Effect Of Dc Electric Field Research Articles

Effect of DC electric field on coalescence and breakup behaviors of binary emulsion nanodroplets

In this paper, molecular dynamics simulations are carried out to investigate the effect of a DC electric field on the coalescence and breakup behaviors of binary emulsion nanodroplets. The results indicate that the raised strength of the electric field promotes the efficiency of the electrocoalescence, and simultaneously a polarizing layer is formed by the strong hydrogen bonds. The polarizing layer inhibits the internal component to separate from the droplet through reducing the interfacial tension between the water and n-octane components. Moreover, the increases in volume content of the internal component promote the electrocoalescence first and then inhibit it in the same electric field, which depends on the competition between the electrostatic attraction and the inertia of the droplets themselves. Meanwhile, the increases in the volume content break the effect of the hydrogen bond and induce the local liquid gap thinning. Therefore, the breakup of the binary emulsion droplets with a larger volume content happens more easily at the thinner edges. In addition, the critical electric field strength corresponding to the breakup of the droplets increases first and then decreases with the volume fraction increasing, which is better for recovering the oil component but worse for the efficiency of electrocoalescence.

The Effect of Electric Field Configuration on the Thermo-Chemical Conversion of Straw Pellets

Abstract With the aim to control and improve the thermo-chemical conversion of straw pellets, the experimental investigations of the DC electric field effect on the combustion dynamics and heat energy production were made. The electric field effect on the gasification/combustion characteristics was studied using three different positions of the positively charged electrode in flame. First, the electrode was positioned coaxially downstream the flame flow. Next, the electrode was positioned coaxially upstream the flame flow and, finally, the electrode was positioned across the downstream flow. The bias voltage of the electrode varied in the range from 0.6 up to 1.8 kV, while the ion current in flame was limited to 5 mA. The results of experimental investigations show that the DC electric field intensifies the thermal decomposition of straw pellets and enhances mixing of volatiles with air causing changes in combustion dynamics and heat energy production, which depend on position and the bias voltage of the electrode. The increase in the average volume fraction of CO2 (by 6 %) and the decrease in the mass fraction of unburned volatiles in the products (CO by 60 % and H2 by 73 %) for the upstream field configuration of the electrode and the ion current 0.5–1.8 mA indicate more complete combustion of volatiles.

An experimental study on the effect of DC electric field on impinging flame

This work presents an experimental study the effects of DC electric field on a laminar premixed flame which impinges on a plate. Positive DC and ground levels of voltage are applied to the plate and burner, respectively. A reverse application of the electric field is also tested. Detailed measurements are undertaken to understand the ionic wind effect on flame impingement heat transfer.Testing shows a favorable effect of positive field on flame stability, as the flame stands leaner combustion. When a sufficiently high voltage is applied, discharge occurs which breaks down the electric field. The results of thermal field testing reveal that the temperature change observed is due to flame shape distortion caused by ionic wind. It is found that ionic wind is majorly physical in nature, inducing the changes in flame stability and temperature through a force. Further, it is mainly the post-combustion part of the flame, instead of reaction zone, bears such force.Under positive field, the burner nozzle is rapidly heated by the flame. However, flame impingement heat transfer has no significant change under either positive or reverse field. It is because heat loss from the post-combustion flame to plate is less altered by DC fields. To further study the ionic wind effect, a co-flow is introduced to the flame, and the standard deviation data of flame temperature indicate that ionic wind insignificantly changes the mixing between flame and ambient air. It confirms that ionic wind is mainly a force effect, with negligible chemical effect in the scope of this work.

Effect of moderate DC electric field on formation of surfactant-laden drops

The continuous formation of mm-scale surfactant-laden aqueous drops in oil was studied under an applied DC electric field of 0–267 kV/m. The parameters varied included the flow rate of dispersed phase, the electric field strength, the viscosities and densities of dispersed and continuous phase and the surfactant type (anionic or cationic) and concentration. An increase in the electric field strength resulted in a decrease of the drop size due to increasing stresses on the drop interface. The size reduction continued until transition to the irregular regime. The values of critical electric field strength for this transition increased with an increase in both the flow rate and the viscosity ratio between the dispersed and continuous phase. The critical electric field strength and the size of the drops formed in the periodic dripping regime were independent of the electric field polarity. The effect of the electric field increased with a decrease of interfacial tension and density difference between the dispersed and continuous phase.

