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Sample records for barrier plasma actuators

  1. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexander

    2014-01-01

    Traditional approaches for active flow separation control using dielectric barrier discharge (DBD) plasma actuators are limited to relatively low speed flows and atmospheric conditions. This results in low feasibility of the DBDs for aerospace applications. For active flow control at turbine blades, fixed wings, and rotary wings and on hypersonic vehicles, DBD plasma actuators must perform at a wide range of conditions, including rarified flows and combustion mixtures. An efficient, comprehensive, physically based DBD simulation tool can optimize DBD plasma actuators for different operation conditions. Researchers are developing a DBD plasma actuator simulation tool for a wide range of ambient gas pressures. The tool will treat DBD using either kinetic, fluid, or hybrid models, depending on the DBD operational condition.

  2. Dielectric barrier discharge plasma actuator for flow control

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry Florievich

    Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low

  3. Mixing Layer Excitation by Dielectric Barrier Discharge Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Ely, Richard; Little, Jesse

    2012-11-01

    The response of a mixing layer with velocity ratio 0.28 to perturbations near the high-speed side (U2=11 m/s, ReL = 0.26 × 106) of its origin from dielectric barrier discharge plasma actuators is studied experimentally. Both alternating current (ac) and nanosecond (ns) pulse driven plasma are investigated in an effort to clarify the mechanisms associated with each technique as well as the more general physics associated with flow control via momentum-based versus thermal actuation. Ac-DBD plasma actuators, which function through electrohydrodynamic effects, are found to generate an increase in mixing layer momentum thickness that is strongly dependent on forcing frequency. Results are qualitatively similar to previous archival literature on the topic employing oscillating flaps. Ns-DBD plasma, which is believed to function through thermal effects, has no measureable influence on the mixing layer profile at similar forcing conditions. In the context of previous archival literature, these results suggest different physical mechanisms govern active control via ac- and ns-DBD plasma actuation and more generally, momentum versus thermal perturbations. Further investigation of these phenomena will be provided through variation of the boundary/mixing layer properties and forcing parameters in the context of spatially and temporally resolved experimental data. Supported by: AFOSR and Raytheon Missile Systems.

  4. Dielectric Barrier Discharge Plasma Actuator for Flow Control

    NASA Technical Reports Server (NTRS)

    Opaits, Dmitry, F.

    2012-01-01

    This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

  5. Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Ashpis, David E.; Laun, Matthew C.

    2013-11-01

    DBD plasma actuators generate a wall-jet that can be used for active flow control. We used an analytical balance to measure the thrust generated by the actuator, it is a common metric of its performance without external flow. We found that the measured force is afflicted by several problems; it drifts in time, not always repeatable, is unstable, and depends on the manner the voltage is applied. We report results of investigations of these issues. Tests were conducted on an actuator constructed of 1/4 inch thick high-density polyethylene (HDPE) dielectric with 100 mm long offset electrodes, with applied voltages up to 48 kV p-p and frequencies from 32 Hz to 2.5 kHz, and pure Sine and Trapezoidal waveforms. The relative humidity was in the range of 51-55%, corresponding to moisture range of 10,500 to13,000 ppm mass. Force readings were up to 500 mg, (approximately 50 mN/m). We found that the measured force is the net of the positive thrust generated by the wall-jet and an ``anti-thrust'' acting in the opposite direction. We propose a correction procedure that yields the plasma-generated thrust. The correction is based on voltage-dependent anti-thrust measured in the low frequency range of 20-40 Hz. We found that adjacent objects in a test setup affect the measured thrust, and verified it by comparing experiments with and without a metal enclosure, grounded and ungrounded. Uncorrected thrust varied by up to approximately +/-100%, and the corrected thrust variations were up to approximately 30%. Supported by NASA's FAP/Aerospace Sciences Project.

  6. Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.

    2012-01-01

    This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.

  7. Numerical analysis of plasma evolution on dielectric barrier discharge plasma actuator

    SciTech Connect

    Nishida, Hiroyuki; Abe, Takashi

    2011-07-01

    Time evolution of the discharge plasma in the dielectric barrier discharge (DBD) plasma actuator was simulated by the simple fluid model in which the electron and single positive ion species were considered. The characteristics of the discharge plasma evolution were investigated in detail, and the following results were obtained. When the positive-going voltage is applied, the streamer discharge is formed periodically. The periodically formed streamer expands from the exposed electrode, and its length becomes longer than the previous one. Periodic breakdown of the gas and step-by-step plasma expansion are also observed during the negative-going voltage; however, the streamer is not formed and the breakdown frequency is much higher. The simulation results with a triangular applied voltage waveform show the same characteristics as observed in the experiment; large discharge current spikes are observed during both the positive- and negative-going voltage phase, and the plasma in the negative-going voltage phase expands more smoothly than that in the positive phase because of its higher breakdown frequency. It was shown that even the simple numerical model could provide valuable insights into the physics of DBD plasma actuator; this indicates that the positive ions and electrons play a prominent role in determining the general characteristics of the plasma evolution.

  8. Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

    2008-01-01

    We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

  9. The Influence of Relative Humidity on Dielectric Barrier Discharge Plasma Flow Control Actuator Performance

    NASA Astrophysics Data System (ADS)

    Wicks, M.; Thomas, F. O.; Corke, T. C.; Patel, M.

    2012-11-01

    Dielectric barrier discharge (DBD) plasma actuators possess numerous advantages for flow control applications and have been the focus of several previous studies. Most work has been performed in relatively pristine laboratory settings. In actual flow control applications, however, it is essential to assess the impact of various environmental influences on actuator performance. As a first effort toward assessing a broad range of environmental effects on DBD actuator performance, the influence of relative humidity (RH) is considered. Actuator performance is quantified by force balance measurements of reactive thrust while RH is systematically varied via an ultrasonic humidifier. The DBD plasma actuator assembly, force balance, and ultrasonic humidifier are all contained inside a large, closed test chamber instrumented with RH and temperature sensors in order to accurately estimate the average RH at the actuator. Measurements of DBD actuator thrust as a function of RH for several different applied voltage regimes and dielectric materials and thicknesses are presented. Based on these results, several important design recommendations are made. This work was supported by Innovative Technology Applications Company (ITAC), LLC under a Small Business Innovation Research (SBIR) Phase II Contract No. N00014-11-C-0267 issued by the U.S. Department of the Navy.

  10. Phase effect on flow control for dielectric barrier plasma actuators

    SciTech Connect

    Singh, K. P.; Roy, Subrata

    2006-07-03

    Active control of flow has a wide range of applications. Specifically, mitigation of detachment due to the weakly ionized gas flow past a flat plate at an angle of attack is studied using two asymmetric sets of electrode pairs kept at a phase lag. The equations governing the dynamics of electrons, helium ions, and neutrals are solved self-consistently with charge-Poisson equation. The electrodynamic forces produced by two actuators largely depend on the relative phase between the potentials applied to rf electrodes and distance between them. A suitable phase and an optimum distance exist between two actuators for effective separation control.

  11. Noise control of a flow around a cylinder using high-frequency dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Kopiev, V. F.; Belyaev, I. V.; Zaytsev, M. Yu.; Kazansky, P. N.; Kopiev, V. A.; Moralev, I. A.

    2015-03-01

    The effect of high-frequency dielectric barrier discharge plasma actuators on the noise of a flow around a circular cylinder is experimentally studied. It is shown that the plasma actuators are able to reduce the vortex noise of a cylinder within the range of velocities typical for aeroacoustic applications.

  12. Energy deposition characteristics of nanosecond dielectric barrier discharge plasma actuators: Influence of dielectric material

    NASA Astrophysics Data System (ADS)

    Correale, G.; Winkel, R.; Kotsonis, M.

    2015-08-01

    An experimental study aimed at the characterization of energy deposition of nanosecond Dielectric Barrier Discharge (ns-DBD) plasma actuators was carried out. Special attention was given on the effect of the thickness and material used for dielectric barrier. The selected materials for this study were polyimide film (Kapton), polyamide based nylon (PA2200), and silicone rubber. Schlieren measurements were carried out in quiescent air conditions in order to observe density gradients induced by energy deposited. Size of heated area was used to qualify the energy deposition coupled with electrical power measurements performed using the back-current shunt technique. Additionally, light intensity measurements showed a different nature of discharge based upon the material used for barrier, for a fixed thickness and frequency of discharge. Finally, a characterisation study was performed for the three tested materials. Dielectric constant, volume resistivity, and thermal conductivity were measured. Strong trends between the control parameters and the energy deposited into the fluid during the discharge were observed. Results indicate that efficiency of energy deposition mechanism relative to the thickness of the barrier strongly depends upon the material used for the dielectric barrier itself. In general, a high dielectric strength and a low volumetric resistivity are preferred for a barrier, together with a high heat capacitance and a low thermal conductivity coefficient in order to maximize the efficiency of the thermal energy deposition induced by an ns-DBD plasma actuator.

  13. Simulation of an asymmetric single dielectric barrier plasma actuator

    SciTech Connect

    Singh, K.P.; Roy, Subrata

    2005-10-15

    Continuity equations governing electron and ion density are solved with Poisson's equation to obtain spatial and temporal profiles of electron density, ion density, and voltage. The motion of electrons and ions results in charge separation and generation of an electrostatic electric field. Electron deposition downstream of the overlap region of the electrode results in formation of a virtual negative electrode that always attracts the charge separation. The value of charge separation e(n{sub i}-n{sub e}) and the force per volume F=e(n{sub i}-n{sub e})E have been obtained near the dielectric surface for the 50th cycle. Domain integration of the force F=e(n{sub i}-n{sub e})E has been obtained for different plasma densities, frequencies, and rf voltage wave forms. The time average of the x force is positive and the y force is negative over the domain; therefore there is an average net force on the plasma in the positive x and negative y directions. This will result in a moving wave of plasma over the dielectric surface in the positive x direction, which can find application in flow control.

  14. Dielectric Barrier Discharge (DBD) Plasma Actuators Thrust-Measurement Methodology Incorporating New Anti-Thrust Hypothesis

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.

    2014-01-01

    We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a large diameter, grounded, metal sleeve.

  15. Dissipated power and induced velocity fields data of a micro single dielectric barrier discharge plasma actuator for active flow control☆

    PubMed Central

    Pescini, E.; Martínez, D.S.; De Giorgi, M.G.; Francioso, L.; Ficarella, A.

    2015-01-01

    In recent years, single dielectric barrier discharge (SDBD) plasma actuators have gained great interest among all the active flow control devices typically employed in aerospace and turbomachinery applications [1,2]. Compared with the macro SDBDs, the micro single dielectric barrier discharge (MSDBD) actuators showed a higher efficiency in conversion of input electrical power to delivered mechanical power [3,4]. This article provides data regarding the performances of a MSDBD plasma actuator [5,6]. The power dissipation values [5] and the experimental and numerical induced velocity fields [6] are provided. The present data support and enrich the research article entitled “Optimization of micro single dielectric barrier discharge plasma actuator models based on experimental velocity and body force fields” by Pescini et al. [6]. PMID:26425667

  16. Airflow influence on the discharge performance of dielectric barrier discharge plasma actuators

    SciTech Connect

    Kriegseis, J.; Tropea, C.; Grundmann, S.

    2012-07-15

    In the present work, the effect of the airflow on the performance of dielectric barrier discharge plasma-actuators is investigated experimentally. In order to analyze the actuator's performance, luminosity measurements have been carried out simultaneously with the recording of the relevant electrical parameters. A performance drop of about 10% is observed for the entire measured parameter range at a flow speed of M = 0.145 (U{sub {infinity}}=50 m/s). This insight is of particular importance, since the plasma-actuator control authority is already significantly reduced at this modest speed level. The results at higher Mach numbers (0.4

  17. Dielectric barrier discharge plasma actuator to control turbulent flow downstream of a backward-facing step

    NASA Astrophysics Data System (ADS)

    Sujar-Garrido, P.; Benard, N.; Moreau, E.; Bonnet, J. P.

    2015-04-01

    The objective of these experiments was to determine the optimal forcing location and unsteady forcing actuation produced by a single dielectric barrier discharge plasma actuator for controlling the flow downstream of a backward-facing step. The investigated configuration is a 30-mm-height step mounted in a closed-loop wind tunnel. The flow velocity is fixed at 15 m/s, corresponding to a Reynolds number based on the step height equal to 3 × 104 ( Re θ = 1400). The control authority of the plasma discharge is highlighted by the time-averaged modification of the reattachment point and by the effects obtained on the turbulent dynamics of the reattached shear layer. Several locations of the device actuator are considered, and a parametric study of the input signal is investigated for each location. This procedure leads to the definition of an optimal control configuration regarding the minimization of the reattachment length. When the actuator—that produces an electrohydrodynamic force resulting in an electric wind jet—is located upstream the separation point, it can manipulate the first stages of the formation of the turbulent free shear layer and consequently to modify the flow dynamics. Maximum effects have been observed when the high voltage is burst modulated at a frequency f BM = 125 Hz with a duty-cycle of 50 %. This forcing corresponds to a Strouhal number based on the momentum thickness equal to 0.011, a value corresponding to the convective instability or Kelvin-Helmholtz instability of the separated shear layer.

  18. Theoretical modeling of pulse discharge cycle in dielectric barrier discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Sato, Shintaro; Ohnishi, Naofumi

    2016-07-01

    Simple models based on two-dimensional simulations are proposed to estimate intervals of periodically observed current pulses with a positive-going voltage in a dielectric barrier discharge plasma actuator. There are two distinct peaks in one streamer discharge; one is related to the formation of an ion cloud and the other is related to a filamentary discharge that is identified as a streamer. Simulation results show that the intervals of the current pulses depend on the slope of the applied voltage. For the ion-cloud formation phase, we model the time evolution of electron number density at the exposed electrode with ionization frequency. For the ion-cloud expansion phase, a positive ion cylinder model is proposed to estimate the electric field generated by surface charge on the dielectric. These models well reproduce the discharge intervals obtained in the numerical simulations.

  19. On the classification of dielectric barrier discharge plasma actuators: A comprehensive performance evaluation study

    NASA Astrophysics Data System (ADS)

    Kriegseis, J.; Duchmann, A.; Tropea, C.; Grundmann, S.

    2013-08-01

    The increasing popularity and maturity of plasma actuators for many flow control applications requires a common standard for plasma actuator performance evaluation. In the present work, a comprehensive comparative study of existing and new evaluation measures is presented, based on results from identical plasma-actuator configurations. A power-flow diagram is introduced that covers the entire range of power stages from the energy source to the flow-control success. All individual power stages are explained, existing controversial definitions are clarified, and an evaluation guideline is applied to previously obtained data. Finally, the defined systematic analysis is applied to the results of a recently conducted plasma-actuator in-flight experiment.

  20. Modeling and Simulation of Aerodynamic Single Dielectric Barrier Discharge Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Orlov, Dmitri; Font, Gabriel

    2008-11-01

    This work presents different approaches to modeling of the plasma actuator, an electrical flow control device, which is now widely used in aerodynamics for separation control, lift enhancement, drag reduction and flight control without moving surfaces. Study of the physics of the discharge in air at atmospheric pressure was performed using particle (PIC-DSMC) and fluid plasma simulations. Based on the experimentally obtained data electro-static and lumped-element circuit models were developed for engineering purposes. Numerical flow simulations were performed to study the effect of the plasma body force on the neutral fluid. The results agreed well with the experiments. An application of the plasma actuators to the leading-edge separation control on the NACA 0021 airfoil was studied numerically. The results were obtained for a range of angles of attack. Improvement in the airfoil characteristics was observed in numerical simulations at high angles of attack in cases with plasma actuation.

