Research On Dynamic Characteristics Of Droplet Under External Electric Field

The research on the behavior of droplets under the action of electric field has application value in large amounts of engineering fields.Especially in the oil-water separation process of oil treatment,the traditional mechanical demulsification method and chemical treatment method have some disadvantages and limitations.How to achieve better separation effect has always been a technical difficulty.Therefore,the paper studies the dynamic characteristics of droplets under external electric field,which provides a solution for oil-water separation in crude oil treatment.The droplets in the oil-water mixture are mainly of medium size(4-5.5 mm)and some of smaller size(less than 4 mm).According to the actual parameters,a visual experimental system is built.Under the action of a uniform DC electric field,the medium-sized droplet will first stretch in the vertical direction with the increase of electric field strength,and the top of the droplet will gradually become a Taylor cone,and then the droplet will break up and produce a daughter droplet.The breakup will occur repeatedly,and lots of daughter droplets will move up and down between the plates.The daughter droplets will collide with each other,and will also collide with the original droplet on the plate.The exchange of charges between each other also happens at the same time When the number of daughter droplets between the plates is enough,the liquid bridge in the form of a pearl chain will be formed by connecting the upper and lower plates at a certain time,and violent discharge will occur.Under the action of a uniform DC electric field,small-sized droplets will elongate with the increase of electric field strength,and finally bounce from the plate.Then,the droplet will move between the plates.With the increase of electric field strength,the velocity of droplet will be accelerated.Further increasing the field strength,the droplet will break up and produce two daughter droplets,which continue to move between the plates.When the field strength increases again,the daughter droplets will coalesce,but because of the lack of stability,the coalesced droplet will break up again and produce more daughter droplets.At a certain time,a large number of daughter droplets will connect the upper and lower plates to form a columnar liquid bridge.Under the action of the DC electric field,the droplets with smaller initial equivalent diameter will form a columnar liquid bridge with a short duration(<1 s),and the discharge phenomenon is not obvious,and the bulge in the middle of the liquid bridge is taken as the precursor of fragmentation;The droplet with middle equivalent diameter will form a pearl chain liquid bridge,and its discharge phenomenon is more intense,and bubbles and black substances will be generated;The droplet with larger equivalent diameter will form a cap columnar liquid bridge,which is similar to the columnar liquid bridge,with shorter duration and no obvious discharge phenomenon.According to the above research results,a new type of oil-water separation device is proposed,which consists of two parts: mixture charging device and oil-water separation electric field.Through experiments,we proved the feasibility of the oil-water separation device.