Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Barrier discharge.
Дисертації з теми "Barrier discharge"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Barrier discharge".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Vander, Wielen Lorraine C. "Dielectric barrier discharge-initiated fiber modification." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7091.
Повний текст джерела
2
Vander, Wielen Lorraine C. "Dielectric barrier discharge-initiated fiber modification." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/ipstetd-1054/.
Повний текст джерела
3
Roveda, Fabio <1984>. "Numerical analysis of Dielectric Barrier Discharge." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4572/.
Повний текст джерелаАнотація:
A numerical investigation of dielectric barrier discharge aimed to simulate the electro hydro dynamic interaction is presented. A discharge drift diffusive model according to the Townsend avalanche is described and used to duplicate the plasma kinetics of a DBD actuator. The discharge characteristics dependence upon dielectric material and applied voltage are simulated and the EHD force field according to a simplified approach is presented and discussed.
The coupling of DBD results with a fluid dynamic code is also shown.
Finally, a new non invasive diagnostic technique for EHD interaction based on Schlieren imaging is computationally validated.
4
Stanfield, Scott Alan II. "A SPECTROSCOPIC INVESTIGATION OF A SURFACE-DISCHARGE-MODE, DIELECTRIC BARRIER DISCHARGE." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1261582116.
Повний текст джерела
5
Dufresne, Michel 1962. "Fluid model of dielectric barrier gas discharge." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34520.
Повний текст джерелаАнотація:
A two-fluid model of dielectric barrier gas discharge is presented in this thesis. The model predicts the physical structure of the gas discharge obtained between two electrodes, when one is covered with a dielectric material: It predicts the distribution of the electron and ion particle densities, electron energy, and electric field strength. It is a self-consistent numerical model, in which the dielectric properties of the dielectric material are included and the geometry of the electrodes is taken into account, thus coupling the charged-particle transport to the electric field.New boundary conditions are developed for the electron gas at the anode; the results indicate that the common boundary conditions frequently used in the literature give solutions with non-physical behavior. The new boundary conditions give solutions with the expected physical behavior.
The equations of the model are formulated numerically using a Galerkin finite element method and solved using the Newton iteration method. New universal matrices for the finite element method are presented which can be used to construct complex finite element matrices, by replacing integrals with matrix products, in a consistent and uniform manner independent of element shape, dimensionality, and order.
Solutions for DC, pulse-waveform and time-harmonic applied electrode voltages for geometries with and without a dielectric barrier are presented. The regulating effect of the dielectric barrier by surface charge accumulation is shown for discharge under constant applied voltage, assuming a static temperature for the electron gas, for the full self-consistent model. Also, simulations of dielectric barrier discharge with applied pulse-waveform voltages are compared with simulations of applied time-harmonic voltages. The results show very similar period-averaged electric fields, electron temperature profiles, charged particle densities, and total conduction current densities. However, a much higher period-integrated ionization rate is obtained from voltage pulse simulations, compared to time-harmonic voltage simulations. Therefore, we obtain a greater reaction rate for an equivalent conduction current, in a period-averaged sense, for a discharge driven by pulse-waveform applied voltages than with time-harmonic applied voltages. Such a difference was not observed for simulations without the dielectric barrier.
6
Dufresne, Michel. "Fluid model of dielectric barrier gas discharge." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ36971.pdf.
Повний текст джерела
7
Grundmann, Sven. "Transition control using dielectric barrier discharge actuators /." Aachen : Shaker, 2008. http://d-nb.info/990886751/04.
Повний текст джерела
8
Zhou, Yingjia. "Optimisation of ozone generation using dielectric barrier discharge." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30240.
Повний текст джерелаАнотація:
The aims of the research include understanding the fundamental kinetics of ozone generation using dielectric barrier discharge and investigating the potential to optimize the process to improve ozone generation efficiency. The kinetics of ozone generation and its limitations are reviewed. The discharge characteristics of single filaments are investigated by analysing its equivalent circuit and the distribution of current magnitude. The parallel-plane electrode is used for the investigation of the relationship between current distribution, reduced electric field and ozone generation efficiency. The maximum ozone efficiency of the experiment is 207 g/kWh at the reduced electric field of 120 Td. With the increase of reduced electric field from 120 Td to 280 Td, the ozone generation efficiency drops to 109 g/kWh. The meshed electrode configuration was employed to optimize the ozone efficiency. The highest ozone efficiency achieved is over 330 g/kWh at ~ 100 Td which is twice higher than the commercial ozone generator. It is found that the distribution of external current amplitude using meshed electrode is narrower compared to planar plates. To further understand ozone generation kinetics, the gas discharge is generated at cryogenic temperature of -183 °C using liquid oxygen. The liquid ozone is produced and the highest ozone efficiency achieved is ~ 460 g/kWh. The ozone dissociation reactions involving atomic oxygen and free electrons and the humidity effect at cryogenic temperature of -183 °C were effectively limited.
9
Grundmann, Sven [Verfasser]. "Transition Control using Dielectric Barrier Discharge Actuators / Sven Grundmann." Aachen : Shaker, 2008. http://d-nb.info/1161304355/34.
Повний текст джерела
10
Urabe, Keiichiro. "Spectroscopic Study of Dielectric Barrier Discharge at Atmospheric Pressure." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157532.
Повний текст джерела
11
Medini, Federico. "Physico-chemical characterization of a surface barrier discharge plasma source." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Знайти повний текст джерелаАнотація:
Cold Atmospheric pressure Plasmas (CAP) generated by Dielectric Barrier Discharges (DBDs) are being studied and developed for an ever-widening range of applications in both biomedical and industrial areas.
In particular surface DBDs (SDBDs), consisting of a planar powered electrode separated from a grounded mesh by a thin dielectric layer, have been gaining great interest for their ability to produce highly reactive atmospheres at close-to-environmental temperature and almost independent from the electrical properties of the target, which is treated in the afterglow of the surface plasma.
The active chemistry initiated in the afterglow of SDBDs operated in air is characterized by the presence of long-lived reactive oxygen and nitrogen species such as O3, NOx and HNOx, which are recognized to play an important role in many industrial and biomedical applications based on the use of the plasma afterglow.
Knowing the kinetics of all the chemical species produced in the plasma and in its afterglow is then fundamental to control and optimize the processes for which SDBDs are being used.
This project focuses on the physico-chemical characterization of a SDBD plasma source developed by the research group in Industrial Application of Plasmas (AIP - DIN - Alma Mater Studiorum), supplied with a high voltage AC generator with tunable frequency and duty cycle.
First a study of the surface power density (SPD) variation as a function of voltage, frequency and duty cycle was made. Then the kinetics of O3/NO2/NO3 concentrations in the plasma afterglow were studied by means of OAS measurements.
This project’s main aim is to gather additional knowledge on the kinetics of the produced reactive species, comparing the results with the ones from other works from literature, providing additional evidence about SPD being the driving parameter for plasma afteglow kinetics.
A second aim is to provide a set of data that can be used as input and validation for future modelling tools.
12
Davis, Amanda Kathryn. "Nanosecond Pulse Dielectric Barrier Discharge Plasma Actuation in Supersonic Flow." Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/243933.
Повний текст джерелаАнотація:
Boundary layer control is a topic of constant concern in the area of aerodynamics. This study addresses a possible new method of affecting boundary layers and shock structure in supersonic flow. Nanosecond pulse dielectric barrier discharge plasma actuators are tested on a flat plate in a supersonic wind tunnel. Effects were observed using schlieren imaging to analyze changes in density gradients in the flow. While no noticeable results were found, the flow Mach numbers and electrical characteristics tested were very limited in variety due to complications with discharge formation and plate design. Much was learned to suggest improvements for further testing and this will facilitate later tests of similar technologies in this area of interest.
