The Numerical Simulation Of Jet And Modeling Of Atomization In Vacuum Spray Method

Vacuum spray method is a new method for the preparing of polymer thin films. It has attracted a great deal of interest because of its advantage such as dense films fabrication, uniform film thickness can be controlled and preparation of gradient thin films, etc. In this paper, we studied the film-forming process and the influential factors of preparation of nano-functional film through spraying polymer solution in vacuum, meanwhile used the software of Fluent to simulate the nozzle jet flow field. FLUENT is an application of fluid dynamics simulation software, which has been applied widely. As far as known to the writer, there has been no systematic study of using FLUENT software to simulate gas flow in the vacuum. First, we made sure the lowest pressure that the Fluent can work, then simulated a variety of common shaped pipes, on this basis, we set the primary atomization model of the broken jet fluid combined with the turbulent motion.This paper outlines the current situation and research progress of the solution spray method under vacuum conditions both at home and abroad, and the theory of jet atomization. By simulating different structure of the nozzles, the spray pressure and the physical features of the fluid medium, we analyzed the influences implicated on the nozzle jet flow field. From the analyses of the simulated velocity, pressure and the kinetic energy turbulent flow of the nozzle jet flow field, we get the conclusion that the situation with pressure of lOMPa, greater flow channel dangled and larger diameter of the nozzle have a better atomization of the jet flow field and smaller the average diameter of droplets. We also found that under vacuum condition, the impact of environment on the jet motion is so small that its effects on droplet fragmentation can be neglected. Based on the results and combined with internal nozzle flow condition, we establish the physical and mathematical model for the primary atomization of the jet flow breakup, which takes the turbulent flow as the main cause combining changes of the jet surface wave and is based on the foundation of the conservation of energy, and get the critical condition of atomization and breakup of the nozzle jet under vacuum condition the model is Preliminarily verified by Sauter Mean Diameter, further, through the model we get different Sauter Mean Diameter distribution of different liquids. The study provides the initial conditions for the study of secondary atomization under vacuum, and also lays a theoretical foundation for further research of droplet atomization under vacuum conditions.