| Hydrocyclone can efficiently separate oil and water from conventionally produced fluid and has been widely used in oil fields.However,with the increasing viscosity and emulsification degree in the produced liquid,relying on separate centrifugal separation can not meet the actual needs.Therefore,it is proposed to introduce the electric field into the hydrocyclone to enhance oil-water separation performance.In this paper,the mechanism and force of droplet coalescence under the coupled field are firstly analyzed theoretically.At the same time,the experiments on droplet coalescence characteristics under a single electric field and coupled field are carried out to study the change in the average droplet size under different operating parameters.Compared with the single electric field,the feasibility of the coupled field to promote droplet coalescence is verified,and the influence of different parameters on droplet coalescence under the coupled field is revealed,which provides a basis and guidance for subsequent research.An electric field-cyclone field coupling device for oil-water separation is designed,and the main structure and working principle of the coupling device are expounded.In the coupling device,an electric field is applied to the internal flow field of the cyclone through an external high-voltage pulse power supply,so that the emulsion droplets in the cyclone are polarized and coalesced,to enhance the centrifugal separation ability of the cyclone.The main structural parameters of the coupling device are simulated and optimized,and the optimal structure size of the coupling device is determined.At the same time,the coupling structure is equivalently analyzed based on the electric field distribution characteristics of the coaxial cylinder,and the internal electric potential and electric field distribution rules of the coupling device are analyzed by numerical simulation.Based on the force and coalescence model of droplets under the action of the electric field,the electric field-cyclone field coupling numerical calculation model was established by using a user-defined function,and the main operating parameters（processing capacity,voltage amplitude,frequency,split ratio）were calculated.The velocity distribution,oil phase distribution,pressure loss and separation efficiency of the coupling device were analyzed under different parameters.The influence of different operating parameters on the separation performance of the coupling device was revealed,and the optimal operating parameters were obtained to improve the overall separation performance of the coupling device.The experimental platform for emulsion oil and water separation under the coupling device was used to conduct laboratory experimental research on voltage amplitude,frequency,treatment capacity,split ratio and water content,and the influence law of different operating parameters on the separation performance of the coupling device was obtained.The treatment capacity,split ratio and voltage amplitude have a great influence on the separation efficiency,while the frequency and water content have relatively little influence.The rationality of the simulation results of the coupling model is verified by comparing the experimental results and simulation values under different operating parameters.Through experiments,it was obtained that the coupling device has a good separation effect when the treatment capacity is 5.1 m3·h-1,the voltage amplitude is 7-8 k V,the frequency is 400 Hz,the current split ratio is 0.75-0.80 and the water content is 10%.Through the results of numerical simulation and laboratory experiments,it is found that the coupling device has an obvious strengthening effect on the oil-water separation effect of the emulsion,which provides a new idea for the efficient treatment of oil-water emulsion. |
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