Research On Coalescence Characteristics Of Water Droplets In Oil Under Electromagnetic Synergy

Improving the coalescence efficiency of water droplets in oil is the difficulty and technical key to promote oil-water separation in oil gathering and transportation.The synergetic treatment of electric field and magnetic field is a multi-field coupling technology that strengthens the coalescence of droplets.Understanding the influence of its characteristic parameters on oil-water separation and clarifying its mechanism are key issues that need to be resolved.By combining high-speed microscopy experiments and oil-water separation experiments,the influence of the characteristic parameters of the synergetic field on the performance of oil-water separation is obtained,and the influence of electromagnetic synergy on the dynamic behavior of single and double droplets is revealed.The characteristics of oil-water separation and the coalescence characteristics of water droplets in the oil under the electromagnetic synergy are studied.Through theoretical research,a theoretical model of the polarized electromagnetic force is established,and combined with the influence characteristics of electromagnetic synergy on the coalescence behavior of double droplets,the mechanism of electromagnetic synergy to strengthen oil-water separation is put forward,which is of great significance for developing electromagnetic strengthening coalescence devices.The main research contents and conclusions are as follows:The experimental research system for the dynamic behavior of droplets adopts a high-speed microdevice and the solution of an opening window on the magnet.The dynamic response behavior of droplets under the action of electric field force and polarized electromagnetic force can be captured,which provides an experimental basis for revealing the influence mechanism of electromagnetic synergy on the motion and coalescence behavior of droplets.The deformation and displacement behaviors of the pure interface single droplet,the dispersed salt ion single droplet,and the adsorbed surfactant molecule droplet in the AC electric field and magnetic-AC synergistic field are compared by high-speed microscopic experiment.The influence law of conductivityσand interfacial tensionγon the longitudinal displacement velocity v_y^*of the droplet is obtained,the main factors that promote the longitudinal displacement of the three types of droplets are identified.The longitudinal displacement of the droplet is promoted by the polarized electromagnetic force.In aggravating the longitudinal displacement of the droplet,the effect of salt ion transport is more significant than that of the interface stretching deformation.The influence of electromagnetic synergy on the coalescence behavior of two droplets was investigated experimentally.The approaching velocity v^*,the critical coalescence field strength E_c and the evolution coefficient C₁ of the liquid bridge of two droplets with equal physical properties in the AC electric field and magnetic-AC synergistic field are compared.The results show that,compared with a single AC electric field,the critical coalescence electric field strength E_c is higher and the liquid bridge diameter evolution coefficient C₁ is smaller for the dispersed salt ion double droplets in the magnetic-AC synergistic field with the same electric field intensity,while E_c is higher and C₁ is larger for the adsorbed surfactant molecule double droplets.Besides,the effects of electric field strength,ion intensity,and surfactant concentration on E_c and C₁ of the double droplets in the magnetic-AC synergistic field are also explored.Based on the experimental results,the influence mechanism of ion enrichment induced by electromagnetic synergy,ant the influence mechanism of electromagnetic synergy on the orientation of surfactant molecules is proposed.The experimental system of oil-water separation is designed and built,the emulsion with the average diameter of dispersed droplets less than 100μm is used as the medium.The influence of the type of external field,the configuration of the synergetic field,the sequence of electric field and magnetic field,the intensity of the magnetic field and the frequency of the electric field on the oil-water separation performance are explored,and the characteristic parameters which make the separation efficiency higher are clarified.The results show that the performance of enhancing oil-water separation is the best when the AC electric field and steady magnetic field distribute vertically and act synchronously.In the theoretical study of the characteristics of electromagnetic synergy aggravating the longitudinal displacement of a single droplet,it is found that the polarized electromagnetic force is produced by the orientation polarization of water molecules.A theoretical model of the polarized electromagnetic force is proposed by exploring the polarization response behavior of droplets in the magnetic-AC synergistic field,considering the polarization coefficient,polarization time,and magnetic field strength.The forces acting on droplets in the electromagnetic synergetic field and the effect of polarized electromagnetic force on droplet displacement are analyzed.Moreover,combined with the influence characteristics of the electromagnetic field on the coalescence behavior of double droplets,the physical mechanism of electromagnetic synergy to strengthen oil-water separation is proposed.Based on the model,the influence mechanism of characteristic parameters on oil-water separation performance is discussed and analyzed.