Jiaxiang Yang

Effect of water on sulfur dioxide (SO2) and nitrogen oxides (NOx) removal from flue gas in a direct current corona discharge reactor

A direct current (dc) corona discharge reactor composed of needle-plate electrodes in a glass container filled with flue gas was designed. To clarify the influence of water on discharge characteristics, water was introduced in the plasma reactor as electrode where plate electrode is immersed, under the application of dc voltage. Experiment results show that (1) corona wind forming between high-voltage needle electrode and water by corona discharge enhances the cleaning efficiency of flue gas due to the existence of water and the cleaning efficiency will increase with the increase of applied dc voltage within definite range and (2) both removal efficiencies of NOx and SO2 increased in the presence of water, which reach up to 98% for SO2, and about 85% for NOx under suitable conditions. These results play an important role in flue gas cleanup research.

Study of the influence of injected charge on streaming electrification

In this paper, the influence of injected charge on streaming electrification of transformer oil has been investigated using a combined model. The experimental results reveal that there are relations between the injected charge, the charge density and the leakage current, and the polarity effect of injected charge exist in the influence on streaming electrification. The influence of injected charge is attributed to the interaction between the electric double layer and the injected charge. The effect of oil velocity on injected charge has been analyzed also.

Experimental investigation of surface charge distribution on insulator in vacuum under impulse voltage

In this study, the surface charge distribution on insulators in vacuum has been investigated under an impulse voltage (0.7/4 /spl mu/s) with a non-uniform field electrode system. The insulators studied were 99.9% alumina specimens with the shape of right circular cylinders about 5 mm thick and 20 mm in diameter. Using an electrostatic probe with a shield in the form of capacitive voltage divider that was connected to an electrometer, the surface charge distribution on insulators were measured. The applied impulse voltage, and the corresponding current waveforms, the signal of luminosity were also observed during the voltage application. We investigated the surface charge distributions at different impulse voltage levels, at different shot number with a same voltage level, at the situations after a flashover occurred. Based on the experimental results, we found that the surface charge density on the insulators is increased with the increase of the applied voltage, the shot number has little influence at the same voltage level, and the charge density is decreased a lot after a flashover occurs. Its also found that the increase of charge density is often accompanied by preflashover events.

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

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.

Wavelet transform denoise of PD signal on coaxial cylinder electrodes

The paper presents the basic principle and method of dealing with PD (partial discharge) signals using wavelet transform. It is demonstrated that wavelet transform is a useful and effective tool for extracting PD pulse signals from noise. It makes more certain that failures caused by the PD which happens in the GIS, GIC and GIL, could be precisely measured, predicted and monitored.

Research on plasma explosion of metal wire in water

If a high-density energy is fed into a metal wire in water from high-pulsed power source, the metal wire will explode in a short time in a plasma state. The generated shock wave by the plasma explosion will spread out to arbitrary directions. By using a mechanical binding device or an electromagnetic binding set, the explosion process can show a propulsion effect in a presented direction. In the experiment, steel wires with different diameters and lengths are used as conductive metal load in plasma explosion. A model tube with a bottom shape of paraboloid of revolution is used as mechanical binding device to restrain the shock wave from shooting in a certain direction. The experimental results show that the pressure at sensor location increases with the energy fed into the load and decreases with the distance from the sensor to the explosion source. The energy pumped into the load is larger, the longer the acting time of pressure. It can also be viewed that the highest amplitude of pressure appears at the first peak of shock wave, and the followed peaks decreases quickly. The experimental results also show that with a proper binding method, the plasma explosion of metal wire in water can generate a significant propulsion effect.

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.

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.

Influence of moisture absorption on space charge property of MgO/LDPE nanocomposite

In order to understand the change rule and its mechanism for the space charge property of Magnesium oxide (MgO)/ LDPE nanocomposites after damp, the moisture absorption weight and space charge properties of wet LDPE and MgO/LDPE were studied. Experiments results show that moisture absorption has a strong influence on dielectric properties of MgO/LDPE nanocomposite. After nanocomposite had been exposed for a week under the 40% relative humidity conditions, the improved space charge property of the composite at high electric field above 20kV/mm, were decreased obviously compare to dry MgO/LDPE. It is believed that moisture absorption may lead to a weakening of original interfacial charge distribution. On contrary, at low electric field, the MgO/LDPE system showed the strong suppression effect of aditional carriers migration caused by absorbed moisture.