Space Charge Density Distribution Research Articles

Dynamic Effect of Overscreening on Electrochemical and Thermal Properties of EDLC Electrodes during Charging/Discharging Cycles

Overscreening was commonly observed during charging/discharging cycles of electric double layer capacitors(EDLCs). This study presented a two-dimensional continuum electrochemical thermal model with a distribution function for concentration considering overscreening to investigate how overscreening affected the dynamic formation of electric double layer (EDL) near electrodes in macroscale. The results indicated that ion distribution was co-affected by EDL formation and overscreening near the electrode. Correspondingly, layered space charge density distribution resulted in a thicker diffuse layer, whose thickness was determined by the sum of co-ion and counter-ion diameters. Additionally, the diffuse layer capacitance was proportional to the reciprocal of counter-ion diameter, while the total capacitance was proportional to a linear combination of counter-ion and the larger ion diameters. Moreover, the shift from endothermic to exothermic for the total heat generation rate was dominated by heat of mixing, and was caused by the local ion mixing due to overscreening, resulting in local entropy increase. The results of this study can be used to further investigate the effect of overscreening on ion transient transport dynamic and heat generation rates.

Numerical Study of the Influence of Using Semicircular Corrugated Collecting Plate and Inverted Semicircular Corrugated on the Electrostatic Precipitator

Electrostatic precipitators (ESPs) play a crucial role in removing harmful particles in various industries. Ongoing studies continuously strive to improve their performance and efficiency, leveraging the inherent advantages of ESPs. Researchers are exploring various types of collecting and discharge electrodes to achieve this. This study specifically focuses on comparing two types of collecting electrodes, Semicircular Corrugated Plates (SCPs) and inverted Semicircular Corrugated Plates (InvSCPs), against Flat Plates (FPs) as a reference case. Three distinct forms of ESPs were simulated, and the SCP and InvSCP designs were evaluated against the FPs, specifically assessing the impact of modifying the collecting electrode design on key electrostatic precipitator characteristics, such as electrical field distribution, space charge density distribution, particle trajectories, and particle collection efficiency. Notably, the study found that using SCP resulted in the highest particle collection efficiency compared to InvSCP and FP for the same range of particles.

Exploring effect of charge dissipation in charged powder space on electric field distribution in silo

The electric field distribution is important for understanding the underlying mechanism of electrostatic discharge in silos and for developing anti-static strategies. However, the charge dissipation of charged powder usually is not well modeled in the existing electric field simulation, resulting in inaccurate estimation of the electric field in silos. This paper studied the electric field distribution in a cylindrical silo based on the space charge density distribution created by the charged particles. The influences of the normalized filling time, gap distance, and the silo height-to-diameter ratio on the electric field were explored. The results indicate that the area with a larger space charge density shrinks from the heap bottom to the heap surface, leading to a decline in the electric field and suggesting a lower probability of electrostatic discharge at the larger normalized filling time. Continuous decrease of the gap distance when the heap surface is close to the silo ceiling will lead to a sharp increase in the electric field, regardless of the charge dissipation. The silos with a height-to-diameter ratio greater than 2 are demonstrated to have a lower probability of electrostatic discharge and a space higher utilization ratio.

Research of the effect of different corrugated dust collection plates on particle removal in electrostatic precipitators

In this paper, a multi-physics field coupled model of electric, flow and particle fields was constructed by COMSOL to compare the effects of three different corrugated dust collector plates on electric field distribution, airflow field, particle trajectories and dust removal efficiency in an electrostatic precipitator, and to compare them with a conventional electrostatic precipitator with a parallel plate structure. The results indicated that the corrugated dust collection plate influenced the electric field within the ESP channel, while the wire plate spacing directly affected the size and distribution of space charge density. Furthermore, the corrugated dust collection plate also affected the EHD flow within the channel, with the D2-ESP and D3-ESP being the most strongly influenced by the ionic wind. By comparing the dust removal efficiency of the four ESPs, we found that D2-ESP has the highest dust removal efficiency, followed by D3-ESP, then Flat-ESP, and finally D1-ESP. The ranking order of the four ESPs' dust removal efficiency is consistent with the ranking order of the space charge density within the four ESP channels, which shows that the size of the space charge density directly affects the dust removal efficiency of ESPs. Numerical simulation results show that the change of wire plate spacing is the main reason why corrugated ESP affects the dust removal efficiency of electrostatic precipitators.

