Sebastian Gnapowski

Post-breakdown dielectric recovery characteristics of high-pressure liquid co 2 including supercritical phase

The paper describes results of experimental studies to evaluate the effects of phase-change and/or density variation at the post-breakdown on the dielectric recovery characteristics of liquid and supercritical CO2. The study aims to explore the possibility of using supercritical CO2 to develop high-repetition-rate pulsed-power switches. The experimental setup consisted of a sphere-to-sphere 10 mm radius electrodes configuration with 50 μm gap distance. Three phases of pressurized CO2; subcritical liquid state (SLS), liquid with pressure higher than critical point (LHCP), and supercritical phase (SC), were used for the experiments. Experimental results revealed that SC CO2 has a very short recovery time making it an appropriate fluid for MHz range highly-repetitive switches. Post-breakdown stage in SLS consisted of gas phase and liquid phase at the plasma channel between the electrodes, with the alternative expansion-contraction motion behavior of gas bubble determining dielectric recovery characteristics. Post-breakdown stages in SC were similar to those in LHCP, generating a low density region at the post-breakdown, where the state of density variation determined dielectric recovery characteristic. The low density region could be compressed by the surrounding medium, resulting in a considerably shorter recovery time.

Observation of Underwater Streamer Discharges Produced by Pulsed Power Using High-Speed Camera

Pulsed power, used to produce underwater discharges, has been the subject of numerous studies to elucidate its mechanisms and applications. This paper reports on observation by a high-speed camera of the production and progress of streamer discharges created using a magnetic pulse compression pulsed power generator with maximum output energy of 40 Joules per shot in the medium of both tap and distilled water. Bubble production along streamers, bubble collapse, generation of shock waves, and extinction of bubbles was also observed by a high-speed camera.

Softening of vegetables by pulsed power

Pulsed Power has been applied to foods for the extraction of vegetable juice and sterilization of foods. The juice from sugar beet increased with pulsed electric fields. Since the aging of Japans population is advancing, the softening of foods becomes important to keep the quality of life. Here, the effect of pulsed power on hardness of vegetables is investigated using a magnetic pulse compression system. The vegetables are set between the plane electrodes placed into the tap water. The hardness of carrot decreases with the shot number of pulsed power. The temperature inside the carrot increases a little.

Algae treatment effects by pulse power discharge in the water

Summary form only given. The detailed study presented here has shown the effects of atmospheric streamer discharge plasma on undesired micro-organisms in water like algae. Algae are water organisms classified separately from plants. They are known to cause many hazards to humans and the environment. Many factories and holiday places have problems with removing algae. This study presents data about pulse power discharge in the water with algae was presented. Algae were treated by high voltage pulsed discharge (using copper pin electrode). Plasma discharge effects like, shock wave, hydroxyl radical, electric field and ultraviolet light were investigated. Generally, plasma and plasma-chemical processes accompanying plasma discharges in water have received little study to date. This study shows the electric discharge phenomenon is useful to inactivation algae in the water and the killing effect of algae is showing. High voltage electrical discharge in water has been considered as a potential method of water treatment to kill microorganisms, negating the use of chemicals such as chlorine that leads to disinfection by-products which may additionally compromise human health.

NEW POSSIBILITY FOR THE USE OF PLASMA DISCHARGES TO IDENTIFY AMBER AND CHANGES IN AMBER STRUCTURE

Pulsed power discharge applied in air to the amber surface was found to cause improvement in its appearance and color changes such as to red, a color not natural to amber but attractive for jewelry. Needle and plate electrodes were used during experiments. Pulsed power discharges in air particularly turned amber red at the edges and around the needle electrode. Discharges in water did not change amber structure because discharge occurring on the surface does not cross the amber structure. Discharges in silicone oil had a different effect, with most discharge passing through the amber structure, causing fine cracks. Unfortunately, the absence of a consistent am ber structure causes difficulty in selecting the correct discharge (shock wave) power. Using new technology, we have changed the appearance a very old material-amber (about 40 – 60 million years old) – to make it more attractive for customers; this technology is also useful for detecting artificial amber (costume jewellery) without causing damage to the product.

