Numerical Simulation Study On Influence Factors Of Droplets Coalescence In Electric Field

Oil-water separation in emulsified state is an indispensable key production link in oil-field development and production.Dehydration of crude oil under high-voltage electric field is one of the most universal application high-efficiency oil-water separation technologies.And the separation efficiency depends on the coalescence process of charged droplets in the dispersed phase.Therefore,the multi-physics coupling software COMSOL is used to numerically simulate the high-voltage electric field droplet coalescence process,and the key influencing factors are analyzed.Based on the phase field method of Cahn-Hilliard equation,the behavior of dispersed phase droplets under electric field is established by the coupling of two-phase flow field and electric field.The deformation,motion and coalescence process of charged droplets under high voltage electric field are simulated.The distribution of charge density,electric field force and flow field are studied from the microscopic point of view,and the principle of droplet deformation and coalescence is discussed.Many factors affecting droplet deformation and coalescence are studied.The simulation results show that under the action of the alternating electric field,increasing the droplet diameter,electric field strength and initial space charge density,reducing the electric field frequency,the initial relative spacing and the continuous phase flow velocity can increase the deformation degree,the deformation oscillation amplitude and the instantaneous velocity,also improving coalescence efficiency.And for the added space charge density,how it affects the coalescence process from the perspective of instantaneous velocity and deformation of the droplet.Comparative analysis of the effect of droplet electrification on droplet coalescence in different working conditions.The results show that the droplets carry electricity to effectively promote droplet coalescence,and prove that the initial space charge promotes droplet coalescence by increasing the instantaneous velocity of the droplets.The numerical simulation method is used to reveal the principle of oil-water separation under high-voltage electric field from the coalescence process of charged droplets in the dispersion phase.It can provide theoretical basis for the design and working condition setting of oil-water separator in high-pressure electric field of oil-field,and guide the efficient development of oil-field.It also enriches the theory of electrochemical research.