1,720,986 research outputs found
Self-tuning high-voltage and high-frequency sinusoidal power supply for dielectric barrier discharge plasma generation
Full text linkIn this paper a high-voltage sinusoidal power supply controlled by Arduino DUE micro-controller is described. This generator can feed a dielectric barrier discharge (DBD) load with sinusoidal voltages up to 20 kV peak and frequencies in the range 10–60 kHz, with a maximum output power of 200 W. Output voltage can be produced either in a continuous mode, or with on/off modulation cycles, according to treatment/application requirements. This power source is equipped with on-board diagnostics used to measure the output voltage and the charge delivered to the load. With a sample frequency of 500 kHz, Arduino DUE allows to evaluate both the high voltage and the average power feeding the discharge without the use of an expensive external measurement setup. Lissajous techniques are utilized to calculate discharge average power in a quasi-real-time manner. When a load is connected to high-voltage terminals, a self-tuning procedure is carried out to obtain the best working frequency. This parameter allows to minimize power-electronic component stress and to maximize generator efficiency
Inactivation of Eimeria spp. oocysts in aqueous environment assisted by a gas-liquid dielectric barrier discharge
No full textAmong human and animal diseases agents, parasites are those that show, with very few exceptions, an environmental resistance far superior with respect other pathogens [1]. This is due to the complex structure of the wall of their infective stages, that makes them particularly resistant to almost all physical and chemical agents. In this work, a novel technique to inactivate coccidian parasites in liquid environment has been investigated and implemented. A Petri dish filled with 20 ml of water contaminated by Eimeria spp. oocysts has been placed within a plasma reactor constituted by a lower HV exposed electrode and an upper grounded copper strip electrode covered by a ceramic slab (Fig. 1). The reactor has been supplied with sinusoidal and nanosecond-pulsed voltage waveforms varying the application time. In both cases an atmospheric pressure Dielectric Barrier Discharge (DBD) has been ignited in the air gap above the liquid surface and in contact with it [2]. The temperature of the solution and its pH level were not significantly changed by plasma treatment. The concentration of ozone and hydrogen peroxide increase by increasing treatment time [2]. Plasma treatment efficacy has been detected considering a representative population of 100 oocysts. For both discharges, treatment efficacy has been found to be dose dependent (Fig. 2). After an energy dose treatment of about 100 kJ/l, the number of sporulated oocytes are roughly halved with respect the control sample. Results are statistically significant with a p<0.01 in the worst case.
[1] N.C. Smith, F.J. Lunden, H.D. Chapman, Parasitology Today, 14, 215-218 (1998).
[2] Neretti G, Taglioli M, Colonna G and Borghi C A, Plasma Sources Sci. Technol. 26, 015013 (2017)
A multi-stage model for dielectric barrier discharge in atmospheric pressure air
Full text linkIn this paper, a multi-stage numerical methodology for the description of the Dielectric Barrier Discharge physics in air is discussed. The behavior of the heavy species is computed using drift-diffusion equations. Electrons are taken into account by solving a non-linear formulation of electrostatics. The physical effects of the steamer discharges are modelled by means of a simplified 0D approach. The model also includes a semi-implicit 0D model for the assessment of the elementary chemical processes occurring in air. The developed methodology is employed for the simulation of a volumetric Dielectric Barrier Discharge reactor. The obtained species number density and surface charge deposition rates and are shown and discussed
Effect of nanofillers in HVDC insulations on surface partial discharge activity
No full textOne of the most important parts of HVDC cable systems are terminations and joints, since they are often points of failure. The field distribution and dynamics of those regions are strongly influenced by the electrical properties of surfaces, due to the presence of strong tangential electric fields able to locally incept surface partial discharges or breakdown. This paper has the main purpose to assess the influence of nanofillers on the mobility of electrostatic surface charge buildup, and the effects on Partial Discharge inception and repetition rate characteristics of HVDC dielectrics. Flat specimens were produced and tested using different thermoplastic dielectrics, some of which belonging to the family of nano-filled materials. Results show that nanofillers have a profound effect on electrostatic charge buildup, strongly reducing their mobility
Measurement of the charge distribution deposited by an annular plasma synthetic jet actuator over a target surface
No full textAnnular plasma synthetic jet actuators demonstrated their ability to produce a tubular flow normal to the surface where the dielectric barrier discharge (DBD) is ignited. These fluid-dynamic actuators enhance the delivery of reactive species towards the target to be treated. In these actuators, long life charged particles are generated within the plasma region and then carried on by the induced flow. In this work, the potential distribution induced by charges deposited over an insulating target has been measured. Surface DBD actuators, made with different dielectric materials, have been supplied by different sinusoidal voltages at a constant average power supplying the discharge. Actuators with the exposed electrode connected to both the high voltage potential and grounded have been tested. The charge distribution accumulated on a target surface perpendicular to the flow has been measured at different time intervals with the plasma on. Charges advected by the flow are always positive. The potential distribution on the target surface generated by the charges has been measured. For both configurations, firstly an M-shaped distribution develops and, later on, it becomes bell-shaped. A charge build-up mechanism has been found to be faster when the exposed electrode is connected to the high voltage terminal. The target has been placed at a variable distance from 1 to 5 cm from the actuator surface. At a distance of 5 cm, induced potentials are two times smaller than those with the target at 1 cm. Measurements allow us to estimate a charge flux toward the target on the order of 1011 particles (cm2 s)−1. The results presented in this work show that the presence of charged particles in the jet flow outside the plasma could be an important factor to be accounted for when these plasma actuators are used for treatment purposes (indirect plasma treatment)
