Xiaochun Chi

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.

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 influence of water on corona discharge in the flue gas

In this paper a novel type of a water film corona discharge experiment model is designed. 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). The mechanism of the formation of corona discharge in the pollution flue gas containing sulfur dioxide (SO/sub 2/) and nitrogen oxides (NO/sub x/) is investigated under the conditions that there are different concentration of sulfur dioxide and nitrogen oxides of the flue gas and different applied voltages. Based on this the emphasis is on studying the influence of water on corona discharge in flue gas. The experimental results show that the corona wind forming between high-voltage electrode and water film by corona discharge enhances the cleansing efficiency of the flue gas because of the existence of the water film, and the cleaning efficiency will increase with the increase of the voltage under a definite range of applied voltage. According to this effect a water film electrical corona reactor that we design is used to treat the flue gas of the boiler, and the result shows it not only makes the removal efficiency of dust up to 100%, but also makes about 98% of SO/sub 2/ and 85% of NO/sub x/ removal respectively under suitable conditions. This project is very significant for the prevention of acid rain and the treatment of dust of flue gas and the improvement on the traditional electrical dust precipitator.

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.

Effect of water on flue gas cleaning and the discharge characteristics

To clarify the influence of water on discharge characteristics, water was put in the plasma reactor as electrode and the current and voltage characteristics of corona discharge were investigated under the application of dc voltage. Two different types of electrode systems (needle to plane, needle to water) were used. In the case when DC high voltage was applied to the needle electrode, corona of the same polarity with the voltage applied to the needle was observed. The experimental results show both the removal rate of NO and SO/sub 2/ are improved in the needle to water reactor than that of needle to plane reactor. NO is mostly oxidized into NO/sub 2/ by the reaction with O and O/sub 3/ and NO/sub 2/ is change into HNO/sub 3/ by the reaction with OH, which is generated from H/sub 2/O. Most of the SO/sub 2/ removal is attributed to the absorption into the water.

The experimental investigation of heat transfer enhancement of dielectric fluid in electrostatic field

The insulating fluid with low boiling point R11 was selected as working fluid and an experimental model was designed and made. The experiment on condensation heat transfer inside this model was conducted under electrostatic field. The experiment results showed that the electrostatic field can enhance the condensation heat transfer of the dielectric fluid inside the model greatly, and the heat transfer coefficient was mainly affected by applied electric field, heat flux and the relative position of the electrode. This electric field enhanced condensation technology show much reference value for refrigeration and heat transfer engineering.