  1. Electrical and optical characteristics of the radio frequency surface dielectric barrier discharge plasma actuation

    NASA Astrophysics Data System (ADS)

    Wei-Long, Wang; Hui-Min, Song; Jun, Li; Min, Jia; Yun, Wu; Di, Jin

    2016-04-01

    Electrical characteristics and optical emission spectrum of the radio frequency (RF) surface dielectric barrier discharge (SDBD) plasma actuation are investigated experimentally in this paper. Influences of operating pressure, duty cycle and load power on the discharge are analyzed. When the operating pressure reaches 30 kPa, the discharge energy calculated from the Charge–Voltage (Q–V) Lissajous figure increases significantly, while the effective capacitance decreases remarkably. As the duty cycle of the applied voltage increases, the voltage–current waveforms, the area of Q–V loop and the capacity show no distinct changes. Below 40 W, effective capacitance increases with the increase of load power, but it almost remains unchanged when load power is between 40 W and 95 W. The relative intensity changes little as the operating pressure varies from 4 kPa to 100 kPa, while it rises evidently with the pressure below 4 kPa, which indicates that the RF discharge mode shifts from filamentary discharge to glow discharge at around 4 kPa. With the increase of load power, the relative intensity rises evidently. Additionally, the relative intensity is insensitive to the pressure, the duty cycle, and the load power. Project supported by the National Natural Science Foundation of China (Grant Nos. 11472306, 51276197, and 51336011).

  2. Simulation Tool for Dielectric Barrier Discharge Plasma Actuators at Atmospheric and Sub-Atmospheric Pressures: SBIR Phase I Final Report

    NASA Technical Reports Server (NTRS)

    Likhanskii, Alexandre

    2012-01-01

    This report is the final report of a SBIR Phase I project. It is identical to the final report submitted, after some proprietary information of administrative nature has been removed. The development of a numerical simulation tool for dielectric barrier discharge (DBD) plasma actuator is reported. The objectives of the project were to analyze and predict DBD operation at wide range of ambient gas pressures. It overcomes the limitations of traditional DBD codes which are limited to low-speed applications and have weak prediction capabilities. The software tool allows DBD actuator analysis and prediction for subsonic to hypersonic flow regime. The simulation tool is based on the VORPAL code developed by Tech-X Corporation. VORPAL's capability of modeling DBD plasma actuator at low pressures (0.1 to 10 torr) using kinetic plasma modeling approach, and at moderate to atmospheric pressures (1 to 10 atm) using hydrodynamic plasma modeling approach, were demonstrated. In addition, results of experiments with pulsed+bias DBD configuration that were performed for validation purposes are reported.

  3. Power consumption, discharge capacitance and light emission as measures for thrust production of dielectric barrier discharge plasma actuators

    SciTech Connect

    Kriegseis, J.; Grundmann, S.; Tropea, C.

    2011-07-01

    A new procedure of determining the time resolved capacitance of a plasma actuator during operation is introduced, representing a simple diagnostic tool that provides insight into the phenomenological behavior of plasma actuators. The procedure is demonstrated by presenting example correlations between consumed electrical energy, size of the plasma region, and the operating voltage. It is shown that the capacitance of a plasma actuator is considerably increased by the presence of the plasma; hence a system that has previously been impedance matched can be considerably de-tuned when varying the operating voltage of the actuator. Such information is fundamental for any attempts to increase the energy efficiency of plasma-actuator systems. A combined analysis of the capacitance, light emission, size of the plasma region, force production, and power consumption is presented.

  4. Contribution of positive and negative ions to the electrohydrodynamic force in a dielectric barrier discharge plasma actuator operating in air

    SciTech Connect

    Boeuf, J. P.; Lagmich, Y.; Pitchford, L. C.

    2009-07-15

    We present a parametric study of the electrohydrodynamic force generated by surface dielectric barrier discharge plasma actuators in air for sinusoidal voltage waveforms. The simulation results confirm that momentum is transferred from the charged particles to the neutral species in the same direction during both positive and negative parts of the cycle. The momentum transfer is due to positive ions during the positive part of the cycle (electrode above the dielectric layer is the anode), and to negative ions during the negative part of the cycle. The relative contribution of the positive and negative parts of the cycle depends on the voltage amplitude and frequency. The model predicts that the contribution of negative ions tends to be dominant at low voltage frequencies and high voltage amplitudes.

  5. Modeling of dielectric barrier discharge plasma actuators driven by repetitive nanosecond pulses

    SciTech Connect

    Likhanskii, Alexandre V.; Shneider, Mikhail N.; Macheret, Sergey O.; Miles, Richard B.

    2007-07-15

    A detailed physical model for an asymmetric dielectric barrier discharge (DBD) in air driven by repetitive nanosecond voltage pulses is developed. In particular, modeling of DBD with high voltage repetitive negative and positive nanosecond pulses combined with positive dc bias is carried out. Operation at high voltage is compared with operation at low voltage, highlighting the advantage of high voltages, however the effect of backward-directed breakdown in the case of negative pulses results in a decrease of the integral momentum transferred to the gas. The use of positive repetitive pulses with dc bias is demonstrated to be promising for DBD performance improvement. The effects of the voltage waveform not only on force magnitude, but also on the spatial profile of the force, are shown. The crucial role of background photoionization in numerical modeling of ionization waves (streamers) in DBD plasmas is demonstrated.

  6. Bluff Body Flow Control Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Thomas, Flint

    2005-11-01

    In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.

  7. Mechanisms for laminar separated-flow control using dielectric-barrier-discharge plasma actuator at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Sato, Makoto; Nonomura, Taku; Okada, Koichi; Asada, Kengo; Aono, Hikaru; Yakeno, Aiko; Abe, Yoshiaki; Fujii, Kozo

    2015-11-01

    Large-eddy simulations have been conducted to investigate the mechanisms of separated-flow control using a dielectric barrier discharge plasma actuator at a low Reynolds number. In the present study, the mechanisms are classified according to the means of momentum injection to the boundary layer. The separated flow around the NACA 0015 airfoil at a Reynolds number of 63 000 is used as the base flow for separation control. Both normal and burst mode actuations are adopted in separation control. The burst frequency non-dimensionalized by the freestream velocity and the chord length (F+) is varied from 0.25 to 25, and we discuss the control mechanism through the comparison of the aerodynamic performance and controlled flow-fields in each normal and burst case. Lift and drag coefficients are significantly improved for the cases of F+ = 1, 5, and 15 due to flow reattachment associated with a laminar-separation bubble. Frequency and linear stability analyses indicate that the F+ = 5 and 15 cases effectively excite the natural unstable frequency at the separated shear layer, which is caused by the Kelvin-Helmholtz instability. This excitation results in earlier flow reattachment due to earlier turbulent transition. Furthermore, the Reynolds stress decomposition is conducted in order to identify the means of momentum entrainment resulted from large-scale spanwise vortical structure or small-scale turbulent vortices. For the cases with flow reattachment, the large-scale spanwise vortices, which shed from the separated shear layer through plasma actuation, significantly increase the periodic component of the Reynolds stress near the leading edge. These large-scale vortices collapse to small-scale turbulent vortices, and the turbulent component of the Reynolds stress increases around the large-scale vortices. In these cases, although the combination of momentum entrainment by both Reynolds stress components results in flow reattachment, the dominant component is identified as

  8. Diagnostics for characterisation of plasma actuators

    NASA Astrophysics Data System (ADS)

    Kotsonis, Marios

    2015-09-01

    The popularity of plasma actuators as flow control devices has sparked a flurry of diagnostic efforts towards their characterisation. This review article presents an overview of experimental investigations employing diagnostic techniques specifically aimed at AC dielectric barrier discharge, DC corona and nanosecond pulse plasma actuators. Mechanical, thermal and electrical characterisation techniques are treated. Various techniques for the measurement of induced velocity, body force, heating effects, voltage, current, power and discharge morphology are presented and common issues and challenges are described. The final part of this report addresses the effect of ambient conditions on the performance of plasma actuators.

  9. Experimental investigation of dielectric barrier discharge plasma actuators driven by repetitive high-voltage nanosecond pulses with dc or low frequency sinusoidal bias

    NASA Astrophysics Data System (ADS)

    Opaits, Dmitry F.; Likhanskii, Alexandre V.; Neretti, Gabriele; Zaidi, Sohail; Shneider, Mikhail N.; Miles, Richard B.; Macheret, Sergey O.

    2008-08-01

    Experimental studies were conducted of a flow induced in an initially quiescent room air by a single asymmetric dielectric barrier discharge driven by voltage waveforms consisting of repetitive nanosecond high-voltage pulses superimposed on dc or alternating sinusoidal or square-wave bias voltage. To characterize the pulses and to optimize their matching to the plasma, a numerical code for short pulse calculations with an arbitrary impedance load was developed. A new approach for nonintrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the schlieren technique, burst mode of plasma actuator operation, and two-dimensional numerical fluid modeling. The force and heating rate calculated by a plasma model was used as an input to two-dimensional viscous flow solver to predict the time-dependent dielectric barrier discharge induced flow field. This approach allowed us to restore the entire two-dimensional unsteady plasma induced flow pattern as well as characteristics of the plasma induced force. Both the experiments and computations showed the same vortex flow structures induced by the actuator. Parametric studies of the vortices at different bias voltages, pulse polarities, peak pulse voltages, and pulse repetition rates were conducted experimentally. The significance of charge buildup on the dielectric surface was demonstrated. The charge buildup decreases the effective electric field in the plasma and reduces the plasma actuator performance. The accumulated surface charge can be removed by switching the bias polarity, which leads to a newly proposed voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a high-voltage low frequency sinusoidal voltage. Advantages of the new voltage waveform were demonstrated experimentally.

  10. Plasma actuators for bluff body flow control

    NASA Astrophysics Data System (ADS)

    Kozlov, Alexey V.

    The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding

  11. Flow control of an elongated jet in cross-flow: Film cooling effectiveness enhancement using surface dielectric barrier discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Audier, P.; Fénot, M.; Bénard, N.; Moreau, E.

    2016-02-01

    The case presented here deals with plasma flow control applied to a cross-flow configuration, more specifically to a film cooling system. The ability of a plasma dielectric barrier discharge actuator for film cooling effectiveness enhancement is investigated through an experimental set-up, including a film injection from an elongated slot into a thermally uniform cross-flow. Two-dimensional particle image velocimetry and infrared-thermography measurements are performed for three different blowing ratios of M = 0.4, 0.5, and 1. Results show that the effectiveness can be increased when the discharge is switched on, as predicted by the numerical results available in literature. Whatever the blowing ratio, the actuator induces a deflection of the jet flow towards the wall, increases its momentum, and delays its diffusion in the cross-flow.

  12. Novel applications of plasma actuators

    NASA Astrophysics Data System (ADS)

    Ozturk, Arzu Ceren

    The current study investigates the effectiveness of two different dielectric barrier discharge plasma actuator configurations, a 3-D annular geometry for use in micro thrusters and internal duct aerodynamics and a jet vectoring actuator that acts as a vortex generator and flow control device. The first configuration consists of a closed circumferential arrangement which yields a body force when a voltage difference is applied across the inner and outer electrodes separated by a dielectric. The primary flow is driven by this zero-net mass flux jet at the wall that then entrains fluid in the core of the duct. PIV experiments in both quiescent flow and freestream are conducted on tubes of different diameters while varying parameters such as the modulation frequency, duty cycle and tunnel speed. The values of the induced velocities increase with the forcing frequency and duty cycle although there is a peak value for the forcing frequency after which the velocity and thrust decrease for each thruster. The velocities and thrust increase as the inner diameter of the tubes are increased while the velocity profiles show a great difference with the (l/di) ratio; recirculation occurs after going below a critical value. Experiments in the wind tunnel illustrate that the jet exit characteristics significantly change upon actuation in freestream flow but the effect tends to diminish with increasing inner diameters and tunnel speeds. Using staged arrays of these thrusters result in higher velocities while operating at both in phase and out of phase. The jet vectoring configuration consists of a single embedded electrode separated from two exposed electrodes on either side by the dielectric. The embedded electrode is grounded while the exposed electrodes are driven with a high frequency high voltage input signal. PIV measurements of the actuator in a freestream show that vectoring the jet yields stronger vortices than a linear configuration and increasing the difference between

  13. Dielectric barrier discharge-based plasma actuator operation in artificial atmospheres for validation of modeling and simulation

    NASA Astrophysics Data System (ADS)

    Mangina, R. S.; Enloe, C. L.; Font, G. I.

    2015-11-01

    We present an experimental case study of time-resolved force production by an aerodynamic plasma actuator immersed in various mixtures of electropositive (N2) and electronegative gases (O2 and SF6) at atmospheric pressure using a fixed AC high-voltage input of 16 kV peak amplitude at 200 Hz frequency. We have observed distinct changes in the discharge structures during both negative- and positive-going voltage half-cycles, with corresponding variations in the actuator's force production: a ratio of 4:1 in the impulse produced by the negative-going half-cycle of the discharge among the various gas mixtures we explored, 2:1 in the impulse produced by the positive-going half-cycle, and cases in which the negative-going half-cycle dominates force production (by a ratio of 1.5:1), where the half-cycles produce identical force levels, and where the positive-going half cycle dominates (by a ratio of 1:5). We also present time-resolved experimental evidence for the first time that shows electrons do play a significant role in the momentum coupling to surrounding neutrals during the negative going voltage half-cycle of the N2 discharge. We show that there is sufficient macroscopic variation in the plasma that the predictions of numerical models at the microscopic level can be validated even though the plasma itself cannot be measured directly on those spatial and temporal scales.

  14. Cylinder Flow Control Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Kozlov, Alexey; Thomas, Flint

    2007-11-01

    In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. Two optimized quartz dielectric plasma actuators mounted on the cylinder surface utilizing an improved saw-tooth waveform high-voltage generator allowed flow control at Reynolds number approaching supercritical. Using either steady or unsteady actuation, it is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. PIV based flow fields and wake velocity profiles obtained with hot-wire anemometry show large reductions in vortex shedding, wake width and turbulence intensity.

  15. Research on Plasma Synthetic Jet Actuator

    NASA Astrophysics Data System (ADS)

    Che, X. K.; Nie, W. S.; Hou, Z. Y.

    2011-09-01

    Circular dielectric barrier surface discharge (DBDs) actuator is a new concept of zero mass synthetic jet actuator. The characteristic of discharge and flow control effect of annular-circular plasma synthetic jet actuator has been studied by means of of numerical simulation and experiment. The discharge current density, electron density, electrostatic body force density and flowfield have been obtained. The results show annular-circular actuator can produce normal jet whose velocity will be greater than 2.0 m/s. The jet will excite circumfluence. In order to insure the discharge is generated in the exposed electrode annular and produce centripetal and normal electrostatic body force, the width and annular diameter of exposed electrode must be big enough, or an opposite phase drove voltage potential should be applied between the two electrodes.

