fluid field simulated is regarded as the boundary condition of the inner wall of the three-way catalytic converter.The temperature field of the three-way catalytic converter is simulated and calculated.The temperature distribution of the three-way catalytic converter under the working condition is obtained.3.The thermal stress and thermal deformation of the three-way catalytic converter are simulated,the thermal stress distribution and thermal deformation of the three-way catalytic converter under the working condition are obtained.The thermal fatigue life of the three-way catalytic converter is analyzed,the thermal fatigue life cloud of the three-way catalytic converter is obtained.The simulation result shows that due to the thermal stress concentration at the cracked area of the three-way catalytic converter.The fatigue life does not meet the design requirement,so the structure of the three-way catalytic converter needs to be optimized.4.The structure of the three-way catalytic converter is optimized.The thermal stress,thermal deformation and thermal fatigue life of the optimized three-way catalytic converter are analyzed.The analysis results show that the thermal stress of the optimized three-way catalytic converter decrease in the cracked position,and the thermal fatigue life can meet the design requirement.Through the modal calculation of the optimized exhaust hot end terminal system,it shows that the structure optimization of the three-way catalytic converter will not cause resonance failure.5.The thermal shock test of the optimized the three-way catalytic converter is performed.The result shows that the optimized the three-way catalytic converter can meet the design requirement.After the bench test,the three-way catalytic converter was assembled on a vehicle to carry out the vehicle durability test about 160000 km.After the road test,no destruction of the three-way catalytic converter is found.The optimized three-way catalytic converter can meet the requirement.