Three Dimensional Numerical Simulation Of The Mixture Process Of Fuel And Air For Port Fuel Injected Gasoline Engine

At present, under the pressure of environment pollution and energy crisis, people are setting higher and higher standards about emission performance of engine the same as increasingly demanding for engine good performance. Because of this, the researchers, both at home and abroad, has been done a lot of research about it. Most of these studies are in the the mixture-formation quality. In the past, they ware usually established on the basis of experiments because of the limit of computational capabilities. In recent years, with the rapid increase of calculating level, the numerical simulation of flow field of Engine has developed into the important part of virtual technology of vehicle.In the development of the spark-ignition engine, port fuel injected gasoline engine has been played a backbone role, so port fuel injected gasoline was chosen as the research object in the project.On the basis of previous studies, CFD three-dimensional numerical calculation of the mixture process of fuel and air of an engine was performed in this paper with AVL-Fire. The three-dimensional results of the flow characteristics which include velocity, equivalence_ratio, turbulence kinetic energy and total pressure of the cylinder were got. Because of the symmetric structures of the two valves, tumble is the main forms of the large scale rolling flow in cylinder. There are corresponding relations between turbulence kinetic energy, pressure field velocity field of the cylinder:the distribution of core area of turbulent kinetic energy consistent with the change of Airflow vortex center; and also corresponding to the distribution of low-pressure core in the cylinder.In order to research the influence of some parameters to the mixture-formation quality, the numerical simulation of flow field of Engine was done after changing the fuel injection angle, fuel injection time and engine speed, and the related results was got in the paper. The simulation results show that:1) The change of fuel injection angle has greatly influence on the concentration distribution and a little influence on airflow velocity and turbulence intensity of the cylinder.2) The mixture distribution in cylinder is well-distributed at closed-valve-injection mode. But the equivalence_ratio is lower then normal value, and there is higher equivalence_ratio place under exhaust valve seat, which is against emissions. The equivalence_ratio is higher at open-valve-injection mode, which is helpful for accurate control of the fuel quantity.3) The running speed has greatly influence on velocity and concentration of mixture. So the increased benefits after changing the structure parameters and running parameters of the engine should be considered comprehensively.The three-dimensional numerical simulation of mixture formation could obtain much information in short time and provide theoretical evidences for the designing and improving of engine.