Fatigue Analysis For Marine Low-speed Engine Piston With Thermal-mechanical Coupling

With the rapid development of China's shipbuilding industry,and far lower than the domestic production rate of ships in developed countries,the localization of Marine components is full of development opportunities.As the heart of the ship's diesel engine,the localization of high-performance diesel engine is becoming more and more important.Diesel engine is towards high detonation pressure at home and abroad,the direction of the high power and high speed development,the diesel engine is faced with higher temperature and the combustion chamber blasting pressure and bad situation,therefore,as the core component of Marine diesel engine piston will withstand higher thermal stress and mechanical stress,the fatigue resistance of reason of piston has become one of the key factors influencing the performances of diesel engine.The main contents of this paper are as follows:(1)Using GT-power software,the one-dimensional combustion model of diesel engine combustion chamber was built,and the combustion reaction results were analyzed.By increasing the fuel injection quantity way for improvement of the output power of diesel engine,diesel engine power output and temperature and pressure in cylinder,and the changes of convective heat transfer coefficient of combined with the empirical formula to calculate the piston heat transfer coefficient of each area on this basis,using ABAQUS software to simulate the piston temperature field calculation results,the temperature field and the temperature change with diesel engine power output.(2)Based on piston parameters,the relationship between piston inertia force and crank Angle is analyzed.Calculation of bolt pre-tightening force,combined with the piston temperature field calculation and analysis of diesel engine under different working conditions and the output power stress and strain of the piston,piston stress and strain and the working condition of diesel engine and the relationship between the output power,study on piston sealing performance under different working conditions,in order to improve work safety of diesel engine piston.(3)On the basis of the theory of piston fatigue analysis,by introducing the results of piston stress analysis,FEMFAT software is used to analyze the safety coefficient and fatigue danger area of the main parts of the piston.Based on the S-N curve,the theoretical service life of the fatigue danger area on the piston is predicted,and the relationship between service life and power is revealed.Based on the above work,the temperature field stress field and reliability of the piston are basically judged,and the rationality of the analysis process is tested.By analyzing the stress and deformation of piston parts under the condition of thermal-mechanical coupling,this paper studies the fatigue characteristics of piston parts of Marine low-speed diesel engines,and designs an evaluation flow of piston performance,which provides a judgment flow for piston type selection and improving the anti-fatigue performance of piston.