Journal of Electrostatics最新文献

Plasma jets are an atmospheric pressure plasma source that projects streamers outside the bounds of the plasma device. The electric field produced by these streamers can generate a current in the substrate before the streamer contacts the substrate. This displacement current is a strong function of the proximity of the streamer to the surface. We develop a basic model of the streamer traveling towards the substrate that can determine the streamer location and velocity from the measured displacement current. This simple approach shows good agreement with optical imaging equipment and can provide a means to rapidly quantify the streamer velocity.

Dielectrophoresis (DEP) is an effective technique for manipulating particles in microfluidic devices. The DEP force depends on the frequency and square gradient of the electric field, as well as the fluid and particle dielectric properties. An efficient system for manipulating particles can be designed by adjusting these factors. This study aims to develop an efficient microsystem for particle trapping using dual-frequency DEP force. The microfluidic system is divided into two parts of focusing and attracting. The negative DEP (nDEP) force in the focusing part concentrates particles near the microchannel axis. The positive DEP (pDEP) force in the attractive area then absorbs particles into the internal chamber via electrodes. In general, the main advantage of the present design is the maximum trapping of incoming particles (with a trapping rate of over 95%) regardless of their initial location. In this study, numerical modeling was first done in three dimensions to sort and trap the microparticles. Then, a microchip was designed, built, and tested in a laboratory to validate the results and confirm the microfluidic system behavior. Finally, a parametric study was conducted to figure out the best voltage range of the electric fields in the microfluidic system.

This study presents experimental results of the particle layer growth with the operation of a small-scale ESP as a flue gas cleaning method from domestic biomass combustion. The retention efficiency of the ESP is maintained above 90% for 40 h of operation, which is in agreement with its natural regeneration by partial collapses of the dust layer. The measurements of profile and thickness of the dust layer endorse the aforementioned collapses as discontinuous re-entrainment events that are also identified as abrupt peaks on the particle concentration at the outlet of the ESP and drops on the current values.

We derived theoretical formulations for the fluid threshold of conducting and insulating sand particles under an imposed electric field. Our analysis reveals a non-monotonic dependency of the fluid threshold on particle diameter, imposed electric field, and surface charge density. For conducting particles, electrostatic forces lead to a reduction of the fluid threshold by up to 31%. In contrast, for negatively charged insulating particles, electrostatic forces enhance the fluid threshold by up to 76%. Unexpectedly, electrostatic forces either enhance or inhibit the fluid threshold by up to 30%, depending on the imposed electric field and surface charge density.

Electrohydrodynamics (EHD) is a way to produce low energy-consuming airflow without moving components. The basis of airflow by EHD is corona discharge. A way to generate corona discharge is done, among others, via needle-type emitter electrodes whose shape and arrangement play a crucial role in the effectiveness of the discharge. Until now, the needle shape was chosen somewhat arbitrarily, although it impacts the energy consumption of the EHD process. We lack systematic studies on the impact of needle shape on the EHD discharge process and associated airflow to help engineers and scientists choose the best shape. This in-silico study screens the impact of the needle shape parameters on EHD performance in terms of electrical power consumption and airflow generation. The study aims to find the ideal EHD needle shape for unrestricted and confined flow. For this purpose, we test three different geometrical configurations. The first configuration is a free-flow single-needle configuration. The second configuration adds a dielectric nearby, which represents a needle enclosure. Lastly, a configuration including a dielectric and a converging nozzle is examined. All studies use a 2D-axisymmetric, fully automatized EHD physics-based model. The first set of parametric studies explores the inherent geometrical properties of the needle shape, like tip radii (10–250 $\mu m$), needle cone angle (10–70°), and needle diameters (0.5–2 mm). The second set of parametric studies investigates the operation conditions, such as the emitter-collector distance (10–40 mm), the nozzle contraction ratio (0.04–1), and the operating voltage (6–32 kV). The results of the free-flow configuration show qualitative agreement with experiments on existing needle products. The ideal energy-saving needle shape for free flow configuration features a short conical tip length (i.e., a large angle $\ge 30°$), a diameter of 2 mm, and a needle rip radius of 100 $\mu m$. The situation changes when a dielectric is present, and a sharp angle of 10° is favorable to reduce energy consumption. Since a dielectric inverts the optimal needle shape, it makes sense to customize it for a particular application in EHD airflow generation. We provide performance maps that can be used as design charts. This study is a guideline to optimize EHD devices further to reduce energy consumption and increase airflow speed.

