Multiphysics Coupled Simulation And Parameter Sensitivity Analysis Of Marine Diesel Engine Cylinder Head

Cylinder head,as the key components of diesel engine,has complicated structure and harsh working environment.Its reliability is closely related to the whole diesel.This paper is based on the development and design of key components for medium and high speed marine diesel engine.In order to accurately predict the reliability of the cylinder head design,a multi-physics coupled simulation of the cylinder head was carried out.With the enhancement of the marine diesel engine's index,the cylinder head is facing the problem of increased thermal load.First,the optimization of the cylinder head structure was carried out.Then the influence and sensitivity analysis of different factors on the thermal load of the cylinder head are studied.It is of great significance to provide a reference for controlling the thermal load of high-strengthed cylinder head in a more directional manner in the future.The main research contents are as follows:(1)Based on the multi-physics theory involved in the cylinder head,a diesel engine thermodynamic model,a cooling water CFD model,finite element model for thermal and mechanical were established.The determination of the heat transfer boundary of the cylinder head,the fluid-structure coupling of the cylinder head and the thermo-mechanical coupling of the cylinder head were mainly studied.In this paper,a method for loading the hot side boundary by combining the division of the fire surface and the radial fitting curve equation is proposed.The macro file is written to realize the automatic mapping of cold boundary.Through the study of modeling and solving methods,the technical approach of multi-physics coupled simulation of the cylinder head was given.(2)In order to achieve the goal of increasing the safety margin of the cylinder head fire surface temperature,the thinning of the cylinder head bottom plate was studied.The results show that the thermal load of the cylinder head optimization scheme is reduced compared to the original scheme.By reducing the cylinder head bottom plate by 2mm,the temperature of the cylinder head fire surface is reduced by 5-6?.The minimum fatigue safety factor of the optimization scheme is 1.58,which is higher than the cylinder head fatigue safety factor limit of 1.4.This show that the cylinder head optimization scheme meets the reliability requirement.(3)The effects of three factors on the thermal load of the cylinder head were studied using a combination of orthogonal experiment and numerical simulation.The results show that the primary and secondary effects on the thermal load of the cylinder head are: the thermal conductivity of the material,the heat transfer coefficient of the fire surface,and the flow of cooling water.