| Magnetic field corona discharge with spraying water is a new-style technique, which has a particular advantage in capturing aerosol particles. This technique is promising for electrostatic precipitators because of its high efficiency and no-clean property. In the current study, both discharging and charging characteristics of magnetic field corona discharges, corona discharge with spraying and magnetic field corona discharge with spraying water were studied and compared. So the theoretical foundation of applying the technique of magnetic field corona discharge with spraying water in pre-chargers and electrostatic precipitators were established.The research contents and conclusions are as follows:1) The magnetic field corona discharges and corona discharges with spraying water were effectively combined, and a new-style pre-charger was designed. This new-style pre-charger can not only avoid conglutinations of glutinous aerosol particles, but also it is useful for electrostatic capturer to further capture fine aerosol particles after the dusts are charged by this pre-charger. This could provide helpful reference for the future design of more advanced devices in capturing glutinous aerosol particles.2) The discharge characteristics of magnetic field corona discharges were studied and the variations in current were revealed. In the magnetic field negative corona discharges, the corona discharge current was enhanced perhaps because the collisions between the gas molecules and free electrons increased in the ionization region due to the Larmor movements or deflexions of free electrons. It is assumed that the increase of the discharge currents only attributes to the enhanced ionization process in the small ionization region, but is not relevant to the lengthening trajectory of free electrons in the inter-electrode non-corona region. On the whole, the increase of the discharge current is mainly determined by two factors: (1) The collision number between the free electrons and the gas molecules in the ionization region; and (2) The mean energy of free electrons. The relative increase of collision number as well as the mean energy of free electrons changes along the two opposite directions with the changing magnetic field or electric field. Therefore, the relative increase of corona discharge current could achieve a maximum value. For the electrostatic precipitators with magnetic field corona discharges, the relative increase of the discharge current could attain the maximum value when the using magnetic field is about 0.43T and the mean electric field intensity is 4 kV/cm. And at the same time the electrostatic precipitators also achieve the highest efficiency.3) The charging mechanism of corona discharges was studied under magnetic field. The electrostatic capturer was used to capture aerosol particles after the dusts were respectively charged by magnetic field corona discharge pre-charger and conventional pre-charger. The results showed that it is adaptive for magnetic field corona discharge to charging fine dusts. According to this, the charging mechanism could be analyzed and revealed. When the magnetic field is used, the concentration of negative ions increases, which is favorable for diffusion charging. As a result, the capture efficiency is enhanced. So the capability for charging aerosol particles of magnetic field corona discharges was better than that of conventional pre-chargers.4) The comparative researches on both positive- and negative- earthed atomizing corona discharges were carried out. In the atomizing positive corona discharge, the volume of corona region expanded. But the similar phenomenon has not occurred in the atomizing negative corona discharge. The reason is that steady Trichel pulses was formed in negative corona discharge, so the voltage at first increased sharply, and then reduced quickly. As a result, both the energy input and expanding of ionization region were restrained due to this discharge mode. On the contrary, steady glow discharges could be formed in conventional needle-plate corona discharges, because the discharge configuration was formed between the numerous cone-jet mode and plate electrode, which was similar to needle-plate configuration. In the atomizing corona discharge, the influence of space charges on electric field was enhanced near the corona region because of the enhanced ionization. The distribution of electric field was primarily analyzed in the atomizing corona discharge. Otherwise, the proper flux is essential. The influences of flux on both currents and atomizing drips were analyzed. The corona starting voltage decreased when the proper flux was used, but increased when the excessive flux was selected. Given the proper flux, the drips of several tens microns were dominated in granulometric distribution.5)The mutual influences between magnetic field and electric field were studied when both magnetic field and electric field were used in corona discharges. The reason why the discharge currents were enhanced is that the collision numbers increase between free electrons and air molecules or water molecules, moreover, the ionization of water molecules is easier than air molecules because the ionization energy of water molecules is lower than that of air molecules. Another possible reason for the currents increasing is the distortion of discharge alleyway of corona plasma when the magnetic field was applied. When the magnetic field was used, the entire corona plasma is more uniform. So the efficiency of ionization collisions was enhanced. Otherwise, the interelectrode distance was decreased because of the thaler tapers, and the curvature radius of thaler tapers was smaller than that of the discharge electrode. Therefore, the discharge currents were obviously enhanced. But the corona starting voltage decreased because of the influences of both space charges and curvature radius of discharge electrode. The influences of flux on discharges were analyzed when the magnetic field was fixed. And the electric field distribution was primary analyzed in the magnetic field corona discharge with spraying water. The electric field distribution was consistent with conventional corona discharges, except that the concentration of space charges was thicker and the influence of space charges was enhanced.6)The efficiency of electrostatic capturer was higher when magnetic field corona discharges with spraying water was used than only magnetic field or atomizing water was applied. The possible reason is the increasing concentration of interelectrode space charges benefit from magnetic field and atomizing water. In addition, water drips might be assistant action for capturing dusts. In magnetic field negative-corona discharges with spraying water, the accumulated space charges were larger than the other discharge mode and the space charges electric field is contrary to the original electric field, so the moving speed of negative ions and electrification drips in the charging region were decreased, in contrast, the concentrations of negative ions and electrification drips were increased. Therefore, the charging efficiency of magnetic field corona discharges is highest among the four pre-chargers.7)The diameters and charging quantity of small drips were measured. And based on the charging quantity of drips and granulometric distribution, the charging mechanisms of the magnetic field corona discharges with spraying water and the corona discharges with spraying were primarily analyzed.
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