Electrification Characteristics Research Articles

Contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation

The issue of electrostatic safety in liquid hydrogen systems has garnered increasing attention, especially concerning the potential threat of electrostatic explosions due to the collision-electrification phenomenon of solid oxygen particles formed after air leakage in liquid hydrogen pipelines. To delve into the contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation, a mathematical model based on the computational fluid dynamics-discrete element method (CFD-DEM) two-phase flow dynamics has been developed. This model integrates the Hertz contact theory for describing particle collision processes and the condenser model for describing particle collision-electrification. The reliability of this model has been validated in existing literature through its ability to capture the flow characteristics of two-phase flow and the electrification characteristics of particle groups. Using density functional theory to compute the solid oxygen work function and considering the low-temperature properties of liquid hydrogen, a series of numerical studies on the flow sedimentation and electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen pipelines have been conducted. The results indicate that particles carry negative charges after colliding with stainless steel pipe walls, with single charge exchange magnitudes of approximately 10−12C for particle-wall continuous collision processes and 10−14C for particle-particle collision processes, resulting in particle charge-to-mass ratios on the order of tens of μC/kg at the outlet interface. The impact of electrostatic forces on particle motion is significant and cannot be overlooked. Furthermore, the effects of velocity, particle diameter, and pipe diameter on particle charge characteristics have been thoroughly analyzed. At low flow velocities, severe particle settlement occurs, leading to increased collision frequency between particles and walls and significant charge accumulation. Increasing flow velocity can mitigate particle settlement and reduce charge levels. Changes in particle and pipe diameters have a minor impact on particle settlement but can increase single charge amounts with larger particle diameters and intensify particle charging with reduced pipe diameters due to shortened radial travel distances, leading to increased collision frequency. Our study meticulously illustrates the charge characteristics of individual particles and particle groups, providing a theoretical basis for assessing the electrostatic safety of liquid hydrogen transportation systems under extreme conditions.

The impact of aerosols as ice nucleating particle on microphysics and electrification in the cumulus model

Here, a heterogeneous ice nucleation parameterization associated with aerosol acting as ice nucleating particle (INP) was implanted into a two-dimensional numerical cumulus model. To explore the impact of INP on microphysical and electrical processes, a comparison was conducted with the original approach, which employs an empirical formula. Simulation results indicate that INP greatly impacted microphysical evolution in the heterogeneous ice nucleation process, reducing total liquid precipitation amounts and causing a slight precipitation delay, as well as increasing the diameter and mixing ratio of ice crystals and the expansion of the vertical distribution of ice crystals. This led to a notable change in electrification in thunderstorms. The increase of ice crystal diameter was the dominant contributor to the enhancement of electrification using the new parameterization. Additionally, unlike the structure of thunderclouds in a mature stage, which always retains a normal dipole structure adopting the empirical formula, a tripole structure developed a lower positive charge, and the polarity inversion with upper negative and lower positive charges occurred when the new parameterization was adopted. This predominately was the result of abundant ice crystals present below the reversal temperature. The electrification characteristics of thunderstorms may have a close connection with lightning activity. It has been found that charge structure changed significantly in the two cases, with the tripolar charge structure facilitating the production of inverted intra-cloud (IC) flashes and negative Cloud-to-ground (CG) flashes simulated by the new parameterization; additionally, clouds simulated using the empirical formula may be able to develop normal IC lightning and positive CG flashes. Therefore, it will be very meaningful to obtain greater insight into the characteristics of thunderstorms electrification in cumulus model with aerosols.

Dielectric materials for high-performance triboelectric nanogenerators

Triboelectric nanogenerator (TENG), as a micro-nano power source or self-powered sensor, has shown great prospects in various industries in recent years. The TENG output performance is closely related to the contact electrification characteristics of the triboelectric dielectric material. Herein, we first introduce the relevant fundamental theory and models of TENG and tribo-dielectrics. Then, we introduce the material selection, modification method (including surface modification and bulk modification) and structural design strategy of TENG dielectric material. Surface and bulk modification mainly involve surface roughness control, surface functional group regulation, and optimization of dielectric parameters. In terms of dielectric structural design, the principle of charge transport, trapping, and blocking layers as well as typical techniques to improve the dielectric properties of TENGs through multi-layer structures are highlighted. Finally, challenges and directions for future research are discussed, which is conducive to the fabricating of high-performance TENG dielectric materials.

