Nowadays, dielectric barrier discharge (DBD) has been widely used in many fields, such as material surface treatment, environmental protection, plasma etching and ozone synthesis, because of its moderate electron density, temperature and energy. To study the DBD in atmospheric air, a one-dimension fluid model is presented in this paper, which uses a mixture of nitrogen and oxygen to simulate the air environment. The model is used to numerically investigate the influences of the amplitude and frequency of sinusoidal AC voltage on the dielectric barrier discharge characteristics. The voltage amplitude range from 9 kV to 15kV, and the voltage frequency range from 8 kHz to 12 kHz. The results clearly show that the DBD in atmospheric air is strongly affected by the amplitude and frequency of applied voltage. The average electron volume density reaches 10 17 /m 3 , which is consistent with the experimental value of atmospheric pressure dielectric barrier discharge. In addition, when the applied voltage frequency is 10kHz, obvious discharge current peaks can be observed at 11kV, and the discharge current shows single peak every half cycle as well as apparent positive and negative asymmetry. The amplitude of discharge current peaks varies from tens of milliamps to a few amperes with a pulse width of hundreds of nanoseconds. However, if the frequency of the applied voltage is reduced, multiple peaks can be observed in each cycle of discharge current. Furthermore, this paper also studies their influence on the electric field strength of the air gap, the surface charge of the dielectric, and the distribution of charged particles in the discharge region. Finally, the formation mechanism of multi-peak discharge current is analyzed.
Based on COMSOL Multiphysics, dielectric barrier DISCHARGE (DBD) at atmospheric pressure in nitrogen and oxygen environment was investigated in detail. Due to the geometric symmetry of discharge, a one-dimensional model was introduced to simplify the simulation process. The results showed that compared with nitrogen, the discharge current in oxygen displayed more symmetric waveform, which indicated simultaneous existence of positive ions and negative ions owing to the gas electronegativity. And at the maximal discharge current, there are obvious minimum point of electrical field curve in oxygen discharge, owing to the density difference of positive and negative ions at different position of discharge gap. It also proves that the gas electronegative could lead to greater electron density gradients, higher discharge power and less uniform discharge. The electrical field curve at the moment of maximal current is selected as the characteristic parameter to distinguish gas property, electropositivity or electronegativity gas. The electrical field appear a minimum point in discharge gap, presented the shape of letter V, in electronegative gas discharge. According the mentioned characteristic curve, it is useful to determine the electronegativity of working gas.
Aircraft icing poses a significant safety risk and, in severe cases, can result in a flight accident. The anti-icing and deicing technology based on the surface dielectric barrier discharge (SDBD) plasma actuators has the advantages of fast response, simple structure, easy deployment, and no aerodynamic loss. This paper summarized the effects of power, structure, dielectric and other parameters of SDBD actuators on anti-icing and deicing performance, and analyzed anti-icing and de-icing mechanisms of SDBD actuators under the synergistic effect of thermal effects and aerodynamic airflow. In addition, development prospects and research directions of the SDBD anti-icing and de-icing technology in aspects of anti-icing and de-icing rules, actuator ontology and anti-icing and de-icing diagnosis technology were given.
Power transformer is one of the key equipment of the power grid, and its operation reliability directly affects the safe and efficient operation of the power grid. The main cause of transformer accidents is insulation failure. Therefore, aging characteristics and mechanism of oil-filled transformer oil-paper insulation has important academic value as well as application significance. Based on the quantum chemical simulation, this paper systematically studies the physical parameters of the transformer insulating paper molecules and their dissociation process. The results showed that as for the cellulose molecule with a degree of polymerization of 10, the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital was 4.2038 eV. As for its repeating unit cellobiose, the 1,4-β-glycoside bond would be broken firstly, whose equilibrium bond length was 1.41813 Å. Moreover, the bond energy was 54.18 kcal/mol, and the energy of the corresponding equilibrium configuration was -1298.2662 Hartree. Subsequently, the cellulose would generate a large amount of D-monoglucose monomer and some free radicals. The results in this paper contributed to establishing the model and the mechanism of oil-paper insulation aging process, and further identifying the aging degree of transformer and improving the reliability of transformer operation.
Carbon emission reduction, as one of the core drivers of energy transformation, can effectively promote clean energy development and mitigate the global greenhouse effect. In the context of the development of the global energy internet, large-length HVDC cables for long-distance and cross-regional power transmission occupy an essential position in the power internet. However, the accumulation of electric charges in the large-length HVDC cables is inevitable, and would threaten the safe operation of the cables, reduce their service life and might even cause insulation fault. Therefore, it is indispensable to study the electric charges in large-length HVDC cables. This article provides a brief overview of electric charge generation, measurement and dissipation in HVDC cables, and summarizes the important research issues in recent years, which can provide informative guide for both online monitoring and life assessment of large-length HVDC cables.
Based on high pulsed power technology, electrical explosion has been utilized to generate controllable underwater shock waves with high pressure. To further magnify the amplitude, a developing technique that using energetic materials ignited by the plasma of microsecond wire explosion has been put forward. To study the plasma material interaction, we investigated the mixture powders of ammonium nitrate, ammonium perchlorate and aluminum in two mass formulas (A: 45%AN/40%AP/15%Al, B: 65%An/25%Ap/15%Al) which were ignited by exploding tungsten wire (diameter 0.3 mm and length 60 mm). Results showed that the shock wave pressure waveforms of different formulas were quite similar. When the charge mass was 30 g, the area impulse of the shock wave generated by the B load was $15.7 \text{MPa}\cdot \mu \mathrm{s}$ larger than that of the A load, while the peak pressure was only 0.35 MPa lower than that of the A load. Since the explosion heat of AN was −365.5 kJ/mol, and that of AP was −293.72 kJ/mol, assuming that the reactants react completely, the volume of gas produced per unit mass of AN would be 1.19 times that of AP, and the explosion heat would be 1.83 times that of the latter. Therefore, the B formula with higher AN mass fraction was more powerful. Moreover, as the mass of the charge increases, the area impulse showed a certain increase but gradually saturated. This is probably because with the mixture powders gradually compacting, the internal air gap was reduced, and the reaction tended to a negative oxygen balance. Therefore, the reaction failed to proceed to the final decomposition product. Finally, a simple AN/AP/Al load mass and formula scheme suitable for microsecond exploding wire plasma was proposed.
Dielectric barrier discharge (DBD) can generate low temperature plasma under atmospheric pressure, with great research value and bright application prospect. Compared with filamentary DBD, homogeneous DBD has obvious advantages such as the mildness and uniformity of discharge. This paper provided a brief review of DBD research history and paid considerable attention to homogeneous DBD at atmospheric pressure. By summarizing the latest diagnostic technology and numerical simulation methods, this paper reported some of the most important results of DBD characteristics and mechanism in recent decades. In addition, typical DBD plasma applications in biomedical fields, food safety, environmental pollution control were introduced. Technical problems that came up in present DBD research and application development were analysed. And the outlook for the DBD technology was given.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
