Effects of O2 addition on the plasma uniformity and reactivity of Ar DBD excited by ns pulsed and AC power supplies

Dielectric barrier discharges (DBDs) have been widely used in ozone synthesis, materials surface treatment, and plasma medicine for their advantages of uniform discharge in atmospheric pressure and high plasma-chemical reactivity. To further improve the plasma treatment efficiency and activity, a small amount of admixture can be introduced into working gases (usually Ar, He, N2), while it can affect plasma uniformity significantly. In this paper, oxygen is added into Ar nanosecond (ns) pulsed and AC DBDs DBD and the effect of the added oxygen on the uniformity and reactivity have been investigated with optical and electrical methods. The plasma uniformity is quantitatively analyzed by Gray Value Standard Deviation (GVSD) of discharge images. The optical emission spectroscopy (OES) measurement of the emission lines with different energy thresholds can reveal the tendency of T e under different operation conditions. The n e are estimated from the electrical analysis. It is found that the ns pulsed DBD shows a much better uniformity than AC DBD. With the addition of O2, the uniformity of ns-pulsed Ar DBD gets worse for the O2- negative ions by the attachment of electron on O2 distorts the space electric field and promotes the filamentary formation. While, in AC Ar DBD, the added O2 can reduce the n e and brightness of filaments, which enhances the plasma uniformity. Overdose O2 molecules cause drops of n e and T e to plasma extinction. The results can help to realize the establishment of the reactive and uniform atmospheric low temperature plasma sources.

THE INFLUENCE OF CATHODE MATERIAL ON THE CHARACTERISTICS OF PULSED NEGATIVE CORONA IN OXYGEN

Change in time for the shape of the discharge current pulses of the pulsed negative corona in oxygen with cop-per and stainless steel cathodes has been studied for two discharge modes. The change lies in the decrease of the pulse amplitude and duration at half maximum. It is shown that for stainless steel cathodes, the amount of electric charge transferred in one pulse of the discharge current is 15% greater than for copper cathodes. It is also shown that under the maximum load mode, the amount of charge transferred in one pulse of the discharge current is de-creased with time by 10% for both types of cathodes. It is shown that ozone synthesis in the electrode system with copper cathodes is 25% more efficient.

A Novel Dielectric Barrier Discharge (DBD) Reactor with Streamer and Glow Corona Discharge for Improved Ozone Generation at Atmospheric Pressure

Discharge mode is an important parameter for ozone synthesis by dielectric barrier discharge (DBD). Currently, it is still challenging to stably generate glow discharge with oxygen at atmospheric pressure. In this paper, a DBD reactor with a layer of silver placed between the electrode and the dielectric layer (SL-DBD) was developed. Experimental results show that both streamer and glow corona discharge were stably generated under sinusoidal excitation with a 0.5 mm discharge gap in a parallel-plate DBD, due to the increased electric field strength in the discharge gap by the silver layer. It was also found that, in the SL-DBD reactor, glow corona discharge enhances the discharge strength by 50 times. The spectral peak of O at 777 nm in SL-DBD is increased to 28,800, compared with 18,389 in a reactor with a streamer only. The SL-DBD reactor produces ozone with a concentration of as high as 150 g/m3 and shows good stability in an 8 h durability test.

DEVELOPMENT AND RESEARCH OF A HIGH-PERFORMANCE ELECTRONIC DEVICE FOR OZONE SYNTHESIS IN A VIBRATION DRYER

The article analyzes the features of drying grain raw materials using a vibrating dryer, in which the drying agent is a mixture of heated air in combination with ozone of a certain concentration. Based on the analysis to intensify this process, we propose to develop a high-performance electronic device for ozone synthesis. The scientific study considers oscillations that increase and update the heat transfer surface regardless of the method of supply of the drying agent. Due to this, the removal of moisture intensifies, the drying speed increases. Having conducted a search and analyzed the process of vibration drying, we can say that in the future will progress two main trends in their development. This is the use of vibration in combination with the action of ozone on the raw material entering the drying. Ozone interacts with the membrane structure of bacteria, fungi, the structural unit of viruses, which leads to a violation of its barrier function and their death. The bactericidal effect of ozonation is superior to the effect of ultraviolet quartz radiation. Bactericidal effect from quartz irradiation for 60 minutes identical to the bactericidal effect of ozone for 3 minutes Ozone has a high penetrating ability and also shows antibacterial activity against gram-positive flora, Escherichia coli, epidermal staphylococcus. This method is the most effective general method of controlling the dynamic state of the processed raw materials. The analysis allows us to suggest possible solutions for the use of low-frequency oscillations for separation processes and outline the prospects for their application. It is proved that the existing equipment is used with significant energy consumption and high cost. The constructions and technologies considered in the work do not completely exhaust the possibilities of using vibration and ozone, although they testify to the expediency of their application and combination not only in agricultural production, but also in other industries in order to intensify processes and obtain quality products.

INVESTIGATION OF OZONE SYNTHESIS IN THE NEGATIVE PULSED CORONA DISCHARGE IN OXYGEN AT THE COMBINED SUPPLY VOLTAGE

The influence of combined supply voltage parameters (bias voltage and voltage pulse amplitude) on efficiency of ozone synthesis in the negative pulsed corona discharge in oxygen was obtained. Pulse overvoltage led to intensification of discharge processes. Bias voltage applied during the discharge channel relaxation essentially increased the efficiency of ozone synthesis. It was established that the “optimal” bias voltage which provides maximum ozone generation doesn’t depend on voltage pulse amplitude, but depends on input oxygen concentration and generated ozone concentration.