The Flow And Fluid-Solid Coupled Heat Transfer Analysis Of The Diesel Engine Cooling System

Flow and heat transfer problems of automobile diesel engine cooling system have been much concerned, which not only takes direct impact on the diesel engine cooling efficiency, load of the high-temperature parts, heat distribution and energy usage of the engine, but also affects the cooling uniformity in each cylinder, charging efficiency, oil and gas mixing, burning, flame propagation, heat transfer, pollutants generation, etc, especially for the high-enhanced multi-cylinder diesel engine. In the research of cooling fluid flow and heat transfer problems on diesel engine, it is difficult for us to get detailed information when using measuring instruments just because of the complex structure of diesel engine. And compared with experiment, taking 3-d numerical simulation method to solve flow and heat transfer problems can greatly reduce research cost, save resources, cut down the development cycle. Moreover, some results can be got which are regarded difficult or can not be measured. During the study of flow and heat transfer problems, traditional method is to calculate fluid and solid heat-transfer respectively, which requires constantly adjust the hypothetical boundary conditions during heat-transfer calculation. This process is more tedious, and there are certain disparities between calculation results and actual situation considering of the heat transfer condition inhomogeneity in the boundary solid-liquid on the condition. In addition, in diesel engine cooling fluid heat calculation, less consideration was taken about the boiling heat transfer.Focusing on these problems above, the paper takes a 3-d numerical flowing simulation research on the diesel engine cylinder body water jacket and cylinder-head water cavity, which have got the results of velocity field and stress field. Besides, fluid-structure coupling heat transfer calculation was taken between cylinder head part coolant flow field and cylinder head itself, which have got the results of fluid area and solid regional temperature field as well. Moreover, the paper also have explored cylinder head water cavity fluid-solid coupling research under the situation of the boiling heat transfer, the fluid area temperature field was obtained in the end.The paper mainly studied the flow and fluid-solid coupled heat-transfer problems for a diesel engine, and numerical simulation was taken by STAR-CCM+ that large general-purpose CFD software in order to get a deep research of the flow and heat transfer problems of engine cooling system. The calculation grids of cylinder body water jacket and cylinder head water cavity geometric model mainly use hexahedral grid and boundary layer grid was put on walls, so that the grids both adapt to the complex geometric surfaces of the cooling system, but also further ensure the quality of the grid. The paper adopts finite volume method to solve Fluid motion control equations, the standard k-εturbulence model and standard wall equation on the basis of the usage of incompressible viscous fluid turbulent flow.The main research contents of this paper are as the following:1)Aiming at the research of flowing problems of cylinder engine block water jacket and cylinder head water cavity for a six cylinder diesel engine, it selected appropriate physical model and mathematical model through analysis and comparison, combined the known fluid domain with related parameters and applied reasonable and accurate boundary conditions so as to get velocity field of the fluid in engine body, cylinder-head and both connections. Then, the import and export pressure loss was obtained through the inlet area average pressure monitoring.2)The paper also studied the cylinder-head water cavity flow and fluid-solid coupled heat-transfer problems for a single cylinder diesel engine in the situation of non-boiling(no steady flow),and selected appropriate physical model both for fluid domain and solid domain respectively, determined reasonable boundary conditions according to former documents published, so that it got the temperature distribution of fluid domain and solid domain. 3)This paper also explored the boiling heat transfer (no isothermal transient flow),reset the physical model and boundary conditions of fluid domain after the add of boiling model, by which the temperature distribution, VOF(Volume of Fluid)contour surface pressure distribution of fluid domain were received in the end, as well as the fluid and solid heat transfer coefficient images.