  16. Dielectric barrier discharge-based plasma actuator operation in artificial atmospheres for validation of modeling and simulation

    SciTech Connect

    Mangina, R. S.; Enloe, C. L.; Font, G. I.

    2015-11-15

    We present an experimental case study of time-resolved force production by an aerodynamic plasma actuator immersed in various mixtures of electropositive (N{sub 2}) and electronegative gases (O{sub 2} and SF{sub 6}) at atmospheric pressure using a fixed AC high-voltage input of 16 kV peak amplitude at 200 Hz frequency. We have observed distinct changes in the discharge structures during both negative- and positive-going voltage half-cycles, with corresponding variations in the actuator's force production: a ratio of 4:1 in the impulse produced by the negative-going half-cycle of the discharge among the various gas mixtures we explored, 2:1 in the impulse produced by the positive-going half-cycle, and cases in which the negative-going half-cycle dominates force production (by a ratio of 1.5:1), where the half-cycles produce identical force levels, and where the positive-going half cycle dominates (by a ratio of 1:5). We also present time-resolved experimental evidence for the first time that shows electrons do play a significant role in the momentum coupling to surrounding neutrals during the negative going voltage half-cycle of the N{sub 2} discharge. We show that there is sufficient macroscopic variation in the plasma that the predictions of numerical models at the microscopic level can be validated even though the plasma itself cannot be measured directly on those spatial and temporal scales.

  17. Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators: New Anti-Thrust Hypothesis, Frequency Sweeps Methodology, Humidity and Enclosure Effects

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.

    2014-01-01

    We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust, or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a grounded large-diameter metal sleeve. Strong dependence on humidity is also shown; the thrust significantly increased with decreasing humidity, e

  18. Airflow acceleration performance of asymmetric surface dielectric barrier discharge actuators at different exposed needle electrode heights

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-12-01

    The use of plasma, created by asymmetric surface dielectric barrier discharge (ASDBD), as aerodynamic actuators to control airflows, has been of widespread concern over the past decades. For the single ASDBD, the actuator performance is dependent on the geometry of actuator and the produced plasma. In this work, a new electrode configuration, i.e., a row of needle, is taken as an exposed electrode for the ASDBD plasma actuator, and the electrode height is adjustable. The effects of different electrode heights on the airflow acceleration behavior are experimentally investigated by measuring surface potential distribution, ionic wind velocity, and mean thrust force production. It is demonstrated that the airflow velocity and thrust force increase with the exposed electrode height and the best actuator performance can be obtained when the exposed electrode is adjusted to an appropriate height. The difference, as analyzed, is mainly due to the distinct plasma spatial distributions at different exposed electrode heights.

  19. Robust, Flexible and Lightweight Dielectric Barrier Discharge Actuators Using Nanofoams/Aerogels

    NASA Technical Reports Server (NTRS)

    Sauti, Godfrey (Inventor); Xu, Tian-Bing (Inventor); Siochi, Emilie J. (Inventor); Wilkinson, Stephen P. (Inventor); Meador, Mary Ann B. (Inventor); Guo, Haiquan N. (Inventor)

    2015-01-01

    Robust, flexible, lightweight, low profile enhanced performance dielectric barrier discharge actuators (plasma actuators) based on aerogels/nanofoams with controlled pore size and size distribution as well as pore shape. The plasma actuators offer high body force as well as high force to weight ratios (thrust density). The flexibility and mechanical robustness of the actuators allows them to be shaped to conform to the surface to which they are applied. Carbon nanotube (CNT) based electrodes serve to further decrease the weight and profile of the actuators while maintaining flexibility while insulating nano-inclusions in the matrix enable tailoring of the mechanical properties. Such actuators are required for flow control in aeronautics and moving machinery such as wind turbines, noise abatement in landing gear and rotary wing aircraft and other applications.

  20. Stabilization of boundary layer streaks by plasma actuators

    NASA Astrophysics Data System (ADS)

    Riherd, Mark; Roy, Subrata

    2014-03-01

    A flow's transition from laminar to turbulent leads to increased levels of skin friction. In recent years, dielectric barrier discharge actuators have been shown to be able to delay the onset of turbulence in boundary layers. While the laminar to turbulent transition process can be initiated by several different instability mechanisms, so far, only stabilization of the Tollmien-Schlichting path to transition has received significant attention, leaving the stabilization of other transition paths using these actuators less explored. To fill that void, a bi-global stability analysis is used here to examine the stabilization of boundary layer streaks in a laminar boundary layer. These streaks, which are important to both transient and by-pass instability mechanisms, are damped by the addition of a flow-wise oriented plasma body force to the boundary layer. Depending on the magnitude of the plasma actuation, this damping can be up to 25% of the perturbation's kinetic energy. The damping mechanism appears to be due to highly localized effects in the immediate vicinity of the body force, and when examined using a linearized Reynolds-averaged Navier-Stokes energy balance, indicate negative production of the perturbation's kinetic energy. Parametric studies of the stabilization have also been performed, varying the magnitude of the plasma actuator's body force and the spanwise wavenumber of the actuation. Based on these parametric studies, the damping of the boundary layer streaks appears to be linear with respect to the total amount of body force applied to the flow.

  1. Use of Plasma Actuators as a Moving-Wake Generator

    NASA Technical Reports Server (NTRS)

    Corke, Thomas C.; Thomas, Flint O.; Klapetzky Michael J.

    2007-01-01

    The work documented in this report tests the concept of using plasma actuators as a simple and easy way to generate a simulated moving-wake and the disturbances associated with it in turbines. This wake is caused by the blades of the upstream stages of the turbine. Two types of devices, one constructed of arrays of NACA 0018 airfoils, and the one constructed of flat plates were studied. The airfoils or plates were equipped with surface mounted dielectric barrier discharge (DBD) plasma actuators, which were used to generate flow disturbances resembling moving-wakes. CTA hot-wire anemometry and flow visualization using a smoke-wire were used to investigate the wake independence at various spacings and downstream locations. The flat plates were found to produce better results than the airfoils in creating large velocity fluctuations in the free-stream flow. Different dielectric materials, plasma actuator locations, leading edge contours, angles of attack and plate spacings were investigated, some with positive results. The magnitudes of the velocity fluctuations were found to be comparable to existing mechanical moving-wake generators, thus proving the feasibility of using plasma actuators as a moving-wake generator.

  2. Dielectric barrier discharge actuator for vehicle drag reduction at highway speeds

    NASA Astrophysics Data System (ADS)

    Roy, Subrata; Zhao, Pengfei; DasGupta, Arnob; Soni, Jignesh

    2016-02-01

    We propose and demonstrate reduction of aerodynamic drag for a realistic geometry at highway speeds using serpentine dielectric barrier discharge actuators. A comparable linear plasma actuator fails to reduce the drag at these speeds. Experimental data collected for linear and serpentine plasma actuators under quiescent operating conditions show that the serpentine design has profound effect on near wall flow structure and resulting drag. For certain actuator arrangement, the measured drag reduced by over 14% at 26.8 m/s (60 mph) and over 10% at 31.3 m/s (70 mph) opening up realistic possibility of reasonable energy savings for full scale ground vehicles. In addition, the power consumption data and drag reduction effectiveness for different input signals are also presented.

  3. Three-dimensional effects of curved plasma actuators in quiescent air

    SciTech Connect

    Wang Chincheng; Durscher, Ryan; Roy, Subrata

    2011-04-15

    This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength ({lambda}) and amplitude ({Lambda}) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.

  4. Scalability of Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2008-01-01

    Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

  5. Investigation of flow separation control by nanosecond pulsed dielectric barrier discharge actuators

    NASA Astrophysics Data System (ADS)

    Grech, N.; Leyland, P.; Peschke, Ph.; Ott, P.

    2015-06-01

    The ability of nanosecond pulsed dielectric barrier discharge (DBD) actuators to control flow separation was investigated on a NACA (National Advisory Committee for Aeronautics) 0015 profile for velocities up to 24 m/s (Re = 230,000). The optimal location for the actuator was determined from oil flow experiments. Moderate voltage levels were applied (3 and 6 kV) and the actuator was operated at frequencies ranging from 0.058 to 10 kHz in pulse and burst modes. The peak effectiveness of the actuator occurred at reduced frequency values of around 1. Plasma influence was observed at all tested angles of attack (up to 26°) and the stall angle was delayed by 8°.

  6. Comparisons of Force Measurement Methods for DBD Plasma Actuators in Quiescent Air

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

    2009-01-01

    We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators with cylindrical exposed electrodes, as the electrode diameter decrease the force efficiencies increase much faster than a previously reported linear trend. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. Actuators with rectangular cross-section exposed electrodes do not show the same rapid increase at small thicknesses. We have also shown that the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

  7. Shock Generation and Control Using DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.

    2012-01-01

    This report is the final report of a NASA Phase I SBIR contract, with some revisions to remove company proprietary data. The Shock Boundary Layer Interaction (SBLI) phenomena in a supersonic inlet involve mutual interaction of oblique shocks with boundary layers, forcing the boundary layer to separate from the inlet wall. To improve the inlet efficiency, it is desired to prevent or delay shock-induced boundary layer separation. In this effort, Innovative Technology Applications Company (ITAC), LLC and the University of Notre Dame (UND) jointly investigated the use of dielectric-barrier-discharge (DBD) plasma actuators for control of SBLI in a supersonic inlet. The research investigated the potential for DBD plasma actuators to suppress flow separation caused by a shock in a turbulent boundary layer. The research involved both numerical and experimental investigations of plasma flow control for a few different SBLI configurations: (a) a 12 wedge flow test case at Mach 1.5 (numerical and experimental), (b) an impinging shock test case at Mach 1.5 using an airfoil as a shock generator (numerical and experimental), and (c) a Mach 2.0 nozzle flow case in a simulated 15 X 15 cm wind tunnel with a shock generator (numerical). Numerical studies were performed for all three test cases to examine the feasibility of plasma flow control concepts. These results were used to guide the wind tunnel experiments conducted on the Mach 1.5 12 degree wedge flow (case a) and the Mach 1.5 impinging shock test case (case b) which were at similar flow conditions as the corresponding numerical studies to obtain experimental evidence of plasma control effects for SBLI control. The experiments also generated data that were used in validating the numerical studies for the baseline cases (without plasma actuators). The experiments were conducted in a Mach 1.5 test section in the University of Notre Dame Hessert Laboratory. The simulation results from cases a and b indicated that multiple

  8. Study of Unsteady Flow Actuation Produced by Surface Plasma Actuator on 2-D Airfoil

    NASA Astrophysics Data System (ADS)

    Phan, Minh Khang; Shin, Jichul

    2014-10-01

    Effect of flow actuation driven by low current continuous or pulsed DC surface glow discharge plasma actuator is studied. Schlieren image of induced flow on flat plate taken at a high repetition rate reveals that the actuation is mostly initiated near the cathode. Assuming that the actuation is mostly achieved by ions in the cathode sheath region, numerical model for the source of flow actuation is obtained by analytical estimation of ion pressure force created in DC plasma sheath near the cathode and added in momentum equation as a body force term. Modeled plasma flow actuator is simulated with NACA0012 airfoil oscillating over a certain range of angle of attack (AoA) at specific reduced frequencies of airfoil. By changing actuation authority according to the change in AoA, stabilization of unsteady flow field is improved and hence steady aerodynamic performance can be maintained. Computational result shows that plasma actuation is only effective in modifying aerodynamic characteristics of separated flow. It turns out that plasma pulse frequency should be tuned for optimal performance depending on phase angle and rotating speed. The actuation authority can be parameterized by a ratio between plasma pulse frequency and reduced frequency.

  9. Experimental Investigation on Airfoil Shock Control by Plasma Aerodynamic Actuation

    NASA Astrophysics Data System (ADS)

    Sun, Quan; Cheng, Bangqin; Li, Yinghong; Cui, Wei; Jin, Di; Li, Jun

    2013-11-01

    An experimental investigation on airfoil (NACA64—215) shock control is performed by plasma aerodynamic actuation in a supersonic tunnel (Ma = 2). The results of schlieren and pressure measurement show that when plasma aerodynamic actuation is applied, the position moves forward and the intensity of shock at the head of the airfoil weakens. With the increase in actuating voltage, the total pressure measured at the head of the airfoil increases, which means that the shock intensity decreases and the control effect increases. The best actuation effect is caused by upwind-direction actuation with a magnetic field, and then downwind-direction actuation with a magnetic field, while the control effect of aerodynamic actuation without a magnetic field is the most inconspicuous. The mean intensity of the normal shock at the head of the airfoil is relatively decreased by 16.33%, and the normal shock intensity is relatively reduced by 27.5% when 1000 V actuating voltage and upwind-direction actuation are applied with a magnetic field. This paper theoretically analyzes the Joule heating effect generated by DC discharge and the Lorentz force effect caused by the magnetic field. The discharge characteristics are compared for all kinds of actuation conditions to reveal the mechanism of shock control by plasma aerodynamic actuation.

  10. Stressed glass technology for actuators and removable barrier applications.

    SciTech Connect

    Schwing, Kamilla, J.; Warren, Mial E.; Glass, Sarah Jill; Tappan, Alexander Smith

    2007-07-01

    There are commercial and military applications in which a material needs to serve as a barrier that must subsequently be removed. In many cases it is desirable that once the barrier has served its function that it then be reduced to small pieces. For example, in pipelines and in downhole drilling applications, valves are needed to function as barriers that can sustain high pressures. Later the valves must be removed and essentially disappear or be rendered to such a small size that they do not interfere with the functioning of other equipment. Military applications include covers on missile silos or launch vehicles. Other applications might require that a component be used once as an actuator or for passive energy storage, and then be irreversibly removed, again so as not to interfere with the function or motion of other parts of the device. Brittle materials, especially those that are very strong, or are pre-stressed, are ideal candidates for these applications. Stressed glass can be produced in different sizes and shapes and the level of strength and pre-stress, both of which control the fragmentation, can be manipulated by varying the processing. Stressed glass can be engineered to fracture predictably at a specific stress level. Controlling the central tension allows the fragment size to be specified. The energy that is stored in the residual stress profile that results from ion exchange or thermal tempering processes can be harnessed to drive fragmentation of the component once it has been deliberately fractured. Energy can also be stored in the glass by mechanical loading. Energy from both of these sources can be released either to perform useful work or to initiate another reaction. Once the stressed glass has been used as a barrier or actuator it can never be ''used'' again because it fragments into many small unrecognizable pieces during the actuation. Under some circumstances it will interfere with the motion or functioning of other parts of a device. Our

  11. Investigation of microscale dielectric barrier discharge plasma devices

    NASA Astrophysics Data System (ADS)

    Zito, Justin C.

