Chuntian Chen

The influence of interface phenomenon on removal of NO and SO 2 in corona discharge reactor with water film

In this paper, we describe the fundamental interface phenomenon between needle electrode and water, and experimentally investigated an effect of streamer polarity on the reduction of SO/sub 2/ and NO by using DC corona discharge plasma reactor. The reactor is composed of needle-plate electrodes that are placed in a glass container filled with the flue gas, (the plate electrode is immersed in the water). We emphasized studying the influence of water on the gas discharge. The experimental results show that the corona wind forming between high-voltage needle electrode and water by corona discharge enhances the cleaning efficiency of the flue gas because of the existence of water, and the cleaning efficiency will increase with the increase of applied DC voltage within a definite range. According to this effect a water film electrical corona reactor design is used to treat the simulated flue gas, and the result shows it gains not only the removal efficiency of SO/sub 2/ up to 98%, but also about 85% of NO/sub x/ removal under suitable conditions.

The Anti-Gravity Phenomena in EHD Heat Pipe Model

A heat pipe model of electrohydrodynamical (EHD) enhancement heat transfer has been designed and made. The insulating liquid was selected as working fluid and the copper wire whose diameter was 1mm was used as the high voltage electrode. The temperature in the inlet and outlet of both the vaporization section and the condensation section, the saturation vapor pressure inside this model were measured respectively under different applied dc voltage and different tilt angle, that is, the vaporization section was placed higher than the condensation section. The experiment results indicate that the circumfluence between the condensation section and the vaporization section was improved with the increase of the applied dc voltage. Such EHD enhancement heat transfer technology can be practically employed in the heat transfer engineering, and has some reference values for the investigation of heat pipes used in the case of anti-gravity.Copyright

About interior insulating design and rectifying of the 35kV power cable joints

The qualities of power cables joints play a crucial part in electrical systems providing high safety and reliability electricity power for consumers, and 35kV prefabricated cable joints up to now are popular products, so their interior insulating design principles, electric field distributions and dielectric coordination are in details represented in this paper, especially, using the finite element method for rectifying the joint structures, modifying stress cone profiles, furthermore, the calculating programs are created and the useful results are given.

The heat transfer effect of insulating liquids in EHD model pipe

An electrohydrodynamic (EHD) heat transfer enhancement model was designed and made. This model consists of three parts: vaporization section, adiabatic section and condensation section. The insulating liquid was used to be the working fluid and the copper-wire which diameter is I mm was used to be the high voltage electrode. The proper insulation coordination was designed as well. The temperature difference in the inlet and outlet of the coolant in the vaporization section and the condensation section, and the saturation vapor pressure in the model were measured under different dc high voltage and different tilt angle, that is, the vaporization section was placed higher than the condensation section. The experiment results indicate: Such EHD enhancement heat transfer technology can be practically employed in refrigerating and heat transfer engineering, and has special value for the investigation of antigravity heat pipes.

Improvement of NO removal rate by plasma reaction and Taylor cones in corona discharge reactor

The authors have developed a new type of corona discharge reactor combining plasma reaction with Taylor cones formed on the water surface, which improve the removal rate of NO in flue gas. A multi-needle to plate discharge geometry was used in this reactor. When the plate electrode covered with water film is energized by high voltage, a multitude of Taylor cones form and collapse randomly and continuously. The tips of the cones provide points for electrical discharge, which initiate active special generation. Experimental results showed that the combination of corona discharge plasma with Taylor cones is very effective method in NO removal, because NO was effectively oxidized to HNO/sub 3/ by plasma reaction and absorbed in the water. A very high removal efficiency of up to 80% was achieved with dc high voltage.

Endurance behavior of the SF/sub 6//N/sub 2/ mixtures experiment under AC and impulse voltages

The aims are to develop new kinds of insulating mediums being technically as well as economically attractive and fully understand the electronegative gas characteristic of endurance voltages, mechanism of partial discharge and widen their using areas in the high voltage system experiments. The article presents the experiment procedures, contents are involved in as follow: point-plane, point-point, co-axial cylindrical and co-centric sphere electrode systems, and industrial purity SF/sub 6/ and its mixture combining N/sub 2/ are filled into the experiment chamber in different partial pressure and applied the AC and impulse voltages in different pressures. The mechanism of initiated PD potentials and breakdown of the SF/sub 6/ and SF/sub 6//N/sub 2/ have been analyzed theoretically according to the molecular structure and physical characteristics of the electro-negative vases, the research works are helpful to develop and widen using fields of the SF/sub 6/ and its mixtures in high voltage engineering.

