Streamer discharges in liquids and their applications

Abstract

Industrial applications using pulsed power technologies have been developed in many fields. One of them is the treatment of exhaust gas by using uniformly produced streamer discharges. Streamer discharges in liquid also generate extremely high electric fields at the tip of streamers, as well as high energy electrons, ozone, other chemically active species, ultraviolet rays and shock waves. All of these may be utilized to sterilize microorganism and to decompose molecules and materials. Large-volume streamer discharges in water have been produced in order to realize industrial applications. A wire to plane electrode configuration has been used. The discharge in water shows similar optical radiation to that in an atmospheric gas as provided by evidence from still photographs. The influence of polarity, conductivity, electrode geometry and hydrostatic pressure on the streamers in liquid, the mechanism of streamer discharges and possible industrial applications of streamers in liquids, are discussed in the present work.

Electrical Properties Associated with Discharge Developments in Water Subjected to Impulse Voltages

“…The reducing rate of the post-ionization resistance for higher water resistivities were larger than that for lower water resistivities, as the conduction currents increase sharply with decreasing water resistivity. The calculated post-ionization resistance ' 2 R shows the same tendency with the variation of 2 R , however the resistance ' 2 R is lower than the resistance 2 R . The difference between the resistances ' 2 R and 2 R comes from the error factors in the expended ionization region caused by streamer discharges not being correct hemispherical shapes and the maximum length of streamer propagation was employed as the radius of expended ionization region.…”

“…The pre-ionization resistance 1 R for the water resistivity of 200 Ω·m was about 3 kΩ and it was proportionally reduced to less than 180 Ω for a water resistivity of 10 Ω·m. On the other hand, the measured post-ionization resistances 2 R for different applied voltage are lower than half of the preionization resistances at the same applied voltages. As expected, the post ionization resistances 2 R are inversely proportional to peak voltages because the length of the streamer propagation increases with increasing the applied voltages.…”

“…On the other hand, the measured post-ionization resistances 2 R for different applied voltage are lower than half of the preionization resistances at the same applied voltages. As expected, the post ionization resistances 2 R are inversely proportional to peak voltages because the length of the streamer propagation increases with increasing the applied voltages. When ionization is initiated, the ionization region around the tip of the needle electrode, operating as a radically expended electrode, decreases the post-ionization resistance.…”

“…The pre-ionization resistance 1 R , the measured postionization resistance 2 R and the calculated post-ionization resistance '…”

“…To analyze the ionization phenomena, the two time parameters are defined as shown in Fig. 7 (b): where the time-lag 1 t is the time to ionization threshold (preionization time) and the time-lag 2 t is the time to the second current peak (post-ionization time). Also, the preionization resistance 1 R is defined as the voltage divided by the current at the time of 1 t and the post-ionization resistance 2 R is calculated by the same method at time 2 t .…”