The role of e-learning in educational processes

The subject of this article contains selected methods of optimization of educational work using selected computer tools, such as e-learning. The use of information technologies is a common feature of teaching methods, which include e-learning. Through a distance learning, teaching and learning process became accessible from anywhere, at any age and time. Virtual contact between the teacher and the student is in many cases far more convenient for both of them. Training and e-learning courses are very popular. They are carried out not only in school or academic environment but also in the business one. Distance education is used as a tool to support learning process, and its use may allow easy management of materials, allowing to create flexible educational methods.

PPPS-2013: Increase in input power and change of streamer length during rotation of electrode

An increase in ozone production efficiency is sought by scienti sts due to the important role ozone plays in improving the human environment such as maintaining higher water and air quality. Ozonizers with electrode rotating systems are a possible way to increase ozone synthesis efficiency. Important question sare why rotating electrodes increase ozone concentration and how they can be controlled. Phenomena determining the increase of ozone concentration must be identi fied. In our case, a gold rotating electrode was used to eliminate surface oxidation effect. The oxygen flow rate was 0.5 l/min, applied voltage 10 kV (peak to peak), and frequency about 12 kHz. Ozone concentration increased to about two times higher than that of the case with a non-rotation. In addition, input power and discharge area were found to increase with rotating speed. Both ozone concentration and ozone production efficiency improved with the use of a rotating electrode compared to t h a t with a non-rotating electrode. One reason may be the increase of discharge length of micro-discharges during electrod e rotation. Discharge streamer changed in both shape and length, with the length increasing 10-20%. The produced ozone increased with increa sing electrode rotation speed, and the efficiency of ozone production improved by 30 % by rotation. In addition, the discharge area became more intense and ozone concentration increased with rotation. When micro-discharges become longer during rotation, generating an increased number of collisions becomes possible, leading to higher ozone concentration; this is also be expected to lead to higher efficiency of ozone generation.

Change of amber structure by pulsed power discharge

Amber is made from tree resin in a process that takes around 100 million years. It is used for the manufacture of jewelry and ornamental objects [1]. During experiments, a needle and plate electrode were used. Two types of magnetic pulse compression circuits (MPC) were used to apply pulse power discharges. Applied voltage was around 25 kV and 4.5 Joules per shot. During experiments 30 pps was applied. The number of shots was about 300. Pulse power discharges were done in air and silicone oil. In the case of air experiments, discharges were not passed inside amber; instead, discharge was run over the ambers surface. After discharges, amber became red in color and smooth like glass. Red color amber is not natural and is thus more attractive for jewelry and customers. Different results were achieved during discharges in silicone oil. Discharges in silicone oil had a different effect, with most discharges passing through the amber structure, causing fine cracks. Unfortunately, much artificial amber is sold as genuine amber because identification of genuine amber is difficult. Pulsed power technology is also useful for detecting artificial amber (costume jewelry) without causing damage to the product. For these experiments, we used four types of artificial amber under the same parameters as for genuine amber including shot number and voltage. Amber was identified by using pulse power discharge.

Increase in input power and change of streamer length during rotation of electrode

An increase in ozone production efficiency is sought by scientists due to the important role ozone plays in improving the human environment such as maintaining higher water and air quality. Ozonizers with electrode rotating systems are a possible way to increase ozone synthesis efficiency. Important questions are why rotating electrodes increase ozone concentration and how they can be controlled. Phenomena determining the increase of ozone concentration must be identified. In our case, a gold rotating electrode was used to eliminate the surface oxidation effect. The oxygen flow rate was 0.5 l/min, applied voltage 10 kV (peak to peak), and frequency approximately 12 kHz. Both ozone concentration and ozone production efficiency improved with the use of a rotating electrode compared to that with a non-rotating electrode, with ozone concentration increasing to about two times higher than that of the case with non-rotation. In addition, input power and discharge area were found to increase with rotating speed. These increases may be due to the increase of discharge length of micro-discharges during electrode rotation. Discharge streamer changed in both shape and length, with the length increasing 10-20%. Ozone produced increased with increasing electrode rotation speed, and the efficiency of ozone production improved by 30% by rotation. In addition, the discharge area became more intense with rotation. Longer micro-discharges during rotation allows generation of an increased number of collisions, leading to higher ozone concentration, which in turn is expected to lead to higher efficiency of ozone generation.