Radu Burlica

Pulsed Plasma Gliding-Arc Discharges With Water Spray

Pulsed gliding-arc discharge (PGD) (25 kV, 18 W, and 170 Hz) was produced between two divergent electrodes using an ignition coil in place of the conventional ac transformer. The time courses of pH, conductivity, and the formation of hydrogen peroxide in pure water with a variety of different carrier gases were determined in the PGD and ac-gliding (ACG)-arc reactors. The energy yield for the destruction of an organic blue dye in the PGD reactor is approximately 150 times higher than in the ACG-arc reactor with Ar carrier, and the energy yields for the formation of hydrogen peroxide are 270 and 260 times higher in the PGD reactor than in the ACG-arc reactor with Ar and 02 carrier gases, respectively.

Effects of the Voltage and Current Waveforms and Discharge Power on Hydrogen Peroxide Formation in Water-Spray Gliding Arc Reactors

This paper deals with the effects of discharge power and voltage and current waveforms on the formation of hydrogen peroxide (H2O2) from liquid water sprayed as a fine aerosol into a plasma formed by a gliding arc discharge. The formation rates of H2O2 were determined for different values of the power injected into the reactor (1-7 W), as well as for different means of applying the power [pulsed, alternating current (ac), and direct current (dc)], with argon carrier. For the same power injected into the plasma, the pulsed power was more efficient than the ac power which was, in turn, more effective than the dc power for the generation of H2O2. Energy yield increased with water flow up to 10 mL/min and thereafter was constant with a maximum of about 6 g/kWh.

The study of an electric spark for igniting a fuel mixture

The ignition sparks provided by the classical system do not always assure a fast and complete combustion of the hydrocarbon-air mixture. For this reason have been made a lot of studies, most of them trying to implement new types of electronic ignition systems, including power supply and the spark plug itself, which must provide faster, more complete and more efficient-fuel burning, so overall a lower impact on the environment. The aim of such system consists in the generation of an electrical discharge between the spark plug electrodes able to assure a larger and more homogenous volume of the plasma in the engine cylinder. The implementing of such a system involves conducting complex electrical, mechanical, chemical and physical analysis, to validate its benefits in comparison to the classical system. The new type of ignition system with two sparks uses a spark plug with three electrodes. The first one is connected at the high voltage, the second at the ground and the third, located between the two others, free of potential. This paper proposes a complex and comparative study to the classical ignition system. Measurement of the electrical parameters and the physical analysis were done mainly by testing ignition systems in a reactor with air. The mechanical and chemical parameters were measured using an engine stand four-stroke.

Optical Diagnostics of Electrical Discharge Water-Spray Reactors for Chemical Synthesis

Low-power (250-500 mW) pulsed gliding-arc discharge reactors that utilize water sprayed as a fine aerosol into an argon carrier gas have been previously shown to produce molecular hydrogen (H2) and hydrogen peroxide (H2O2) with high energy yields. In this paper, optical emission spectroscopy in the range of 230-1000 nm is used to assess the formation of radicals in the plasma region of the reactor as functions of spatial position and liquid flow rate. Radical intensities of OH (309 nm) were the highest at 10 mm downstream from the point of discharge initiation, and the gradient of the OH radical intensities between 10 and 15 mm was higher for the higher liquid flow rates that correspond to the highest production rates and efficiencies of hydrogen peroxide. These results support the hypothesis that hydrogen peroxide production efficiency increases with rapid OH radical quenching.

Effect of Pressure on Discharge Initiation and Chemical Reaction in a Liquid-Phase Electrical Discharge Reactor

The effect of pressure on liquid-phase electrical discharges was investigated by using a stainless steel high-pressure reactor combined with a high-voltage pulse forming network. The initiation breakdown voltage was obtained under various pressures up to 1380 kPa (200 lb/in2 ). The discharge characteristics including current and voltage waveforms as well as power per pulse were determined. The effect of pressure on streamer chemical reactions was also investigated by measuring the formation rate of hydrogen peroxide (H2O2) in the solution. Experimental results showed that the initiation voltage is linearly dependent on pressure. The initiation voltage and power were correlated to the increase of heat requirement to vaporize liquid water with increasing pressure. On the other hand, when the input voltage exceeds the initiation voltage such that a stable discharge can be formed, the discharge characteristics are not affected by pressure. Hydrogen peroxide generation was also not affected by external pressure for conditions with stable discharge. To explain the aforementioned results, the bubble theory of liquid-phase breakdown initiation is discussed.

