Research On The Characteristics Of Coalescence And Fracture Of Ionical Droplets Under Electric Field

At present,as many oil fields in the world gradually enter the high water cut period,the water content of the crude oil produced increases year by year.When the water content of crude oil is too high,equipment corrosion will occur during transportation,storage,and reprocessing after mining and this phenomenon will reduce the working efficiency and service life of related equipment.Electrostatic demulsification refers to a technique in which an electric field is applied to an emulsion formed by an oil-water mixture,so that water droplets containing ions move and gather under the action of the electric field,thereby performing oil-water separation.At present,the microscopic mechanism that affects the coalescence of droplets in the form and intensity of electric fields in electrostatic demulsification technology and the ions in water droplets is not yet clear.In this paper,the molecular dynamics simulation method is used to study the dynamic process of coalescence and fracture separation of droplets under the action of electric field from a microscopic point of view,and to discuss the influence of droplet size,electric field strength and electric field type on the coalescence process.The main research contents are as follows:Firstly,the coalescence and fracture characteristics of droplets under the action of a DC electric field are studied.Under the action of a DC electric field,the critical electric field strength of the two droplets coalescing is 0.52 V/nm,and the critical cone angle is 42°;?rhen the electric field strength is lower than the critical electric field strength,the droplets coalesce and combine to form a large droplet,while when the electric field strength is greater than the critical electric field strength,the droplets partially or completely break after contacting and coalescing.Through research,it was found that when the applied electric field intensity is between 0.53 and 0.80 V/nm,the droplets partially break up due to the transfer and neutralization of positive and negative ions in the connecting liquid bridge;When the electric field strength is greater than 0.80 V/nm,the electric field force plays a leading role,causing the droplet to completely break or break.Secondly,the droplet coalescence and fracture characteristics under the action of an alternating electric field are studied.Under the action of an alternating electric field,as the frequency of the electric field increases,the critical electric field strength of the ion-containing droplets increases,and the time required for the corresponding droplets to contact decreases;When the electric field intensity is 0.60?0.80 V/nm,the droplet shape(L/H)becomes gradually smaller as the electric field frequency increases.When the electric field frequency is 1.25 GHz and the electric field intensity is 0.50V/nm,the two droplets are in contact and coalesce and merge the best effect(at this time,the shrinkage function value reaches 0.97).When the electric field frequency is 10.0GHz and the electric field strength is between 0.60?0.77V/nm,the shape of large droplets oscillates obviously after the droplets coalesce.Among them,the largest amplitude occurs when the electric field strength is 0.77V/nm.Finally,the effect of droplet size on the coalescence and fracture process of ion-containing droplets under DC electric field was studied.The results show:Under the action of a DC electric field,as the diameter of the droplet becomes larger,the critical electric field strength gradually decreases;When the electric field strength is the critical electric field strength,the velocity of the center of mass of the right droplet also increases as the diameter of the right droplet increases;And when the electric field strength is between 0.80?1.5 V/nm,as the diameter of the right droplet decreases,the degree of deformation L/H of the right droplet increases.Three conditions are required for the formation of liquid bridges during droplet coalescence and their stable existence:the droplets complete ion exchange to achieve charge balance(even through partial breakage of the right droplet);the difference in diameter between the two droplets is large enough;the electric field strength is small.