Numerical Simulation Of Coolant Flow In Gasoline Engine Water Jacket

The affection of the coolant flow in engine cooling system is focused on the cooling effective, heat load of the parts, the distribution and usage of heat energy. Therefore, it is necessary to design a cooling systems for the internal combustion engine which can maintain its status in the best job, in order to absorb excess heat conduction in real time. There are two ways to improve the cooling capacity of cooling system: improve the cooling capacity of coolant adjust the ventilation of radiator. In the water jacket cooling liquid directly absorbs heat from the cylinder block and cylinder head, so the structure of cooling water directly affects the cooling effect of the engine parts. Because the water jacket of cylinder block is at the internal, and the structure is complex, it is difficult to carry out the research of flow test and heat transfer. As in recent years to improve the performance of computer hardware and development of computational fluid dynamics, numerical simulation will gradually become an important method for studying the coolant flow.Numerical simulation method is based on computational fluid dynamics theory, and it is the important ways to solve the 3D flow problem. In the past, the information of flow was obtained by a large number of tests but now by the simulation. Compared with the data of experimental, the accuracy and reliability of the calculated results are satisfactory.Numerical simulation method has the following three advantages: Firstly, the results of the analysis to identify the main factors that affect performance, so that we can guide the experimental work in theory, reduce blindness test. Secondly, get many results which are difficult to measure or test can not be measured, and it is an important supplement to the experimental study. Finally, conducive to optimizing the structure of the water jacket design, in order to find the best structure of the program.In this thesis, the calculation methods of the numerical simulation including the control equation of the cooling water flow for engine, the mathematics mode, the method of discretion, the calculation of the discrete equation are introduced. The domestic and overseas status and development trend of the cooling water flow research are discussed.The 3.D model of the water jacket are set up by Pro/Engineer. Because of the complex structure of water jacket, it is very difficult and unnecessary to set up a same precisely model for the jacket. Therefore, to ensure that the structure of flow field is same, and the simplified 3.D models are used, which are most analogic to the real water jacket.The ICEM software is used to meshing grid . The principle of meshing grid is to maintain coherence between the computational field and the real flow domain. On the premise of maintaining computational precision, the size and type of grid shall be adjusted and the number of grid shall be reduced to increase the computational efficiency. According to the complicated structure of water jacket, unstructured grid Tetra and Prism are used to mesh water jacket. The total grid number is about 2.4 million.Subsequently, the flow fields (speed field and pressure field) are computed and displayed, and then the results are post processed and analyzed both by using FLUENT, one important kind of CFD software. And steady calculation model are chosen in this research. The cooling water jacket flow in the water jacket is supposed to be adiabatic and incompressible viscous turbulent flow. The finite volume method was used to solve the fluid flow control equations, standard k-εturbulent model and standard wall function. The segregated implicit solver and upwind second order precision were used. Main content:1,First of all, to extract water jacket from the set of structural model of the geometric solid model and combined model. Second, divided up computational Grid in the water jacket model.2,According to the actual movement of objects to select the ideal status of the physical model, use appropriate algorithms, and definition appropriate boundary conditions for numerical calculation. Then analyse and evaluate the calculating results with post-processing software. Then calculated data compared with the experimental data to verify the accuracy of the calculation.3,A ccording to the speed, heat transfer coefficient and pressure to improve the program about the structure of the water jacket, and then to carry out simulation based on these program.The main conclusions of the work:1,In this thesis, the location of water pump will affect the cooling water jacket. Since the low position of water jacket due to the complexity of the velocity distribution in the entrance of water jacket of the exhaust side (water-pump export position), therefore exist the vortex flow and dead zone, so that this part have the high heat load. By raising position of the water pump, water flow speed at the top of cylinder block water jacket was increased, so the water jacket obtains a good cooling.2,Analysis in this thesis, changing the structure of the upward water hole for the cooling of water jacket play an important role. By changing the size of the upward water hole, not only improve the rate of water flow of low velocity zones, but also have a very good adjustment on the water quantity of the upward water hole, so that it has a better uniformity of cooling.3,In this thesis, after considering the three options, the cooling effect of the program three is best, but it processes difficulty, and isn't suitable for applications in engineering. Program one is processed easily, and could provide very good cooling effect.