13
Zhang, Yiyun S. M. Massachusetts Institute of Technology Department of Aeronautics and Astronautics. "Pulsed nanosecond dielectric barrier discharge in nitrogen at atmospheric pressure." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127118.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 85-87).
Small power devices are of strong interest as many electronics are made more compact. Those portable power sources are widely used in aerospace applications such as small UAVs and satellite thrusters. Typically, these portable devices rely on batteries, but small power generators based on hydrocarbon fuel micro-combustors have much higher energy densities. However, flame instability and extinction are difficult to avoid at small scales. Because of the high surface to volume ratio, significant heat loss and radical quenching at the walls take place. To address this challenge, plasma has shown capabilities in facilitating combustion through thermal, kinetic and transport effects. In this work, a preliminary study of plasma discharge at atmospheric pressure is conducted as the first step to understand Plasma-Assisted Combustion (PAC) at micro scales.
Among various electric discharge mechanisms, Dielectric Barrier Discharge (DBD) is chosen due to its ability to generate non-thermal plasma at atmospheric pressure with a simple geometry and a low power consumption. Repetitive Pulsed Nanosecond Discharge (RPND) technique is also studied. It provides repetitive high voltage pulses on the order of 10 - 20 nanoseconds and is a common technique in non-equilibrium plasma generation. A 1D DBD model is constructed for a volume discharge. It couples particle continuity equations with Poisson's equation, and solves for electric field and charged particle number densities. The numerical model is discretized in space and time to obtain charged particles evolution and electric properties. The model is firstly validated with open literature for both AC and RPND, and is then applied to our DBD setup at atmospheric pressure. In addition, a nitrogen (and air) discharge experiment is designed and operated with RPND.
Preliminary results show the capability to generate sustainable and uniform plasma at atmospheric pressure. The appearance is that of a uniform glow plasma free of micro-discharges. Several experimental findings help to understand the discharge physics and set a foundation for future applications in micro-scale combustion.
by Yiyun Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
14
Mouele, Emile Salomon Massima. "Water treatment using electrohydraulic discharge system." University of the Western Cape, 2014. http://hdl.handle.net/11394/4330.
Повний текст джерелаАнотація:
>Magister Scientiae - MScIn South Africa, water pollution problems have continued to increase due to increasing anthropogenic activities. The increasing number of organic contaminants in various water sources can be attributed to industrial development, population growth and agricultural run- off. These activities have impacted negatively on the availability and accessibility to sustainable clean water resources, exposing citizens to water borne diseases such as cholera, diarrhoea and typhoid fever; commonly reported among children. Advanced oxidation technologies such as dielectric barrier electrohydraulic discharge (EHD), also referred to as dielectric barrier discharge (DBD), have the ability to decompose persistent organics and eliminate microbes. DBD offers advantages such as efficiency, energy saving, rapid processing, use of few or no chemicals, and non-destructive impact on the ecosystem. The system is also capable of generating ozone, hydrogen peroxide, singlet oxygen, superoxide radicals, hydroxyl radicals and other active species. The combination of these reactive species has been reported to degrade biological and chemical pollutants rapidly and efficiently. In this study, the DBD system was optimized by investigating the effect of physico-chemical, electrical parameters and reactor configurations on Methylene Blue (MB) decolouration efficiency. The physico-chemical parameters included MB concentration, solution pH and conductivity, solution volume, NaCl electrolyte concentration in the electrode compartment and air flow rate. As for electrical parameters, the effects of voltage, electrode type and size on MB decolouration efficiency were studied. The effect of the aforementioned parameters on MB decolouration efficiency was assessed by varying one parameter at a time. The following physico-chemical parameters: time (from 0 - 60 minutes), pH (2.5 - 10.5), solution conductivity (5 - 20 mS/cm), MB concentration (0.5 – 10 mg/L), solution volume (500 – 2000 mL), NaCl electrode electrolyte concentration (10 – 50 g/L) and air flow rate (2– 4 L/min) were varied in their respective ranges under the applied experimental conditions: reactor air gap 2 mm, solution volume 1500 mL, NaCl electrolyte concentration of 50 g/L in the electrode compartment, voltage 25 V (7.8 kV), airflow rate 3 L/min, 0.5 mm silver electrode and a running time of 60 minutes. As for electrical parameters, voltage (from 20 - 25 V), electrode type (copper, silver and stainless steel) and electrode diameter (0.5 – 1.5 mm) were also altered individually at the applied experimental conditions. The reactor air gap was varied from 2 to 6 mm. At the same experimental conditions, the free reactive species generated mainly H2O2 and O3, were detected and quantified using the Eisenberg and indigo methods, respectively. The optimum physico-chemical parameters were found to be MB concentration 5 mg/L, concentration of NaCl electrolyte used in the central compartment of the DBD reactor 50 g/L, solution pH 2.5, solution conductivity 10 mS/cm, air flow rate 3 L/min, solution volume 1500 mL and an optimum contact time of 30 minutes. The optimum electrical parameters were found to be: applied voltage 25 and 1.5 mm silver electrode. The following parameters MB concentration, solution conductivity and pH, applied voltage and reactor configuration significantly affected MB decolouration efficiency compared to parameters such as solution volume, the inlet air flow rate, electrode type and size and NaCl electrolyte concentration in the electrode compartment, which were less effective in enhancing MB decolouration. Moreover, for all DBD experiments performed at the applied experimental conditions, complete decolouration of MB was achieved in the first 30 minutes. However, trends between the optimized parameters and MB decolouration efficiency were mostly observed after 10 minutes. The optimized DBD system reduced the treatment time from 30 to 20 minutes without any chemical additives. Moreover, at 5 mg/L MB under the applied optimum conditions, it was proved that besides 99% of MB decolouration reached after 60 minutes, 53% of total organic carbon (TOC) removal was also achieved. The chemical oxygen demand (COD) characterizing MB toxicity was less than 5 mg/L before as well as after the DBD experiment. After 10 minutes of experiment under the following conditions: Applied voltage 25 V, MB concentration 5 mg/L, solution pH (in between 6.04 and 6.64), solution volume 1500 mL, air flow rate 3 L/min, 0.5 mm silver electrode and a contact time of 60 minutes, about 3.73 x 10-5 mol/L H2O2 was produced which decreased to 2.93 x 10-5 mol/L 10 minutes later, while O3 concentration was initially very low and could not be detected. However, 0.5 mol/L of O3 was detected after 20 minutes of operating time, thereafter, H2O2 concentration decreased continuously with time while that of O3 fluctuated as the treatment time increased. Likewise, the energy density for the production of free reactive species reached 0.87 g/ kWh in the first 10 minutes due to the presence of chromophoric functional groups such as =N+(CH3)2 in MB structure that had to be destroyed. Thereafter, the energy consumption decreased progressively to zero with an increase in treatment time due to the destruction of =N+(CH3)2 groups in MB structure with time. The correlation between the rise in the of H2O2 concentration and energy density after 10 minutes was probably due to dissociation of OH- OH bonds in H2O2 by UV light to yield OH radicals which unselectively may have attacked MB dye. Thus, MB decomposition in the current DBD reactor was mostly initiated by H2O2 and O3. The irradiation of H2O2 by UV light generated in the DBD system was found to accelerate dye decomposition in the first 30 minutes of the experiment. The UV-vis analysis of treated MB samples confirmed that the complete decolouration of MB achieved in the first 30 minutes was due to the destruction of the chromophoric [=N+(CH3)2] group in Methylene blue structure, while the FT-IR confirmed the presence of traces of various functional groups such as C=C, C=O, C=N, NH, NH3, NO2, etc. characteristics of carboxylic acids, amines, amides, nitrogen based compounds (salts), aliphatic and unsaturated by-products remaining in the bulk solution after treatment. The salts analysis after treatment showed that 16 mg/L of nitrates and nitrites and 1.1mg/L of sulphates mainly originating from air and MB decomposition were present in the treated samples. The EHD/DBD system used in this study offers an approach to partially treat water/wastewaters and its optimization was able to significantly enhance the decomposition of the target MB dye as indicated by the reduction of total organic carbon (TOC) from 8.3 mg/L to 3.9 mg/L. Compared to previous research, this study successfully optimised a complete double cylindrical dielectric barrier discharge (DBD) reactor at ambient condition without any chemical additives.