    This dissertation presents research performed on reduced-scale dielectric barrier discharge (DBD) plasma actuators. A first generation of microscale DBD actuators are designed and manufactured using polymeric dielectric layers, and successfully demonstrate operation at reduced scales. The actuators are 1 cm long and vary in width from tens of microns to several millimeters. A thin-film polymer or ceramic material is used as the dielectric barrier with thicknesses from 5 to 20 microns. The devices are characterized for their electrical, fluidic and mechanical performance. With electrical input of 5 kVpp, 1 kHz, the microscale DBD actuators induce a wall jet with velocity reaching up to 2 m/s and produce 3.5 mN/m of thrust, while consuming an average power of 20 W/m. A 5 mN/m plasma body force was observed, acting on the surrounding air. Failure of the microscale DBD actuators is investigated using thermal measurements of the dielectric surface in addition to both optical and scanning electron microscopy. The cause of device failure is identified as erosion of the dielectric surface due to collisions with ions from the discharge. A second generation of microscale actuators is then designed and manufactured using a more reliable dielectric material, namely silicon dioxide. These actuators demonstrate a significant improvement in device lifetime compared with first-generation microscale DBD actuators. The increase in actuator lifetime allowed the electrical, fluidic and mechanical characterization to be repeated over several input voltages and frequencies. At 7 kVpp, 1 kHz, the actuators with SiO2 dielectric induced velocities up to 1.5 m/s and demonstrated 1.4 mN/m of thrust while consuming an average power of 41 W/m. The plasma body force reached up to 2.5 mN/m. Depending on electrical input, the induced velocity and thrust span an order of magnitude in range. Comparisons are made with macroscale DBD actuators which relate the actuator's output performance and power

  12. Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials

    NASA Technical Reports Server (NTRS)

    Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

    2014-01-01

    A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

  13. Plasma actuators for separation control on stationary and oscillating airfoils

    NASA Astrophysics Data System (ADS)

    Post, Martiqua L.

    Given the importance of separation control associated with retreating blade stall on helicopters, the primary objective of this work was to develop a plasma actuator flow control device for its use in controlling leading-edge separation on stationary and oscillating airfoils. The plasma actuator consists of two copper electrodes separated by a dielectric insulator. When the voltage supplied to the electrodes is sufficiently high, the surrounding air ionizes forms plasma in the regions of high electrical field potential. The ionized air, in the presence of an electric field gradient, results in a body force on the flow. The effect of plasma actuator was experimentally investigated and characterized through a systematic set of experiments. It was then applied to NACA 66 3018 and NACA 0015 airfoils for the purpose of leading-edge separation control. The effectiveness of the actuator was documented through surface pressure measurements on the airfoil, mean wake velocity profiles, and flow visualization records. For the stationary airfoil, the actuator prevented flow separation for angles of attack up to 22°, which was 8° past the static stall angle. This resulted in as much as a 300% improvement in the lift-to-drag ratio. For the oscillating airfoil, the measurements were phase-conditioned to the oscillation motion. Three cases with the plasma actuator were investigated: steady actuation, unsteady plasma actuation, and so-called "smart" actuation in which the actuator is activated during portions of the oscillatory cycle. All of the cases exhibited a higher cycle-integrated lift and an improvement in the lift cycle hysteresis. The steady plasma actuation increased the lift over most of the cycle, except at the peak angle of attack where it was found to suppress the dynamic stall vortex. Because of this, the sharp drop in the lift coefficient past the maximum angle of attack was eliminated. The unsteady plasma actuation produced significant improvements in the lift

  14. Noise control of subsonic cavity flows using plasma actuated receptive channels

    NASA Astrophysics Data System (ADS)

    Das Gupta, Arnob; Roy, Subrata

    2014-12-01

    We introduce a passive receptive rectangular channel at the trailing edge of an open rectangular cavity to reduce the acoustic tones generated due to coherent shear layer impingement. The channel is numerically tested at Mach 0.3 using an unsteady three-dimensional large eddy simulation. Results show reduction in pressure fluctuations in the cavity due to which sound pressure levels are suppressed. Two linear dielectric barrier discharge plasma actuators are placed inside the channel to enhance the flow through it. Specifically, acoustic suppression of 7 dB was obtained for Mach 0.3 flow with the plasma actuated channel. Also, the drag coefficient for the cavity reduced by over three folds for the channel and over eight folds for the plasma actuated channel. Such a channel can be useful in noise and drag reduction for various applications, including weapons bay, landing gear and branched piping systems.

  15. Turbine Tip Clearance Active Flow Control using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Vanness, Daniel

    2005-11-01

    A low-speed linear cascade was used to examine the tip gap leakage flow and leakage vortex that exists within the low pressure turbine stage of a gas-turbine engine. The cascade array is composed of nine Pratt & Whitney ``PakB" blades, with the center blade having a variable tip gap up to five percent chord. Reynolds numbers based on axial chord varied from 10^4 to 10^5. Static pressure taps located at the midspan and near the tip of the blade were used to characterize the blade pressure distribution. A five-hole probe was also traversed in the downstream blade wake to ascertain velocity vectors and total pressure loss. Flow control in the form of a single-dielectric-barrier plasma actuator mounted on the blade tip was used to alter the leakage vortex by acting on the blade tip separation bubble, the blade tip shear layer instability, or the gap flow jet instability through the production of high frequency unsteady disturbances. The flow was documented through measurements with and without flow control for varying tip gaps and Reynolds numbers. The effect of the actuation on the tip leakage vortex and efficiency are investigated.

  16. Active flow control over a backward-facing step using plasma actuation

    NASA Astrophysics Data System (ADS)

    Ruisi, R.; Zare-Behtash, H.; Kontis, K.; Erfani, R.

    2016-09-01

    Due to the more stringent aviation regulations on fuel consumption and noise reduction, the interest for smaller and mechanically less complex devices for flow separation control has increased. Plasma actuators are currently among the most studied typology of devices for active flow control purposes due to their small size and lightweight. In this study, a single dielectric barrier discharge (SDBD) actuator is used on a backward-facing step to assess its effects on the separated turbulent shear layer and its reattachment location. A range of actuating modulation frequencies, related to the natural frequencies of shear layer instability (flapping) and vortex shedding instability, are examined. The particle image velocimetry technique is used to analyse the flow over the step and the reattachment location. The bulk-flow experiments show negligible effects both on the shear layer and on the reattachment location for every frequency considered, and the actuator is not able to induce a sufficient velocity increase at the step separation point.

  17. Numerical and Experimental Investigation of Plasma Actuator Control of Modified Flat-back Airfoil

    NASA Astrophysics Data System (ADS)

    Mertz, Benjamin; Corke, Thomas

    2010-11-01

    Flat-back airfoil designs have been proposed for use on the inboard portion of large wind turbine blades because of their good structural characteristics. These structural characteristics are achieved by adding material to the aft portion of the airfoil while maintaining the camber of the origional airfoil shape. The result is a flat vertical trailing edge which increases the drag and noise produced by these airfoils. In order to improve the aerodynamic efficiency of these airfoils, the use of single dielectric barrier discharge (SDBD) plasma actuators was investigated experimentally and numerically. To accomplish this, a rounded trailing edge was added to traditional flat-back airfoil and plasma actuators were used symmetrically to control the flow separation casued by the blunt trailing edge. The actuators were used asymmetrically in order to vector the wake and increase the lift produced by the airfoil similar to adding camber.

  18. Boundary Layer Control by Means of Plasma Actuators

    SciTech Connect

    Quadros, R.

    2007-09-06

    The development of controlled transition in a flat-plate boundary layer is investigated using Large Eddy Simulations (LES) with the dynamic Smagorinsky model. The analysis of flow control with the objective to optimize the effects of Tollmien-Schlichting waves on a flat plate by means of plasma actuators was studied. The plasma effect is modeled as a body force in the momentum equations. These equations are solved in a uniform grid using a 2nd-order finite difference scheme in time and space. The response of plasma actuators operating in different time-dependent conditions, produced by transient or periodic inputs at different frequencies, is also analyzed.

  19. Efficient needle plasma actuators for flow control and surface cooling

    NASA Astrophysics Data System (ADS)

    Zhao, Pengfei; Portugal, Sherlie; Roy, Subrata

    2015-07-01

    We introduce a milliwatt class needle actuator suitable for plasma channels, vortex generation, and surface cooling. Electrode configurations tested for a channel configuration show 1400% and 300% increase in energy conversion efficiency as compared to conventional surface and channel corona actuators, respectively, generating up to 3.4 m/s air jet across the channel outlet. The positive polarity of the needle is shown to have a beneficial effect on actuator efficiency. Needle-plate configuration is demonstrated for improving cooling of a flat surface with a 57% increase in convective heat transfer coefficient. Vortex generation by selective input signal manipulation is also demonstrated.

  20. Vane Separation Control in a Linear Cascade with Area Expansion using AC DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Kleven, Christopher; Corke, Thomas

    2013-11-01

    Experiments are presented on the use of AC dielectric barrier discharge (DBD) plasma actuators to prevent flow separation on vanes in a linear cascade with area expansion. The inlet Mach number to the cascade ranged from 0.3 to 0.5, and the vane chord Reynolds numbers ranged from 0 . 9 ×106 to 1 . 5 ×106 . Three cascade designs with different amounts of area expansion, providing different degrees of adverse pressure gradients, were examined. Surface flow visualization revealed a 3-D separation bubble with strong recirculation that formed on the suction side of the vanes. The pattern agreed well with CFD simulations. Plasma actuators were placed on the suction sides of the vanes, just upstream of the flow separation location. Quantitative measurements were performed in the wakes of the vanes using a 5-hole Pitot probe. The measurements were used to determine the effect of the plasma actuator separation control on the pressure loss coefficient, and flow turning angle through the cascades. Overall, the plasma actuators separation control increased the velocity magnitude and dynamic pressure in the passage between the vanes, resulted in a more spanwise-uniform flow turning angle in the vane passage, and significantly lowered the loss coefficient compared to the baseline.

  1. Ionic wind measurements on multi-tip plasma actuators

    NASA Astrophysics Data System (ADS)

    Messanelli, F.; Belan, M.

    2016-03-01

    This work presents an experimental investigation about the effects of triangular tips on the active electrodes of plasma actuators. The tests are performed on two sets of actuators, corona and DBD, parameterized by means of the tip sharpness and the tips number per unit length. A total number of 30 actuators is considered. The devices are evaluated on the basis of the far field ionic wind velocity, that has been chosen as a representative test common to both kinds of actuator. The dataset includes velocity profiles and maps, that can be integrated to give mass ows and electromechanical effciencies. Some results are also presented in the parameter space defined by tip sharpness and tips number per unit length: this gives the chance of defining optimal electrode shapes within each set. In general, the longitudinal velocity of the gas increases downstream of the tips in all the actuators tested, but the velocity field is modified to different extents in the two kinds of actuators, and is more complicated for the DBDs than for the coronas. The tips also increase the effciency of all the actuators, particularly for the corona set, where even the stability is remarkably improved.

  2. A rapidly settled closed-loop control for airfoil aerodynamics based on plasma actuation

    NASA Astrophysics Data System (ADS)

    Wu, Z.; Wong, C. W.; Wang, L.; Lu, Z.; Zhu, Y.; Zhou, Y.

    2015-08-01

    This paper presents an experimental investigation on the response of the slope seeking with extended Kalman filter (EKF) deployed in a closed-loop system for airfoil aerodynamics control. A novel dielectric barrier discharge (DBD) plasma actuator was used to manipulate the flow around the NACA 0015 airfoil. Experiments were performed under different freestream velocities U ∞, covering the chord Reynolds number Re from 4.4 × 104 to 7.7 × 104. Firstly, the advantages of applying this DBD plasma actuator (hereafter called sawtooth plasma actuator) on the airfoil were examined in an open-loop system at Re = 7.7 × 104. The sawtooth plasma actuator led to a delay in the stall angle α stall by 5° and an increase in the maximum lift coefficient by about 9 %. On the other hand, at the same input power, the traditional DBD plasma actuator managed a delay in α stall by only 3° and an increase in by about 3 %. Secondly, the convergence time t c of the lift force F L at Re from 4.4 × 104 to 7.7 × 104 was investigated for two closed-loop systems. It has been demonstrated that the t c was about 70 % less under the slope seeking with EKF than that under the conventional slope seeking with high-pass (HP) and low-pass (LP) filters at Re = 7.7 × 104. The reduction in t c was also observed at a different Re. Finally, the slope seeking with EKF showed excellent robustness over a moderate Re range; that is, the voltage amplitude determined by the control algorithm promptly responded to a change in Re, much faster than that of the conventional slope seeking with HP and LP filters.

  3. Reduction of aerodynamic friction drag of moving bodies using a Microwave-Dielectric-Barrier-Discharge actuator controlling the boundary layer

    NASA Astrophysics Data System (ADS)

    Pierre, Thiery

    2015-11-01

    A new plasma device named M-DBD (Microwave Dielectric Barrier Discharge) is used for controlling the boundary layer in order to reduce the drag force. A compact resonant UHF structure comprising a resonant element in the form of a quarter-wave antenna creates a mini-plasma insulated from the UHF electrodes by mica sheets. Additional electrodes induce an electric field in the plasma and transiently move the ions of the plasma. The high collision rate with the neutral molecules induce the global transient flow of the neutral gas. The temporal variation of the applied electric field is chosen in order to obtain a modification of the local boundary layer. First tests using an array of M-DBD plasma actuators are underway (see Patent ref. WO 2014111469 A1).

  4. Experimental Investigation on Aerodynamic Control of a Wing with Distributed Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Han, Menghu; Li, Jun; Liang, Hua; Niu, Zhongguo; Zhao, Guangyin

    2015-06-01

    Experimental investigation of active flow control on the aerodynamic performance of a flying wing is conducted. Subsonic wind tunnel tests are performed using a model of a 35° swept flying wing with an nanosecond dielectric barrier discharge (NS-DBD) plasma actuator, which is installed symmetrically on the wing leading edge. The lift and drag coefficient, lift-to-drag ratio and pitching moment coefficient are tested by a six-component force balance for a range of angles of attack. The results indicate that a 44.5% increase in the lift coefficient, a 34.2% decrease in the drag coefficient and a 22.4% increase in the maximum lift-to-drag ratio can be achieved as compared with the baseline case. The effects of several actuation parameters are also investigated, and the results show that control efficiency demonstrates a strong dependence on actuation location and frequency. Furthermore, we highlight the use of distributed plasma actuators at the leading edge to enhance the aerodynamic performance, giving insight into the different mechanism of separation control and vortex control, which shows tremendous potential in practical flow control for a broad range of angles of attack. supported by National Natural Science Foundation of China (Nos. 51276197, 51207169 and 51336011)

  5. Optimum Duty Cycle of Unsteady Plasma Aerodynamic Actuation for NACA0015 Airfoil Stall Separation Control

    NASA Astrophysics Data System (ADS)

    Sun, Min; Yang, Bo; Peng, Tianxiang; Lei, Mingkai

    2016-06-01

    Unsteady dielectric barrier discharge (DBD) plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA0015 airfoil by measuring the surface pressure distribution of the airfoil. The performance of the DBD aerodynamic actuation for airfoil stall separation suppression is evaluated under DBD voltages from 2000 V to 4000 V and the duty cycles varied in the range of 0.1 to 1.0. It is found that higher lift coefficients and lower threshold voltages are achieved under the unsteady DBD aerodynamic actuation with the duty cycles less than 0.5 as compared to that of the steady plasma actuation at the same free-stream speeds and attack angles, indicating a better flow control performance. By comparing the lift coefficients and the threshold voltages, an optimum duty cycle is determined as 0.25 by which the maximum lift coefficient and the minimum threshold voltage are obtained at the same free-stream speed and attack angle. The non-uniform DBD discharge with stronger discharge in the positive half cycle due to electrons deposition on the dielectric slabs and the suppression of opposite momentum transfer due to the intermittent discharge with cutoff of the negative half cycle are responsible for the observed optimum duty cycle. supported by National Natural Science Foundation of China (No. 21276036), Liaoning Provincial Natural Science Foundation of China (No. 2015020123) and the Fundamental Research Funds for the Central Universities of China (No. 3132015154)

  6. A plasma aerodynamic actuator supplied by a multilevel generator operating with different voltage waveforms

    NASA Astrophysics Data System (ADS)

    Borghi, Carlo A.; Cristofolini, Andrea; Grandi, Gabriele; Neretti, Gabriele; Seri, Paolo

    2015-08-01

    In this work a high voltage—high frequency generator for the power supply of a dielectric barrier discharge (DBD) plasma actuator for the aerodynamic control obtained by the electro-hydro-dynamic (EHD) interaction is described and tested. The generator can produce different voltage waveforms. The operating frequency is independent of the load characteristics and does not require impedance matching. The peak-to-peak voltage is 30 kV at a frequency up to 20 kHz and time variation rates up to 60 kV μs-1. The performance of the actuator when supplied by several voltage waveforms is investigated. The tests have been performed in still air at atmospheric pressure. Voltage and current time behaviors have been measured. The evaluation of the energy delivered to the actuator allowed the estimation of the periods in which the plasma was ignited. Vibrational and rotational temperatures of the plasma have been estimated through spectroscopic acquisitions. The flow field induced in the region above the surface of the DBD actuator has been studied and the EHD conversion efficiency has been evaluated for the voltage waveforms investigated. The nearly sinusoidal multilevel voltage of the proposed generator and the sinusoidal voltage waveform of a conventional ac generator obtain comparable plasma features, EHD effects, and efficiencies. Inverse saw tooth waveform presents the highest effects and efficiency. The rectangular waveform generates suitable EHD effects but with the lowest efficiency. The voltage waveforms that induce plasmas with higher rotational temperatures are less efficient for the conversion of the electric into kinetic energy.

