Falling Liquid Droplets Discharge

Abstract This paper reports the phenomenon of two plasma segments forming when a water droplet descends, one between the upper part of the droplet and the outlet tube and the other between the lower part of the droplet and the water surface in the container. The study reveals that as the water droplet descends, the length of the upper plasma gradually increases, while the length of the lower plasma decreases until the lower plasma disappears upon contact between the water droplet and the water in the container. At this point, the discharge voltage decreases from 6.5 kV to 5.9 kV, and the discharge current increases from 17 mA to 20 mA. Further investigation reveals that this decrease in voltage drop is equal to the value of the voltage of cathode fall. Additionally, the study finds that the rotational temperature of this plasma reaches 2100 K, with an electron density of 1014/cm³. Furthermore, it is intriguing to note that the descent speed of the droplet is significantly greater than that of a freely falling droplet. Further research indicates that this is due to an instant water channel explosion-induced downward impact on the droplet caused by plasma generation at the upper part of the droplet. The advantage of this device lies in the fact that the plasma only comes into direct contact with water, without any contact with metal electrodes, thus eliminating the issue of electrode corrosion. Furthermore, since the water is in dynamic flow, it facilitates the dissolution of reactive gaseous components into the water, making it suitable for applications related to plasma-activated water and similar purposes.