DC bias electric field and stress dependence of piezoelectric parameters in lead zirconate titanate ceramics – Phenomenological approach

The piezoelectric material behavior, including loss mechanism, under external DC electric field and stress biases have been extensively studied in lead zirconate titanate ceramics. However, in order to achieve a better understanding of these effects, development of a comprehensive model is required. The purpose of this paper is to develop a phenomenological model to explain the nonlinear nature of piezoelectric parameters under DC bias electric field and stress. Therefore, the Landau-Devonshire energy function considering external biases was developed and accordingly the material properties were derived, based on first order approximation. In order to explain the compliance and piezoelectric constants change higher order elastic and electrostrictive terms were introduced into the Gibb's free energy function.Accordingly, thermodynamic theory parameters, including higher order parameters, of a soft PZT were measured and characterized based on inverse permittivity behavior near Curie temperature. Finally, the phenomenological model predictions of material property changes under DC bias electric field and compressive stress were compared with experimental data reported by our group. The proposed model succeeded to explain the material properties change under external biases. Furthermore, the effect of DC electric field and compressive stress on loss parameters were explained based on domain wall motion.

Shaping the Cytoskeleton with Electric Fields

Endogenous electric fields are present in many biological processes including at the edge of healing wounds and can direct cell migration. Here we measure the effect of DC electric fields on actin polymerization dynamics. We find that actin waves are guided by DC electric fields for multiple cell types. Giant Dictyostelium discoideum cells (produced via electrofusion) allow us to measure electric field response of actin waves located far from the leading or trailing edge of a cell, and thus decouple cell polarity and shape from actin wave responses. We also use nanoridges, fabricated substrate nanotopographies, which alter the actin waves from the broad, two-dimensional waves seen on flat substrates to one-dimensional waves traveling along the nanoridges. Our data reveal new insights into the mechanism behind cell migration via DC electric fields with actin waves playing a key role in cell response and control.

Simulation of Internal and External Electric Field of UHV DC Polar Bus Arrester under Pollution Conditions

Due to the adsorption effect of DC electric field on pollution particles, the pollution accumulation of DC arrester is more serious than that of AC arrester. In addition, the UHV DC polar bus arrester also has a parallel resistance pole inside, the external electric field and the internal radial electric field will be affected by the pollution distribution. In this paper, the electric field simulation model of UHV DC polar bus arrester under the condition of pollution was established, which was used to calculate and analyze the electric field on the surface of the insulating coat and the radial electric field between the resistance pole and the insulating coat when the overall pollution and the local dry belt of the arrester occur. The results showed that the overall pollution of the arrester would lead to the increase of the surface field strength and the internal radial field strength. While the value was small, it would not cause corona and flashover. When the partial dry belt occurred, it would form the partial high surface field strength and radial field strength on the surface of skirt and the air gap between the resistance piece and the insulating coat, which would cause flashover on the surface of the insulating jacket, corona discharge and penetration discharge between the resistance piece column and the insulating coat.

Effect of fine bubbles on frictional properties -Effects of DC electric field on FB behavior-

Effect of fine bubbles on frictional properties -Effects of DC electric field on FB behavior-

Flame spread over twin electrical wires with applied DC electric fields

The effect of DC electric field on the characteristics of flame spread over polyethylene-insulated twin electrical wires was studied by varying wire gap (S) and voltage (VDC). Under an applied electric field, the flame spread rate (FSR), flame width, leaning direction of the interacting twin flames varied substantially with varying the voltage and wire gap. The flame spread rate was initially larger for the wire with negative voltage (spreading flame with negative charge; SF−) than the wire with positive voltage (SF+), but the two eventually became the same in the developed region when a quasi-steady state was reached. The FSR behavior could be classified into two regimes; twin flame spread (regime I) and single flame spread (regime II) after the extinction of SF+. Under regime I, three sub-regimes were identified depending on the wire gap and voltage. For the twin flame spread, the flame spread rate initially decreased with increasing voltage as the flame leaned toward the burnt wire. As the two flames interacted, the flame spread rate increased because of the ionic wind effect, and eventually decreased because of the loss of molten PE mass and the electrospray phenomenon. In regime II after the extinction of SF+, the single flame spread showed a transient behavior since the influences of electric field from burnt and unburned wire sections of SF+ wire varied with flame spread. When the voltage was increased even further, SF– was extinguished by streamer generation and, at excessive voltages, an electrical short occurred. The flame spread rates for twin flame spread were best correlated with the electric field intensity in the form of |VDC|0.91/S0.72.

Stable X-islands of quadrupole mass filter.

Quadrupole mass filters are normally operated as narrow band pass filters by appropriate choices of rf and DC voltages corresponding to Mathieu a and q values near the apex of the first stability region. We add an auxiliary quadrupole excitation potential to the main drive voltage. As a result, stability islands appear on the () plane. The method of the islands mapping on the () plane is discussed in detail. The DC electric field's effect responsible for removing "shadowing" islands has been studied using a combination of analytic theory and computer modeling. We call a narrow stability region elongated along an iso- line an X-island. Two such stability islands were found where operation is possible without mass spectra interference when the DC potential is used. Those islands are formed by quadrupole potentials with relative excitation frequencies and , where Many other stability X-islands are presented in detail and illustrated by their transmission contours. This data is necessary for experimental testing of the separation mode at those islands. The study demonstrates how to use X-islands to achieve relatively high resolution 4000-12,000 at the transmission of about 28-15%, respectively.