  7. Experimental investigation of effects of airflows on plasma-assisted combustion actuator characteristics

    NASA Astrophysics Data System (ADS)

    Liu, Xing-Jian; He, Li-Ming; Yu, Jin-Lu; Zhang, Hua-Lei

    2015-04-01

    The effects of the airflow on plasma-assisted combustion actuator (PACA) characteristics are studied in detail. The plasma is characterized electrically, as well as optically with a spectrometer. Our results show that the airflow has an obvious influence on the PACA characteristics. The breakdown voltage and vibrational temperature decrease, while the discharge power increases compared with the stationary airflow. The memory effect of metastable state species and the transportation characteristics of charged particles in microdischarge channel are the dominant causes for the variations of the breakdown voltage and discharge power, respectively, and the vibrational temperature calculated in this work can describe the electron energy of the dielectric barrier discharge plasma in PACA. These results offer new perspectives for the use of PACA in plasma-assisted combustion. Project supported by the National Natural Science Foundation of China (Grant Nos. 51436008, 50776100, and 51106179).

  8. Simulation of DBD plasma actuators, and nanoparticle-plasma interactions in argon-hydrogen CCP RF discharges

    NASA Astrophysics Data System (ADS)

    Mamunuru, Meenakshi

    The focus of this work is modeling and simulation of low temperature plasma discharges (LTPs). The first part of the thesis consists of the study of dielectric barrier (DBD) plasma actuators. Use of DBD plasma actuators on airfoil surfaces is a promising method for increasing airfoil efficiency. Actuators produce a surface discharge that causes time averaged thrust in the neutral gas. The thrust modifies the boundary layer properties of the flow and prevents the occurrence of separation bubbles. In simulating the working of an actuator, the focus is on the spatial characteristics of the thrust produced by the discharge over very short time and space scales. The results provide an understanding of the causes of thrust, and the basic principles behind the actuator operation. The second part of this work focusses on low pressure plasma discharges used for silicon nanoparticle synthesis. When reactive semiconductor precursor gases are passed through capacitively coupled plasma (CCP) radio frequency (RF) reactors, nano sized particles are formed. When the reactors are operated at high enough powers, a very high fraction of the nanoparticles are crystallized in the chamber. Nanoparticle crystallization in plasma is a very complex process and not yet fully understood. It can be inferred from experiments that bulk and surface processes initiated due to energetic ion impaction of the nanoparticles are responsible for reordering of silicon atoms, causing crystallization. Therefore, study of plasma-particle interactions is the first step towards understanding how particles are crystallized. The specific focus of this work is to investigate the experimental evidence that hydrogen gas presence in argon discharges used for silicon nanocrystal synthesis, leads to a superior quality of nanocrystals. Influence of hydrogen gas on plasma composition and discharge characteristics is studied. Via Monte Carlo simulation, distribution of ion energy impacting particles surface is studied

  9. Experimental Study of RailPAc Plasma Actuator for High-Authority Aerodynamic Flow Control in One Atmosphere

    NASA Astrophysics Data System (ADS)

    Gray, Miles; Choi, Young-Joon; Raja, Laxminarayan; Sirohi, Jayant

    2014-10-01

    Dielectric barrier discharge (DBD) actuators, a type of electrohydrodynamic (EHD) plasma actuator, have generated considerable interest in recent years. However, theoretical performance limitations hinder their application for high speed flows. Magnetohydrodynamic (MHD) plasma actuators with higher control authority circumvent these limitations, offering an excellent alternative. The rail plasma actuator (RailPAc) is an MHD actuator which uses Lorentz force to impart momentum to the surrounding air. RailPAc functions by generating a fast propagating arc column between two rail electrodes that accelerate the arc through J × B forces in a self-induced B-field. The arc column drags the surrounding air to induce aerodynamic flow motion. Our study of the RailPAc will include a description of the transient arc discharge structure through high-speed imaging and a description of the arc composition and temperature through time-resolved emission spectroscopy. Time-resolved force measurements quantify momentum transfer from the arc to the surrounding air and provides a direct measure of the actuator control authority.

  10. Demonstration of Separation Control Using Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  11. Demonstration of Separation Delay with Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2004-01-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2 percent) and high (2.5 percent) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  12. Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators.

    PubMed

    Biganzoli, I; Capone, C; Barni, R; Riccardi, C

    2015-02-01

    Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow. PMID:25725896

  13. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  14. Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.

    2012-01-01

    The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.

  15. Separation control using plasma actuators: application to a free turbulent jet

    NASA Astrophysics Data System (ADS)

    Labergue, A.; Moreau, E.; Zouzou, N.; Touchard, G.

    2007-02-01

    This experimental work deals with active airflow control using non-thermal surface plasma actuators in the case of a rectangular cross section turbulent jet. A wide-angle diffuser composed of two adjustable hinged baseplates is linked at the jet exit. Two types of actuators are considered: the DC corona discharge and the dielectric barrier discharge (DBD). In both cases, an ionic wind with a velocity of several m s-1 is generated tangentially to the wall surface. Thus, this induced aerodynamic effect is applied in order to create the separation along the lower hinged baseplate. The effects of both actuators on the flow separation are measured by means of particle image velocimetry for velocity up to 30 m s-1. The main results show that the DBD seems more efficient than the DC corona discharge but the effect decreases with the jet velocity. However, in increasing the discharge frequency up to 1500 Hz, it is possible to separate a 30 m s-1 jet. Finally, by reducing the actuators' length in the spanwise direction, results lead to a visualization of the three-dimensional effects on the separation along the lower hinged baseplate.

  16. Plasma Actuators for Turbomachinery Flow Control

    NASA Technical Reports Server (NTRS)

    Miles, Richard, B; Shneider, Mikhail, N.

    2012-01-01

    This report is Part I of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. The period of performance was January 1, 2007 to December 31, 2010. This report includes the project summary, a list of publications and reprints of the publications that appeared in archival journals. Part II of the final report includes a Ph.D. dissertation and is published separately as NASA/CR-2012-2172655. The research performed under this project was focused on the operation of surface dielectric barrier discharge (DBD) devices driven by high voltage, nanosecond scale pulses plus constant or time varying bias voltages. The main interest was in momentum production and the range of voltages applied eliminated significant heating effects. The approach was experimental supplemented by computational modeling. All the experiments were conducted at Princeton University. The project provided comprehensive understanding of the associated physical phenomena. Limitations on the performance of the devices for the generation of high velocity surface jets were established and various means for overcoming those limitations were proposed and tested. The major limitations included the maximum velocity limit of the jet due to electrical breakdown in air and across the dielectric, the occurrence of backward breakdown during the short pulse causing reverse thrust, the buildup of surface charge in the dielectric offsetting the forward driving potential of the bias voltage, and the interaction of the surface jet with the surface through viscous losses. It was also noted that the best performance occurred when the nanosecond pulse and the bias voltage were of opposite sign. Solutions include the development of partially conducting surface coatings, the development of a semiconductor diode inlaid surface material to suppress the backward breakdown. Extension to long discharge channels was studied and a new ozone imaging method developed for more quantitative determination of surface jet

  17. Competition between pressure effects and airflow influence for the performance of plasma actuators

    SciTech Connect

    Kriegseis, J.; Barckmann, K.; Grundmann, S.; Frey, J.; Tropea, C.

    2014-05-15

    The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1–1 bar) and airflow velocities (U{sub ∞}=0−100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

  18. Impact of ns-DBD plasma actuation on the boundary layer transition using convective heat transfer measurements

    NASA Astrophysics Data System (ADS)

    Ullmer, Dirk; Peschke, Philip; Terzis, Alexandros; Ott, Peter; Weigand, Bernhard

    2015-09-01

    This paper demonstrates that the impact of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators on the structure of the boundary layer can be investigated using quantitative convective heat transfer measurements. For the experiments, the flow over a flat plate with a C4 leading edge thickness distribution was examined at low speed incompressible flow (6.6-11.5 m s-1). An ns-DBD plasma actuator was mounted 5 mm downstream of the leading edge and several experiments were conducted giving particular emphasis on the effect of actuation frequency and the freestream velocity. Local heat transfer distributions were measured using the transient liquid crystal technique with and without plasma activated. As a result, any effect of plasma on the structure of the boundary layer is interpreted by local heat transfer coefficient distributions which are compared with laminar and turbulent boundary layer correlations. The heat transfer results, which are also confirmed by hot-wire measurements, show the considerable effect of the actuation frequency on the location of the transition point elucidating that liquid crystal thermography is a promising method for investigating plasma-flow interactions very close to the wall. Additionally, the hot-wire measurements indicate possible velocity oscillations in the near wall flow due to plasma activation.

  19. Investigation of the Flow Structure on a Flat Plate Induced by Unsteady Plasma Actuation with DNS Methods

    NASA Astrophysics Data System (ADS)

    Yu, Jianyang; Chen, Fu; Liu, Huaping; Song, Yanping

    2015-12-01

    An investigation into the flow characteristic on a flat plate induced by an unsteady plasma was conducted with the methods of direct numerical simulations (DNS). A simplified model of dielectric barrier discharge (DBD) plasma was applied and its parameters were calibrated with the experimental results. In the simulations, effects of the actuation frequency on the flow were examined. The instantaneous flow parameters were also drawn to serve as a detailed study on the behavior when the plasma actuator was applied to the flow. The result shows that induced by the unsteady actuation, a series of vortex pairs which showed dipole formation and periodicity distribution were formed in the boundary layer. The production of these vortex pairs indicated a strong energy exchange between the main flow and the boundary layer. They moved downstream under the action of the free stream and decayed under the influence of the fluid viscosity. The distance of the neighboring vortices was found to be determined by the actuation frequency. Interaction of the neighboring vortices would be ignored when the actuation frequency was too small to make a difference. supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China (No. 51121004) and National Natural Science Foundation of China (No. 50976026)

  20. Simulation of Flow Around Cylinder Actuated by DBD Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Yuling; Gao, Chao; Wu, Bin; Hu, Xu

    2016-07-01

    The electric-static body force model is obtained by solving Maxwell's electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge (DBD) plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry (PIV) experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around the cylinder.

  1. Effect of a direct current bias on the electrohydrodynamic performance of a surface dielectric barrier discharge actuator for airflow control

    NASA Astrophysics Data System (ADS)

    Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng

    2015-02-01

    The effect of a DC bias on the electrohydrodynamics (EHD) force induced by a surface dielectric barrier AC discharge actuator for airflow control at the atmospheric pressure is investigated. The measurement of the surface potential due to charge deposition at different DC biases is carried out by using a special designed corona like discharge potential probe. From the surface potential data, the plasma electromotive force is shown not affected much by the DC biases except for some reduction of the DC bias near the exposed electrode edge for the sheath-like configuration. The total thrust is measured by an analytical balance, and an almost linear relationship to the potential voltage at the exposed electrode edge is found for the direct thrust force. The temporally averaged ionic wind characteristics are investigated by Pitot tube sensor and schlieren visualization system. It is found that the ionic wind velocity profiles with different DC biases are almost the same in the AC discharge plasma area but gradually diversified in the further downstream area as well as the upper space away from the discharge plasma area. Also, the DC bias can significantly modify the topology of the ionic wind produced by the AC discharge actuator. These results can provide an insight into how the DC biases to affect the force generation.

  2. Characterisation of plasma synthetic jet actuators in quiescent flow

    NASA Astrophysics Data System (ADS)

    Zong, Haohua; Kotsonis, Marios

    2016-08-01

    An experimental characterisation study of a large-volume three-electrode plasma synthetic jet actuator (PSJA) is presented. A sequential discharge power supply system is used to activate the PSJA. Phase-locked planar particle image velocimetry (PIV) and time-resolved Schlieren imaging are used to characterise the evolution of the induced flow field in quiescent flow conditions. The effect of orifice diameter is investigated. Results indicate three distinct features of the actuator-induced flow field. These are the initial shock waves, the high speed jet and vortex rings. Two types of shock waves with varied intensities, namely a strong shock wave and a weak shock wave, are issued from the orifice shortly after the ignition of the discharge. Subsequently, the emission of a high speed jet is observed, reaching velocities up to 130 m s‑1. Pronounced oscillation of the exit velocity is caused by the periodical behaviour of capacitive discharge, which also led to the formation of vortex ring trains. Orifice diameter has no influence on the jet acceleration stage and the peak exit velocity. However, a large orifice diameter results in a rapid decline of the exit velocity and thus a short jet duration time. Vortex ring propagation velocities are measured at peak values ranging from 55 m s‑1–70 m s‑1. In the case of 3 mm orifice diameter, trajectory of the vortex ring severely deviates from the actuator axis of symmetry. The development of this asymmetry in the flow field is attributed to asymmetry in the electrode configuration.

