Fluid-solid Coupling Heat Transfer Analysis And Research About Gasoline Engine Cooling System

Before the new energy vehicles are widely spread, the internal combustion engine is still the main power source. Because of internal combustion engine is a heat engine conversion device, it will release a large amount of heat when it works, besides the heat that convert into effective mechanical work, there are still 15%~35% heat that pass on to piston, cylinder head, cylinder liner through a variety of ways, these components need to be taken away the excess heat by cooling system in time, otherwise, it will result in the crack of the cylinder head, piston top burning, which will affects the reliability, economy and power performance of the engine. As a result, an engine that with high efficiency and reliable cooling system is crucial.At present, the method for optimization design of engine cooling system is generally that applied test combined with numerical simulation. These two methods have their own advantages and complement each other. The experimental data are generally measured by engine bench test, in terms of numerical simulation methods, liquid-solid coupling method that has both accuracy and efficiency, has been more widely recognized. The analysis of the cooling system focuses on the parameters that temperature of the solid and fluid flow, pressure, temperature and heat transfer coefficient of fluid.In this paper, I choose a model of a four-cylinder gasoline engine as the research object, liquid-solid coupling simulation analyzed the cylinder block, cylinder head and water jacket. The main content of this paper include:①Use GT-Power to construct gasoline engine model, the calculate result compare with the known bench test data, to verify the accuracy of the models, and get the temperature and heat transfer coefficient of the gas in cylinder and gas in inlet and exhausting channels.②Use the method of liquid-solid coupling simulation, with the aid of threedimensional fluid simulation software STAR-CCM+, set up appropriate solving equations and control parameters. Apply reasonable boundary conditions, get the temperature of the cylinder liner and cylinder head as well as cooling fluid field, pressure, temperature and heat transfer coefficient distribution nephogram, and analyze the simulation results.③According to the result of analysis, put forward the improvement scheme, simulation again, compare with the last plan, to verify the rationality and feasibility of the improved scheme.The main conclusions of this paper include:①In view of the cylinder block cooling, improvement measures are: coolant flow rate that between 3, 4 cylinder block water jacket is slow, 1 cylinder inlet upper appears backflow phenomenon, cooling effect between two cylinders is not obvious, so propose the improvement scheme that not to change the position of the pump, but increase the length of inflow pipeline, so it can change the position of water inlet to the place of 2 cylinder on the side of exhaust.②In view of the cylinder head cooling, improvement measures are: because that the structure of the cylinder head bridge of the nose area is complicated, the improvement is difficult, so by expanding the axial cross sectional area of holes appropriately to increase flow of the cooling fluid cylinder to improve the cooling of the cylinder head.③ In view of the improvement scheme, after the simulation, I can get: the described problems get some improved, cylinder cooling fluid flow velocity is more uniform, through flow velocity can reflects the cooling between the two cylinders and the cylinder head bridge of the nose area has increased.