Research On The Flow And Fluid-solid Coupling Heat Transfer Of The Gasoline Engine Cooling Jacket

With the rapid development of the automotive industry and the increasingly stringent emission regulations,many researchers and designers have conducted research on the heat load problem of the engine.As the most complex component of shape and structure of the engine,the cylinder head in working process not only bears high mechanical loads,but also withstands the impact of high temperature gas.Inadequate cooling can easily lead to local overheating of the cylinder head,thus affecting the efficiency and reliability.Therefore,analyzing the flow and heat transfer process of cooling jacket inside the engine and the heat transfer process of cylinder head and other components has great significance for the efficient design and optimization to the structure of engine parts and cooling jacket.A commercial vehicle gasoline engine is taken as the research object in this paper.Firstly,in order to observe the internal flow phenomenon of the cooling jacket and evaluate the rationality of structure,the three-dimensional simulation model of engine cooling jacket is established.The flow process of cooling jacket is calculated by numerical simulation method based on the theory of computational fluid dynamics.The flow characteristics such as velocity distribution,flow distribution,pressure distribution and heat transfer coefficient distribution and so on are obtained.At last,the structure and cooling performance of cooling jacket are analyzed based on the flow field information in cooling jacket.Secondly,the one-dimensional and three-dimensional simulation models of engine are established.The combustion processes in the cylinder are calculated by using one-dimensional and three-dimensional numerical simulation methods.The results of flow field and temperature field in cylinder during combustion process are obtained.The validity of simulation calculations are verified by comparing the temperature and pressure curves obtained under the two methods.At the same time,the wall thermal boundary conditions required in the analysis of coupling heat transfer process are obtained.In order to research the heat transfer processes of cylinder head,cylinder liners and cooling jacket integrally and accurately,a coupled heat transfer model consisting of cylinder head,cooling jacket and cylinder liners is established.The processes of heat transfer in cylinder,cooling jacket,cylinder head and cylinder liners are coupled by using the method of fluid-solid coupling numerical simulation based on the theories of flow and heat transfer equations.The more accurate temperature distribution of cylinder head,cylinder liner and cooling jacket are obtained.The weak links are found out,which provide references for structural optimization design.In addition,the calculation results are analyzed in three conditions of different physical parameters,different inlet rate of flow and different inlet temperature to research the influence of different parameters of coolant on the flow and heat transfer process of cooling jacket.The influences of various factors on the flow field of cooling jacket and the temperature field of cooling jacket,cylinder head and cylinder liners are obtained,which provide some basis for the choice of coolant types and the inlet conditions of cooling jacket.