Numerical Simulation On Spray Characteristics Of Single-hole Nozzle For GDI Engine

With a series of advantages such as high thermal efficiency,high reliability and compact structure,internal combustion engine will still be the main power equipment that human beings rely on for a long time in the future.However,internal combustion engine needs to consume fossil fuels and produce a large number of emissions to pollute the environment.To deal with environmental pollution and energy crisis,China has promulgated strict emission regulations to strictly limit the emission of pollutants in vehicle exhaust.Therefore,improving the thermal efficiency of internal combustion engine and reducing the emission of pollutants has become a key issue.The good atomization quality of liquid fuel in the combustion chamber is the precondition for achieving clean combustion in the combustion chamber.A large number of domestic and foreign scholars have found that the flow characteristics of the liquid fuel inside the nozzle have an important influence on the spray breakup process outside the combustion chamber.Based on the actual engineering requirements and the research foundation of scholars at home and abroad,in this study,a test platform was built to carry out spray test,and the characteristics of spray atomization outside the hole were obtained.this study constructed Euler multiphase flow model based on Euler-Euler method to simulate the internal flow of nozzles.On the basis of these,the Euler-Euler spray model and the Euler-Lagrange spray model were used to simulate the spray atomization characteristics out of the nozzle respectively.The experimental and simulation results were compared and analyzed.The correctness of the model is verified.The main research contents are as follows:A spray visualization experimental platform was constructed for spray test.The development process of the spray outside the hole was recorded by high-speed camera and high intensity continuous light source,and the characteristics of spray atomization outside the hole were analyzed.Based on the Euler-Euler multiphase flow method,the Euler multiphase flow model including liquid phase,vapor phase and air is built to simulate the cavitation flow inside the nozzle,the variation laws of the mass flow at the nozzle outlet,the flow field structure inside the nozzle and the velocity distribution at the nozzle outlet plane with the movement of the nozzle needle valve are analyzed.Taking into account the internal flow conditions of the nozzle,the Euler-Euler spray model is constructed based on Euler-Euler method,and simulate the formation,development and breakup process of the liquid core outside the hole.The distribution of liquid volume fraction outside the hole and the length change of jet liquid core under different injection conditions are obtained,and the internal relationship between the simulation results and the flow inside the nozzle is analyzed.Considering the internal flow conditions of the nozzle,based on the Euler-Lagrange method,the Euler-Lagrange spray model outside the hole is constructed,and the velocity distribution along the spray axis and the transverse velocity distribution at different distances from the outlet of the spray center are obtained at different injection conditions and at different times.The spray penetration and spray cone angle obtained by simulation and experiment were compared with the same injection conditions,the experimental results are very similar to the simulation results,which verify the correctness of the construction of the research model.According to the simulation results and the experimental results of the Euler-Euler spray model,the primary breakup process of the spray outside the hole is analyzed.According to the simulation results of the Euler-Lagrange spray model and experimental results,the secondary breakup process of the external spray is analyzed.