15
Munther, Timothy P. "Characterization of dielectric barrier discharge plasma actuators for flow separation control." Connect to resource, 2007. http://hdl.handle.net/1811/25081.
Повний текст джерелаАнотація:
Thesis (Honors)--Ohio State University, 2007.Title from first page of PDF file. Document formatted into pages: contains vii, 55 p.; also includes graphics. Includes bibliographical references (p. 55). Available online via Ohio State University's Knowledge Bank.
16
Lindon, Michael Allen. "CO2 Dissociation using the Versatile Atmospheric Dielectric Barrier Discharge Experiment (VADER)." Thesis, West Virginia University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3618122.
Повний текст джерелаАнотація:
As of 2013, the Carbon Dioxide Information Analysis Center (CDIAC) estimates that the world emits approximately 36 trillion metric tons of Carbon Dioxide (CO2) into the atmosphere every year. These large emissions have been correlated to global warming trends that have many consequences across the globe, including glacial retraction, ocean acidification and increased severity of weather events. With green technologies still in the infancy stage, it can be expected that CO2 emissions will stay this way for along time to come. Approximately 41% of the emissions are due to electricity production, which pump out condensed forms of CO2. This danger to our world is why research towards new and innovative ways of controlling CO2 emissions from these large sources is necessary.
As of now, research is focused on two primary methods of CO2 reduction from condensed CO2 emission sources (like fossil fuel power plants): Carbon Capture and Sequestration (CCS) and Carbon Capture and Utilization (CCU). CCS is the process of collecting CO2 using absorbers or chemicals, extracting the gas from those absorbers and finally pumping the gas into reservoirs. CCU on the other hand, is the process of reacting CO2 to form value added chemicals, which can then be recycled or stored chemically.
A Dielectric Barrier discharge (DBD) is a pulsed, low temperature, non-thermal, atmospheric pressure plasma which creates high energy electrons suitable for dissociating CO2 into its components (CO and O) as one step in the CCU process. Here I discuss the viability of using a DBD for CO2 dissociation on an industrial scale as well as the fundamental physics and chemistry of a DBD for CO2 dissociation. This work involved modeling the DBD discharge and chemistry, which showed that there are specific chemical pathways and plasma parameters that can be adjusted to improve the CO2 reaction efficiencies and rates. Experimental studies using the Versatile Atmospheric dielectric barrier Discharge ExpeRiment (VADER) demonstrated how different factors, like voltage, frequency and the addition of a photocatalyst, change the efficiency of CO2 dissociation in VADER and the plasma chemistry involved.
17
Ayan, Halim Friedman Gary Friedman Alexander. "Uniform dielectric barrier discharge with nanosecond pulse excitation for biomedical applications /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3078.
Повний текст джерела
18
Wilde, Nicholas David. "Optimization of surface dielectric barrier discharge ion sources for electroaerodynamic propulsion." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127106.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 33-34).
Surface dielectric barrier discharges (SDBDs) are a type of asymmetric dielectric barrier discharge (DBD) that can be used to generate ions and produce aerodynamic forces in air. They have been studied for aerodynamic flow control and proposed for small aircraft propulsion as both direct sources of thrust and as ion sources for "decoupled" electroaerodynamic (EAD) propulsion, in which decoupling ionization from ion-acceleration provides performance and control advantages. SDBDs can also be integrated into aircraft surfaces without introducing additional drag. A challenge for these aerospace applications is minimizing the power draw (or maximizing the efficiency) of these actuators. Optimizing SDBD actuators requires a robust model for SDBD electrical power draw as a function of geometric, material, and electrical properties.
Existing approaches use empirical power law fits to estimate the power of a specific DBD configuration at certain electrical operating points; they are challenging to use in engineering design and optimization as they require experimental measurements for each individual configuration. This thesis proposes the first physics-based model for surface DBD power consumption. The proposed model is based on established models for parallel-plate or "volume" DBDs, and it incorporates the effect of changing plasma length that is specific to SDBDs. This thesis examines SDBDs of three materials, eleven thicknesses, and 394 unique electrical operating points and finds a correlation with R² = 0.99 (n = 394) between experimentally-measured power and model-predicted power. SDBD power measurements extracted from four other experiments from the literature are analyzed with a correlation of R² = 0.97 (n = 101), demonstrating that the model is generalizable to other SDBD constructions.
Ionization rate is also measured to facilitate optimization for use in decoupled EAD thrusters. This work enables the quantitative design and optimization of SDBDs for EAD propulsion and other applications in aerospace and beyond.
by Nicholas David Wilde.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
19
Little, Jesse. "High-Lift Airfoil Separation Control with Dielectric Barrier Discharge Plasma Actuators." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1267836038.
Повний текст джерела
20
Frankhouser, Matthew William. "Nanosecond Dielectric Barrier Discharge Plasma Actuator Flow Control ofCompressible Dynamic Stall." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449188933.
Повний текст джерела
21
Donohue, Kevin Vincent. "Analysis of the Effects of a Dielectric Barrier Discharge on Arthropod Pests." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-06012005-215408/.
Повний текст джерелаАнотація:
Atmospheric pressure plasma discharge (APPD) has been intensely studied in the past fifteen years as a method of sterilization. The effects of APPD on insects were previously unknown. The purpose of this study was to examine whether plasma could be useful for insect and mite control, determine the mode of action on arthropods, and optimize the discharge in order to achieve the shortest APPD treatment times. A positive correlation was found between exposure time to APPD and insect mortality with the level of mortality also increasing with time after treatment for western flower thrips, Frankliniella occidentalis (Pergande), tobacco thrips, Frankliniella fusca (Hinds), Asian tiger mosquito, Aedes albopictus (Skuse), two-spotted spider mite, Tetranychus urticae Koch, and German cockroach, Blattella germanica (L.). Generally, mortality was negatively correlated with the weight of the insect. Cockroaches exposed to APPD for 60, 90, 120 and 180s lost on average 7.5 ± 0.8, 8.1 ± 0.6, 8.7 ± 0.4, and 10.1 ± 1.1 (±1 SEM) mg of water weight, respectively, which was an increase over that of the controls. The metabolic rate of cockroaches exposed to plasma for 180 s increased from 0.80 ± 0.03 to 1.07 ± 0.04 ml of oxygen consumed mg-cockroach -1 h-1 at STP. The level of cuticular hydrocarbons identified by EI GC-MS were not significantly affected by plasma exposure in the green peach aphid, Myzus persicae (Sulzer), German cockroach, and citrus mealybug Planococcus citri (Risso) except for a reduction in n-tritriacontane only in the latter. However, changes in the behavior of cockroaches after plasma exposure including the loss of photo-, vibro-, and thigmotropic responses, inability to right themselves, and hyperexcitatory symptoms, suggests that the site-of-action of APPD in insects is the nervous and/or neuromuscular system. The LT50 of German cockroaches, western flower thrips, and citrus mealybugs 24 h after exposure to a 37°C helium discharge was 333.77, 28.72, and 999.95 s, respectively. The LT50?s 24 h after exposure to a 37°C, 0.5% oxygen/99.5% helium discharge was 232.67, 19.99, <13.83 s, respectively. The LT50 of German cockroaches, western flower thrips, and citrus mealybugs 24 h after exposure to the 50 ± 2°C, helium discharge was 117.80, 13.83, and 26.62 s, respectively. No mortality resulted in German cockroaches or citrus mealybugs after exposure to a helium atmosphere followed by 50°C air, however the LT50 of western flower thrips was 29.04 s, based on the mortality recorded 24 h after treatment. The addition of oxygen or heat to the discharge resulted in higher mortality in cockroaches and mealybugs but not thrips.