Considerations regarding the influence of contact resistance on the contacts of low voltage electrical equipment

The electrical contacts are important elements which can be found on all of the electrical installations from the power source to the consumer. Also, the electrical contacts have an important role in the construction and operation of low voltage electrical equipment. The presence of an electrical contact on a current path always introduce an additional electrical resistance, named contact resistance. In this paper is studied the influence of the voltage drops to contact resistance, respectively to contact temperature of the low voltage electrical equipment.

Optical diagnostics of electrical discharge water spray reactors for chemical synthesis

Low-power (250-500 mW) pulsed gliding-arc discharge reactors that utilize water sprayed as a fine aerosol into an argon carrier gas have been previously shown to produce molecular hydrogen (H2) and hydrogen peroxide (H2O2) with high energy yields. In this paper, optical emission spectroscopy in the range of 230-1000 nm is used to assess the formation of radicals in the plasma region of the reactor as functions of spatial position and liquid flow rate. Radical intensities of OH (309 nm) were the highest at 10 mm downstream from the point of discharge initiation, and the gradient of the OH radical intensities between 10 and 15 mm was higher for the higher liquid flow rates that correspond to the highest production rates and efficiencies of hydrogen peroxide. These results support the hypothesis that hydrogen peroxide production efficiency increases with rapid OH radical quenching.

Confined plasma gliding arc discharges

A confined plasma gliding arc is produced in a reactor with two-electrodes contained within a very narrow channel and water spray injected into the discharge. The evolution of pH and conductivity and the formation of hydrogen peroxide in pure water with different carrier gases and the decolourisation and mineralisation of an organic dye were compared with results for a non-confined three-electrode gliding arc reactor. The energy efficiency for the decolourisation of an organic blue dye in the confined reactor is twice that of the non-confined reactor. Significant levels of total organic carbon are removed in the confined plasma reactor.

The evolution of aqueous solutions properties exposed to a GlidArc discharge

Plasma technologies are considered today by many experts as a new field for new discoveries, with many practical applications in the most various domains of the human activities: chemistry, medicine, industry (food, textiles, steel), etc. The evaluation of all physical and chemical parameters of the plasma leads to a better understanding of the processes that occur during the interaction with various organic or inorganic compounds. The goal of this paper is to study the effect of non-thermal plasma treatment on water and organic solute (soluble dyes) and it aims to examine the intervention of the electrical discharge generated by different types and power inputs of electrochemical reactors, i.e. cold plasma, on pH sensitive substances. This can lead to properties changes of samples and also can be dangerous for the humans.

Hydrogen and hydrogen peroxide formation in the AC water-spray gliding arc reactor

The goal of this paper is to study the formation rates and energy yields of H2 and H2O2 formed from pure water exposed to a non-thermal AC plasma-gliding arc reactor equipped with a spray nozzle. The gliding arc reactor utilizes an AC electrical discharge developed in a gas flowing between two electrodes supplied by one high voltage transformer. Previous works [1, 2, 3] showed that the efficiency of reactive and molecular species formation in water treated by non-thermal plasma depends on the gas-liquid interfacial contact area between the water and the plasma zone. Spraying the liquid through a special two-way nozzle directly into the plasma zone is an effective method to enhance the efficiency of chemical species formation in gliding arc reactors. In the present work, the focus is on hydrogen formation from water spray exposed to plasma generated by an AC gliding arc discharge using Ar as carrier gas for different electrical powers of the discharge and for different water flow rates. The formation rates of hydrogen and hydrogen peroxide were also determined.