Numerical Simulation Research On Characteristics Of Flash Boiling Spray

In order to protect the environment and deal with the energy crisis,a great deal of attention has been focused on the combustion process and the reduction of engine exhaust emission. And the process of fuel injection,atomization and mixture formation are the critical aspects of impact on the combustion and the exhaust emission. So, it is a great significant study of spray characteristics.In this paper, the fuel atomization process of diesel engine is stimulated by Fluent under different conditions, and to study velocity distribution and the size distribution characteristics of droplets when Flash Boiling, and to analyze how the diameter of the nozzle and the initial speed of the droplets affect the atomization, and we compare the results with established experimental data to prove the feasibility of using Fluent to simulate the process of the fuel flash boiling atomization.The results show the discipline of axial velocity, radial velocity distribution of the Flash Boiling Spray particle along its axis: axial velocity of spray particle is getting smaller and smaller, the radial distribution of axial velocity gets more and more flat, which explains that the speed on axis decays faster than the external part of the spray. And it is also shown that with the increase of the spray speed, in the same distance from the nozzle, axial velocity of spray particles are also on the rise; the radial velocity with the increasing distance from the nozzle decreases, the faster the speed of the spray, the faster the attenuation along the radial.The effects on flash boiling atomization of the spray by different inlet velocity and different nozzle diameter: at the same inlet velocity , with the increase in spray time, SMD has a slight increase ,generally speaking, SMD of flash boiling spray stays in a certain scope; with the increase of the inlet velocity, SMD of the fuel particles is gradually increased. In the case of the same inlet velocity, with increasing nozzle diameter, the spray penetration increases. The larger the nozzle is, the larger the SMD is at the beginning of the spray, as the time goes on, SMD reaches unanimity. Besides,downstream flow is stimulated due to the outlet conditions of DME flow inside the nozzle,to verify the simulation.