22
Algwari, Q. Th. "Plasma jet formation and interactions between atmospheric pressure dielectric barrier discharge jets." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545999.
Повний текст джерела
23
Chappell, S. "Active control with dielectric barrier discharge actuators applied to high-lift devices." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359742/.
Повний текст джерелаАнотація:
An experimental investigation examined the capability of dielectric barrier discharge (DBD) actuators to control a high-lift device system. Aerodynamic tests investigated the potential of utilising the actuator to control the flap side-edge vortex flow field. Acoustic tests examined the attenuation of slat noise with a DBD actuator. The sparse knowledge related to the control of a vortex flow field with a DBD actuator necessitated a more fundamental study that used a NACA 0015 wing. From this study, it was shown that the application of control resulted in a more diffused tip vortex. The actuator's ability to control the evolving vortex flow field was weakly dependent on the Reynolds number but strongly dependent on the angle of attack. Consequently, a DBD actuator was applied to a flap side edge. However, it was concluded that the actuator had no discernible effect on the flow field due to its addition of momentum being too low to destabilise the formation of the flap side-edge vortex. The slat research concerned the attenuation of the leading-edge component of high-lift device noise. At an angle of attack of two degrees, several tonal noise components with broadband content appeared in the slat noise spectrum. These noise features were successfully suppressed with a DBD actuator operating in open-loop control. For closedloop control, a quasi-static feedback controller was implemented. Comparable levels of performance were obtained for both control methods with more than a 20 dB reduction achieved in the dominant tonal noise feature. The research conducted shed new light on the application of DBD actuators to control the high-lift device system. However, further research is needed if the device is to be utilised to control flap side-edge flow field. The attenuation of slat tonal noise with broadband content was achieved with the actuator.
24
Karki, Surya B. "Non-thermal Miniature Dielectric Barrier Discharge Plasma for Treatment ofLung Carcinoma Cells." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1523017849495564.
Повний текст джерела
25
Bures, Brian Lee. "Rapid Mortality of Pest Arthropods by Direct Exposure to a Dielectric Barrier Discharge." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-10282004-131510/.
Повний текст джерелаАнотація:
The spread of arthropods due to trade of agricultural commodities and travel of humans is a significant problem in many countries. Limiting the movement of pest species is commonly achieved by the use of chemical pesticides at quarantine facilities. One potential alternative to chemical pesticides is direct exposure of contaminated commodities to ambient pressure electrical discharges. The arthropods are directly exposed to a 5.0 cm helium discharge with power densities on the order of 60 mW/cm3. Direct measurement of chemical species and ambient gas temperature shows the DBD treatment remains effective when the chemically reactive species are suppressed by helium, and when the ambient gas temperature of the discharge is below 40 °C. In addition to gas temperature measurements and chemical species identification, the electron temperature and electron density were measured using the neutral bremsstrahlung continuum technique. This study is the first successful implementation of the neutral bremsstrahlung continuum emission diagnostic to a barrier discharge. The primary advantages of the diagnostic for barrier discharges are the measurement is passive and the spatial resolution is only limited by the collimation of the light and the sensitivity of the detector. Although the electron temperature (1.0-1.5 eV) and electron density (~108 cm-3) are modest, non-chemical dielectric barrier discharge (DBD) treatment of arthropods has proven effective in significantly reducing the population of some arthropods including human body lice, green peach aphids, and western flower thrips. However, the treatment was not universally effective on all arthropod species. German cockroaches and citrus mealy bugs showed substantial resistance to the treatment. The study has shown the treatment does not always induce instant mortality: however, the mortality increases over a 24 hr-period after treatment. Based upon visual observation and the time after treatment to reach maximum mortality, the mode of action is either direct damage to the nervous system or changes to the hydrocarbon layer that protects the arthropods from dehydration.
26
Eriksson, Oscar. "Modeling Dielectric Barrier Discharge plasma actuators to be used for active flow control." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70990.
Повний текст джерелаАнотація:
This Master Thesis work cover the simulation of the movement of charged species exposed to a high gradient electric field, the same environment a plasma actuator produces. The final goal is to use the plasma actuator as an active flow control device to decrease the drag of a body moving in air. This report describes how the problem was set up in COMSOL Multiphysics and the resulting volume force achieved. The volume force is the force generated by the plasma actuator that is acting on the air. To understand the effect of a plasma actuator better experimental work was also performed. The experimental work include what effect a plasma actuator has on a wing that has stalled out and measuring the air velocity obtained from a single plasma actuator. The conclusion is that more work has to be performed to make the plasma actuator a more effective flow control device. This type of work is a way to understand how plasma actuators work and in extension will lead to how a plasma actuator will be used effectively.Detta examensarbete behandlar simuleringen om hur laddade partiklar rör sig när de utsätts för ett elektriskt fält med hög gradient, ett liknande närområde som skapas av en plasma aktuator. Slutmålet är att kunna använda plasma aktuatorer som en aktiv flödeskontroll med avsikt att minimera motsåndet på en stelkropp som rör sig genom luften. Den här rapporten beskriver hur problemet ställs upp i COMSOL Multiphysics och vilken volymkraft som fås utav simulerignen. Volymkraften är den genererade kraft från plasma aktuatorn som aggerar på den omgivande luften. Utöver simuleringen har praktiska experiment gjorts för att förstå effekten från en plasma aktuator bättre. Dessa experiment består av hur en plasma aktuator förändrar luftströmmen över en vinge som redan tappat sin lyftkraft och av att mäta vilken hastighet luften kan nå på grund av en plasma aktuator. Sammanfattnignen är att mer arbete behöver göras för att effektivisera en plasma aktuator om den ska användas för flödeskontrol. Detta arbeta är ett steg i att förstå hur plasma aktuatorer fungerar vilket i förlängningen kommer leda till hur man ska använda en plasma aktuator på bästa sätt.
27
Erfani, Rasool. "Optimisation of dielectric barrier discharge plasma actuators and their application to fluid dynamics." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/optimisation-of-dielectric-barrier-discharge-plasma-actuators-and-their-application-to-fluid-dynamics(44555320-85f1-4e53-afcc-d03f5c2be285).html.
