Journal of Electrostatics最新文献

The recent emphasis on environmental justice by the U.S. EPA has motivated the aerosol research community to develop innovative and cost-effective particulate matters (PMs) control technologies for subpopulations who are frequently exposed to indoor PMs. PM collection by electrostatic precipitation (ESP) has been proposed for indoor usage because it provides advantageous features over conventional fabric filters, such as lower energy consumption and being filterless. However, further research is needed before ESP can be used in indoor spaces, as ESPs suffer from low collection efficiency of submicron particles due to lower particle charging rates. Electrostatic particle clustering can potentially improve the shortcoming of ESPs if electrohydrodynamic (EHD) flow can be manipulated and controlled. A large-scale electrohydrodynamic (EHD) vortex flow was experimentally observed in the streamwise direction of a cylindrical ESP due to variation in current density. The objective of this study is to numerically characterize this novel large-scale EHD vortex flow for drag reduction and its potential ability to induce electrostatic particle clustering for submicron particles. The numerical model developed in COMSOL Multiphysics® solves the large-scale EHD vortex flow by coupling electrostatic physics with RANS k-$\varepsilon$ turbulent flow physics, involving three numerical domains. The results show that increasing the inlet velocity by one order of magnitude increases the maximum velocity near the discharge electrode by 1.25%. In addition, under negligible inlet velocity, the ionic flow dominates, leading to pulsated EHD/Re² numbers $\sim$ 1000 in the regions near the discharge and collection electrodes. The peak EHD$\#$ can be increased by 1.75% as the discharge voltage increases from 20 to 26 kV. The large-scale EHD vortex flow can modify the turbulent boundary layer and result in reduction in viscous drag near the collection electrode under low inlet velocity and high discharge voltage, which can potentially lead to prolonged entrainment of submicron particles for electrostatic particle clustering.

To establish an evaluation technique of the degradation degree of silicone rubber (SiR) surfaces, we first fabricated artificially degraded SiR surfaces. The fabrication process consisted of 5 steps and a 1-cycle test required 24 h. We fabricated the degraded SiR surfaces by a 1-cycle or a 2-cycle test. Next, the artificially degraded SiR surface was exposed to surface discharge (SD). The hydrophobicity recovery time on artificially degraded SiR surface increased with the increase in SD treatment time. It was found that the degradation degree of the SiR surface can be evaluated by hydrophobicity recovery time after SD treatment.

Electrostatic precipitators (ESP) are an effective means of reducing particulate matter emissions from biomass combustion. This study presents a comprehensive evaluation of the performance of an ESP integrated in a 240 kW wood chip boiler. The boiler-integrated ESP is commercially available and is evaluated in-situ using two types of wood chips, unlike previous studies, which mainly focuses on prototypes or lab-based constructions. The obtained results indicate a mass-based ESP efficiency of 94%–96%, surpassing previously reported values for small-scale boiler-integrated ESPs. Furthermore, the number-based ESP efficiency is 83%–92%, which is in line with values reported in literature. Despite the promising performance, the widespread adoption of integrated ESPs in small-scale appliances faces challenges due to the lack of financial, regulatory and energetic incentives. Nevertheless, the application of ESPs in this context remains crucial in addressing local air pollution and reducing the overall environmental impact of small-scale biomass combustion. To facilitate broader implementation, further research and policy initiatives are necessary. This study provides valuable insights into the true effectiveness of a small-scale ESP in mitigating particulate matter emissions.

The leader discharge is the primary process in long air gap discharge. However, there is currently a lack of detailed observation of the development process of leader discharge in equipotential live-line work (EPLW) gaps. Therefore, this study utilizes an electrical and optical synchronous observation platform to measure the key parameters of leader discharge in two typical EPLW gaps with gap distance of 2 m–3.5 m. Research results indicates that the worker's posture has significant effect on the leader characteristics of EPLW gaps. The longer the length of the worker's body-parts stretch out the bundle conductor and the small diameter of the discharge part is, the lower the leader inception voltage and inception current are. The average leader velocity of worker facing the tower is 5.93–7.67 cm/μs, however the leader velocity of worker facing the conductor is 7.43–9.59 cm/μs. The bending frequency of the leader channel of these two typical EPLW gaps both rise with the increase of gap distance. The axial deflection angle of worker facing the conductor gap is 27.87°, which is larger and more dispersive than that of worker facing the test tower gap. These test results can provide important references for determination of minimum approach distance and optimization of equipotential entering path for live-line work.

