Research On The Active Species Produced By Pulse Discharge In Water

Using needle-to-plane electrodes plasma discharge in water,active species generated has been studied in this paper. Hydroxyl radicals, hydrogen atom,oxygen atom are measured on-line by spectrum method. Hydrogen peroxide is measured after discharge by chemical method. We investigate what influence the gas constituent and the gas-flow rate which be inlet water, the conductive of water , the distance between the two electrodes and the voltage contribute to the formation rate of active species. The experimental results and analyse indicate that as follow: 1) In plasma discharge in water there are two type: streamer corona and spark breakdown. With the increment of the gas-flow rate and the voltage, discharge will strengthen, streamer discharge will transit to spark breakdown. The light intensity can be considered as the transition marker, specially in oxygen-water mixture discharge, because the light intensity of H atom is little ifluenced by other species. 2) When the distance of the two electrodes is longer (5cm), it can form more stable streamer discharge. When the distance is shorter (3cm), it is easy to occur spark breakdown. When oxygen is inlet, it is easy to form spark breakdown. While nitrogen is inlet, it can form more stable streamer discharge, the streamer is little longer than that when oxygen is inlet. 3) In streamer discharge (the distance of two electrodes is 5cm), hydrogen peroxide formed in nitrogen-water mixture discharge is more than that in oxygen-water mixture discharge. In spark breakdown(the distance of two electrodes is 3cm),hydrogen peroxide formed in nitrogen-water mixture discharge is obviously little than that in oxygen-water mixture discharge. 4) With the increment of the initiate conductive of water, the concentration of hydrogen peroxide raise. When the initiate conductive of water increasing continuously, it begins to descend. When the conductive is about 40μS/cm, it reaches maximum. 5) In streamer discharge (the distance of two electrodes is 5cm), the conductive of water increases obviously with the increment of discharge time, what's more, the increasing range is very large in nitrogen-water mixture discharge. In spark breakdown (the distance of two electrodes is 3cm), the conductive of water varies little, there is minish current in oxygen-water mixture discharge. 6) With the increment of discharge time, the water tempreture raises. The experimental result above-mentioned can instruct to improve the formation rate of active species and reduce power.