Research on Formation of High Density Space Charge consisting with Charged Droplets and Air Discharge

在无电极的空间电荷云中发生放电，形成由带电液滴组成的空间电荷云。带电液滴由无空气喷嘴产生，该喷嘴在喷嘴尖端附近配备有感应充电电极。液滴的带电量取决于带电电极的质量和几何形状，本文研究了插入带电液滴云中的接地针电极尖端的电晕点放电。云被限制在一个圆柱形的接地电极，直径为1米，高度为2米，以确定云的大小。得到的云的最大电荷密度为2.6 μ C/m^3。当接地的针电极插入带电云的中心时发生电晕放电。在负电荷云中，当针电极半径较小时，产生正辉光电晕。讨论了无气喷嘴感应充电法喷射的带电液滴云中气隙的闪络特性。液滴的带电量在-200至+200 μ C/kg之间，形成约13 μ C/m^3的空间电荷。测量了1.2 × 50 μ s冲击电压作用于带电云团内棒球间隙时的闪络电压和闪络时间。随着荷质比的增大，正电荷云内正极棒的闪络电压显著增大。与未带电液滴内的闪络电压相比，闪络电压提高了80%。在任一极性的云中，负极棒的闪络电压都下降了约20%。结果表明，间隙中的带电液滴对放电过程有显著影响。

To occur electrical discharge in a space charge cloud without electrode, space charge cloud consisted with charged droplets was formed. The charged droplets were produced by an airless nozzle equipped with an induction charging electrode near the tip of the nozzle. The charge quantity of the droplets depends on the mass quantity and the geometry of the charging electrode.Corona point discharge at the tip of a grounded needle electrode inserted into a charged droplet cloud has been investigated. The cloud is confined within a cylindrical grounded electrode 1m in diameter and 2m in height to define the size of the cloud. The maximum charge density of the cloud obtained was 2.6muC/m^3. Corona discharge occurred when the grounded needle electrode was inserted into the center of the charged cloud. In a negative charged cloud, positive glow corona occurred when small radius of needle electrode was used. However, positive streamer corona was observed when a large radius of needle electrode was used.Flashover characteristics of air gap within charged droplet cloud ejected from an airless nozzle using induction charging method are discussed. The droplets are charged in the range-200 to +200muC/kg forming the the space charge of approximately 13muC/m^3. The flashover voltage and the time lag to flashover were measured when 1.2X50mu s impulse voltage applied to a rod-sphere gap within the charged cloud. Flashover voltage for positive rod markedly increased within positive charged cloud by increasing the charge-to-mass ratio. The increase of flashover voltage was up to 80% in comparison with flashover voltage within uncharged droplets. Flashover voltage for negative rod decreased about 20% in the cloud of either polarity. The results show that charged droplets in the gaps affect discharge process significantly.