Повний текст джерелаАнотація:
The standard dielectric barrier discharge (DBD) plasma actuator, in which an asymmetric arrangement of electrodes leads to momentum coupling into the surrounding air, has already demonstrated its capability for flow control. The effect of some parameters such as dielectric thickness, dielectric temperature, voltage amplitude, driving frequency, different configurations and arrangements on actuator performance are examined. The new configuration of DBD which uses multiple encapsulated electrodes (MEE) has been shown to produce a superior and more desirable performance over the standard actuator design. As the number of encapsulated electrodes increases and other variables such as the driving frequency and voltage amplitude are considered, finding the optimum actuator configuration for increasing the induced velocity becomes a challenge. The surrogate modelling optimisation provides a cheap and yet efficient method for systematically investigating the effect of different parameters on the performance of the plasma actuator. The effect of the optimum actuator configuration on the aerodynamic performance of an aerofoil under leading edge separation and wake interaction conditions is examined. The plasma actuator is placed at the leadingedge of a symmetric NACA 0015 aerofoil which corresponds to the location of the leading edge slat. The aerofoil is operated at a chord Reynolds number of 0.2×10 6. Surface pressure measurements along with the mean velocity profile of the wake using pitot measurements are used to determine the lift and drag coefficients, respectively. Particle image velocimetry (PIV) is also utilised to visualise and quantify the induced flow field. In comparison with reported literature on the standard DBD configuration, the MEE setup employed here is shown to provide a better means of flow control for the control of aerofoil separation. The characteristicsof a DBD plasma actuator when exposed to an unsteady flow generated by a shock tube is also investigated. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualise the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shocktube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma.
28
Hale, Craig. "Development of dielectric barrier discharge plasma actuators and their application at subsonic speeds." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/development-of-dielectric-barrier-discharge-plasma-actuators-and-their-application-at-subsonic-speeds(27f80126-1236-420c-8d8d-645d6bd9ab22).html.
Повний текст джерелаАнотація:
Plasma actuators are electrical devices that generate a wall bounded jet without the use of any moving parts. For aerodynamic applications they can be used as flow control devices to delay separation and augment lift on a wing. The aim of this project is to initially develop a system capable of generating and sustaining a plasma that generates a wall bounded jet. The next step is to investigate the effect of varying the number and distribution of encapsulated electrodes in the dielectric layer. Finally the best case design is applied at the leading edge and flap shoulder of a NACA0015 aerofoil with a 20% flap. Utilising a transformer cascade, plasma has been generated for a variety of input voltages. In the quiescent environment of a Faraday cage the velocity flow field is recorded using particle image velocimetry (PIV). Through understanding of the mechanisms involved in producing the wall jet and the importance of the encapsulated electrode a novel actuator design was investigated. The actuator design distributes the encapsulated electrode throughout the dielectric layer. The experiments have shown that actuators with shallow initial encapsulated electrodes induce velocities greater than the baseline case at the same voltage. Actuators with a deep initial electrode are able to induce the highest velocities as they can operate at higher voltages without breakdown of the dielectric. The best actuator case is applied to the aerofoil for Reynolds numbers of 1:97x10⁵, 2:63x10⁵ and 3:29x10⁵. The lift and drag are recorded using pressure measurements around the aerofoil surface and across the aerofoil's wake. PIV is utilised to visualise the flow field. The trailing edge actuator produces a step increase in lift for pre-stall angles of attack and delays stall by 1° at Re = 1:97x10⁵. The leading edge actuator has limited impact on the flow for the no flap deflection case due to the actuator location. As the flap deflection increases the leading edge actuator is able to influence the flow. Repositioning of the leading edge actuator has the ability to reattach the flow around the fore portion of the aerofoil at a post stall angle of alpha = 18°.
29
Ozkan, Alp. "CO2 splitting in a dielectric barrier discharge plasma: understanding of physical and chemical aspects." Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/239300.
Повний текст джерелаАнотація:
Le dioxyde de carbone, principal gaz à effet de serre lié aux activités humaines, est considéré comme l’un des gaz les plus problématiques pour notre environnement ces dernières années, principalement à cause du réchauffement climatique qu’il engendre. C’est pour cette raison que l’augmentation de sa teneur dans l’atmosphère nous concerne tous quant aux conséquences futures pour notre planète. Afin de limiter l’émission de CO2, sa conversion en composés à valeur ajoutée présente un grand intérêt et est possible notamment via des procédés plasmas. Plus particulièrement, les décharges à barrière diélectrique (DBD) sont utilisées depuis quelques années pour générer des plasmas froids opérant à pression atmosphérique, principalement pour des applications en traitement de surface, mais également pour le traitement d’effluents gazeux.Lors de cette thèse, nous nous sommes focalisés sur le processus de dissociation du CO2 en CO et O2 via un réacteur DBD à flux continu et avons analysé sa conversion et son efficacité énergétique via différentes études. Celles-ci ont été réalisées grâce à plusieurs méthodes de diagnostic, comme par exemple la spectrométrie de masse utilisée pour déterminer la conversion et l’efficacité du processus, la spectroscopie d’émission optique, l’oscilloscope pour une caractérisation électrique, etc. afin d’avoir une meilleure compréhension du comportement des décharges CO2.Dans un premier temps, nous avons réalisé une étude détaillée d’un plasma CO2 pur où nous avons fait varier différents paramètres, tels que le temps de résidence, la fréquence, la puissance, la pulsation de la haute tension et l’épaisseur et la nature du diélectrique. Le CO2 donne lieu généralement à une décharge filamentaire, consistant en de nombreuses microdécharges réparties au niveau de la zone du plasma. Celles-ci constituent la principale source de réactivité dans une DBD. Un aperçu détaillé de l’aspect physique de ces microdécharges a été réalisé grâce à la caractérisation électrique, permettant de mieux comprendre les propriétés électriques de la décharge et des microdécharges. En effet, nous avons pu déterminer l’importance de la tension présente au niveau du plasma, de l’intensité du courant plasma, du nombre de microdécharges et de leur temps de vie sur l’efficacité du processus de dissociation de CO2.Ensuite, nous avons conclu ce travail avec des études combinant le CO2 en phase plasma avec de l’eau ou du méthane afin de produire des molécules à valeur ajoutée telles que les syngas (CO et H2), mais aussi des hydrocarbures (C2H6, C2H4, C2H2 et CH2O) dans le cas de l’ajout du méthane. A travers ces études, nous avons obtenu une meilleure connaissance de la chimie et de la physique qui ont lieu dans ce type de plasma.Carbon dioxide appears as one of the most problematic gases for the environment, mostly because it is responsible for global warming. This is why its increasing concentration into the atmosphere, mainly due to anthropogenic activities, is a real concern for planet Earth. In order to prevent the release of large amounts of CO2, its conversion into value-added products is of great interest. In this context, plasma-based treatments using dielectric barrier discharges (DBDs) are nowadays more and more used for the conversion of this gas. In this thesis, we investigated the CO2 splitting process into CO and O2 via a flowing cylindrical DBD and we studied its conversion and energy efficiency by means of several diagnostic methods, such as mass spectrometry to determine the conversion and energy efficiency of the process, optical emission spectroscopy for gas temperature measurements, and an oscilloscope for electrical characterization, in order to obtain a better understanding of the CO2 discharge itself.First, we focused on an extensive experimental study of a pure CO2 plasma where different parameters were varied, such as the gas residence time, the operating frequency, the applied power, the pulsation of the AC signal, the thickness and the nature of the dielectric. CO2 discharges typically exhibit a filamentary behavior, consisting of many microdischarges, which act as the main source of reactivity in a DBD. A detailed insight in the physical aspects was achieved by means of an in-depth electrical characterization, allowing more insight in the electrical properties of the discharge and more specifically in the microdischarges, which are spread out throughout the active zone of the plasma. It was found throughout this work that the plasma voltage, which reflects the electric field and thus determines how the charged particles are accelerated, the plasma current, which reflects the electron density, but also the number of microdischarges and their average lifetime, play an important role in the efficiency of the CO2 dissociation process. It was revealed that the microdischarge number is important as it represents the repartition of the locations of reactivity. Indeed, as the microfilaments are more spread out in the same discharge volume, the probability for the CO2 molecules to pass through the reactor and interact with at least one microdischarge filament becomes more important at a larger number of microfilaments.The second part of the thesis was dedicated to discharges combining CO2 and H2O or CH4, both being hydrogen source molecules. The combined CO2/H2O or CO2/CH4 conversion allows forming value-added products like syngas (CO and H2), but also hydrocarbons (C2H6, C2H4, C2H2 and CH2O), at least in the presence of methane. Throughout this study, we tried to obtain a better knowledge of the chemistry and physic behind these conversion processes.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
30
Droubi, Ashraf El. "Investigation of the efficiency of a novel three electrode configuration for the dielectric barrier discharge." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-03102018-144641/.