Effect of DC electric field on water droplets' movement and icing process on insulator

Icing has a great effect on insulation of power networks. In order to know the insulator icing properties under electric field and help simulating the icing process precisely, the effects caused by electric field are investigated in this research. Taking glass insulator LXY-120 as samples, the electric field were calculated, based on which, the movement of charged water droplets was analysed. The simulation results show that, the electric forces can change the trajectory of water droplets by different degree which is affected by the collided position, relative distance, wind velocity and the size of water droplet, and the biggest track shift happens under the insulator shed with a rate larger than 120%. As a result, the collision efficiency β1 can increase up to 23% while MVD and wind velocity are both small. Through a series of icing contrast experiments in an artificial climate chamber, it is proved that the electric field can promote the dry-growth icing process with more ice growing directions and a higher icing rate, meanwhile, it affects the wet-growth icing showing as bending icicles and a lower icicle growing rate.

Negative-resistance behavior of bulk Ag2O–TeO2–V2O5 oxide glasses

The bulk 3-component xAg2O–40TeO2–(60 − x)V2O5 oxide glasses with different silver oxide contents of x = 0, 10, 20, 30, 40 and 50 mol% were prepared using the standard press-melt quenching method. The effect of the high DC electric field on the DC conductivity of the mentioned glasses was investigated using the gap-type electrode configuration. At the regime of low DC electric fields, the conduction of these samples was ohmic, whereas at high electric fields regime, present bulk samples show nonlinear behavior (i.e., non-ohmic conduction). The current–voltage characteristics show increasing deviation from Ohm’s law with increasing current density, implying the non-ohmic behavior in close coincidence with Poole–Frenkel effect (PFE) which occurs at electrical fields nearly above 104 (V/cm); so, samples show the switching phenomena at a threshold voltage (Vth) from resistive state to conductive state. Based upon PFE, the lowering factor of potential barrier (βPF) was determined for the understudied samples. Also, results show that generally the threshold voltage in which switching phenomenon occurs increases by increasing the electrode distance and decreases by increasing the sample temperature, but Vth shows two distinct regions of 0 ≤ x ≤ 20 and 20 < x ≤ 50, in which the highest value of Vth is devoted to the case of x = 20 mol% with respect to other glasses; this result implies the structural change and then probable formation of crystallites in the amorphous matrix to be hard for the mentioned case, which is in good agreement with the previously reported mechanical aspects.

Effect of hydrogen enrichment and electric field on lean CH4/air flame propagation at elevated pressure

Electric assisted combustion for hydrogen enriched hydrocarbons may even extend the lean burn limit and provide the further improvement on combustion stability. This study investigates the effect of hydrogen enrichment and DC electric field on lean CH4/air flame propagation. Electric field inside the chamber was generated by mesh and needle electrodes. Effect of hydrogen enrichment on the ion mole fraction in the flame was discussed based on reaction mechanism included neutral and ion reactions. The flame propagation images, flame displacement speed were used to evaluate the combined influences of hydrogen enrichment and electric field on propagating flame. Results showed that the hydrogen addition would increase positive ions mole fraction and the peak value is mainly determined by H3O+. This would be due to that CH increases with hydrogen fraction, which is the main species in the initial reaction for the ion reactions. Electric field effect about flame propagation was suppressed with hydrogen addition due to the competition between the increment in ion mole fraction and the decrement in flame time. Electric assisted combustion is more evident at leaner conditions and elevated pressure. The ratio of ionic wind velocity to flow velocity may be the determined factor to predict the electric field effect about propagating flame. The tendency based on this ratio is in accordance with the experimental results for various hydrogen fraction and equivalence ratio at elevated pressure.

Electric response induced by second sound in superfluid helium

The electric response of superfluid helium was measured when a second sound standing wave was generated in a resonator cavity. The results were qualitatively in agreement with that of other research laboratories, but the normalized signal strength was one order of magnitude larger reflecting the difference in electrode structure. The temporal phase difference between the electric oscillation and the temperature oscillation was measured and compared with the analysis. The result excluded a hypothesis that the electric response was induced by the velocities of the relative motion of normal and superfluid components of liquid helium. We suggested a hypothetical explanation of the electric response based on the oscillation of chemical potential of electrons in helium atoms. The effect of an external dc electric field was examined and no effect was observed. The heater power dependence of the temperature oscillation and the electric oscillation showed the qualitative agreement with the original experiment.

