Design3D Numerical Analysis Based On Multi-fields Coupling On Cylinder Head Of China-Ⅴ Diesel Engine

In the engine research and design, how to extend finite element structuralanalysis to the limit deformation analysis, coupled analysis of thermal stress andmechanical stress, and other physical fields coupled analysis by more accuratemethods, this is a long-term problem that needs the accumulated experience andtechnological progress. This paper treated a commercial diesel engine of the forwarddevelopment process as the research object, through CAE finite element analysis toolsto predict the temperature field of the engine cylinder head and to analysis couplingstress and strain under multi-fields conditions.First, the CAD machine model was created. In order to be similar to the actualwork environment as close as possible, we have not greatly simplified the mainstructure of the cylinder block, cylinder head, cooling water jacket and oil core andhave only simplified peripheral attachments of the cylinder block, cylinder head, thecylinder head bolt and the cylinder gasket.Then, the heat transfer model consisted of cylinder block, gasket and cylinderhead was established, the temperature field of model was analyzed by using thefluid-solid coupled method. At first, CFD simulation analysis of cylinder gas andcooling water jacket has been done by using software AVL-FIRE, the combustion heattransfer boundary and cooling water jacket heat transfer boundary were obtained; thenheat transfer boundary was projected to the structural surface elements and thetemperature analysis model was calculated. By the above analysis, we decided themass flow of cooling water and researched the impact of the mass flow of coolingwater to the thermal condition of the cylinder head.Finally, the structure finite element model consisted of the cylinder block, gasketand the cylinder head was established, the thermal stress of cylinder head and thecoupling stress and strain of cylinder head under thermal load and mechanical loadwas analyzed by using the indirect method, that was, first the whole temperature fieldwas solved by thermodynamic calculation, the structure finite element model wascalculated by loading the above calculation results of the temperature field as apredefined field and loading the mechanical load (including cylinder head bolt preload,the valve seat over surplus force and peak cylinder pressure). We mainly analyzed thesynthesis stresses and the synthesis deformation of the cylinder head under the eachpeak cylinder pressure and compared with the stress field and the deformation field of the cylinder head under a single mechanical load, and researched the impact of theeach peak cylinder pressure to the high-cycle fatigue of the cylinder head.Conclusion: the simulation results showed that the temperature field, the thermalstress，the coupling stress and deformation and the high cycle fatigue of cylinder headcould satisfy the strengthened index of engine design. By the manufacture and the testof engine, we could have a conclusion that the multi-fields coupling method isavailable in the finite element analysis of the cylinder head.