磁场对电晕放电电场及细小粉尘荷电的影响

磁增强正负电晕放电用于细小气溶胶颗粒荷电,研究结果表明,磁增强正负电晕放电预荷电器对细小粉尘的荷电是有效的;磁增强正电晕放电预荷电器的荷电效率低于磁增强负电晕放电预荷电器。与传统的电晕放电相比,磁增强正负电晕放电中电晕区附近积累更多的正离子,使得空间电荷对极间电场的影响增强;在磁增强负电晕放电中,负离子的浓度再次被提升,更有益于细小粉尘荷电;在磁增强正电晕放电中,电晕区中的电场强度被削弱,而荷电区中的电场强度被增强。分析认为,磁增强正电晕预荷电器的效率比传统正预荷电器要高。

Influences of Magnetic Field on both Electric Fields and Charging Fine Aerosol Particles

The magnetically enhanced negative- and positive-corona discharge pre-chargers were used for charging fine aerosol particles. The magnetically enhanced corona discharge involes a local magnetic field being formed near the discharge electrode by using small permanent magnets to enhance the corona discharge current due to the Larmor movements of free electrons, which, in turn, help ionization of the gas molecules in the corona region. The results show that the pre-charger works well for charging fine particles. The corona discharge currents are enhanced by the Larmor movements of free electrons by increase of concentration of space charges in the charging region. It is shown that the charging efficiency of the pre-charger for magnetically enhanced positive-corona discharge is not as good as that of the magnetically enhanced negative-corona discharge. The influence of space-charges on the original inter-electrode electric field is enhanced because more space charges accumulate in the inter-electrode region in magnetically enhanced positive- and negative-corona discharges as compared with conventional corona discharges. In the magnetically negative-corona discharge, the intensity of electric field is enhanced by the electric field of space-charges in the corona region, but is weakened in the charging region. So the concentration of negative ions is enhanced again, which is beneficial for charging fine aerosol particles. On the other hand, in the magnetically enhanced positive-corona discharge, the intensity of electric field is weakened in the corona region, and is enhanced in the charging region. Therefore, the concentration of positive ions is decreased to some extent in the charging region, but the ionization enhanced by the Larmor movements of free electrons is stronger than the ionization weakened by accumulated positive ions in the magnetically enhanced positive-corona discharge. So the efficiency of charging fine aerosol particles is higher for a pre-charger for magnetically enhanced positive-corona discharge than that for conventional positive pre-charger.