Study On Droplet Dynamics In High-frequency Pulsed Electric Field

Since demulsification in oilfields is very difficult now, the new demulsification method utilising high-frequency electric field needs to be undertaken more study. By simulating droplet behavior in this field, electric demulsification mechanism and parameters for electric demulsification are studied further.In this paper, smoothed particle hydrodynamics method is used to simulate droplet behavior in high-frequency pulsed electric field. Several typical examples, such as one-dimensional shock wave, Poiseuille flow and Couette flow, are simulated, by which, validity of SPH method application in the code is verified. And it is useful to the latter simulation.In view of electric demulsification mechanism and characteristics, the dynamic model of one droplet in stabilized voltage electric field is established. In the same way, we write code and simulate the deformation and breakup of the droplet. In order to verify the validity of the simulation results, the simulation results are compared with the experimental results of John S. Eow, which shows the simulation results are very good. Then the factors which affect the deformation of the droplet such as electric intensity, permitivity, interfacial tension and the size of the droplet are analysed. We find that there exists a critical electric intensity EC , which is the onset of droplet breakup occuring. when E0 ? EC, The droplet will be prolate shape, while, if E0 ? EC, the droplet will burst into smaller droplets. So, in demulsification, the electric intensity should be better not over EC ; the higher of the permitivity value of the continuous phase is, the faster the deformation of the droplet will be, and the final deformability will be higher; If the interfacial tention of a liquid-liquid system is higher, droplet will be deformed less by an external electric field; Smaller droplets are also generally deformed less.In view of complexity of high-frequency pulsed electric demulsification, droplet deformation, breakup and coalescence are simulated in high-frequency pulsed electric field. It is found that deformtaion velocity in the field is much slower; and only if the elctric intensity is big enough, small droplets can aggregate together. This is useful to demulsification by high-frequency pulsed electric field in choosing electirc intensity, frequency, etc.