Повний текст джерелаАнотація:
Having gained popularity in the last decade, the dielectric barrier discharge (DBD) has been studied in numerous ways as a device for air acceleration. A major interest of all these works has been concentrated on achieving higher efficiency and producing higher jet velocities. These studies considered alternative geometries, different voltage waveforms etc., yet none of these studies tackle the inherently inefficient process of force creation and actuation in a DBD. Air acceleration has been attributed to the electric force that switches direction on each voltage half cycle (that is due to the nature of the discharge mechanism) yet has a forward resulting force. The present thesis considers the phenomenon of memory charge accumulation on the dielectric surface and reasons that the backward force in the second half cycle can be reversed by further migration of the memory charges to an added exposed anode. Hence a novel 3-electrode configuration is presented. Flow velocity investigations showed a 27% improvement in efficiency in comparison with the traditional 2-electrode actuator. This meant a 0.4m/s gain along the velocity profile. During the investigation process, a new discharge mechanism was encountered. This was characterized by the double discharge lines along the exposed electrode edges while in the presence of a \"floating\" encapsulated electrode.Tendo ganho popularidade na última década, a descarga de barreira dielétrica (DBD) foi estudada de várias maneiras como um dispositivo para aceleração do ar e controle aerodinâmico. Um grande interesse de todos esses trabalhos foi concentrado em alcançar maior eficiência e produzir maiores velocidades de jato. Alguns desses estudos consideraram geometrias alternativas, diferentes formas de onda de tensão, etc., mas nenhum desses estudos aborda o processo inerentemente ineficiente de criação e atuação da força em um DBD. A Aceleração do ar tem sido atribuída à força elétrica que muda de direção em cada meio ciclo (que é devido à natureza do mecanismo de descarga), mas que tem uma força resultante para a frente. A presente tese considera o fenômeno de acumulação de carga de memória na superfície dielétrica e raciocina que a força contraria no segundo meio ciclo da descarga pode ser revertida por migração dessas cargas de memória para um ânodo adicional exposto. Assim, uma nova configuração de 3 eletrodos é apresentada. Investigações de velocidade do fluxo mostraram uma melhoria de 27% na eficiência em comparação com o tradicional atuador de 2 eletrodos. Isso significou um ganho de 0,3 m/s ao longo do perfil de velocidade. Durante o processo de investigação, foi encontrado um novo mecanismo de descarga. Isso foi caracterizado por uma dupla descarga ao longo das bordas do eletrodos expostos, enquanto na presença de um eletrodo encapsulado \"pendurado\".
31
Lovascio, Sara. "Cold Plasma deposition of organosilicon films with different monomers in a dielectric-barrier discharge." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00815260.
Повний текст джерелаАнотація:
Cette thèse porte sur une étude fondamentale sur le dépôt des couches minces d'organosiliciés par des Décharges à Barrière Diélectrique (DBD), un procédé très intéressant pour l'application aux textiles. La plupart des dépôts des couches d'oxyde de silicium sont déposées à partir du précurseur hexaméthyle silixone (HMDSO).De plus très peu d'études sont consacrées aux mécanismes de dépôt des couches à la pression atmosphérique. Dans cette étude les propriétés des couches minces déposées par DBD alimentées par Ar/HMDSO/O2, Ar/PMDSO (pentaméthyldisiloxane)/O2 et Ar/TMDSO (tetraméthyldisiloxane)/O2, avec différentes proportions de l'oxygène, ont été confrontées aux analyses, par GC-MS, des gaz sortant du réacteur. Nous avons trouvé que l'ajout d'O2 au gaz d'alimentation n'améliore pas l'activation du précurseur organosilicié, même s'il augmente la puissance injectée. En revanche il influence fortement la composition chimique des dépôts et favorise une forte réduction de la concentration des sous-produits dans le gaz sortant du réacteur. Sans ajout de l'O2, des couches minces obtenues contiennent beaucoup de carbone , avec rétention de la structure du précurseur de départ. En réduisant le nombre de -CH3 dans le précurseur (HMDSO>PMDSO>TMDSO), le nombre et l'abondance des sous-produits détectés dans le gaz sortant du réacteur diminuent fortement. Il semblerait que les unités de répétition diméthylsiloxane et hydrométhylsiloxane jouent un rôle important dans l'oligomérisation des trois précurseurs. Différents mécanismes d'activation, ainsi que différents procédés de formation des groupes Si-OH dans les dépôts, ont été proposés pour les trois précurseurs.
32
Cooper, Moogega Fridman Alexander A. "Elucidation of levels of bacterial viability post-non-equilibrium dielectric barrier discharge plasma treatment /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3181.
Повний текст джерела
33
Schneck, William Carl III. "Multi-Physics Model of a Dielectric Barrier Discharge Flow Control Actuator with Experimental Support." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/65004.
Повний текст джерелаАнотація:
This dissertation presents an experimentally supported multi-physics model of a dielectric barrier discharge boundary layer flow control actuator. The model is independent of empirical data about the specific behavior of the system. This model contributes to the understanding of the specific mechanisms that enable the actuator to induce flow control.
The multi-physics numerical model couples a fluid model, a chemistry model, and an electrostatics model. The chemistry model has been experimentally validated against known spectroscopic techniques, and the fluid model has been experimentally validated against the time-resolved shadowgraphy. The model demonstrates the capability to replicate emergent flow structures near a wall. These structures contribute to momentum transport that enhance the boundary layer’s wall attachment and provide for better flow control.
An experiment was designed to validate the model predictions. The spectroscopic results confirmed the model predictions of an electron temperature of 0.282eV and an electron number density of 65.5 × 10⁻¹²kmol/m³ matching to within a relative error of 12.4% and 14.8%, respectively. The shadowgraphic results also confirmed the model predicted velocities of flow structures of 3.75m/s with a relative error of 10.9%. The distribution of results from both experimental and model velocity calculations strongly overlap each other. This validated model provides new and useful information on the effect of Dielectric Barrier Discharge actuators on flow control and performance. This work was supported in part by NSF grant CNS-0960081 and the HokieSpeed supercomputer at Virginia Tech.Ph. D.
34
Olenici-Craciunescu, Stefan-Bogdan [Verfasser]. "Micro capillary dielectric barrier plasma jet discharge : Characterisation by optical spectroscopy / Stefan-Bogdan Olenici-Craciunescu." Dortmund : Universitätsbibliothek Technische Universität Dortmund, 2011. http://d-nb.info/1018125493/34.
Повний текст джерела
35
Kerr, Maria. "The grafting of collagen to medically relevant polymers through an atmospheric pressure dielectric barrier discharge." Thesis, University of Ulster, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536466.
Повний текст джерела
36
Wolkenhauer, Arndt. "Plasma treatment of wood and wood-based materials by dielectric barrier discharge at atmospheric pressure /." Göttingen : Sierke, 2009. http://d-nb.info/993076556/04.