Metallic particle effect on the gas PD in co-axial cylinder electrodes

High voltage apparatus, for example GIS, insulated in a gas dielectric easily show partial discharge (in short PD), because of particle impurities, particularly some kinds of metallic particles. The PD failures are very dangerous and detrimental, because they could destroy the insulating system of the high voltage apparatus, result in a great deal of economic damage and imperil personal safety. Co-axial cylinder electrodes have been made to simulate the high voltage apparatus structure and service conditions under various applied voltages and existence of some types of metallic particles of different materials (for instance, copper, stainless steel, steel) with variable diameters, lengths and geometry. Through practical experiments in the laboratory, the relationships between PD inception voltage, PD quantities, length, materials and geometry have been obtained. Meanwhile the PD signals have been recorded by the measurement systems. The position of the particles shows different waveform and behavior, so that it could provide a way to detect the PD failure characteristics, location and attribution, and help to analyze, judge and assess the service conditions.

Effect of doped Co 2 O 3 on Dielectric Properties of ZnO Varistor

This paper researches the effect of doped Co₂O₃ on the dielectric properties of ZnO varistor. With the increasing mol percentage of Co₂O₃, the conductivity of ZnO grain reducing, the turning point of the voltage drops to a lower position of the current density. According to the analysis of capacitance and voltage, the decrease of grain conductivity can attribute to the carrier concentration decrease which is caused by the reduction of interstitial Zn_i or concentration of oxygen vacancy V₀. The doped Co₂O₃ will also reduce the dielectric loss of nonlinear resistance. The varistor may apply to metal oxide arrester.

Dynamic behaviors of SF 6 discharge process in short parallel-plate gaps

The two-dimensional hydrodynamic discharge model is presented based on the hydrodynamic mechanics theory and gas discharge characteristics, with a uniform applied field, during the discharge process of SF6 at atmospheric pressure, and it is established by adopting Poisson equation in conjunction with the continuity equations for electrons, negative and positive ions, besides, the photo - ionization is also considered in the proposed model. The Finite Difference-Flux Corrected Transport technique is used in numerical simulation of discharge process, in order to improve the accuracy and efficiency. Then the gap-space electric field distribution, space ions distribution are revealed from the microscopic mechanism, and the evolutions of the charged particles are obtained in detail, furthermore, the tempo-spatial critical point of the avalanche-to-streamer in this model is discovered, the influence of applied voltage and initial plasma charge density on the streamer characteristic are also investigated. The results show that the initial plasma charge density is closely related to the gradient slope of the gap-space electric field distribution and electron density distribution, meanwhile, the electric field strength, the propagation velocity and charge density of the streamer head increase with increasing applied voltage. Above results analysis can be in favor of further study of the discharge mechanism and provide the theoretical support for electrical equipment designed.

Dynamic behaviors of barrier discharge in air-dielectric at atmospheric pressure

With the purpose of study air-gap discharge phenomena at atmospheric pressure and deeply understanding behavior of barrier discharge in air-dielectric, the one dimensional and self-consistent fluid model of the gas discharge is established based on the electron and ion continuity and momentum transfer equations coupled to Poissons equation, then the micro discharge progress of the air-dielectric and its influence of the surface charge accumulation on dielectric barriers under alternating voltage are analyzed and demonstrated in detail. The models of numerical simulations of dielectric barrier discharges of a plane-parallel electrode arrangement covered with solid dielectric and comprising an air gap are made up, and the results of simulation are obtained for the case when the applied field in the gas exceeds its breakdown threshold and discharge current pulses can be formed, i.e. charge transfer in the gas phase takes place in the form of an electron avalanche discharge, simultaneously, the facts were found that the temporal and spatial distributions of the electric field, electron density and the ion density obtained in the electron avalanche discharge at atmospheric pressure could improve the air-gap discharge performance, furthermore, the calculated discharge current patterns are found to agree structurally and also to correctly display the predicted avalanche.