Simultaneous separation and analysis of multiple doxorubicin hydrochloride liposomes forms in serum by circular nonuniform electric field gel electrophoresis

BackgroundLiposomal formulations have traditionally been considered the most therapeutically effective drug delivery systems (DDS). However, their pharmacokinetics study and efficacy assessment are still challenging given size heterogeneity and unknown forms in vivo. The pharmacodynamic evaluation that solely analyzes total drug concentration is unfit for the liposomal formulation study. Hence, it is crucial to develop effective strategies for the separation and analysis of different forms of liposomal formulations in order to contribute to the study of pharmacokinetic profiles associated with both liposome-incorporated and non-liposomal drugs. (84) ResultsA laboratory-built circular nonuniform electric field gel electrophoresis (CNEFGE) system was developed in this study for simultaneous separation and analysis of various forms of doxorubicin hydrochloride (DOX•HCl) liposomes. Liposomes were effectively fractionized based on their size and higher concentration in situ in the concentration zone, obtaining liposome recovery >95 % and a 3.04 concentration factor. It was found that the technique could be used to evaluate not only the size distribution of liposomes but also the drug loading capacity related to size. The charge-to-size-based separation mechanism has also allowed the simultaneous separation of liposome-entrapped drugs, protein-bound drugs, and free drugs in various forms, and the technique has been successfully employed in serum. Moreover, the quantification analysis of liposomes incubated with serum for 72 h showed that the proportion of the ratio of DOX•HCl in liposome-entrapped drugs, protein-bound drugs, and free drugs is approximately 97:2:1. (143) SignificanceUsing the separation principle of gel electrophoresis and the electrification characteristics of drug carriers, this study developed and implemented an efficient approach for the simultaneous separation and concentration of multiple forms of drug liposomes in vivo. This approach offers a wide range of applications in the pharmacokinetics, efficacy, and safety evaluation of drug carriers and liposomes. (56).

Contact Electrification Characteristics of Polytetrafluoroethylene and Metal

In industrial production, the contact electrification phenomenon between materials will cause equipment damage and bring potential safety hazards to personnel, so it is necessary to study the contact electrification mechanism of materials. In order to explore the contact electrification characteristic mechanism between polytetrafluoroethylene and brass, aluminum alloy, a contact separation electrification test platform was built to pay attention to the change rule of surface potential of composite materials under contact pressure, environmental relative humidity, temperature and material temperature difference. The test results show that the surface potential first increases and then decreases slightly with the increase of contact pressure, and the surface potential is stable when the contact pressure is greater than 7 KN; The contact electrification of materials decreases with the increase of relative humidity; At 15°C ~35°C, the material surface potential is proportional to the temperature; With the temperature difference between the two test materials becoming larger, the contact potential shows a law of first increasing and then decreasing. Through the analysis of the contact electrification characteristics of materials under different conditions, it can provide a direction for further research on the contact electrification mechanism and industrial electrostatic protection.

Flow electrification characteristics of liquid hydrogen in pipe flow

Flow electrification occurs when a dielectric liquid flows along the wall surface, and it may cause electrostatic hazards such as spark discharges. Flow electrification issues of liquid hydrogen should be carefully treated since its low electrical conductivity and dangerous flammability. In this study, flow electrification characteristics of liquid hydrogen in pipe flow are numerically investigated. A theoretical model coupling the electric field and the flow field is introduced to govern the behaviour and distribution of charges, and an interface discharge model is adopted to describe the charge transfer boundary condition. The theoretical model is validated by comparing the simulation with experiment data, and the results show a good agreement with the averaged related deviation below 10%. The result of a common case, with flow velocity u of 1 m/s, pipe radius a 0.01 m, and length L 1 m, shows that the charge density, streaming current, and the electric potential of liquid hydrogen flow are in the magnitude of 10−12 C·m−3, 10−16 A and 10−2 V, respectively. Flow parameters, including flow velocity and pipe size, have a certain effect on the flow electrification characteristics of liquid hydrogen flow. By dimensionless parameterization, it is found that Reynolds numbers (Re), r/a, and x/a are exactly three orthogonal parameters determining the charge density distribution. Furthermore, the effects of electrical conductivity on the distribution of charges and charge dissipation have also been discussed. Finally, the safety assessment of the liquid hydrogen transportation system has been discussed, with extra consideration of the impurities and gas-liquid two-phase flow regime. To sum up, this work presents an in-depth and comprehensive insight into the flow electrification of liquid hydrogen flow, which is of great significance to the transportation safety of liquid hydrogen.

Research on nano H2/O2 bubble generating mechanism and characteristics.