Повний текст джерела
37
DuBois, Cameron J. "Flow Control on an Airfoil Under Reversed Flow Conditions Using Nanosecond Dielectric Barrier Discharge Actuators." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366253477.
Повний текст джерела
38
Elam, Dana. "A direct numerical simulation of dielectric barrier discharge (DBD) plasma actuators for turbulent skin-friction control." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/49964/.
Повний текст джерелаАнотація:
Turbulent skin-friction control is the subject of much research and the use of transverse (spanwise) oscillating motions offers the means of obtaining a significant reduction in skin-friction. Dielectric barrier discharge (DBD) actuators can be used to generate spanwise oscillating waves but the difficulty in placing a sensor in the area of plasma gives rise to problems in recording near-wall velocities. A modified version of the Shyy et al. (2002) DBD model was integrated into a direct numerical simulation (DNS). This numerical model was used in a series of two-dimensional simulations, in initially quiescent ow, and the results were compared to results reported from experimental investigations. A close affinity was found confirming that the DBD model is satisfactory. Both a temporal and a spatial, spanwise oscillating ow were investigated. Only one plasma profile was investigated. Three actuator spacings were investigated. Only the largest actuator spacing resulted in a gap between each plasma profile that was larger than the plasma profile width itself. A spatially uniform plasma configuration produced larger DR% than spanwise wall oscillation for both spatial and temporal waves, maximum DR = 51% compared to a DR = 47% for a spanwise wall oscillation. Increased skin-friction reductions originated from the displacement of the Stokes layer. The spatial wave produced lower skin-friction values than temporal waves for all the configurations. For both spatial and temporal waves the performance of the discrete configurations in producing an overall skin-friction reduction decreased with increasing actuator spacing. Using both temporal and spatial waves, the configuration with the largest spacing, which is relatively small, did not produce a drag reduction for any case that was tested.
39
Butterworth, Thomas D. "The effects of particle size on CO2 reduction in packed bed dielectric barrier discharge plasma reactors." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11603/.
Повний текст джерелаАнотація:
Utilisation of CO2 emissions for production of synthetic fuels as an energy storage vector has the potential to be an economically viable mechanism to assist in the mitigation of anthropogenic climate change. Packed bed plasma reactors (PBRs) are a potential technology that could be utilised for reduction of CO2 to CO as one of the steps in the fuel production process. Current understanding of the behavior of plasma discharges within PBRs is very poor, and the effects of many of the parameters that can be varied are still unknown. This thesis aims to investigate the effects of particle size (180 μm to 2000 μm - random shape) of two different commonly used packing materials (Al2O3 and BaTiO3) on the conversion of CO2 in PBRs. The reactor behavior is observed through determination of product gas composition and plasma power consumption in order to determine CO2 conversion and reactor efficiency. Electrical characterisation techniques are used to determine reactor burning voltage, and capacitances. These capacitances are subsequently used to quantify the occurrence of reactor partial discharging over a range of different operating conditions. The results indicate that smaller particles (down to 180 μm) can significantly increase CO2 conversion by up to 70%, provided that the voltage applied is sufficiently high to generate a discharge in the void spaces of the packing material. However, with decreasing particle size, the reactor burning voltage is found to increase exponentially, as well as the tendency of the reactor towards partial discharging. Consequently, there are two recommendations: I. Higher electric field strengths should be used by researchers working with packed bed reactors II. Reactor capacitances, including the effective dielectric capacitance, should be reported for all packed bed reactor experiments in order to determine whether partial reactor discharging behavior is occurring.
40
Lee, An-Ping, and 李安平. "Characteristics of Atmospheric Pressure Coaxial Dielectric Barrier Discharge and Surface Dielectric Barrier Discharge in Helium." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/93720341671464768857.
Повний текст джерела
41
Liou, Bang-Tsui, and 劉邦旭. "Order-Disorder Transition of Filamentary Discharge in Atmospheric Dielectric Barrier Discharge System." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/07027033872626581122.
Повний текст джерелаАнотація:
碩士國立中正大學
物理學系暨研究所
102
In industries, the dielectric barrier discharge systems are operated at atmospheric pressure which show the advantages for surface processing and plasma chemistry. Typically, two electrodes separated by several millimeters and operated with sinusoidal A.C. voltage with frequency in range of tens kHz. The dielectric layer between two electrodes can greatly limit the strength of the discharge current. In filamentary discharge regime, small discharge channels are formed in the gaseous layer which look like bright filaments. Despite the filamentary discharge is widely applied to the industrial products, the discharge mechanism is not clear. In our research, the filamentary discharge is investigated with different electrode geometries. The gap dependence of the discharge is briefly discussed. The breakdown mechanism of single filamentary discharge is investigated in the needle-to-plane electrodes setup which shows consistent scaling relation with electron avalanche. The interaction between the filamentary discharges is investigated in the plane-toplane electrodes setup. The disorder-order transition of the discharge spots is observed as the increase of the gap distance. It is found that the structural transition of the filamentary discharges is strongly related to the mutual Coulomb interaction between the charge piles. Finally, we report the investigation of the filamentary discharges in the wedged plane-to-plane electrodes setup. As the gap distance increases, the continuous structural transition of the discharge pattern is found. We further confirm the discharge process is dominated by the gap distance.
42
Wang, Yin-Chin, and 王穎志. "Numerical Modeling of One-Dimensional Nitrogen Barrier Discharge." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/07677454120826085515.
Повний текст джерелаАнотація:
碩士國立交通大學
機械工程系所
97
A simulation of low temperature nitrogen dielectric barrier discharge (DBD) at atmosphere pressure is proposed in this thesis. The parallelized fluid modeling is used to simulate the pure nitrogen discharge. All of the model equations are discretized using fully coupled Newton-Krylov-Schwarz algorithm, in which the preconditioner and linear matrix solver are overlapping additive Schwarz method and Bi-CGStb/GMRES scheme. The transport coefficients of nitrogen plasma and chemical reaction rate are obtained from BOLSIG, which is a Boltzmann solver can evaluate electron energy distribution function by the user given cross sections. A chemistry module take care the reactions in fluid modeling, in which pure nitrogen chemistry in this thesis include 8 species, N2, N2(A3), N2(B3), N2(C3), N2(a’1), N2+, N4+ and electron. 30 reaction channels are considered which include excitation, ionization and recombination reactions. The total currents of simulation and experiment are compared, and it reveals that the simulation result is corresponding to the experiment data. The power absorption is evaluated, and it shows that the absorbed power of ions is higher than the electron. According to the number densities of electron and positive ions simulated, it shows that the discharge is Townsend-like discharge. Furthermore, the influence of different dielectric permittivity and different discharge gap are discussed.
43
Zhang, Ji-You, and 張季佑. "CO2 conversion in a dielectric barrier discharge plasma." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/p3t4c5.
Повний текст джерелаАнотація:
碩士國立交通大學
機械工程系所
106
The present study is to apply a coaxial dielectric-barrier plasma discharge to CO2 conversion. Three different carrier gases, argon, helium and nitrogen are used. The plasma reactor consists of a ground electrode, made of a wire mesh wrapped outside of the quartz tube, and a stainless steel screw rod as the power electrode inside the quartz tube. Based on Lissajous approach, the plasma power is around 25W. Concentrations of CO2 and CO are measured with gas chromatography. It is found that the absolute conversion of CO2 and the yield of CO increase with concentration of the carrier gas. The absolute conversion of CO2 is 6.82%, 5.1% and 5.75% for nitrogen, helium and argon. The yield of CO is 7.0%, 4.71% and 5.69% for nitrogen, helium and argon. The CO2 conversion efficiency and CO yield are found to decrease when the quartz tube is packed with glass beads, in contrary to what is found in literature studies. The deteriorated results are due to a combination of the reduced residence time of gas flow in the plasma reactor and the decreased plasma power.
