The generation of electric currents by the laminar flow of dielectric liquids

Walmsley, H.L.; Woodford, G.

doi:10.1088/0022-3727/14/10/011

Cited by 65 publications

(29 citation statements)

References 12 publications

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“…In their treatments of the fully developed streaming current in both laminar (24) and turbulent (25) flows these authors specialize Eq. 2.13 by omitting the K terms.…”

Section: Streaming Currents In Conducting Systemsmentioning

confidence: 99%

Electrification by liquid dielectric flow

Gasworth

1986

Conference on Electrical Insulation &Amp; Dielectric Phenomena - Annual Report 1986

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The charging of insulating surfaces by the flow of semi-insulating liquids is investigated with a view towards identifying ways to forestall insulation failure in liquid-cooled power distribution equipment. Both fully developed and fully mixed turbulent flows are considered, the former as a model for the flows in insulating tubes, the latter approximating conditions in certain practical elements such as pumps and expansion regions. Models are developed for the space-time evolution of charge and electrical stress that emphasize the interplay between electrokinetic charge generation, convective transport, ion diffusion and self-precipitation, and conduction driven by the generated fields themselves.Experiments are designed to allow measurement of the currents influent to the insulating tube or expansion region, and either the accumulating surface charge or the generated electric field. Apart from the imposed flow conditions, the liquid conductivity is controlled by a commercial antistatic agent, while the external configuration of conductors is prescribed with an awareness of the contribution of external image charges to the generated fields. Results indicate that significant electrical stresses stem from the transfer of a net charge to the flow upstream of the insulating element, and migration of the entrained ions in a space charge field that is predominantly normal to the the insulating surface. Leverage over the flow-induced stresses is afforded by the external conductor configuration, control of bulk and surface conductivities, and control of the influent convection current with a properly designed expansion region inserted just upstream of the insulating element.Physicochemical features of the liquid-insulating solid interface are probed in two supplementary experiments that make use of a multi-phase helical winding around a section of an insulating tube. In the first experiment the flow is imposed and half of the phases are excited with a sinusoidal potential. Convective displacement of the resulting standingwave perturbation in the entrained volume charge density is detected as an imbalance in the currents carrying perturbation image charge to two of the unexcited phases. The response is interpreted in terms of the undisturbed convection current, the surface conductivity, and the conductivity gradient at the interface. In the second experiment, the flow is induced by a traveling-wave excitation of the winding with the objective of investigating the charge injection process at the same interface. ACKNOWLEDGEMENTSWith the fresh perspective that comes from extending my contacts outside of the Continuum Electromechanics Lab, I am struck by the uniqueness and depth of the education I've received, all the more so because so much of it has been shaped by one man, Professor James Melcher. To his credit as an educator, the form of this thesis is as much a product of the careful grounding in fundamentals he has provided over the years, beginning long before this project commenced, as of discussions specific...

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“…In their treatments of the fully developed streaming current in both laminar (24) and turbulent (25) flows these authors specialize Eq. 2.13 by omitting the K terms.…”

Section: Streaming Currents In Conducting Systemsmentioning

confidence: 99%

Electrification by liquid dielectric flow

Gasworth

1986

Conference on Electrical Insulation &Amp; Dielectric Phenomena - Annual Report 1986

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“…However the physicochemical process at the origin of the phenomenon is still under investigation. Indeed, even if several models have been proposed [6][7][8], experiments made recently with oil flows past pressboards do not follow the predictions [9].…”

Section: Introductionmentioning

confidence: 98%

“…This reservoir is used as a tranquilization vessel to ensure a neutrality of the liquid at the entrance of the capillary. After the liquid has flown in the capillary it is collected in the collecting vessel (6). The electric charge transported by the liquid due to the flow electrification process in the capillary is measured with a picoammeter Keithley (11) connected to a recorder (12).…”

Section: Introductionmentioning

confidence: 99%

Flow electrification process: the physicochemical corroding model revisited

Paillat

Cabaleiro

Romat

et al. 2009

IEEE Trans. Dielect. Electr. Insul.

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Though the phenomenon of flow electrification has been observed for several decades, the physicochemical process appearing at the solid/liquid interface creating the double layer is not yet totally understood. In particular, returns from experiments made with oil and pressboard seems to show that the wall current density at the interface for a diffuse layer under development is not only a function of the chemical behaviour of the interface but also of the flow wall shearing stress. The present work concerns analysis of experiments made with heptane flows through a stainless steel capillary of varying length. In that case also, even if the wall material is conductive and not porous, divergences appear with the classical physicochemical model predictions, while a model taking into account the effect of the wall shearing stress on the interfacial process seems to have a much better agreement with the experiments, especially, for high laminar Reynolds numbers.

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“…However, in order to obtain analytical solutions some simplifications are needed. For instance, some authors assume the reactions' kinetics to be too slow [20][21][22][23][24], or too fast [25][26][27] when compared to charge relaxation time. In this work, we present and solve the differential equation that governs the transient formation of an EDL when a liquid at rest is put in contact with a solid wall, in the case of weak space charge density (which allows for the linearization of the equation).…”

Section: Introductionmentioning

confidence: 99%

Transient electrical double layer dynamics in a quiescent fluid

Cabaleiro

Paillat

Touchard

2014

IEEE Trans. Dielect. Electr. Insul.

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From the moment a liquid is put in contact with a solid, physico-chemical reactions occur at their interface. These reactions have been modeled over the years by preferential adsorption or corrosion. Whatever the model, they lead to a charge distribution called electrical double layer (EDL), formed by a charge layer at the solid wall, and a diffuse charge layer of opposite sign in the liquid. In this work we focus on the formation of the EDL when a plane wall is put in contact with a quiescent fluid. The governing equations and a semi-analytical solution are presented. A simpler solution can be found by assuming the instantaneous formation of the charge density profile. The semi-analytical solution presented in this work is compared to the former at different reaction rates leading to the conclusion that for fast enough wall reactions, the instantaneous charge density profile cannot be assumed.

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The generation of electric currents by the laminar flow of dielectric liquids

Cited by 65 publications

References 12 publications

Electrification by liquid dielectric flow

Electrification by liquid dielectric flow

Flow electrification process: the physicochemical corroding model revisited

Transient electrical double layer dynamics in a quiescent fluid

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