In this research, electrolysis water is used to produce hydrogen and oxygen for carrying out the vertical cutting through high-speed water in order that the bubbles will be refined for generating the nano H2/O2 bubble liquid. In the meantime, a Nanobubble Generator is developed to verify the basic characteristics of the produced nano H2/O2 bubbles. Its purpose is to identify the maximum concentration of bubbles in the nano H2/O2 bubble liquid, the bubble production efficiency and bubble electrification characteristics as well as the effect of reducing the pipe flow friction resistance together with the characteristics of nanobubbles containing varied gases. By verifying the nano H2/O2 bubbles, it is hoped that the flowing rate of the hollow electrode can be elevated.

Tracking Spatiotemporal Patterns of Rwanda’s Electrification Using Multi-Temporal VIIRS Nighttime Light Imagery

After recovering from the Rwanda Genocide in the last century, Rwanda is experiencing rapid economic growth and urban expansion. With increasing demand for electricity and a strong desire to achieve the Sustainable Development Goals (SDGs), it is significant to further investigate the electrification progress in Rwanda. This study analyzes the characteristics of electrification in Rwanda from 2012 to 2020 using VIIRS nighttime light imagery. Firstly, by analysis of the nighttime light change patterns on a national scale, we find that the electrification in Rwanda is seriously unbalanced, as electrification progress in Kigali is much faster than that in the rest of the country. Secondly, there is a common phenomenon where power grid expansion in Rwanda fails to keep pace with rapid urbanization, especially in areas with an inadequate electricity infrastructure foundation. Quantitatively, original electricity infrastructure level shows a positive impact on the grid access of new settlements, with an R2 value of 0.695 in the linear regression. In addition, new settlements inside the urban boundary tend to achieve more extensive grid access compared to those outside the boundary. Finally, the grid access rates are calculated on multi-spatial scales. By comparing the calculated results with the official electricity access rate data, we analyze the development of off-grid access in Rwanda. The results imply that, since 2016, off-grid access has rapidly developed in Rwanda, especially in the rural areas, playing an important role in achieving the SDGs.

Research on the relevance of flow electrification characteristics under AC and DC voltages

Research on the relevance of flow electrification characteristics under AC and DC voltages

Decarbonizing rural residential buildings in cold climates: A techno-economic analysis of heating electrification

Given the need for decarbonization of the heating sector and the acute need of a propane replacement in the U.S. Upper Midwest, this study quantifies the techno-economic characteristics of sustainable heating electrification in isolated rural, residential buildings in cold climates without natural gas supply. Archetypal buildings are modeled under four levels of electrification. At each electrification level, a parametric solar photovoltaic (PV) sizing analysis is performed and the total life cycle cost, renewable fraction and greenhouse gas (GHG) emissions are calculated based on the primary energy supply for each building type. Cost optimal solutions are stress-tested with multi-dimensional sensitivity analyses. The results show that the total life cycle cost favors heating electrification in all cases and combining PV with heat pumps can reduce residential building GHG emissions by up to 50% immediately. This effect will grow over time, with over 90% reduction of building emissions if renewable energy targets are met. In using primary energy and emissions along with the multi-dimensional sensitivities, this study unique demonstrates the complex techno-economic interactions of PV and heat pumps. It is concluded that electrification is an economically viable decarbonization method for cold climates both now and in the future.

Study of Power Reliability and Power Quality Problems of the Ethiopian-Djibouti Railway Distribution Networks

The structure of railway electrification system is a single-phase line, it uses power electronics devices and has a time varying load characteristic. This is a cause of considerable current unbalance, harmonics and variable reactive power consumption. This usually leads to power quality problems affecting the proper operation of the equipment. Because of the train's unique operation and electrification characteristics, power quality has been a major problem in railway networks. Throughout the history of railway electrification, many research were dedicated to power quality studies. A variety of power conditioning devices have been explored and deployed to traction systems. In this paper, a power quality problem investigation is done by evaluating and measuring major power quality parameters to confirm the mentioned problems on the Ethio-Djibouti railway line. The power quality quantities are measured using Chauvin Arnoux CA 8335 device and relevant data for power quality analysis are extracted using POWER log 5.8 software. Moreover, the power reliability is also evaluated for the same railway network by considering two substations, respectively the Hurso and Adigala substation. The power reliability studies are carried out by considering the recorded outage data due to Overvoltages for a period of one year. The measured data indicates a low power factor which even amounts 0.2, a maximum current unbalance values of 70% and harmonic distortion of 50%. The longest power outage due to over-voltage was 202 hours in January at Adigala substation with a power supply availability of 0.70 p.u in the 2020 years.

