Theoretical Analysis And Numerical Simulation Of Electrospray Process

Electrospray is one of the important branches of electrohydrodynamics,which is widely studied.It is a procedure that breakup the liquid into fine droplets with the action of electric forces overcoming the surface tension of the liquid.Compared with other atomization techniques,electrospray has some unique advantages,such as,high charge to mass ratio,which can prevent the conglomeration of droplets and make them penetrate into the ambient atmosphere easily with proper electric field. Otherwise,the more important advantage is that can produce fine droplets with sizes of monodispersity,and just few parameters need to be controlled.With social development,the electrospray technology on high voltage of liquid has gained more and more attentions.Its function which applied in industry, agriculture and spaceflight aspect etc.is outstanding in saving material,improving liquid work efficiency,reducing environmental pollution and so on.Atomization of the different conditions will produce different patterns atomization,the key and difficulty of the technique is to obtain stable uniform droplet stream.However,there are a lot of factors that have influences on the uniformity of droplet stream,therefore only when the condition that all spray parameters match each other is satisfied,and then uniform droplet stream can be obtained.In this thesis,the mathematic model of the flow field for uniform droplet spray process was established.The influence of spray parameters on droplet spray process had been studied via theoretical analysis and numerical simulation.All the research establishes a theoretical base for the application of electrospray.On the basis of deep research about the history and development of electrostatic atomization,the author concluded the electro-hydrodynamics about electrospraying, derived the formulas about calculations of the spray flow rate,spray voltage,spray current,droplet diameters etc.Data on a trial basis,the mathematic model of the flow field and temperature field for uniform droplet spray cone-jet process was established, the electrospray process was analyzed.Then the commercial computational fluid dynamics code was extended to simulate the aerosol emitted by electrospraying,by which the author calculated the properties of spatial electric field,air flow as well as the charged aerosol,explained how they affect each other,and analysis the vaporization of a droplet.At last,the improvement of the system of electrospray was given.The model had been realized via zoning mesh code,the droplet was simulation by DPM model and process,the electric equation was load by UDS,and the influence of electric field to momentum equation by UDF.The simulation results in this thesis can lay a theoretical foundation for proper determination of process parameters.