Study On The Fuel-air Mixing Process Within The Cylinder Of Ethanol-fueled Direct-injection Engine Based On LES

The internal combustion engine with oil as the main energy source is widely used in various fields of human society.In recent years,the number of cars in China has been increasing.The sustainable development of the internal combustion engine industry is facing the severe test of the shortage of oil resources and environmental pollution.Therefore,the renewable and clean alternative fuel is becoming a research hotspot in the field of internal combustion engine.Ethanol has been widely used as a clean and renewable alternative fuel.As an oxygenated fuel,it has the characteristics of high octane number,good antiknock performance,low theoretical air-fuel ratio,high latent heat of vaporization,wide ignition limit and fast flame propagation,which makes it have a full combustion process in theory.However,due to the slow evaporation rate of ethanol at low temperature,the phenomenon of wet wall will occur due to the incomplete evaporation of injection in cylinder,which will not only affect the combustion air mixing process and quality,but also reduce the ignition performance,and cause the change of combustion mode.Therefore,it is necessary to systematically analyze the combustion process in the cylinder of ethanol engine,especially the system process involving oil gas chamber comprehensive matching,fuel injection and atomization process,and study its influence on the oil gas mixing process in the cylinder of the engine.In this paper,the direct injection ethanol ignition engine is taken as the research object.The three-dimensional computational fluid dynamics software converse is used to simulate the intake,injection and oil-gas mixing process of the ethanol engine.The process of breaking,evaporation and mixing of the fuel in the cylinder of the ethanol engine is simulated at the opening and closing time of various intake valves and at the timing of various injection,and a variety of things in the cylinder are also simulated during the intake and injection process The influence of intake timing and injection timing on the quality of fuel gas mixture in the cylinder of ethanol engine is discussed.The results show that the intake valve timing and injection timing have a significant impact on the fuel gas mixture quality of ethanol engine.Changing the intake valve timing will have a significant impact on the turbulent movement of the engine in the cylinder during the injection process.With the delay of the intake timing,the turbulent movement in the cylinder during the injection process is significantly enhanced.The violent turbulent movement accelerates the ethanol fuel breaking and evaporation,andmakes the turbulence generated in the intake process increase the action time of the fuel breaking and evaporation mixing,which can effectively improve The mixture quality of ethanol fuel in the cylinder.Changing the injection timing will also have an impact on the fuel gas mixture quality of ethanol engine,and before and after the intake valve is closed,the injection will improve the fuel gas mixture quality in the cylinder.Before the intake valve is closed,the injection can effectively improve the fuel gas mixture quality near the cylinder wall away from the direction of the injector.With the delay of the injection timing,the fuel gas mixture quality near the cylinder wall has The quality of oil-gas mixture near the piston head is improved,but the quality of oil-gas mixture near the piston head is poor;after the intake valve is closed,the injection can effectively improve the quality of oil-gas mixture near the piston head.With the delay of injection timing,the quality of oil-gas mixture near the piston head is improved,but the quality of oil-gas mixture near the cylinder wall is poor,and it will lead to the increase of fuel air equivalence ratio near the spark plug.