Study Of Droplet Motion Characteristics Of Water-in-Oil Emulsions Under The Action Of Electric Field

In this paper,molecular dynamics simulation method is used to study the dynamic process of the water-in-oil emulsion droplets aggregation under the action of electric field from the microscopic perspective,and the influence law of electric field strength,electric field type,droplet position,droplet containing ion concentration and other conditions on the aggregation effect is analyzed.The main research content is as follows:Firstly,the motion characteristics of water droplets of oil-in-water emulsions under DC and rectangular AC fields are studied.Under the action of DC electric field,the droplets aggregation law is:Under the working conditions E=0.005V/（?）,E=0.01V/（?）,E=0.015V/（?）and E=0.02V/（?）,the time required for water droplets to make touch is424ps,285ps,361ps and 434ps respectively,while the time consumed from the occurrence of touch to the completion of aggregation is around 300ps.Under the working conditions E=0.035V/（?）,E=0.04V/（?）,and E=0.045V/（?）,the required for water droplets to make touch is 95ps,81ps,and 41ps,respectively,while the time consumed from the occurrence of touch to the completion of aggregation is 454ps,600ps,and800ps,respectively;when the electric field strength is greater than 0.05V/（?）,the droplet is torn by the electric field,can not complete the aggregation;the working condition E=0.03V/（?）is the optimal working condition for water droplets aggregation under DC electric field.Under the action of rectangular AC electric field,the law of droplets aggregation is as follows:under the same electric field strength,the period of electric field has basically no effect on the time of droplets contact,but the time consumed by the droplets to complete aggregation has a great impact;the working condition E=0.045V/（?）-80ps is the optimum working condition for water droplets aggregation under rectangular AC electric field.Secondly,the effects of relative position and ion concentration on the kinematic properties of water-in-oil emulsion droplets under different electric fields were investigated.Compared with the direct current field,the rectangular alternating current can make the water droplets with the center of mass positioned farther apart on the same horizontal line to complete the aggregation.When the angle between the center of mass and the X-axis is≥35.54°,both electric fields cannot make the droplets come into contact and complete the aggregation.In different ion concentrations,the contact time of the water droplets is:t_40N<t_20N<t_60N<t_0N in DC field;t_20N<t_40N<t_0N<t_60N in rectangular AC field;the same ion concentration,rectangular AC field requires more time than DC field to complete the aggregation.Finally,the effects of the ions carried under different electric fields on the motion characteristics of the water-in-oil emulsion droplets and the formation of liquid bridges between droplets were investigated.It is found that when the droplets are close to each other,such as 10（?）apart before relaxation,the droplets can complete the aggregation by their own gravitational force alone.In the DC field,when the two droplets have opposite charges,the direction of the electric field generated by the two droplets coincides with that of the DC field will accelerate the aggregation,while the opposite will move away from each other,while in the rectangular AC field both can complete the aggregation,but the consumption time is different.The formation of liquid bridges between water droplets is closely related to the magnitude of the electric field strength and the concentration of ions near the droplet end of the bridge.