Theoretical and Empirical Analysis on the Transformation of Energy Consumption New Mode

The innovation of energy consumption modes plays an important role in solving energy development problems of China. This paper proposes a theoretical system for the transformation of energy consumption modes. Through the analysis of four elements of energy consumption mode, and their internal and external influence factors, four types of energy consumption new mode are derived, namely, integrated, sharing, intelligent and green patterns. These new modes present the features of digitalization, marketization, high efficiency, electrification and cleaning in the future. Finally, a transformation analysis index system is built to evaluate and prospect the future energy consumption modes. The new energy consumption modes in the future show the features of ‘technology before the market’. The main features of energy consumption modes are digital and efficient in the early stage. In the later period, the characteristics of cleaning, marketization and electrification are obvious.

Effects of space charge on flow electrification characteristics under DC voltage

An closed oil circulating system with plane electrode was built to study the effect of space charge on oil flow electrification under DC voltage. The results reveal that with the increase of applied voltage, the streaming current was always enhanced. However, the polarity of streaming current depends on the sample configuration. If the negative high voltage electrode was exposed to oil layer, streaming current was negative. Otherwise streaming current had a tendency to be positive as applied voltage increased. In experimental model without exposed electrode, the polarity of streaming current was always positive. And the amplitude of streaming current was related to the number of insulating papers placed under electrode. More craft papers placed under negative high voltage electrode led to the increase of streaming current. Based on the bipolar transport model, a new simulation method is proposed to study the effect of charge injection and transportation on flow electrification under DC voltage. The simulation results agree well with the experimental result.

Analysis and research on the man-machine dynamics behaviour coupling mechanism of the super miniature electric vehicle

Safety, energy saving and environmental protection are the three mainstream directions of current automobile industry research. The super miniature electric vehicles (SMEVs) with their lightweight, miniaturisation, electrification, energy saving and environmental protection characteristics will be developed rapidly and popularly in the city road traffic in future. But the mass and size are reduced in the super miniature electric vehicles, to a certain extent, which may affect the cars' performance handling, such as stability, security and comfort. In this paper, the SMEVs market prospect is analysed firstly, next the necessity of research on the vehicle man-machine dynamics behaviour coupling mechanism is discussed. Finally the paper puts forward that the driver-vehicle closed-loop system, driver's seat posture change dynamic system and virtual human body model research are important for the man-machine dynamics coupling research to improve the performances of the SMEVs.

Flow electrification characteristics of oil-pressboard insulation under ac superimposed on DC electric field

Converter transformer plays an important role in the HVDC transmission system. The valve side insulation in converter transformer withstands AC superimposed DC electric field during operation. In order to investigate the flow electrification characteristics of oil-paper insulation under the AC superimposed DC electric field, an oil-paper tube model with concentric cylindrical electrode geometry was built in laboratory. Experiment study on flow electrification under DC electric field was carried using the closed oil circulating system, and the influence rule and mechanism of amplitude of AC superimposed DC electric field, the DC component ratio and oil flow velocity on the flow electrification was analyzed. The experiment results demonstrated that influences of oil flow velocity and amplitude of applied voltage on streaming currents were related to temperature. At low temperature the streaming currents increased linearly with flow velocity and amplitude of applied voltage. Increase the DC component ratio enhanced the streaming currents. At high temperature the streaming currents increased exponentially with flow velocity and showed peak effect with amplitude of applied voltage. The peak point voltage decreased with the DC component ratio. The theoretical analysis based on the experiment results demonstrated that ions generation speed at the oil-paper interface depended on the dissipation speed of positive and negative ions. Saturation of negative ions migration current in the paper and leakage current at the outer electrode lead to peak effect of streaming currents. Changing of temperature can influence the flow electrification characteristics by affecting the ions migration speed and the electric field distribution in the insulation.

Resistance characteristics and electrification characteristics of GIS epoxy insulators under DC voltage