  3. Analytic model and frequency characteristics of plasma synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Zong, Hao-hua; Wu, Yun; Li, Ying-hong; Song, Hui-min; Zhang, Zhi-bo; Jia, Min

    2015-02-01

    This paper reports a novel analytic model of a plasma synthetic jet actuator (PSJA), considering both the heat transfer effect and the inertia of the throat gas. Both the whole cycle characteristics and the repetitive working process of PSJA can be predicted with this model. The frequency characteristics of a PSJA with 87 mm3 volume and different orifice diameters are investigated based on the analytic model combined with experiments. In the repetitive working mode, the actuator works initially in the transitional stage with 20 cycles and then in the dynamic balanced stage. During the transitional stage, major performance parameters of PSJA experience stepped growth, while during the dynamic balanced stage, these parameters are characterized by periodic variation. With a constant discharge energy of 6.9 mJ, there exists a saturated frequency of 4 kHz/6 kHz for an orifice diameter of 1 mm/1.5 mm, at which the time-averaged total pressure of the pulsed jet reaches a maximum. Between 0.5 mm and 1.5 mm, a larger orifice diameter leads to a higher saturated frequency due to the reduced jet duration time. As the actuation frequency increases, both the time-averaged cavity temperature and the peak jet velocity initially increase and then remain almost unchanged at 1600 K and 280 m/s, respectively. Besides, with increasing frequency, the mechanical energy incorporated in single pulsed jet, the expelled mass per pulse, and the time-averaged density in the cavity, decline in a stair stepping way, which is caused by the intermittent decrease of refresh stage duration in one period.

  4. LES of transient flows controlled by DBD plasma actuator over a stalled airfoil

    NASA Astrophysics Data System (ADS)

    Asada, K.; Nonomura, T.; Aono, H.; Sato, M.; Okada, K.; Fujii, K.

    2015-03-01

    Large-eddy simulations (LES) are employed to understand the flow field over a NACA 0015 airfoil controlled by a dielectric barrier discharge (DBD) plasma actuator. The Suzen body force model is utilised to introduce the effect of the DBD plasma actuator. The Reynolds number is fixed at 63,000. Transient processes arising due to non-dimensional excitation frequencies of one and six are discussed. The time required to establish flow authority is between four and six characteristic times, independent of the excitation frequency. If the separation is suppressed, the initial flow conditions do not affect the quasi-steady state, and the lift coefficient of the higher frequency case converges very quickly. The transient states can be categorised into following three stages: (1) the lift and drag decreasing stage, (2) the lift recovery stage, and (3) the lift and drag converging stage. The development of vortices and their influence on control is delineated. The simulations show that in the initial transient state, separation of flow suppression is closely related to the development spanwise vortices while during the later, quasi-steady state, three-dimensional vortices become more important.

  5. Optimization of Airfoil Design for Flow Control with Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Williams, Theodore; Corke, Thomas; Cooney, John

    2011-11-01

    Using computer simulations and design optimization methods, this research examines the implementation of active flow control devices on wind turbine blades. Through modifications to blade geometry in order to maximize the effectiveness of flow control devices, increases in aerodynamic performance and control of aerodynamic performance are expected. Due to this compliant flow, an increase in the power output of wind turbines is able to be realized with minimal modification and investment to existing turbine blades. This is achieved through dynamic lift control via virtual camber control. Methods using strategic flow separation near the trailing edge are analyzed to obtain desired aerodynamic performance. FLUENT is used to determine the aerodynamic performance of potential turbine blade design, and the post-processing uses optimization techniques to determine an optimal blade geometry and plasma actuator operating parameters. This work motivates the research and development of novel blade designs with flow control devices that will be tested at Notre Dame's Laboratory for Enhanced Wind Energy Design.

  6. Documentation and Control of Flow Separation on a Low Pressure Turbine Linear Cascade of Pak-B Blades Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Corke, Thomas c.; Thomas, FLint, O.; Huang, Junhui

    2007-01-01

    This work involved the documentation and control of flow separation that occurs over low pressure turbine (LPT) blades at low Reynolds numbers. A specially constructed linear cascade was utilized to study the flow field over a generic LPT cascade consisting of Pratt & Whitney "Pak-B" shaped blades. Flow visualization, surface pressure measurements, LDV measurements, and hot-wire anemometry were conducted to examine the flow fields with and without separation control. Experimental conditions were chosen to give a range of chord Reynolds numbers (based on axial chord and inlet velocity) from 10,000 to 100,000, and a range of freestream turbulence intensities from u'/U(infinity) = 0.08 to 2.85 percent. The blade pressure distributions were measured and used to identify the region of separation that depends on Reynolds number and the turbulence intensity. Separation control was performed using dielectric barrier discharge (DBD) plasma actuators. Both steady and unsteady actuation were implemented and found to work well. The comparison between the steady and unsteady actuators showed that the unsteady actuators worked better than the steady ones. For the steady actuators, it was found that the separated region is significantly reduced. For the unsteady actuators, where the signal was pulsed, the separation was eliminated. The total pressure losses (a low Reynolds number) was reduced by approximately a factor of two. It was also found that lowest plasma duty cycle (10 percent in this work) was as effective as the highest plasma duty cycle (50 percent in this work). The mechanisms of the steady and unsteady plasma actuators were studied. It was suggested by the experimental results that the mechanism for the steady actuators is turbulence tripping, while the mechanism for the unsteady actuators is to generate a train of spanwise structures that promote mixing.

  7. Turbulent separated shear flow control by surface plasma actuator: experimental optimization by genetic algorithm approach

    NASA Astrophysics Data System (ADS)

    Benard, N.; Pons-Prats, J.; Periaux, J.; Bugeda, G.; Braud, P.; Bonnet, J. P.; Moreau, E.

    2016-02-01

    The potential benefits of active flow control are no more debated. Among many others applications, flow control provides an effective mean for manipulating turbulent separated flows. Here, a nonthermal surface plasma discharge (dielectric barrier discharge) is installed at the step corner of a backward-facing step ( U 0 = 15 m/s, Re h = 30,000, Re θ = 1650). Wall pressure sensors are used to estimate the reattaching location downstream of the step (objective function #1) and also to measure the wall pressure fluctuation coefficients (objective function #2). An autonomous multi-variable optimization by genetic algorithm is implemented in an experiment for optimizing simultaneously the voltage amplitude, the burst frequency and the duty cycle of the high-voltage signal producing the surface plasma discharge. The single-objective optimization problems concern alternatively the minimization of the objective function #1 and the maximization of the objective function #2. The present paper demonstrates that when coupled with the plasma actuator and the wall pressure sensors, the genetic algorithm can find the optimum forcing conditions in only a few generations. At the end of the iterative search process, the minimum reattaching position is achieved by forcing the flow at the shear layer mode where a large spreading rate is obtained by increasing the periodicity of the vortex street and by enhancing the vortex pairing process. The objective function #2 is maximized for an actuation at half the shear layer mode. In this specific forcing mode, time-resolved PIV shows that the vortex pairing is reduced and that the strong fluctuations of the wall pressure coefficients result from the periodic passages of flow structures whose size corresponds to the height of the step model.

  8. Investigation of film cooling from cylindrical hole with plasma actuator on flat plate

    NASA Astrophysics Data System (ADS)

    Xiao, Yang; Dai, Sheng-ji; He, Li-ming; Jin, Tao; Zhang, Qian; Hou, Peng-hui

    2016-08-01

    This paper reports the Computational Fluid Dynamics modeling studies on the effect of plasma aerodynamic actuation on combustor film cooling performance. By comparing Case (i.e. film cooling hole with plasma actuator) result to Base (i.e. film cooling hole without plasma actuator) result, the mechanism of improving film cooling performance by using plasma actuator was analyzed. The results show that the Counter Rotating Vortex Pairs in Base are weakened by a new pair of vortex in Case, which is induced by the plasma-actuator-generated arc-shape-distributed electric body force. This leads to less interaction and less mixing between the main flow and the jet flow. Then it causes enhancement of the stability and the steadiness of the jet flow. Finally the average film cooling effectiveness in Case is higher than that in Base. For Case, the uniformity of temperature distribution along spanwise wall surface is improved as the actuator electrode radian increases, so does the average film cooling effectiveness. The film cooling effectiveness is higher when actuator is closer to the exit of hole.

  9. The effect of plasma actuator on the depreciation of the aerodynamic drag on box model

    NASA Astrophysics Data System (ADS)

    Harinaldi, Budiarso, Julian, James; Rabbani M., N.

    2016-06-01

    Recent active control research advances have provided many benefits some of which in the field of transportation by land, sea as well as by air. Flow engineering by using active control has proven advantages in energy saving significantly. One of the active control equipment that is being developed, especially in the 21st century, is a plasma actuator, with the ability to modify the flow of fluid by the approach of ion particles makes these actuators a very powerful and promising tool. This actuator can be said to be better to the previously active control such as suction, blowing and synthetic jets because it is easier to control, more flexible because it has no moving parts, easy to be manufactured and installed, and consumes a small amount of energy with maximum capability. Plasma actuator itself is the composition of a material composed of copper and a dielectric sheet, where the copper sheets act as an electricity conductor and the dielectric sheet as electricity insulator. Products from the plasma actuators are ion wind which is the result of the suction of free air around the actuator to the plasma zone. This study investigates the ability of plasma actuators in lowering aerodynamic drag which is commonly formed in the models of vehicles by varying the shape of geometry models and the flow speed.

  10. Investigation of film cooling from cylindrical hole with plasma actuator on flat plate

    NASA Astrophysics Data System (ADS)

    Xiao, Yang; Dai, Sheng-ji; He, Li-ming; Jin, Tao; Zhang, Qian; Hou, Peng-hui

    2015-09-01

    This paper reports the Computational Fluid Dynamics modeling studies on the effect of plasma aerodynamic actuation on combustor film cooling performance. By comparing Case (i.e. film cooling hole with plasma actuator) result to Base (i.e. film cooling hole without plasma actuator) result, the mechanism of improving film cooling performance by using plasma actuator was analyzed. The results show that the Counter Rotating Vortex Pairs in Base are weakened by a new pair of vortex in Case, which is induced by the plasma-actuator-generated arc-shape-distributed electric body force. This leads to less interaction and less mixing between the main flow and the jet flow. Then it causes enhancement of the stability and the steadiness of the jet flow. Finally the average film cooling effectiveness in Case is higher than that in Base. For Case, the uniformity of temperature distribution along spanwise wall surface is improved as the actuator electrode radian increases, so does the average film cooling effectiveness. The film cooling effectiveness is higher when actuator is closer to the exit of hole.

  11. Vacuum application of thermal barrier plasma coatings

    NASA Technical Reports Server (NTRS)

    Holmes, R. R.; Mckechnie, T. N.

    1988-01-01

    Coatings are presently applied to Space Shuttle Main Engine (SSME) turbine blades for protection against the harsh environment realized in the engine during lift off-to-orbit. High performance nickel, chromium, aluminum, and yttrium (NiCrAlY) alloy coatings, which are applied by atmospheric plasma spraying, crack and spall off because of the severe thermal shock experienced during start-up and shut-down of the engine. Ceramic coatings of yttria stabilized zirconia (ZrO2-Y2O3) were applied initially as a thermal barrier over coating to the NiCrAlY but were removed because of even greater spalling. Utilizing a vacuum plasma spraying process, bond coatings of NiCrAlY were applied in a low pressure atmosphere of argon/helium, producing significantly improved coating-to-blade bonding. The improved coatings showed no spalling after 40 MSFC burner rig thermal shock cycles, cycling between 1700 and -423 F. The current atmospheric plasma NiCrAlY coatings spalled during 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2-Y2O3 to the turbine blades of first stage high-pressure fuel turbopumps utilizing the vacuum plasma process. The improved thermal barrier coating has successfully passed 40 burner rig thermal shock cycles without spalling. Hot firing in an SSME turbine engine is scheduled for the blades. Tooling was installed in preparation for vacuum plasma spray coating other SSME hardware, e.g., the titanium main fuel valve housing (MFVH) and the fuel turbopump nozzle/stator.

  12. Effect of plasma actuator and splitter plate on drag coefficient of a circular cylinder

    NASA Astrophysics Data System (ADS)

    Akbıyık, Hürrem; Erkan Akansu, Yahya; Yavuz, Hakan; Ertuğrul Bay, Ahmet

    2016-03-01

    In this paper, an experimental study on flow control around a circular cylinder with splitter plate and plasma actuator is investigated. The study is performed in wind tunnel for Reynolds numbers at 4000 and 8000. The wake region of circular cylinder with a splitter plate is analyzed at different angles between 0 and 180 degrees. In this the study, not only plasma actuators are activated but also splitter plate is placed behind the cylinder. A couple electrodes are mounted on circular cylinder at ±90 degrees. Also, flow visualization is achieved by using smoke wire method. Drag coefficient of the circular cylinder with splitter plate and the plasma actuator are obtained for different angles and compared with the plain circular cylinder. While attack angle is 0 degree, drag coefficient is decreased about 20% by using the splitter plate behind the circular cylinder. However, when the plasma actuators are activated, the improvement of the drag reduction is measured to be 50%.

  13. DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Thurman, Douglas R.

    2011-01-01

    Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it

  14. Modeling, fabrication and plasma actuator coupling of flexible pressure sensors for flow separation detection and control in aeronautical applications

    NASA Astrophysics Data System (ADS)

    Francioso, L.; De Pascali, C.; Pescini, E.; De Giorgi, M. G.; Siciliano, P.

    2016-06-01

    Preventing the flow separation could enhance the performance of propulsion systems and future civil aircraft. To this end, a fast detection of boundary layer separation is mandatory for a sustainable and successful application of active flow control devices, such as plasma actuators. The present work reports on the design, fabrication and functional tests of low-cost capacitive pressure sensors coupled with dielectric barrier discharge (DBD) plasma actuators to detect and then control flow separation. Finite element method (FEM) simulations were used to obtain information on the deflection and the stress distribution in different-shaped floating membranes. The sensor sensitivity as a function of the pressure load was also calculated by experimental tests. The results of the calibration of different capacitive pressure sensors are reported in this work, together with functional tests in a wind tunnel equipped with a curved wall plate on which a DBD plasma actuator was mounted to control the flow separation. The flow behavior was experimentally investigated by particle image velocimetry (PIV) measurements. Statistical and spectral analysis, applied to the output signals of the pressure sensor placed downstream of the profile leading edge, demonstrated that the sensor is able to discriminate different ionic wind velocity and turbulence conditions. The sensor sensitivity in the 0–100 Pa range was experimentally measured and it ranged between 0.0030 and 0.0046 pF Pa‑1 for the best devices.

  15. Coherent Structures in a Supersonic Jet Excited by Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Gaitonde, Datta; Samimy, Mo

    2010-11-01

    Simulations are used in conjunction with experimental measurements to understand the coherent structures generated by excitation of a Mach 1.3 jet by eight localized arc filament plasma actuators uniformly distributed just upstream of the nozzle exit. Several modes are excited, including the axisymmetric (m=0), helical (m=1-3), and mixed modes (m=±1, ±2) modes. The Strouhal number for all cases is fixed at 0.3, which corresponds to the most amplified frequency. The simulations reproduce the distinct coherent structures measured in the experiment for each azimuthal mode. Detailed analysis of instantaneous, time- and phase-averaged quantities highlights a complex coherent structure generation, evolution and dissipation process. A key feature observed is the initiation of hairpin-like structures with tips/heads in the outer region of the jet shear layer and legs extending forward and slightly inclined in the direction of the jet axis, where the velocity is higher. The subsequent interactions of these structures yield different composite structures in the downstream region. For example, for m=0, adjacent hairpin structures merge to yield axisymmetric rings, with the legs connecting successive structures in the form of ribs in the braid region; and with m=1 and 2 mode excitation, distinct helical and double-helical structures are observed, respectively, with the hairpins forming substructures in the coils.

