Investigation On Thermal-Fluid-Solid Coupling And Deformation Behavior Of Fastening And Sealing Structure For Diesel Engine

With the rapid development of science and technology,modern engines are moving towards high performance,but it also means that the heat load they bear in the working process is increasing.When the diesel engine works normally,its fastening and sealing structure will bear great heat load.Exhaust manifold,as its main component,has obvious high-temperature expansion deformation,and under the influence of continuous high-temperature and high-pressure impact and engine vibration,it is easy to cause structural damage and sealing failure,mainly manifested in manifold cracking and sealing failure at flange bolt gasket,which reduces the sealing performance and reliability of the fastening and sealing structure of the engine.In this paper,the three-dimensional model of the fastening and sealing structure of a heavy diesel engine is taken as the research object,and the high-temperature deformation behavior and sealing reliability of the fastening and sealing structure of the engine are studied after thermal-fluid-solid coupling.The details are as follows:The geometric model of engine fastening and sealing structure is established,the temperature field and heat transfer coefficient of flow field in exhaust manifold under transient boundary conditions are calculated,and the average temperature field and heat transfer coefficient of fluid outer wall are obtained as the heat transfer boundary conditions of exhaust manifold inner wall.The thermal-fluid-solid coupling simulation calculation model of engine fastening and sealing structure is established,the temperature field and thermal stress field of fastening and sealing structure and its components are solved,the variation law of bolt load with time and the contact pressure distribution of gasket along the circumferential direction are obtained,and the sealing performance of the structure is analyzed.A non-contact measuring platform for flange deformation at high temperature is built to obtain the deformation of flange side at high temperature,analyze the variation law of flange side strain with temperature,and verify the simulation model;The sealing limit equation of gasket is obtained,and the influence law of different time,temperature,medium pressure and residual stress mean on gasket sealing reliability is studied.In this paper,through modeling,simulation,experimental verification and theoretical research,the thermal-fluid-solid coupling simulation model of the fastening sealing structure of diesel engine is established,and the high-temperature deformation behavior of the fastening and sealing structure and the sealing reliability of the exhaust manifold gasket are studied,which lays a foundation for further research on the sealing performance of the exhaust manifold and gasket of the subsequent engine,and is helpful to improve the sealing performance of the diesel engine,and has important research significance and engineering application value.