Measurement of the charge distribution deposited on a target surface by an annular plasma synthetic jet actuator: Influence of humidity and electric field
Full text linkIn this paper, an investigation on an annular Plasma Synthetic Jet Actuator (PSJA) utilizing a Surface Dielectric Barrier Discharge (SDBD) is reported. The work is focused at an investigation of the electric charges transported by the jet produced by the actuator and deposited on a target. Particularly, an assessment of the various factors that may affect the charge deposit process has been carried out. Experiments have been performed in a controlled environment with different electric configurations. This allowed to evaluate how the humidity rate affects and the dynamics of the electric charge build-up process. It was observed that humidity rate weakly affects the charge deposition, being the most notable effect an increase of the deposition time for higher humidity rate. Moreover, the performances of two different power supply systems, working at different voltage and frequency conditions, were compared. The two supplies have been set up do feed the actuator with the same power, in order to assess which voltage-frequency condition is more efficient at depositing electric charge on the target. It was observed that a higher applied electric field produces higher charge deposition rates
Square-Wave-Fed Cockcroft-Walton Voltage Multipliers for Ionic Propulsion in Atmosphere
Full text linkThe development of high-power-density and efficient high-voltage DC/DC power electronic circuits plays a crucial role in ionic propulsion's potential employment. Traditional voltage multipliers (VMs) are typically fed by sinusoidal voltages delivered by a resonant converter coupled with a high-voltage step-up transformer. This paper explores a transformerless solution, achieved by feeding the VM directly with the inverter's square wave output voltage. Although requiring additional multiplier stages to get the same output voltage level, this configuration simplifies the implementation and could be suitable for size- and weight-sensitive applications. The performance and feasibility of the square-wave-fed VMs are evaluated, and it is demonstrated that lower output voltage ripple and drop and better system dynamic response are achieved with this approach
Atmospheric‐pressure plasma actuators: Enhancement of the free charges' transport mechanism
Full text linkCharge particles can increase the biocidal efficacy of nonthermal plasmas in
indirect treatments. The aim of this study is to increase the amount of free
charges produced and delivered by a surface dielectric barrier discharge fluid‐
dynamics actuator. Different linear actuators and supplying conditions have
been considered. Actuators were utilized to produce an ionic wind impinging
an insulating target surface. Charged particles' distribution over the target was
measured with and without a metallic mesh between the actuator and target
itself. Linear actuators have proven to be more effective in charge delivery
with respect to an annular one previously studied by our research team. A two‐ dimensional electrostatic finite‐element analysis has been carried out to get a better insight into this physical behavior
Ozone yield limit in low temperature plasmas based on thermodynamics
No full textAbstract: To investigate ozone yield limit in low temperature plasmas, a detailed thermodynamic model is developed to calculate theoretical ozone yield for the first time. Theoretical ozone yield is calculated both from overall reaction and detailed reactions. In the former case, the highest theoretical ozone yield of 1211 ± 2 g kWh−1 is obtained when final gas temperature equals the initial one, and all energy is effectively utilized to synthesize ozone. When final gas temperature is not equal to the initial one, theoretical ozone yield increases with the increase of oxygen admixture ratio and oxygen conversion ratio as well as the decrease of final gas temperature. Theoretical ozone yields are 921.22 g kWh−1 and 487.54 g kWh−1 in pure oxygen and in synthetic air respectively at final gas temperature of 400 K and oxygen conversion ratio of 10%. When detailed reactions and electron energy distribution function is considered, theoretical ozone yield rapidly increases by enhancing reduced field. Oxygen admixture ratio also has non-negligible effects on ozone yield. A higher oxygen admixture ratio leads to higher energy efficiency. The theoretical ozone yields are 238.92 g kWh−1 and 191.14 g kWh−1 in pure oxygen and in synthetic air at reduced field of 300 Td respectively. Graphical abstract: [Figure not available: see fulltext.]
Real Time Power Control in a High Voltage Power Supply for Dielectric Barrier Discharge Reactors: Implementation Strategy and Load Thermal Analysis
Full text linkAtmospheric-pressure plasma treatments for industrial and biomedical applications are often performed using Dielectric Barrier Discharge reactors. Dedicated power supplies are needed to provide the high voltage frequency waveforms to operate these nonlinear and time-dependent loads. Moreover, there is a growing technical need for reliable and reproducible treatments, which require the discharge parameters to be actively controlled. In this work, we illustrate a low-cost power supply topology based on a push-pull converter. We perform experimental measurements on two different reactor topologies (surface and volumetric), showing that open loop operation of the power supply leads to a temperature and average power increase over time. The temperature increases by Delta T-vol similar to 120 degrees C and Delta T-sup similar to 70 degrees C, while the power increases by Delta P-vol similar to 78% and Delta P-sup similar to 60% for the volumetric (40 s) and superficial reactors (120 s), respectively. We discuss how these changes are often unwanted in practical applications. A simplified circuital model of the power supply-reactor system is used to infer the physical relation between the observed reactor thermal behavior and its electrical characteristics. We then show a control strategy for the power supply voltage to ensure constant average power operation of the device based on real-time power measurements on the high voltage side of the power supply and an empirical expression relating the delivered power to the power supply output voltage. These are performed with an Arduino Due microcontroller unit, also used to control the power supply. In a controlled operation the measured power stays within 5% of the reference value for both configurations, reducing the temperature increments to Delta T-vol similar to 80 degrees C and Delta T-sup similar to 44 degrees C, respectively. The obtained results show that the proposed novel control strategy is capable of following the transient temperature behavior, achieving a constant average power operation and subsequently limiting the reactor thermal stress
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