  16. Shear-flow excitation mechanisms of recessed localized arc-filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Kleinman, R. R.; Bodony, D. J.; Freund, J. B.

    2010-11-01

    Localized arc-filament plasma actuators, placed near the nozzle lip of a laboratory jet, have recently been demonstrated to have sufficient control authority to significantly excite the jet downstream [M. Samimy et al., J. Fluid Mech. 578, 305 (2007)]. This class of plasma actuator, which in this application is recessed in a small cavity near the nozzle lip, causes intense local heating. This heating is thought to be the root mechanism of its influence on the flow, but how this principally entropic thermal source couples with the vortical jet shear layer turbulence downstream is unclear. We investigate this using direct numerical simulations, which match the flow conditions of the corresponding experiment, including Reynolds number, but are two-dimensional to ease computational expense. Despite this obvious modeling approximation, the simulations include the key features of the laboratory system: a thin boundary layer, a plasma-like thermal source in a small recessed cavity, a nozzle lip, and a downstream free shear layer. Results are shown to match the temperature and near-field pressure measured in the laboratory actuators. It is found that the cavity, which was initially included to shield the actuator plasma from the flow, is essential for its action. Thermal expansion within the cavity leads to an ejection of fluid from it, which perturbs the boundary layer and the downstream mixing layer. There is a finite baroclinic torque, but its effects are relatively minor. An alternate actuator designed to mimic the pressure effects of the full actuator, without its concomitant thermal heating, is nearly as effective at exciting the shear layer. An actuator model without the cavity recess does not provide effective actuation. These results suggest that there is significant potential to optimize the actuation authority through design of cavity recesses that augment its effect.

  17. Characterization of linear plasma synthetic jet actuators in an initially quiescent medium

    SciTech Connect

    Santhanakrishnan, Arvind; Reasor, Daniel A. Jr.; LeBeau, Raymond P. Jr.

    2009-04-15

    The plasma synthetic jet actuator (PSJA) is a geometrical variant of the aerodynamic plasma actuator that can be used to produce zero-mass flux jets similar to those created by mechanical devices. This jet can be either three-dimensional using annular electrode arrays (annular PSJA) or nearly two dimensional using two rectangular-strip exposed electrodes and one embedded electrode (linear PSJA). Unsteady pulsing of the PSJA at time scales decoupled to the ac input frequency results in a flow field dominated by counter-rotating vortical structures similar to conventional synthetic jets, and the peak velocity and momentum of the jet is found to be affected by a combination of the pulsing frequency and input power. This paper investigates the fluid dynamic characteristics of linear plasma synthetic jet actuators in an initially quiescent medium. Two-dimensional particle image velocimetry measurements on the actuator are used to validate a previously developed numerical model wherein the plasma behavior is introduced into the Navier-Stokes equations as an electrohydrodynamic force term calculated from Maxwell's equations and solved for the fluid momentum. The numerical model was implemented in an incompressible, unstructured grid code. The results of the simulations are observed to reproduce some aspects of the qualitative and quantitative experimental behavior of the jet for steady and pulsed modes of actuator operation. The self-similarity behavior of plasma synthetic jets are examined and compared to mechanically driven continuous and synthetic jets.

  18. Validated model of arc-filament plasma actuators for control of wall-bounded flows

    NASA Astrophysics Data System (ADS)

    Bodony, Daniel; Natarajan, Mahesh

    2011-11-01

    Plasma actuators based on the electrical arcs between two electrodes have shown promise in controlling high-subsonic and low-supersonic flows. Simulation-based predictions of these flows have often used heuristic models for the effect the plasma has on the flow to be controlled. In this talk we present a two-parameter model of the actuator which combines the unsteady Joule heating induced by the plasma with a thermally perfect model of air. PIV and spectroscopy data are used, in conjunction with simulations, to understand the two parameters and demonstrate how their values are to be determined. The importance of the cavity in which the electrodes are mounted is discussed, as is the role of diffusion. We demonstrate the use of the actuator model by controlling a high-subsonic, separating boundary layer in an S-duct geometry. Supported by the Rolls-Royce Corporation.

  19. Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Du, Hai; Shi, Zhiwei; Cheng, Keming; Wei, Dechen; Li, Zheng; Zhou, Danjie; He, Haibo; Yao, Junkai; He, Chengjun

    2016-06-01

    Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

  20. Numerical and Experimental Investigation on the Attenuation of Electromagnetic Waves in Unmagnetized Plasmas Using Inductively Coupled Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Lin, Min; Xu, Haojun; Wei, Xiaolong; Liang, Hua; Song, Huimin; Sun, Quan; Zhang, Yanhua

    2015-10-01

    The attenuation of electromagnetic (EM) waves in unmagnetized plasma generated by an inductively coupled plasma (ICP) actuator has been investigated both theoretically and experimentally. A numerical study is conducted to investigate the propagation of EM waves in multilayer plasma structures which cover a square flat plate. Experimentally, an ICP actuator with dimensions of 20 cm×20 cm×4 cm is designed to produce a steady plasma slab. The attenuation of EM waves in the plasma generated by the ICP actuator is measured by a reflectivity arch test method at incident waves of 2.3 GHz and 10.1 GHz, respectively. A contrastive analysis of calculated and measured results of these incident wave frequencies is presented, which suggests that the experiment accords well with our theory. As expected, the plasma slab generated by the ICP actuator can effectively attenuate the EM waves, which may have great potential application prospects in aircraft stealth. supported by National Natural Science Foundation of China (Nos. 51276197, 11472306 and 11402301)

  1. Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

    2006-01-01

    The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are

  2. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  3. Control of boundary layer separation and the wake of an airfoil using ns-DBD plasma actuators

    NASA Astrophysics Data System (ADS)

    Ashcraft, Timothy

    The efficacy of nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators for boundary layer separation and wake control is investigated experimentally. A single ns-DBD plasma actuator is placed at the leading edge of a NACA 0012 airfoil model. Both baseline and controlled flow fields are studied using static pressure measurements, Particle Image Velocimetry (PIV) and Constant Temperature Anemometry (CTA). Experiments are primarily performed at Re = 0.74 x 106 and alpha = 18°. CP, PIV and CTA data show that a forcing frequency of F+ = 1.14 is optimal for separation control. CTA surveys of the wake at x/c = 7 indicate three approximate regimes of behavior. Forcing in the range 0.92< F+ < 1.52 results in the best conditions for separation control over the airfoil, but has no dominant signature in the wake at x/c = 7. Excitation in the range of 0.23 < F+ < 0.92 produces a single dominant frequency in the wake while F+ < 0.23 shows behavior representing a possible impulse response or nonlinear effects. PIV data confirm these observations in all three regimes. Cross-correlations of CTA data are also employed to evaluate the two-dimensionality of the excited wake. The initial results presented here are part of an ongoing effort to use active flow control (AFC), in the form of ns-DBDs, as an enabling technology for the study of unsteady aerodynamics and vortex-body interactions.

  4. LES of a Jet Excited by the Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2011-01-01

    The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.

  5. Effect of the duty cycle on the spark-plug plasma synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Seyhan, Mehmet; Erkan Akansu, Yahya; Karakaya, Fuat; Yesildag, Cihan; Akbıyık, Hürrem

    2016-03-01

    A promising novel actuator called Spark-Plug Plasma Synthetic Jet (SPSJ) has been developed in Atmospheric Plasma Research Laboratory at Niğde University. It generates electrothermally high synthetic jet velocity by using high voltage. SPSJ actuator can be utilized to be an active flow control device having some advantages such as no moving parts, low energy consumption and easy to integrate the system. This actuator consists of two main components: semi-surface spark plug (NGK BUHW) as an anode electrode and a cap having an orifice as a cathode electrode. The cap, having a jet exit orifice diameter of 2 mm, has diameter of 4.4 mm and height of 4.65 mm. This study presents the characteristics of SPSJ actuator by using the hot wire anemometer in order to approximately determine jet velocity in quiescent air. Peak velocity as high as 180 m/s was obtained for fe= 100 and duty cycle 50%. The flow visualization indicated that the actuator's jet velocity is enough to penetrate the developed boundary layer.

  6. Surface potential distribution and airflow performance of different air-exposed electrode plasma actuators at different alternating current/direct current voltages

    SciTech Connect

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-04-15

    Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance.

  7. Numerical Study of Control of Flow Separation Over a Ramp with Nanosecond Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Khoo, B. C.; Cui, Y. D.; Zhao, Z. J.; Li, J.

    2016-06-01

    The nanosecond plasma discharge actuator driven by high voltage pulse with typical rise and decay time of several to tens of nanoseconds is emerging as a promising active flow control means in recent years and is being studied intensively. The characterization study reveals that the discharge induced shock wave propagates through ambient air and introduces highly transient perturbation to the flow. On the other hand, the residual heat remaining in the discharge volume may trigger the instability of external flow. In this study, this type of actuator is used to suppress flow separation over a ramp model. Numerical simulation is carried out to investigate the interaction of the discharge induced disturbance with the external flow. It is found that the flow separation region over the ramp can be reduced significantly. Our work may provide some insights into the understanding of the control mechanism of nanosecond pulse actuator.

  8. Active control of massively separated high-speed/base flows with electric arc plasma actuators

    NASA Astrophysics Data System (ADS)

    DeBlauw, Bradley G.

    The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations

  9. Measurement of transient force produced by a propagating arc magnetohydrodynamic plasma actuator in quiescent atmospheric air

    NASA Astrophysics Data System (ADS)

    Choi, Young Joon; Sirohi, Jayant; Raja, Laxminarayan L.

    2015-10-01

    An experimental study was conducted on a magnetohydrodynamic plasma actuator consisting of two parallel, six inch long, copper electrodes flush mounted on an insulating ceramic plate. An electrical arc is generated by a  ∼1 kA current pulse at  ∼100 V across the electrodes. A self-induced Lorentz force drives the arc along the electrodes. The motion of the arc induces flow in the surrounding air through compression as well as entrainment, and generates a transient force, about  ∼4 ms in duration. Experiments were performed on a prototype actuator in quiescent atmospheric air to characterize the motion of the arc and the momentum transferred to the surrounding air. Measurements included transient force and total impulse generated by the actuator as well as the armature voltage and current. The arc shape and transit velocity were determined by high-speed imaging. A peak force of 0.4 N imparting an impulse of 0.68 mN-s was measured for a peak current of 1.2 kA. The force scaled with the square of the armature current and the impulse scaled linearly with the spent capacitor energy. The results provide insight into the mechanisms of body force generation and momentum transfer of a magnetohydrodynamic plasma actuator.

  10. Numerical and Experimental Investigations of Plasma Actuators Based on Magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Kalra, Chiranjeev; Zaidi, Sohail; Shneider, Mikhail; Miles, Richard

    2009-10-01

    Numerical and experimental studies were conducted of magnetically driven DC surface plasma discharges. Their application to supersonic boundary layer control is investigated, specifically the shockwave-turbulent boundary layer interaction problem and the induced separation control is shown. This interaction causes incoming boundary layer thickening and localized pressure loads and high heating rates. In the case of scramjet engine inlet this results in reduced effective cross-section and loss of thrust and efficiency. Magnetogasdynamic flow control is achieved by generating a plasma column close to the wall in boundary layer and dragging the gas close to the wall using Lorentz force due to perpendicular (to flow direction as well as current) magnetic field. The surface plasma column appears as a transverse ``arc'' between two slightly diverging electrodes which is driven by j x B forces so that it sweeps the gas near the surface in the separated region or the recirculation zone, either in the downstream direction or in the upstream direction. Depending on the direction of Lorentz force, separation bubble is either induced in the boundary layer or the shockwave induced bubble is reduced in intensity and probably eliminated. It is shown that these interactions between the plasma and the recirculation zone are non-thermal in nature.

  11. Comparison of plasma treatment and sandblast preprocessing for IPMC actuator

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Chen, Hualing; Wang, Yanjie; Wang, Yongquan; Jia, Shuhai

    2014-03-01

    As a new kind of ionic-driven smart materials, ionic polymer metal composite (IPMC ) is normally fabricated by depositing noble metal (gold, platinum, palladium etc.) on both sides of base membrane (Nafion, Flemion etc.) and shows large bending deflection under low voltage. In the process of fabricating IPMC, surface roughening of base membrane has a significant effect on the performance of IPMC. At present, there are many ways to roughen the base membrane, including physical and chemical ways. In this paper, we analyze the effects of different surface treatment time by plasma etching on surface resistance and mechanical properties of IPMCs fabricated by the treated base membranes. Experimental results show that the base membrane treated by plasma etching displays uniform surface roughness, consequently reducing IPMC's surface resistance effectively and forming more uniform and homogeneous external and penetrative electrodes. However, due to the use of reactive gas, the plasma treatment leads to complex chemical reaction on Nafion surface, changing element composition and material properties and resulting in the performance degradation of IPMC. And sandblast way should be adopted and improved without any changes on element and material structure.

  12. One-dimensional analytical model development of a plasma-based actuator

    NASA Astrophysics Data System (ADS)

    Popkin, Sarah Haack

    This dissertation provides a method for modeling the complex, multi-physics, multi-dimensional processes associated with a plasma-based flow control actuator, also known as the SparkJet, by using a one-dimensional analytical model derived from the Euler and thermodynamic equations, under varying assumptions. This model is compared to CFD simulations and experimental data to verify and/or modify the model where simplifying assumptions poorly represent the real actuator. The model was exercised to explore high-frequency actuation and methods of improving actuator performance. Using peak jet momentum as a performance metric, the model shows that a typical SparkJet design (1 mm orifice diameter, 84.8 mm3 cavity volume, and 0.5 J energy input) operated over a range of frequencies from 1 Hz to 10 kHz shows a decrease in peak momentum corresponding to an actuation cutoff frequency of 800 Hz. The model results show that the cutoff frequency is primarily a function of orifice diameter and cavity volume. To further verify model accuracy, experimental testing was performed involving time-dependent, cavity pressure and arc power measurements as a function of orifice diameter, cavity volume, input energy, and electrode gap. The cavity pressure measurements showed that pressure-based efficiency ranges from 20% to 40%. The arc power measurements exposed the deficiency in assuming instantaneous energy deposition and a calorically perfect gas and also showed that arc efficiency was approximately 80%. Additional comparisons between the pressure-based modeling and experimental results show that the model captures the actuator dependence on orifice diameter, cavity volume, and input energy but over-estimates the duration of the jet flow during Stage 2. The likely cause of the disagreement is an inaccurate representation of thermal heat transfer related to convective heat transfer or heat loss to the electrodes.

  13. An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile

    SciTech Connect

    Mestiri, R.; Hadaji, R.; Ben Nasrallah, S.

    2010-08-15

    In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

  14. Numerical Simulations of Flow Separation Control in Low-Pressure Turbines using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.

