Experimental Study Of Electrostatic Atomization Process & Mode And Characteristics

Electrostatic atomization technology and equipment have the advantages of simple structure,easy operation and low energy consumption.The liquid flows out through the capillary under the action of external electric field.Different atomization modes can be obtained under different operating parameters are applied.so that,the monodisperse droplets from micron to nano scale can be prepared.Therefore,electrostatic atomization technology has been widely used in electrostatic spraying and printing,fuel injection,film preparation,electrostatic spinning and space propulsion.The atomization characteristics of electrostatic atomization droplets,such as their periodic characteristics,dispersion,jet shape,charge-mass ratio and droplet size,are key factors determining the application fields.In this paper,a detail study of electrostatic atomization characteristics for different atomization modes is carried out by combining theoretical and experimental methods,mainly analyzing the electrostatic atomization characteristics of dripping mode,spindle/micro-dripping mode,and cone-jet mode.In addition,the potential applications are elaborated.The main research contents are as follows:Firstly,the electrostatic atomization experimental system is designed and set up,and three charged modes of charged droplets are explored.The visual study of the electrostatic atomization modes of different liquid mediums such as anhydrous ethanol and deionized water is carried out by using a high-speed camera with a micro zoom lens.The typical electro-spraying modes such as dripping,micro-dripping,spindle,cone-jet and multi-jet are observed.The results show that atomized droplets/jets are subjected to various force fields such as surface tension,coulomb force,polarizing force,resistance,inertia force,and gravity.The electric field forces increases as the improvement of applied voltage,resulting in different atomization modes of electrostatic droplets/jets.Secondly,it investigated the droplet and micro-dripping/spindle modes of electrostatic atomization using deionized water and anhydrous ethanol as the atomization medium.Meanwhile,it determined the charge-mass ratio of droplets,as well as the droplet size and injection period,using displacement and image methods,respectively,and established a theoretical prediction model for droplet size and injection period based on droplet force analysis and continuity equations.The results indicate that as the voltage is increased,the frequency at which droplets of deionized water and ethanol are released increases.Additionally,both atomization processes exhibit a sharp increase in the phase of cycle frequency.At the sudden increase of jet frequency,the corresponding droplet mode changes to the micro-dripping/spindle mode.In the experimental range,the relationship between the charged amount of droplets and the liquid flow rate is not obvious,and the particle size of droplets gradually decreases as the voltage is increased.As a result,the droplet and micro-dripping/spindle modes are applicable to a variety of applications,including microcapsule preparation and on-demand titration printing,etc.Finally,the electrostatic atomization characteristics in cone jet mode were investigated using a variety of electrostatic atomization stabilized cone-jet applications.（e.g.,electrostatic spinning,additive manufacturing,thin film preparation,etc.）.In this paper,relevant dimensionless parameters characterizing cone jet atomization were introduced to determine the range of operating parameters for generating stable cone jet atomization patterns for atomizing media liquids such as ethanol.After that,the jet fragmentation pattern at the end of the jet was explored.It is demonstrated that the stable cone jet mode exists at a given voltage and flow rate.As the flow rate increases,the crushing pattern at the cone jet’s end gradually changes from an axisymmetric curvilinear unstable pattern to a non-axisymmetric kinked unstable pattern.The droplet particle size decreases with increasing voltage and decreases with decreasing flow rate in the stable cone jet mode.Furthermore,the relationship between the dimensionless flow rate q₀/q _Vand the dimensionless particle size d/d₀ is consistent with previous authors’size scaling law.Therefore,the kinked unstable fragmentation mode produces the largest size dispersion effect of droplets.