Study On The Ways Of Strengthening Heat Transfer Of ICE Cooling System

Cooling system is an important part of the engine. Nowadays, as the ceaseless development of engine power, it will inevitably produce higher temperature of the cylinder, as a result, more heat energy is transferred to the combustion chamber components, internal combustion engine cooling problem becomes more and more prominent and it has become a bottleneck restricting the development of internal combustion engine. The working performance of cooling system directly impacts the life of the engine, fuel economy and other more important indicators of combustion engine. Therefore, optimal design of the cooling system is a key issue in the internal combustion engine design.This paper employs direct fluid-solid coupling method, utilizes different ways to enhance heat transfer in CA6DE2-23type diesel engine cooling system. The related research and heat transfer between combustion chamber components and cooling system are studied. This paper main work and innovation points include:First of all, the conventional cooling water was employed in the cooling system of the internal combustion engine with the fluid-solid coupling numerical simulation method, through the analysis of the coolant pressure loss, the coolant heat transfer coefficient distribution and the temperature field to evaluate the flow of the coolant and cooling characteristics; through the analysis of the highest temperature and temperature gradient of engine combustion chamber components, to evaluate the heat load of internal combustion engine combustion chamber components.Secondly, according to the enhanced heat transfer characteristics of nanofluid and employed nanofluid instead of current medium-cooling water to engine cooling system, based on the single phase and Euler-Euler multi-phase model of nanofluid, CFD fluid-solid coupling numerical simulation means was adopted to analyze the nanofluid application value in engine cooling system, then according to the result of numerical simulation, compared nanofluid with conventional cooling water in terms of heat transfer effect. The study found that after adding nanofluid, the internal combustion engine cooling water cavity flow field and pressure loss is not particularly evident changes, but it has a sharp increase in heat transfer effect, and the highest temperature of combustion chamber components and the temperature gradient of combustion chamber fire face area are significantly reduced; The results of numerical calculation of multi-phase flow model, considering the interaction between two phase, is more accurate than only considering the physical property change of single phase flow model. Finally, took advantage of the strengthening heat transfer characteristics of sub-cooled boiling to establish a fluid-solid coupling two phase flow boiling model of six-cylinder diesel engine on the basis of Euler homogeneous model, then made the three-dimensional flow heat transfer calculation in internal combustion engine cooling system. At the beginning of calculation, boiling phenomenon is not taken into account to analyze the coolant flow characteristics and heat exchange between combustion components and cooling system. After that, complete the calculation of two-phase flow boiling heat transfer model based on the same grid and boundary condition, compared the result with no phase change model, analyze the effects of phase transformation factors on heat transfer of the cooling system, it turns out that heat transfer coefficient of the fluid near wall increased significantly under the condition of phase transformation, and that if only considering the forced convection heat transfer, ignored boiling phenomenon in the water jacket, it will overestimate the highest temperature of the cylinder head fire face and water cavity wall respectively25k、38k, this will directly affect thermal load safety evaluation of engine combustion chamber components.