A numerical solver for investigating the space charge effect on theelectric field in liquid argon time projection chambers

This paper reports the development of a numerical solver aimed to simulate the interaction between the space charge (i.e. ions) distribution and the electric field in liquid argon time projection chamber (LArTPC) detectors. The ion transport equation is solved by a time-accurate, cell-centered finite volume method and the electric potential equation by a continuous finite element method. The electric potential equation updates the electric field which provides the drift velocity to the ion transport equation. The ion transport equation updates the space charge density distribution which appears as the source term in the electric potential equation. The interaction between the space charge distribution and the electric field is numerically simulated within each physical time step. The convective velocity in the ion transport equation can include the background flow velocity in addition to the electric drift velocity. The numerical solver has been parallelized using the Message Passing Interface (MPI) library. Numerical tests show and verify the capability and accuracy of the current numerical solver. It is planned that the developed numerical solver, together with a Computational Fluid Dynamics (CFD) package which provides the flow velocity field, can be used to investigate the space charge effect on the electric field in large-scale particle detectors.

The effect of combining wavy and W-type collecting electrodes on the properties of electrostatic precipitators

Electrostatic precipitators (ESPs) are commonly used in industry to remove hazardous particles from flue gases using corona discharge. The optimization of collecting electrodes and corona wires arrangement has a significant influence on the particle collection. Many researchers are attempting to enhance current models in multiple forms. This study seeks to analyze the new design of collecting plates, which are a mix of wavy and W-type collecting electrodes, and how they affect electrostatic precipitators’ characteristics. The simulation results of electrical characteristics on the particle collecting efficiency, space charge density distribution, and electrical field distribution in the mixed type of collecting plates are presented. To validate this design, the mixed-type findings were evaluated with those obtained from flat plates (FPs). By using the proposed mixed design also improves collecting efficiency compared with FPs’ results.

Multi-scale characteristics of the spatial distribution of space charge density that determines the vertical electric field during dust storms

Multi-scale characteristics of the spatial distribution of space charge density that determines the vertical electric field during dust storms

An Emerging Mineral‐Based Dielectric Material: Intrinsic Dielectric Properties and Modulated

AbstractHigh energy density polymer nanocomposites reinforced with high dielectric constant ferroelectric nanoparticles exhibit great potential for energy storage applications in modern electronic and electrical systems. However, further improvements in the Ue of polymer nanocomposites with a higher breakdown strength (Eb) is of utmost importance. Tuning the permittivity from the filler center to the surrounding matrix in composites can alleviate local charge concentrations. Here, a gradient dielectric constant buffer layer is constructed via induced selectively titanium dioxide is inserted into the multilayer aluminosilicate. This gradient‐structured buffer layer remarkably weakened the charge density around the ferroelectric particles, which gave rise to high breakdown strength and increased the energy density of the polymer nanocomposites. Furthermore, the density functional theory (DFT) calculation reveals an active charge transfer between buffer layer and poly(vinylidene fluoride‐co‐hexafluoropropylene). The space charge density distribution is simulated via finite element methods to verify the experimental dielectric breakdown results in the nanocomposite films. Therefore, this work provides a new strategy to balance the coupling relationship between energy density and breakdown strength.

Study and Numerical Simulation of Negative and Positive Corona Discharge: A Review

Two models to describe the phenomenon of corona discharge are presented: the first is known as the plasma model which with plasma chemistry defines the volumetric and surface reactions among charge carriers such as electrons, positive, and negative ions. This model uses Poisson's equation and a formulation of the space-charge density to calculate the electric field necessary to solve the species transport equations. Besides, only the plasma model determines the density of the charge carriers. The second is a simplified model which describes the corona discharge in terms of current conservation coupled with Poisson's equation. This model does not have any connection with the attributes of plasma chemistry. Both models propose solutions for the electric potential and space charge density distribution from the corona electrode to the ground electrode.

