Finite Element Analysis Of A Diesel Engine Cylinder Head On A Plateau

The diesel engine is one of the most commonly used power machinery nowadays,and it is widely used in railway traction,oil well exaction,various ships,automobiles and other mechanical fields.Given the high altitude terrain of the western region,and gradually made new demands on the transport capacity of the plateau transport.Diesel engines,as the most important power core of heavy trucks and locomotives,must adapt to the severe conditions of the plateau: low temperature and low oxygen content in order to exert their power for the development of the western region.The cylinder head assembly of one of the core components of a diesel engine system,not only a complicated structure,while at the same time extremely complex working environment,in addition to withstanding the explosion pressure and thermal stress of the cylinder,it is also subjected to multi-physical fields such as the temperature field generated by the cold zone water jacket,the high temperature flue gas of the intake and exhaust pipes,and the pre-tightening force of the bolts,greatly increase the difficulty of analyzing the cylinder head stress of diesel engines.In this paper,a finite element thermal-mechanical coupling analysis of a 16 V diesel engine cylinder head is carried out.In the process of numerical calculation of the cylinder head temperature field,the temperature boundary conditions of the cylinder head traditionally adopt two methods: One is to directly apply it after estimation based on actual working conditions and empirical formulas.The other is to analyze the fluid domain of the cooling water jacket inside the cylinder,and directly map the analysis results to the solid domain contact surface in contact with the water domain.Although the former is simple to calculate,it requires important engineering practical experience and the calculation error is large,so the latter is adopted.The calculation in this paper mainly includes four parts:(1)Use Fluent to analyze the flow and heat transfer of the overall cylinder head water jacket,find the cylinder with the worst coolant flow effect,so as to conduct fluid-solid coupling and thermal-mechanical coupling analysis.Checking the cylinder head is subjected to the maximum stress meets the design requirements.(2)Analyze the heat exchange between the cylinder head and the coolant water jacket,conduct a fluid-solid coupling analysis on the cylinder with the worst heat exchange effect,and obtain the heat transfer boundary conditions between the cylinder head and the cold water jacket.(3)Import the thermal boundary calculated in the second part as a known condition into the Static Structural module in Workbench,and on this basis apply bolt pre-tightening force,explosive force of the cylinder,and temperature field of high temperature flue gas.(4)Checking a cylinder head meets the set requirements,not only need to study the static mechanical properties of the thermal-mechanical coupling of the cylinder head,but also need to analyze the dynamic performance of the cylinder head,therefore,the free modal and constrained modal analysis of the cylinder head of the diesel engine is carried out.The purpose of modal analysis is to obtain the natural frequency and vibration mode of the cylinder head,compare the natural frequency of the cylinder head with the excitation frequency of diesel engine ignition,and avoid resonance at the excitation frequency of diesel engine ignition.