Now that gas insulated switchgear (GIS) for ac systems are becoming increasingly compact as specifications are rationalized, more consideration of their insulation characteristics for residual dc voltage is required. Furthermore, with dc power transmission technology drawing more and more global attention, clarifying the insulation characteristics of GIS for dc voltage is increasingly important. In this paper, to understand the insulation characteristics of epoxy resin, which is widely used for GIS insulating spacers, factors determining the resistivity of the epoxy insulator surface layer under dc voltage were initially investigated on an experimental basis. Consequently, it emerged that the bulk resistance was more dominant than the surface resistance for the dc resistance of epoxy resin due to the dependency of the test sample resistance value on their radius. Since the electric field might be concentrated if some part of this insulator surface layer showed non-uniform resistivity, the influence of the curing agent, one of the potential causes of this non-uniformity, was subsequently investigated with its content as a parameter. As a result, the volume resistivity in the long-term region was likely to decline or vary for epoxy resin containing less curing agent due to the presence of numerous polarized components unreacted with curing agent. In addition, the presence of micro protrusions or similar, if any, on the insulator surface or electrode is considered to cause electrification due to the concentration of electric field on the surface layer. Accordingly, the relationship between their surface roughness and electrification level was investigated using gaps between insulators or an electrode and an insulator facing each other, respectively. Consequently, where the surface roughness of the insulator or electrode was high, a current component with a large damping time constant, considered attributable to electrical charges moving across the gap, appeared after the charging current components and an electrification condition was observed.

Electrical characteristics of natural and synthetic insulating fluids

Mineral oil with high insulation performance and cooling capability is currently used for oil-immersed transformers. However, mineral oil is derived from petroleum and thus is a limited resource. In a search for mineral oil substitutes, we investigated the characteristics of silicone and ester oils. The electrical performance was assessed in terms of the breakdown and streaming electrification characteristics and the volume resistivity. The burning characteristics of each oil type were also investigated. The temperature dependence of the breakdown voltage in an oil unit and the surface breakdown characteristics in a composite insulating system comprising an insulating oil and an oil-immersed insulator were determined. We also investigated the temperature dependence of the charge density in oil. The charge density in silicone and mineral oils increased with temperature, with maximum values at ~ 100°C and ~ 60°C, respectively. By contrast, the charge density in ester oil decreased with increasing temperature and was maximum at ≤30°C.

Effect of the Addition of Benzotriazole on the Streaming Electrification Properties in Transformer Oil

Accidents can occur as a result of streaming electrification when transformer oil is used as an insulating oil in large ultra-high voltage transformers. Methods for adding a streaming electrification inhibitor to reduce the streaming electrification has been studied extensively. In this paper, in order to develop a method for reducing streaming electrification effectively, 4 different specimens were prepared by the addition of benzotriazole (BTA) to a virgin specimen with constant stirring. The specimens were examined to determine the appropriate amount of BTA addition that would suppress the streaming electrification most effectively. The results showed that the streaming electrification characteristics of the specimen in the streaming transformer oil were best when the amount of BTA addition was about 10 ppm. The streaming electrification current was reduced by adding 30 ppm BTA until the temperature reached 65°C. The polarity of the streaming electrification current was negative when the temperature exceeded 65°C. Therefore, the streaming electrification current, which can be a cause of transformer accidents, can be suppressed in large ultra high voltage transformer oil. This paper reports on the optimal amount of BTA addition and the best conditions for controlling the streaming velocity of transformer oil.

Comparison of the insulation characteristics of environmentally-friendly oils

We have investigated the performance of silicone oil as an insulation medium with the aim of developing environmentally-friendly, flame-retardant electric power equipment. In this paper, the insulation characteristics of silicone oil and ester oil, which is the alternative insulating oil candidate, have been investigated and compared. The insulation characteristics examined in this paper are the streaming electrification characteristics including electrification phenomena generated when an insulating oil streams, dielectric breakdown characteristics with increasing temperature and the surface breakdown characteristic when the insulator is placed between electrodes. The range of temperature investigated was 30 to 130 °C. Both kraft and aramid paper were used for the insulator. In the comparison between silicone and ester oil, it was found that the insulation performance of the ester oil was better than that of the silicone oil. We have considered possible mechanisms for these results.

Breakdown Characteristics and Streaming Electrification Characteristics of Flame Retardant Silicone Oil

We have investigated the performance of the silicone oil as alternative oil to the mineral oil that is used as an insulation medium of the oil immersed transformer. There are various methods of evaluating the performance, we especially investigated the breakdown characteristics and the streaming electrification characteristics. In the breakdown characteristics, the insulation performance under the influence of changing the temperature, and the electrode shape was investigated. Moreover, the insulation performance in the composite insulation system that was composed of the insulation oil and the oil immersed insulator was investigated. From these results, we found that in the oil gap model, the breakdown voltage of silicone oil was lower than that of mineral oil by 15%. In contrast, in the composite insulation system, breakdown voltage of combination with silicone oil is higher than that of combination with mineral oil. In the streaming electrification characteristics, the difference of the amount of electrification under the influence of changing the kinds of solid insulators and the temperature was investigated. As a result, we found that silicone oil has the maximum of the amount of electrification at a high temperature compared with mineral oil.