The aim of this study is to investigate the wettability control performance of a fluorocarbon-coated nanofiber membrane under the electrowetting process. The outcome nanofiber membrane was evaluated for chemical composition, morphology, surface roughness, and wettability. Through the electrowetting process, we give an estimate of some major effects as fine nanofibers, small liquid volume, low anode-cathode separation distance, and polar molecular droplets. We simply used COMSOL Multiphysics with finite element electrostatic mode to simulate electric field distribution changes for some different situations. The results of this study should assist in understanding the electrowetting on nanofiber membrane surfaces.

The presence of electric charges within liquid is relatively unexplored despite its role in electrochemical energy storage and industrial safety. Quantifying charge distribution in liquids and at solid/liquid interfaces is therefore crucial to the efficiency and longevity of devices. Over time, metrologies using stimulus to measure space charges in solids have been transposed to liquids. The stimulus disturbs electrostatic equilibrium to induces electrical response. This study builds upon measuring electric charges in the Electrical Double Layer (EDL) using the Pressure-Wave-Propagation (PWP) method. It presents how the pressure wave amplitude, the liquid conductivity and the liquid nature impact the electrical response.

Contact electrification (CE) is a physical phenomenon that occurs between two materials. When two materials with different electron affinity are contacted, electrons move along the contacting surfaces due to triboelectrification. The result of this effect is direct current. In this study, the triboelectric current is generated by the bindington energy generated by sliding a water drop on n-type, p-type and GaAs p-n junction. In addition, since the water drop is transparent, it is illuminated with 100 mW/cm² while sliding and tribovoltaic and photovoltaic effects are evaluated together. The fact that the current value obtained was in the order of microampere (μA) showed that GaAs can be used in triboelectric nanogenerators (TENGs).

High-voltage silicone insulators can be used in climatic conditions such as rain or fog since they are hydrophobic. However, water droplets lead to discharges, which reduces hydrophobicity of the silicone rubber which is, in turn, is a first step to failure of an insulator. To increase the resistance of the rubber to the discharges, it is necessary to study the discharges between droplets in detail.

The present work is devoted to the study of the loss of hydrophobicity of silicone rubber due to rolling droplets and discharges between them on the inclined silicone rubber sample under AC voltage of 35 kV. An experimental setup used in the work has been developed based on Dynamic Drop Test (DDT) and makes it possible to study discharges only between droplets, and avoid contact of droplets with the electrodes.

Simultaneous observation of droplets and discharges made it possible to distinguish characteristic events and to divide the loss of hydrophobicity into stages. Experiments showed that the behavior of the droplets changed gradually, while the discharges were observed only at the last stage. Presumably, the resistance of rubber to discharges is not the only factor that determines the time of loss of hydrophobicity. The very beginning of the process of loss of hydrophobicity should be investigated further.

This work focuses on applying the phenomenon of ion concentration polarization to design and investigate a micropump model that is a kind of electroosmotic micropump. Numerical study is conducted for ion concentration polarization in the manner that generates electro-osmosis flow and pumping effect. The formation of the extended space charge layer and the actions of the electric field upon this layer is applied to generate electro-osmosis flow to drive flow in the system. It is clarified that pumping effect can be enhanced by improving the geometry configurations. Multiple simulations are conducted to obtain an optimal micropump design.

The article deals with the solution to the increased level of environmental pollution by emissions of solid particles from small sources. The research aimed to build an efficient electrostatic precipitator directly in the combustion device, ensuring simple maintenance and low space requirements. During the measurements on the experimental equipment, the average production of particulate matter was measured with and without the use of an electrostatic precipitator. Three combustion modes were used during the measurements: minimum, optimal and maximum performance. The results of the measurements showed up to 52.3 % efficiency in removing particles from flue gases.