Breakup mode transformation of leaky dielectric droplet under direct current electric field

Huang, Xin; He, Limin; Luo, Xiaoming; Yang, Donghai; Shi, Kaiyue; Yan, Huijie

doi:10.1016/j.ijmultiphaseflow.2017.07.007

Cited by 25 publications

(7 citation statements)

References 29 publications

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“…The numerical simulations of droplet C under DC electric field are implemented by using the coupled level set and volume of fluid (CLSVOF) method. The details of numerical methodology, the grid independence test, and the accuracy verification are reported in our previous publications. , Under DC electric field, positive charges are induced on the right hemispherical surface of each droplet, and negative charges are induced on the left hemispherical surface. The electric force is perpendicular to the droplet surface and points outward.…”

Section: Resultsmentioning

confidence: 99%

“…The interfacial tension remains almost constant after the interface is saturated. The transition concentration is regarded as the critical micelle concentration (CMC), above which the micelles are assembled in the volume phase. − Below the CMC, the interfacial tension is linearly dependent on the logarithm of the concentration over a large range. Above the CMC, the interfacial tension remains almost constant.…”

Section: Methodsmentioning

confidence: 99%

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Coalescence, Partial Coalescence, and Noncoalescence of Two Free Droplets Suspended in Low-Viscosity Oil under a DC Electric Field

Huang

Luo

et al. 2020

J. Phys. Chem. B

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Enhancing the electric field strength can facilitate the approach of droplets and the drainage of liquid film. However, two droplets do not coalesce but bounce off after contact under an excessively high electric field strength. To reveal the underlying mechanism, the dynamic behaviors of two free droplets suspended in low-viscosity silicone oil under a DC electric field were investigated herein. Three distinct behavior modes were successively observed by a high-speed camera with the increase in electric field strength: coalescence, partial coalescence, and noncoalescence. The mechanisms and key criteria of partial coalescence and noncoalescence were explored by studying the competition between electric force and interfacial force. The theoretical formula of critical electric field strength for droplet coalescence was derived and validated by experiments. The results indicated that the electric capillary number Ca can be used as the criterion to identify the behavior modes of two free droplets. The droplets undergo partial coalescence or noncoalescence when Ca > 0.11; otherwise, the droplets experience coalescence.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Coalescence, Partial Coalescence, and Noncoalescence of Two Free Droplets Suspended in Low-Viscosity Oil under a DC Electric Field

Huang

Luo

et al. 2020

J. Phys. Chem. B

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“…Especially in the petrochemical industry, a high-voltage electric field is extensively used for dehydrating crude oil emulsion in oil fields and refineries because of its high-efficiency and environmental friendliness. − The settling velocity of a droplet is linearly proportional to the radius of the droplet . After the electric field is applied, electric forces are induced on the surface of the droplet due to the differences in the permittivities and conductivities between the oil and water . The electrostatic interaction compels small droplets to approach each other and coalesce into larger droplets, thereby reducing the settling time and improving the separation efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…13 After the electric field is applied, electric forces are induced on the surface of the droplet due to the differences in the permittivities and conductivities between the oil and water. 14 The electrostatic interaction compels small droplets to approach each other and coalesce into larger droplets, thereby reducing the settling time and improving the separation efficiency. The coalescence process of two droplets is divided into two stages: an approach stage before contact and a fusion stage after contact.…”

Section: ■ Introductionmentioning

confidence: 99%

Charge-Transfer-Induced Noncoalescence and Chain Formation of Free Droplets under a Pulsed DC Electric Field

Huang

Luo

et al. 2020

Langmuir

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Electrocoalescence technology is an important method for the demulsification of crude oil emulsion, but its development is restricted by the short circuit caused by droplet chain formation. To reveal the formation mechanism of droplet chains, the electrocoalescence behaviors of two droplets and droplet clusters under pulsed direct current (DC) electric fields are experimentally studied. The two droplets usually successively undergo complete coalescence, partial coalescence, and noncoalescence as the electric field strength increases. The critical electric field strengths for complete coalescence under pulsed DC electric fields with different frequencies are obtained. The effects of the electric field waveform and frequency on the noncoalescence characteristics of two droplets and the stability of droplet chains are explored. The droplet chains under a highfrequency electric field are more stable and longer than those under a low-frequency electric field due to the reduction of the movement distance and the generation of daughter droplets from tip streaming. The reversal of the composition of electric forces due to charge transfer is the fundamental mechanism of noncoalescence of two droplets and chain formation in the emulsion under a pulsed DC electric field.

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“…Nevertheless, the droplet experienced tip streaming when the droplet phase was more viscous than the continuous phase. Huang et al 28 indicated the droplet experienced the mode transformation from jet‐like breakup to dumbbell‐like breakup as the electric capillary number increased. By comprehensively using numerical simulation and microscopic experiment, Karyappa et al 18 studied the effects of electric capillary number and viscosity ratio on the droplet shape before and after the breakup.…”

Section: Introductionmentioning

confidence: 99%

Deformation and breakup of water droplets containing polymer under a DC electric field

et al. 2022

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The deformation and breakup behaviors of droplets containing polymer are investigated by high‐speed photography to reveal the mechanism of electric field collapse when treating the emulsion containing polymer. The results show the electric field collapse process caused by droplet breakup consists of three steps. First, the droplet containing polymer ejects liquid filament under strong electric field. Second, the liquid filament is continuously stretched until it touches positive and negative electrodes. Finally, the severe Joule heating effect appears because the strong electric current flows through the liquid filament. The release of a large amount of heat causes the formation, expansion, and collapse of bubble, resulting in the fracture of liquid filament and the collapse of electric field. The increase of polymer concentration strengthens the Joule heating effect and enlarges the influence scope of bubble expansion and collapse. These findings provide significant guidance for the stable operation of electric dehydrator.

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Breakup mode transformation of leaky dielectric droplet under direct current electric field

Cited by 25 publications

References 29 publications

Coalescence, Partial Coalescence, and Noncoalescence of Two Free Droplets Suspended in Low-Viscosity Oil under a DC Electric Field

Coalescence, Partial Coalescence, and Noncoalescence of Two Free Droplets Suspended in Low-Viscosity Oil under a DC Electric Field

Charge-Transfer-Induced Noncoalescence and Chain Formation of Free Droplets under a Pulsed DC Electric Field

Deformation and breakup of water droplets containing polymer under a DC electric field

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