Study and Numerical Simulation of the Electrical Properties of a Duct-Type Electrostatic Precipitator Using Seven Circular Corona Wires: A Review

The study of electrostatic precipitators (ESP) is of great importance in powder technology. Different physical and chemical processes occur during its operation. The objective of this investigation is to analyze and observe electrical phenomena using mathematical models such as Poisson's equation and the charge conservation equation. To carry out the simulation two flat plates and seven corona wires are geometrically arranged based on an ESP prototype. The general form of partial differential equations mentioned along with the boundary conditions was written in software and associated with the different parts of the geometry. For example, the electric field onset is calculated by Peak's law and set as one of the boundary conditions for the corona wires. Defining the space charge density distribution is an essential part because the next processes inside of ESP depend on this parameter. A specific method that splits the space charge density is used to solve these PDEs. Besides, a review of the concepts of the particle charging process, particle kinetics, and particle collection is introduced. The results obtained from the simulation such as the electric potential, electric field, and space charge density, agree with those proposed in some investigations.

Breakdown Characteristics of Liquid Silicone Rubber in Needle-Plane Configuration Under Polarity Reversal

The results of breakdown voltages in liquid silicone rubber (LSiR) insulation under stepped polarity reversal voltages at a uniform temperature in a needle-plane electrode system are presented in this article. In the presence of defects such as sharp conductor projections or protrusions in the cable insulation stressed under polarity reversal direct current (dc) voltages, the electric field distribution is far more complex due to nonlinear insulation conductivity and time-dependent field distribution. The electric field distribution and space-charge accumulation are intricate functions of factors such as geometry and nonlinear conduction. In this article, a two-dimensional (2-D) axisymmetric model of a needle-plane geometry is developed using the finite-element method to compute the time-dependent field, space charge, and current density distribution under polarity reversal dc, which apparently did not get much attention until now. Interesting results on the effect of polarity transition time and applied polarity time step on the abovementioned distributions are addressed and presented. The pronounced effects of nonlinear conductivity on the time-dependent field distribution are also demonstrated. Furthermore, from the breakdown experiments conducted on tip-plane electrode system for different tip radii and applied time steps, the results put forward a rational and practical estimate of the breakdown field using the proposed model.

The Effect of Corona Wire Position and Radius in a Duct-Type ESP with Wavy Collecting Plates

Electrostatic precipitators (ESPs) have become one of the most effective methods for removing harmful particles from various industries. Many investigations in this subject are constantly developing due to the inherent benefits of using an ESP, and there are many robust initiatives taking place today all over the world. Different configurations of collection and discharging electrodes must be investigated to improve the ESP performance of ESPs. Many studies are working to enhance existing models in different ways. The geometry of the electrodes and the collecting plates is one area that could be improved. This paper investigates the wavy designs of collecting electrodes with varied corona electrode radius (range of variable corona radius (0.07-0.6 mm)) and position in a single-stage ESP. Wavy plates (WPs) and Inverted wavy plates (InvWPs) are compared to flat plates (FPs) using a numerical simulation tool. The results of this work show the impact of changing the corona radius when wavy and inverted wavy collecting electrodes are used on the electric potential, electric field strength, current density, and space charge density distribution, and particle collection efficiency. When compared to InvWPs and FPs, WPs show the highest performance in this range of particles. Although InvWPs can be utilized to reduce current density or space charge density, they do not increase particle collection efficiency.