Fast electric control of the droplet size in a microfluidic T-junction droplet generator

The effect of DC electric fields on the generation of droplets of water and xanthan gum solutions in sunflower oil at a microfluidic T-junction is experimentally studied. The electric field leads to a significant reduction of the droplet diameter, by about a factor of 2 in the case of water droplets. The droplet size can be tuned by varying the electric field strength, an effect that can be employed to produce a stream of droplets with a tailor-made size sequence. Compared to the case of purely hydrodynamic droplet production without electric fields, the electric control has about the same effect on the droplet size if the electric stress at the liquid/liquid interface is the same as the hydrodynamic stress.

Effect of DC electric field on laminar premixed spherical propagation flame at elevated pressures up to 0.5 MPa

ABSTRACTThe effects of DC electric field on laminar premixed CH4/air spherical propagation flames with excess air ratio λ = 1.0, 1.2, 1.4 were investigated in a constant volume combustion chamber at elevated pressures up to 0.5 MPa. Mesh electrodes were used to generate electric field inside the chamber. The flame front structure, flame displacement speed, and pressure-related combustion parameters were derived to evaluate the effects of electric field on flame propagation. The results show that the mean flame displacement speed increases in the electric field direction with the increase of applied voltages and it is more significant at lean conditions. The mean flame displacement speed decreases in the direction perpendicular to the electric field with the voltage at low pressures, while it increases with voltage due to flame instability induced by the electric field at higher pressures. The effect of electric field on flame displacement speed is more obvious with pressure rise. Electric-induced flame instability combined with the hydrodynamic instability both promoted at high pressure lead to much more cracked structure and enhance the flame displacement speed. An obvious acceleration stage during the flame propagation under electric field is also observed. The combustion peak pressure slightly increases and the timing of peak pressure is in advance with the increasing of applied voltage. The flame initiation time derived from pressure decreases with voltage and it is more obvious at higher pressures. In this study, a new ionic wind velocity calculation method was developed based on the ionic wind development degree and conservation of momentum. As pressure increases, the corrected ionic wind velocity decreases, and the tendency is consistent with the experimental results about increment of flame displacement speed at elevated pressures.

The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer

The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer

Simulation Study on the Effects of DC Electric Field on Insulator Surface Pollution Deposit

Energized insulator’s surface contamination is greatly affected by its electric field properties. However, few reports about the electric field influencing mechanism on the pollution deposition have been presented. In this paper, the coupling-physics model of a three-unit XP-160 insulator string was established, and the particles’ deposition process was simulated by using the finite element method. The effects of the electric field on the pollution particles’ motion were analyzed. Research results indicate that the closer to the insulator string, the larger the intersection angle θ between the electric force and its horizontal component. The main function of the electric field on insulator contamination is that it changes the pollution particles’ vertical moving speed, thus accelerating the particles’ deposition process. The particle capture coefficient ratio ck can be used to reflect the pollution degree discrepancy between DC-energized and non-energized insulators. In this paper the ratio ck of the DC-energized to non-energized condition is in the range of 1.04 to 1.98, very close to the field measurement results of the DC pollution ratio k.

Effect of an electric field on friction of silicone rubber against steel in the motor base oil's environment

The paper presents the experimental results of research on the effect of an external DC electric field on the coefficient of friction of silicone rubber (elastomer) during its rubbing against a steel surface in the „pin–on–disc” experimental set-up. In the tests there were used silicone rubber samples, the pure PAG and PAO synthetic base oils and their blends with an antiwear (ZDDP) additive. The coefficient of friction μ was determined under conditions with and without an external DC electric field. A DC electric field was generated between a silicone rubber sample and a rotating steel disc (a friction pair). A sample holder was electrically isolated from other metal parts of a tribometer and was connected to one of the poles of a DC power supply, while the other pole was connected by means of the carbon brushes to a rotating steel disc. The experimental results show that the external DC electric field established between the rotating steel disc and a silicone rubber sample causes the coefficient of friction to decrease. It was also found that the coefficient of friction μ depends on the steel disc's angular velocity n, the contact pressure p, and the type of base oil and its blends with the additive used.

Investigation of the effect of DC electric field on a small ethanol diffusion flame

A small ethanol diffusion flame exhibited interesting characteristics under a DC electric field. A numerical study has been performed to elucidate the experimental observations. The flow velocity, chemical reaction rate, species mass fraction distribution, flame deformation and temperature of the flame in the applied DC electric field were considered. The results show that the applied electric field changes the flame characteristics mainly due to the body forces acting on charged particles in the electric field. The charged particles are accelerated in the applied electric field, resulting in the flow velocity increase. The effects on the species distribution are also discussed. It was found that the applied electric field promotes the fuel/oxidizer mixing, thereby enhancing the combustion process and leading to higher flame temperature. Flame becomes shorter with applied electric field and its deformation is related to the electric field strength. The study showed that it is feasible to use an applied DC electric field to control combustion and flame in small-scale.