Numerical Simulation Of Diesel Fuel Atomization

The advanced diesel engine with high efficiency and low emission is of great value in alleviating the energy crisis and atmospheric control.Good atomization quality will help to optimize the combustion process of diesel engine,so it is important to carry out research on diesel spray.In the current study of diesel spray,the change rules of penetration distance,cone angle and SMD are mostly analyzed in the experiment.Most of the simulation studies are separately analyzing the flow process of the nozzle and the atomization split.In the commonly used calculation models,the VOF model is used to identify the droplets in the atomization process,it needs to match the atomized droplet size,but leads to a huge consumption of computing resources.DDM model is simulated by discretizing diesel,it reduces the amount of calculation but also causes the distortion of near-field injection process.All of the above problems restrict the further study of the complete atomization mechanism.Therefore,on the basis of previous research results,this paper establishes the ELSA(Euler Lagrangian spary and atomization)atomization model of coupled nozzle internal flow,compare the simulation results with the test results,and obtains the following conclusions:(1)In order to realize the accurate calculation of atomization process,the dynamic grid method is used to simulate the cavitation flow in the injector at three dimensional transient.The exit parameters are taken as the boundary condition of the spray entrance to simulate the atomization.In the atomization simulation,the Euler liquid mass in the flow field is captured dynamically,and the conforming section is determined by the sphericity and the particle diameter.The ELSA atomization model based on the transformation of sphericity and particle diameter is realized by transforming the liquid-phase agglomerates into Lagrangian particles.Compared with the experimental results,it is found that the simulation method can accurately represent the development process of each stage of atomization.(2)Based on the above ELSA method,the law of atomization breaking process is studied by changing the inlet pressure of the injector.The research is divided into two parts: continuous phase and discrete phase.In the development process of continuous phase,it is mainly the near-field liquid column breaking process.The reason of liquid column breaking is the disturbance process of liquid column surface wave.The fluctuation of nozzle outlet position provides the initial disturbance for the liquid column surface.After the initial disturbance,the surface wave Gradually,when the difference of surface wave reaches the maximum,the liquid column will be broken;in the discrete phase,it is mainly transformed into Lagrangian particles.It is found that the first broken position in the flow field is at the edge of the liquid column.At this time,the breaking form is liquid film breaking.Along with the breaking process,the penetration speed is also dropping rapidly.When the internal force of the front liquid drop is equal to the air resistance At the same time,the penetration velocity will enter into a quasi equilibrium state.The ELSA calculation method proposed in this paper can reduce the amount of calculation and achieve accurate simulation of the atomization process,which will help to further understand the spray characteristics of diesel.