A comprehensive study of structural, vibrational, electronic properties of celecoxib compound by density functional theory

This paper describes the spectroscopic (FT-IR and UV–Visible), electronic, structural, vibrational properties of celecoxib compound using density functional theory. The optimized geometry structure of the titled molecule is explained by the method of B3LYP with 6–31 + G (d, p) basis set. We found that the simulated optimized geometry of the titled molecule is simulated to the experimental ones. The infrared spectrum of celecoxib compound is represented in the present work. The computational information about the organic molecule can be explained by the charge transfer properties, which is a computational tool for the precise quantum chemical calculations of space charge density distribution and HOMO-LUMO states. The transition states of celecoxib compound have explained by the time-dependent density functional theory (TD-DFT) which is observed by the UV–visible spectrum. Docking research [1] is a modeling method, with the help of docking method we can find out new drug and chemical behavior of the drug which is useful in the application purpose of the drug, the interaction between protein and legends provides the information of the binding energy and physical parameter like partition function, free energy, internal energy, entropy.

Numerical simulation of electric field in cylindrical silo based on non-uniform electrostatic charge distribution caused by particle segregation

Size-induced particle segregation during the silo filling process greatly changes the electrostatic charge distribution, influencing the occurrence of the incendiary electrostatic discharge. However, few studies concern the electric field distribution in this condition. In this work, the non-uniform space charge density distribution obtained in DEM simulation of the particle segregation was used for simulating the electric field. A comparison between the electric fields of segregation and uniform cases was conducted. Results show that the electric field of the segregation case is similar to that of the uniform case in the monopolar charging system. While in the bipolar charging system, the electric field of the segregation case can become different from that of the uniform case due to the bipolar space charge density in particle layers. The neutralization of the charges carried on large and small particles can result in the decline of the electric field. In the case with low net charges, the probability of the electrostatic discharge can be more than three times higher than that in uniform cases once the particle segregation happens. Moreover, the enhancement effect of the particle segregation on the electrostatic discharge can be stronger when the volume fraction of small particles is less than 75%. Reducing the charging efficiency of particles and the repose angle and avoiding particle segregation are preferable approaches to lower the risk of the electrostatic discharge.

Negative differential resistance and rectification effect of the benzoquinone molecules junction sandwiched between the graphene nanoribbon electrodes

Based on the first-principles calculation method combining the density functional theory (DFT) and the nonequilibrium Green’s function (NEGF) method, the negative differential resistance (NDR) and rectification effect of the benzoquinone molecules junction sandwiched between the graphene nanoribbon electrodes are systematically investigated. The current of the device with the central o-benzoquinone and p-benzoquinone molecule has been demonstrated to decrease with the increase of the bias voltage in the range of [± 0.9 V, ± 1.5 V] and [± 0.6 V, ± 1.1 V], respectively, exhibiting a significant NDR effect. In addition, the interesting NDR effect of the device with the central carbon (C) and nitrogen (N) connected o- and p-benzoquinone molecules has been observed in the bias voltage range of [0.9 V, 1.2 V] and [ $$-0.8$$ V, $$-1.0$$ V] , respectively. The current of the device with the central sulfur (S) and oxygen (O) connected o- and p-benzoquinone molecules should decrease with the increase of the bias voltage at the regime of [0.8 V, 1.0 V] while that should be forbidden when a negative bias voltage is applied, illustrating an interesting rectification effect, and the maximum rectification ratio is observed to be up to 57.85 and 55.85, respectively. The obtained NDR and rectification effect are physically explained from the integral of the transmission coefficient in the bias voltage window and the distribution of the real space charge density, and the demonstrated results are believed to be vital for the designing of the molecular switches, molecular rectifying devices and negative differential resistance devices based on benzoquinone molecules junction.

Fluid simulation model and analysis of partial discharge characteristics of tip defects

The tip discharge is modeled and the micro discharge characteristics are studied. The hydrodynamic model of tip discharge in transformer oil is established. The development process of streamer discharge under pulse voltage is analyzed. The distribution of space charge density and space electric field under different pulse voltage amplitude and rising edge is obtained. The numerical results show that: with the increase of applied voltage amplitude, the average velocity of streamer development changes more significantly with the same discharge spacing; the steeper the rising edge pulse is, the faster the average discharge development speed is and the larger the discharge radius is. At the same time, according to the change law of streamer morphology development under AC voltage, the discharge frequency is less, the amplitude is higher, and the phase distribution is narrow when the applied voltage is positive half cycle. When the applied voltage is negative half cycle, the discharge times are more and the phase distribution is wide, and the tip discharge has obvious polarity effect.

