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Branislav PONGRÁC alumni student
PhD. study 2008 - 2014
Supervisor: Zdenko Machala Consultant: -- Title: Study of the Electrospraying of Water in Combination with Atmospheric Pressure Corona Discharge Abstract: This thesis explores the effect of electrospraying of water in combination with
atmospheric positive DC corona discharge in air. The electrospraying effect of liquids
has been a subject of research since the beginning of the last century and found
importance in many diverse fields. Recently, one of the potential uses of water
electrospray, especially large flow rate modes, has become a decontamination of water
from organic and microbial pollutants. The presence of an electrical discharge
generating non-thermal plasma in the spraying zone allows for very efficient mass
transfer of plasma-generated species into water. We used a point-to-plane geometry of
electrodes with a various types of hollow syringe needle anodes opposite to the metal
mesh cathode. We employed the iCCD and high-speed (HS) camera visualization
techniques, oscilloscopic discharge current measurements, total average current
measurements, and optical emission spectroscopy (OES). These were used in order to
visualize the formation of water jets (filaments) in various electrospraying modes and to
investigate the corona discharge behavior during this process. The following modes of
electrospraying typical for water were observed: dripping mode and spindle modes for
low and medium flow rates, and simple jet modes for high flow rates. The geometry of
the HV stressed electrodes had a significant influence on the electrospraying process. A
nozzle was more suitable for stable electrospray generation and a needle for intense
discharge generation. We observed different electrospraying and corona discharge
behavior in dependence on the water flow rate and water conductivity. Generally,
pointy, elongated, and fast spreading water filaments were observed for lower water
conductivity; in contrast to rounder, broader, and shorter quickly disintegrating
filaments for higher conductivity. In addition, with increasing conductivity, the
breakdown voltage for corona-to-spark transition was decreasing. For a limited range of
voltages, the frequency of intermittent water filament generation in spindle modes
agreed well with the frequency of the measured streamer current pulses. After each
streamer, a positive glow corona discharge was established on the water filament tip and
it propagated from the stressed electrode along with the water filament elongation.
These results show a reciprocal character of the intermittent electrospraying of water
and the presence of corona discharge, where both the electrospray and the discharge
affect each other.
MSc. study 2006 - 2008
Supervisor: Zdenko Machala Consultant: -- Title: Decontamination of water by DC electrical discharges Abstract: The aim of the work was the investigation of biodecontamination of water contaminated by Salmonella typhimurium, by using two types of direct current (DC) electrical discharges in atmospheric air, in point-to-plane geometry of electrodes. We used streamer corona and transient spark in both polarities (positive and negative). We also investigated the effect of these discharges on decolorization of water contaminated by organic dyes. It is well known that DC atmospheric discharges generate non-equillibrium plasma with a high electron densitiy and with a relatively low gas temperature (to 650 K). This is important for various environmental applications. These kind of discharges generate high concentrations of various active species and radicals. In our case, the water was flowing directly through the HV needle electrode into the active discharge area. In this configuration we observed the effect of electrospraying of water. In all cases, we observed a significant decrease of bacteria concentration (efficiency 90 %). Also the the decrease of organic dye color intensity was observed. The radicals and active species play a major role in the process of decontamination.
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Active
PhD students:
Jana KŠANOVÁ
Darina KUŽMOVÁ
Ramin MEHRABIFARD
Zuzana OKRUHLICOVÁ
Pankaj PAREEK
Gokul SELVARAJ
Sergei SMIRNOV
Peter TÓTH
MSc/Bc students:
Dominik DIŇA
Alumni
PhD students
MSc students
Bc students
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