CFD And 3-D Nonlinear FEM Simulation Of Fluid And Thermo-Mechanical Coupling Fields In Diesel Cylinder System

In the research and development of marine diesel engines the engine's performance is often easier to achieve the designed requirements, but it is not easy to reach the desired objectives of the service life and reliability of a diesel. Especially, the failure of cylinder system and its parts often occurs under various loads.The cylinder system is a key component of diesel engine, which affects the performance of a diesel seriously and works in the poorest working condition. Because of the parts' complexity in geometry, the thermal stress and mechanical stress distribution of the parts in the cylinder system are uneven when cylinder system carries the load of the pre-tightened bolts and the high temperature and high pressure gas. Therefore the analysis of temperature, stress and deformation of the cylinder system under external loads is very significant for optimization of the diesel engine.Firstly, the development status and trends of marine diesel engine is reviewed and the significance to raise our own ability in the research and development of marine diesel engine is introduced in this thesis; the application of CAE (Computer Aided Engineering) technology in engine design is detailed, and it is mainly discussed that the application of CFD (Computational Fluid Dynamics) and thermo-mechanical coupling analysis is widespread in engine design.According to the drawings provided by Shanghai Marine Diesel Engine Research Institute, 3-D solid models of cylinder system's components are established by using CAD software Unigraphics, including cylinder head, cylinder sleeve, engine body, bolt, water jacket and gasket. The solid meshes of a thermo-mechanical coupling analysis are got by MSC.Patran and the fluid domain grids of CFD analysis are gained by Gambit.By using CFD software FLUENT the fluid field analysis of intake manifold and exhaust manifold is completed based on the control equation of gas and k-εturbulence model and the fluid domain grid gained by Gambit. And the temperature distribution in the manifold is gained. According to the result of temperature in intake and exhaust manifolds, the convective boundary condition of the cylinder head and cylinder sleeve in heat transfer analysis is obtained. Then the heat transfer analysis is carried out and the result accords well with practical experience.The result of heat transfer analysis is considered as temperature load, the preload of bolts and gas explosive pressure are subjected to the boundary as force in thenno-mechanical analysis. After the definition of contact bodies between different components, the final FEA (Finite Element Analysis) model is obtained on the basis of solid meshes. And four conditions are calculated—preload, mechanical load, thermal stress and thenno-mechanical coupling cases.The result shows that the temperature load impacts the distribution of the stress and deformation of diesel remarkably and it leads to a relatively high stress at the bridge zone of cylinder head. And the stress and deformation in other parts is within allowable limits.The analysis in this thesis provides theoretical guidance for the optimization of the structure of marine diesel engine.