44
Bürkle, Sebastian. "Environmental Impacts on Dielectric Barrier Discharge Plasma Actuators." Master's thesis, 2013. https://tuprints.ulb.tu-darmstadt.de/3316/7/B%C3%BCrkle%20Masterthesis%20MPE.pdf.
Повний текст джерелаАнотація:
Plasma actuators based on dielectric barrier discharge promise a bright future in aerodynamical applications. By creating a body force in the surrounding gas through plasma – gas interaction, plasma actuators, operated in quiescent air, induce a weak flow above their surface with a velocity of typically 5-8 m/s, the so called ionic wind. The ionic wind can influence the boundary-layer of any externally applied flow. Thus, plasma actuators are used for flow-control applications with a wide range of different flow velocities, temperatures and pressures.
In the present work, the impact of these environmental conditions on the power consumption, plasma length and resonance behavior of the plasma actuators is studied. It is shown that an increase of the temperature or decrease of the pressure favor the discharge, as they increase the plasma length and the power consumption for a constant voltage amplitude. During the experiments temperatures from ambient temperature up to 600°C were tested and the pressure ranges from ambient pressure down to p = 0.11 bar. Scaling numbers and power laws were found to describe the impact of these parameters on the power consumption and plasma length. A hypothesis that the mean free path of the ions and electrons could be the dominant impact factor on the
discharge was derived. Thus, the temperature and pressure dependence on the mean free path leads to the observed effects. Also, it is shown that the impedance of the plasma actuator, which is a product of an active and passive component of the actuators capacitance, is increased by an increasing temperature or decreasing pressure. This effects lead to a decrease of the resonance frequency of the circuit.
External flows with small velocities between 0 m/s and 21 m/s have no effect on the power consumption and resonance behavior of an actuator. High velocities decrease the power consumption and the impedance, as they reduce the discharge volume and relative discharge duration. These effects are shown in different experiments of a plasma actuator exposed to flow Mach numbers between 0.42 and 0.7.
The second part of this thesis focuses on the investigation of the environmental and voltage impact on filaments in the discharge that are caused by an instability in the discharge process. It is shown that increasing the pressure or flow velocity stabilizes the discharge and thus delays the onset of the formation of filaments towards higher voltages. The temperature seems to have no impact on the onset voltage. These effects are in good agreement with the predications by a theoretical model of the filaments. With the help of streak-camera images it is shown that the filaments only occur during the negative half-cycle. Increasing the voltage amplitude or temperature increases the spacing between the filaments, which typically ranges in between 2 mm and 4 mm. The same effect is achieved by decreasing the pressure. Measurements with a Pitot tube
and particle image velocimetry show that the filaments increase the local velocity of the ionic wind by a factor of roughly 1.1 - 1.6. Thus, the ionic wind of a discharge with filaments looses its two-dimensional character and becomes three-dimensional. This effect may allow advanced flow-control strategies, for example active vortex generation using the discharge filaments.
45
Lin, I.-Min, and 林逸民. "Modification of Polymer Surfaces Using the Post-Discharge Region of an Atmospheric-Pressure Dielectric Barrier Discharge." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/87726300877327137992.
Повний текст джерелаАнотація:
碩士國立交通大學
機械工程系所
97
Plasma treatment of polymers is gaining more and more popularity as a surface modification technique, since it offers numerous advantages over the conventional chemical processes. Plasma surface treatment is an environmentally benign, fast and versatile technology. Modification of the surface properties of polypropylene (PP) films is studied using oxygen and nitrogen dielectric barrier discharge at atmospheric pressure. The discharge was generated between two planar metal electrodes, with the both electrodes covered by quartz and the polymer sample was placed post-discharge region. The surface properties of both treated and untreated polymers were characterized by contact angle measurement. With the change treating distance for N2+O2 plasma, the water contact angle changes from 103o before treatment to a minimum of 26o when Z is 6mm. After long-term aging time in ambient air, the much lowered surface contact angle of processed PP film is found to in part recover but still lower than the untreated material. Through AFM analysis, we also observed the change of surface morphology and roughness before and after plasma treatment. In addition, the effects of plasma treatment on the surface chemical characteristics of the PP films were observed by using X-ray photoelectron spectroscopy (XPS). As the result of analysis, we observed that polar functional groups, such as –CO, –C=O, and –COO were introduced on the PP film surface after atmospheric pressure plasma treatment. The results show that such a plasma treatment is effective.
46
Houser, Nicole. "Manufacturing of Dielectric Barrier Discharge Plasma Actuators for Degradation Resistance." Thesis, 2013. http://hdl.handle.net/1807/42867.
Повний текст джерелаАнотація:
The performance and broader application of dielectric barrier discharge (DBD) plasma actuators are restricted by the manufacturing methods currently employed. In the current work, two methodologies are proposed to build robust plasma actuators for active flow control; a protective silicone oil (PDMS) treatment for hand-cut and laid tape-based actuators and a microfabrication technique for glass-based devices. The microfabrication process, through which thin film electrodes are precisely deposited onto plasma-resistant glass substrates, is presented in detail. The resulting glass-based devices are characterized with respect to electrical properties and output for various operating conditions. The longevity of microfabricated devices is compared against silicone-treated and untreated hand-made devices of comparable geometries over 60 hours of continuous operation. Both tungsten and copper electrodes are considered for microfabricated devices. Human health effects are also considered in an electromagnetic field study of the area surrounding a live plasma actuator for various operating conditions.
47
Orlov, Dmitriy M. "Modelling and simulation of single dielectric barrier discharge plasma actuators." 2006. http://etd.nd.edu/ETD-db/theses/available/etd-10062006-144203/.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Notre Dame, 2006.Thesis directed by Thomas C. Corke for the Department of Aerospace and Mechanical Engineering. "October 2006." Includes bibliographical references (leaves 184-189).
48
Chuang, Yang-ming, and 莊揚名. "The study of ozone generation efficiency by dielectric barrier discharge." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/51615307387267861189.
Повний текст джерелаАнотація:
碩士龍華科技大學
工程技術研究所
99
Ozone have sterilization and disinfection functions, one of functions of running water disinfection, maintaining freshness……etc. Therefore, it is becoming an important issue to know how ozone produces and generation efficiency. This paper is concerning production of ozone by DBD and discussing efficiency of ozone production in different terms, for instance, in different duty cycle, oxygen flowing, cooling water or not and the pitch of screwed electrode. Ozone concentration and generation efficiency will rise higher when Pulse voltage rises higher, Bipolar pulse voltage is lower obviously, producing ozone need less voltage in 50% duty cycle. 50% duty cycle is lower than 10% duty cycle and 30% duty cycle, 1.25 mm and 2.5 mm pitch of electrode screw voltage is lower than 1.75 mm. In ozone generation efficiency ,oxygen flowing , 2 L/min is better than 1 L/min. In cooling water or not, there is no obviously influence in ozone producing voltage and generation efficiency.
49
Karuppasamy, Elangovan. "Destruction of toluene in a dielectric barrier discharge plasma reactor." 2004. http://digital.library.okstate.edu/etd/umi-okstate-1184.pdf.
Повний текст джерела
50
Steer, Warwick. "Etching of polyimide in an atmospheric pressure dielectric barrier discharge." 2000. http://catalog.hathitrust.org/api/volumes/oclc/44639045.html.
Повний текст джерелаАнотація:
Thesis (M.S.)--University of Wisconsin--Madison, 2000.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 54).