The structure of an electronegative magnetized plasma sheath with non-extensive electron distribution

In this paper, an electronegative magnetized plasma sheath model with non-extensive electron distribution is established, and the Bohm criterion affected by the non-extensive parameter q is theoretically derived. The ion Mach number varies with q. The numerical simulation results show that compared with electronegative magnetized plasma sheath with Maxwell distribution (q = 1), the sheath structures with super-extensive distribution (q < 1) and sub-extensive distribution (q > 1) are different. The physical quantities including the sheath potential distribution, ion density distribution, the electron density distribution, negative ion density distribution and the net space charge density distribution are discussed. It is shown that the non-extensive parameter q has a significant influence on the structure of the electronegative magnetized plasma sheath. Due to the Lorentz force, both the magnitude and the angle of the magnetic field affect the structure of the sheath, whether the electrons are Maxwell distributed or non-extensively distributed.

Calculation of Ion Flow Field of Monopolar Transmission Line in Corona Cage Including the Effect of Wind

In this work, the ion flow field of a monopolar transmission line inside the corona cage of a square cross-section is iteratively calculated concerning the effects of wind. The electric field distribution is solved analytically using the charge simulation method (CSM). Meanwhile, the upwind finite volume method (UFVM) with 2nd order accuracy is presented for the distribution of space charge density. Additionally, a dual mesh grid is established in the calculation domain, the interlaced geometric construction of the mesh assures a quick and effective convergence rate. In the final part, a reduced-scaled experiment is designed to examine the feasibility and accuracy of this approach, electric field and ion current density on the bottom side are measured by field mills and Wilson plates. The data numerically computed fits well with that acquired by measurement.

The effect of air pressure on the surface electric field intensity characteristics under negative DC corona discharge in a corona cage

The accuracy of surface electric field (SEF) is important for the research of corona discharge, both in numerical simulation and actual application. However, it is widely considered that the SEF is invariable after corona occurs (Kaptzov’s assumption). This theory makes corona study more convenient, but slightly inconsistent with the actual situation. In this work, the influence of air pressure on SEF intensity and distribution of space charge density under negative DC corona discharge is studied in corona cage via sound pulse method and maximum charge density ratio. The most important finding in this work is that when the voltage gradient is greater than the onset voltage, contrary to popular perception, SEF is not a fixed value and lower than the onset field intensity. And a linear negative correlation between the space charge density and the SEF intensity after the corona initiates is found for the first time. In addition, the SEF intensity has a decreasing trend with the applied voltage rising after corona initiates, and rises slightly with the increase of air pressure. The change of space charge density with applied voltage and air pressure is opposite to the change of electric field.

Humidity effects on the ground-level resultant electric field of positive DC conductors

The effects of humidity on the ground-level resultant electric field around positive DC conductors were studied both experimentally and numerically. Experiments were carried out in an artificial climate chamber, the results of which showed that the photon count and the ground-level resultant electric field strength both increased with increasing relative humidity. Numerical calculations for different values of relative humidity were carried out, including solutions of the positive corona inception voltage and the ion-flow field, for which a photoionization model and the upstream finite element method were employed, respectively. In order to analyze the effects of humidity, three main factors were considered: the ionization coefficient, the attachment coefficient in the photoionization model and the modified ion mobility of the charged water particles. The results indicated that, with increasing relative humidity, increasing values of the effective ionization coefficient were responsible for a reduction in the inception voltage, and the reduction reinforced the ground-level resultant electric field. Moreover, due to the charged water particles and the lower ion mobility with increasing relative humidity, the space charge density distribution was enhanced, which also strengthened the ground-level resultant electric field.