Corona discharge low-temperature plasma technology has good performance in treating dust and removing gaseous pollutants. In this paper, the dust and SO₂ in the flue gas are removed by using the ground electrode atomization negative corona discharge device under the action of a magnetic field, and the discharge characteristics of the device, the removal efficiency of dust and sulfur dioxide, and its influencing factors are studied. The results show that the discharge characteristics and dust removal and desulfurization efficiency of the ground electrode atomization negative corona discharge under the action of a magnetic field are superior to the traditional l corona discharge and are almost affected by the extension of the operating time. Finally, the ground electrode atomization negative corona discharge under the action of a magnetic field is analyzed. The dust removal and desulfurization mechanism of corona discharge provide a reference for the development of dust removal and integrated desulfurization equipment.

Field emission is a well-known technology for generating electrons under vacuum conditions. Here we assess whether gated silicon field emitter microstructures, originally developed for use in space, can ionise air for electroaerodynamic propulsion and other applications. Electron range in air is compared to breakdown voltage over the atmospheric pressure range, to evaluate whether an operational region exists for which the geometry permits electrons to escape and ionise, whilst keeping the voltage low enough to avoid breakdown. An operational region is identified between 500–100 V for pressures corresponding to 0–20 km altitude. This offers low-power and low-mass operation in comparison to existing ionisation technologies. Carbon nanotube field emitters may offer enhanced performance over the silicon emitters. Field electron emission represents a new air ionisation technology which may be appropriate for light-weight, high-altitude aircraft propulsion.

The charge distribution within a hollow conducting cylinder with zero-thickness walls is calculated from the minimum potential energy ($U$) consideration. The surface charge density consists of a diverging term (Jackson, 1975) and a sum of Legendre polynomials with the coefficients determined from the minimum $U$ approach. The sum converges. This allows to express the capacitance in closed form. It is in agreement with Butler (1980). We present electric field lines inside and outside of the cylinder. An electric field pattern can be studied in detail. Most of the numerical analysis is done for the conducting cylinder of the length equal to ten radii. The surface charge density near the edges diverges; and in the middle, it is twenty five percent less than that of a uniformly distributed charge. The self-energy of the conducting cylinder is about 5 percent lower than that of uniformly distributed surface charge.

The life of power transformers faces a growing threat from space charge in oil-paper insulation. Many works explored space charge behavior in this system. This review examined hypotheses and measurement techniques. Findings from earlier studies helped understand space charge production and its impact on the oil-paper surface. The review discussed internal and external factors influencing space charge behavior. Experimental procedures offer technological advantages. Despite some understanding, current methodologies can't predict space charge consequences accurately. The review suggests developing a unique approach to comprehend space charge behavior in oil-paper insulation, safeguarding power transformer functions.

As for practical application of triboelectric nanogenerators (TENGs), corona discharge treatment (CDT) is often utilized further to enhance its power outputs by injecting charges. We report compositional analysis and corresponding triboelectric outputs of Poly(1,1,2,2-tetrafluoroethylene) (PTFE) based TENGs. PTFE and Al based TENGs with various PTFE film thickness are fabricated and their performances are measured with different CDT applied bias. XPS depth profile analysis reveals the relation of triboelectric outputs and depth of oxygen ions. Our discovery may give insight in the future development of high performance TENGs using CDT.