Stable deformation of droplets surface subjected to a high-voltage electric field in oil

• Forces acting on a deformed droplet in a uniform electric field are analysed.
• Dynamics model of the deformation of the drop is developed.
• Internal electric field strengths of prolate and spherical droplets are analysed.
• Model predictions are in good agreement with experimental results.
• System parameters effecting on droplet deformation is discussed.

Electro-demulsification is widely applied to the dehydration of emulsified oil. A droplet exposed to an electric field is polarised in oil and then stretched to a prolate sphere. The internal electric field distributions of prolate-sphere and spherical droplets are analysed in this work. The expressions of force acting on the droplets surface are obtained by establishing a model of stable droplet stretching deformation. An experiment is conducted to determine the draw ratio of water droplets subjected to a high electric field and exposed in four types of base oil. Comparison of the results of the experiment and model shows that the stable deformation of droplets is well predicted by the model. System parameters, such as electric field strength, droplet initial radius, interfacial tension of droplet – oil, permittivity and effect on the deformation of droplets, are also discussed.

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