    2007-01-01

    A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been further developed and improved in order to expand its use to complicated actuator geometries. The new modeling approach eliminates the requirement of an empirical charge density distribution shape by using the embedded electrode as a source for the charge density. The resulting model is validated against a flat plate experiment with quiescent environment. The modeling approach incorporates the effect of the plasma actuators on the external flow into Navier Stokes computations as a body force vector which is obtained as a product of the net charge density and the electric field. The model solves the Maxwell equation to obtain the electric field due to the applied AC voltage at the electrodes and an additional equation for the charge density distribution representing the plasma density. The new modeling approach solves the charge density equation in the computational domain assuming the embedded electrode as a source therefore automatically generating a charge density distribution on the surface exposed to the flow similar to that observed in the experiments without explicitly specifying an empirical distribution. The model is validated against a flat plate experiment with quiescent environment.

  15. Characteristics of sheath-driven tangential flow produced by a low-current DC surface glow discharge plasma actuator

    NASA Astrophysics Data System (ADS)

    Shin, Jichul; Shajid Rahman, Mohammad

    2014-08-01

    An experimental investigation of low-speed flow actuation at near-atmospheric pressure is presented. The flow actuation is achieved via low-current ( \\lesssim 1.0 mA) continuous or pulsed DC surface glow discharge plasma. The plasma actuator, consisting of two sharp-edged nickel electrodes, produces a tangential flow in a direction from anode to cathode, and is visualized using high-speed schlieren photography. The induced flow velocity estimated via the schlieren images reaches up to 5 m/s in test cases. The actuation capability increases with pressure and electrode gap distances, and the induced flow velocity increases logarithmically with the discharge power. Pulsed DC exhibits slightly improved actuation capability with better directionality. An analytic estimation of induced flow velocity obtained based on ion momentum in the cathode sheath and gas dynamics in one-dimensional flow yields values similar to those measured.

  16. Flow control around a circular cylinder using pulsed dielectric barrier discharge surface plasma

    SciTech Connect

    Jukes, Timothy N.; Choi, Kwing-So

    2009-08-15

    Dielectric barrier discharge (DBD) plasma actuators have been used to control the flow around a circular cylinder at Re=15 000, where the near-wake structure was studied using time-resolved particle image velocimetry with simultaneous measurements of the dynamic lift and drag forces. It was shown that the vortex shedding was suppressed when the surface plasma placed near the natural separation point was activated in a pulsed mode at nondimensional frequency, f{sub p}{sup +}, above 0.6 with a force coefficient, C{sub p}, greater than 0.05%. Plasma actuator performance on flow control was summarized by mapping the changes in drag and lift fluctuations as a function of the forcing frequency and the force coefficient. They showed that more than 70% reduction in lift fluctuations was obtained with up to 32% drag reduction at f{sub p}{sup +}=2.0 and C{sub p}=0.32%. Here, narrowing of the wake was observed as the plasma promoted shear-layer roll-ups at the forcing frequency. This, however, did not affect the shear layer on the opposite side of the wake. At nondimensional forcing frequencies less than 0.6, the vortex shedding locked onto a multiple of the plasma frequency to amplify the wake oscillations. This caused more than 85% increase in lift fluctuations with 8% drag increase at f{sub p}{sup +}=0.2 and C{sub p}=0.01%. The efficiency of flow control using DBD plasma was found to be 1%-2% for drag reduction while around 6% for drag increase.

  17. Plasma surface modification and hydrophobic barrier coating of paper

    NASA Astrophysics Data System (ADS)

    Sahin, Halil Turgut

    2001-07-01

    Development of new technologies for production of alternative paper properties with minimal environmental hazards was the goal of this project. In this study, the utilization of various chemicals under radio frequency (RF) plasma environments was investigated for creation of hydrophobic barrier properties and deposition of electrically conductive conjugated thin layers on the surface of paper. Four basic approaches have been utilized to impart hydrophobic barriers to the paper without affecting bulk properties; argon plasma treatment after Teflon-like chemical; 1,1,1,2 tetrafluoroethane (TFE) predeposition, carbon tetrafluoride (CF4) plasma treatment after TFE pre-deposition, carbon tetrafluoride plasma treatment alone and octamethylcyclotetrasiloxane (OMCTSO) plasma treatment of paper under an RF-glow discharge. The chosen chemicals were found to enhance the properties of the paper substrates and surface analysis aided explanation of the mechanism of hydrophobic barrier improvements on paper. An attempt was also made to prepare oriented thin films of pi-conjugated polymers on paper surfaces with a pulsed plasma technique for incorporation of electrically conductive layers. Progressive changes in composition, with varying plasma duty cycles during the plasma polymerization, were observed with thiophene. The results of this study provide additional support for the unusually good control of film chemistry available via the pulsed plasma technique. Electrical conductivity measurements indicated that fragmented thiophene films were obtained under mild plasma conditions, but the discontinuous thiophene film was found to be oriented. The electrical behavior of the thiophene derived deposited layer was dramatically improved with chemical doping. Correlation of the changes of paper surface properties with changes in plasma parameters are partially explained by based on surface chemistry, although other structural features of the paper morphology were also affected to some

  18. FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Dedrick, J.; Boswell, R. W.; Charles, C.

    2010-09-01

    Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally using 2.4 kVp-p (peak to peak) 13.56 MHz rf pulses, 20 µs in duration. The results exhibit different characteristics to plasma actuators, which have similar discharge geometry but are typically driven at frequencies of up to about 10 kHz. However, the electrical measurements are similar to some other atmospheric pressure, rf capacitively coupled discharge systems with symmetric electrode configurations and different feed gases.

  19. Plasma synthetic jet actuator: electrical and optical analysis of the discharge

    NASA Astrophysics Data System (ADS)

    Belinger, A.; Naudé, N.; Cambronne, J. P.; Caruana, D.

    2014-08-01

    Active flow control is based on the development of robust actuators which are reliable, small and easy to integrate. A promising actuator referred to as plasma synthetic jet actuator produces a synthetic jet with high exhaust velocities and holds the promise of enabling high-speed flows. With this high velocity jet, it is possible to reduce fluid phenomena such as transition and turbulence, thus making it possible to increase an aircraft's performance whilst at the same time reducing its environmental impact. This high velocity jet is produced by a pulsed discharge in a microcavity. In this paper, we focus on the properties of the discharge in order to understand the functioning of the actuator. In the first part an electrical description of the discharge in presented. Afterwards, optical measurements (optical emission spectroscopy and ICCD photograph) enable the determination of temperature, volume and duration of the discharge. At the end of the paper we present an electrical model of the discharge, which can be obtained both from electrical measurements and from macroscopic properties of the discharge (temperature, volume). This electrical model can easily be included in electrical simulation software.

  20. Control of supersonic axisymmetric base flows using passive splitter plates and pulsed plasma actuators

    NASA Astrophysics Data System (ADS)

    Reedy, Todd Mitchell

    influenced considerably, the area-integrated pressure was only slightly affected. Normalized RMS levels indicate that base pressure fluctuations were significantly reduced with the addition of the splitter plates. Power-spectral-density estimates revealed a spectral broadening of fluctuating energy for the 1/2 cylinder configuration and a bimodal distribution for the 1/3 and 1/4 cylinder configurations. It was concluded that the recirculation region is not the most sensitive location to apply flow control; rather, the shear layer may be a more influential site for implementing flow control methodologies. For active flow control, pulsed plasma-driven fluidic actuators were investigated. Initially, the performance of two plasma actuator designs was characterized to determine their potential as supersonic flow control devices. For the first actuator considered, the pulsed plasma jet, electro-thermal heating from an electric discharge heats and pressurizes gas in a small cavity which is exhausted through a circular orifice forming a synthetic jet. Depending on the electrical energy addition, peak jet velocities ranged between 130 to nearly 500 m/s when exhausted to quiescent, ambient conditions. The second plasma actuator investigated is the localized arc filament plasma actuator (LAFPA), which created fluidic perturbations through the rapid, local thermal heating, generated from an electric arc discharge between two electrodes within a shallow open cavity. Electrical and emission properties of the LAFPA were first documented as a function of pressure in a quiescent, no-flow environment. Rotational and vibrational temperatures from N2 spectra were obtained for select plasma conditions and ambient pressures. Results further validate that the assumption of optically thin conditions for these electric arc plasmas is not necessary valid, even at low ambient pressure. Breakdown voltage, sustained plasma voltage, power, and energy per pulse were demonstrated to decrease with

  1. Two-dimensional plasma photonic crystals in dielectric barrier discharge

    SciTech Connect

    Fan Weili; Dong Lifang; Zhang Xinchun

    2010-11-15

    A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested.

  2. Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Setareh, Salarieh; Davoud, Dorranian

    2013-11-01

    In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

  3. Effects of plasma spray parameters on two layer thermal barrier

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1981-01-01

    The power level and the type of arc gas used during plasma spraying of a two layer thermal barrier system (TBS) were found to affect the life of the system. Life at 1095 C in a cyclic furnace test was improved by about 140 percent by increasing the power during plasma spray applications of the bond and thermal barrier coatings. This improvement is due to increases in the densities of the bond and thermal barrier coatings by 3 and 5 percent, respectively. These increases in densities are equivalent to about 45 and 30 percent reduction in mean porosities, respectively. The addition of hydrogen to the argon arc gas had the same effect as the reduction in power level and caused a reduction in TBS life.

  4. Reduced-order modeling of high-speed jets controlled by arc filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Sinha, Aniruddha; Serrani, Andrea; Samimy, Mo

    2013-02-01

    Arc filament plasma actuators applied to high-speed and high Reynolds number jets have demonstrated significant mixing enhancement when operated near the jet column mode (JCM) frequency. A feedback-oriented reduced-order model is developed for this flow from experimental data. The existent toolkit of stochastic estimation, proper orthogonal decomposition, and Galerkin projection is adapted to yield a 35-dimensional model for the unforced jet. Explicit inclusion of a "shift mode" stabilizes the model. The short-term predictive capability of instantaneous flow fields is found to degrade beyond a single flow time step, but this horizon may be adequate for feedback control. Statistical results from long-term simulations agree well with experimental observations. The model of the unforced jet is augmented to incorporate the effects of plasma actuation. Periodic forcing is modeled as a deterministic pressure wave specified on the inflow boundary of the modeling domain. Simulations of the forced model capture the nonlinear response that leads to optimal mixing enhancement in a small range of frequencies near the JCM.

  5. A new plasma-driven pulsed jet actuator for flow control

    NASA Astrophysics Data System (ADS)

    Bonnet, Jean-Paul; Acher, Gwenael; Lebedev, Anton; Benard, Nicolas; Moreau, Eric; Electro-Fluido Group Team

    2015-11-01

    Active flow control requires actuators with enough authority and high frequency response. Synthetic jets can have high frequency response but are rather limited in terms of authority providing the exit velocity is limited. Pressurized (flowing) jets have a very high potential in terms of authority particularly for high velocity flow control purposes. However, for most purposes, high frequency modulation (of order of several kHz) is required in order to excite most unstable modes and to operate in closed mode. Rapid mechanical valves are limited in terms of frequency (up to typically a few hundred of Hz). We develop a new generation of plasma-driven pulsation of flowing jet. The principle is to increase the temperature at the sonic throat through a plasma discharge located at the throat. The flow rate being proportional to the square root of the temperature for a perfect gas, for the same settling chamber pressure, the actuator flow rate can be varied. The frequency is then no limited by any mechanical constraint. A demonstrator has been tested with a 1mm sonic throat. The electric discharge is created by a 10 kV voltage applied between the anode and the throat acting as the cathode. Within these conditions, a 30% modulation of the flow rate can be obtained.

  6. Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings

    SciTech Connect

    Hollis, Kendall J; Pena, Maria I

    2010-01-01

    Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

  7. Temporal modulation of plasma species in atmospheric dielectric barrier discharges

    SciTech Connect

    Yang, Aijun; Wang, Xiaohua E-mail: mzrong@mail.xjtu.edu.cn; Liu, Dingxin; Rong, Mingzhe E-mail: mzrong@mail.xjtu.edu.cn; Kong, Michael G.

    2014-07-15

    The atmospheric pressure dielectric barrier discharge in helium is a pulsed discharge in nature and the moment of maximum species densities is almost consistent with peak discharge current density. In this paper, a one-dimensional fluid model is used to investigate the temporal structure of plasma species in an atmospheric He-N{sub 2} dielectric barrier discharge (DBD). It is demonstrated that there exist microsecond delays of the moments of the maximum electron and ion densities from the peak of discharge current density. These time delays are caused by a competition between the electron impact and Penning ionizations, modulated by the N{sub 2} level in the plasma-forming gas. Besides, significant electron wall losses lead to the DBD being more positively charged and, with a distinct temporal separation in the peak electron and cation densities, the plasma is characterized with repetitive bursts of net positive charges. The temporal details of ionic and reactive plasma species may provide a new idea for some biological processes.

  8. Structure of propagating arc in a magneto-hydrodynamic rail plasma actuator

    NASA Astrophysics Data System (ADS)

    Gray, Miles D.; Choi, Young-Joon; Sirohi, Jayant; Raja, Laxminarayan L.

    2016-01-01

    The spatio-temporal evolution of a magnetically driven arc in a rail plasma flow actuator has been characterized with high-speed imaging, electrical measurements, and spectroscopy. The arc draws a peak current of ~1 kA. High-speed framing cameras were used to observe the complex arc propagation phenomenon. In particular, the anode and cathode roots were observed to have different modes of transit, which resulted in distinct types of electrode degradation on the anode and cathode surfaces. Observations of the arc electrical properties and induced magnetic fields are used to explain the transit mechanism of the arc. Emission spectroscopy revealed the arc temperature and species composition as a function of transit distance of the arc. The results obtained offer significant insights into the electromagnetic properties of the arc-rail system as well as arc-surface interaction phenomena in a propagating arc.

  9. Nonintrusive microwave diagnostics of collisional plasmas in Hall thrusters and dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Stults, Joshua

    This research presents a numerical framework for diagnosing electron properties in collisional plasmas. Microwave diagnostics achieved a significant level of development during the middle part of the last century due to work in nuclear weapons and fusion plasma research. With the growing use of plasma-based devices in fields as diverse as space propulsion, materials processing and fluid flow control, there is a need for improved, flexible diagnostic techniques suitable for use under the practical constraints imposed by plasma fields generated in a wide variety of aerospace devices. Much of the current diagnostic methodology in the engineering literature is based on analytical diagnostic, or forward, models. The Appleton-Hartree formula is an oft-used analytical relation for the refractive index of a cold, collisional plasma. Most of the assumptions underlying the model are applicable to diagnostics for plasma fields such as those found in Hall Thrusters and dielectric barrier discharge (DBD) plasma actuators. Among the assumptions is uniform material properties, this assumption is relaxed in the present research by introducing a flexible, numerical model of diagnostic wave propagation that can capture the effects of spatial gradients in the plasma state. The numerical approach is chosen for its flexibility in handling future extensions such as multiple spatial dimensions to account for scattering effects when the spatial extent of the plasma is small relative to the probing beam's width, and velocity dependent collision frequency for situations where the constant collision frequency assumption is not justified. The numerical wave propagation model (forward model) is incorporated into a general tomographic reconstruction framework that enables the combination of multiple interferometry measurements. The combined measurements provide a quantitative picture of the spatial variation in the plasma properties. The benefit of combining multiple measurements in a coherent

  10. Study of internal transport barrier triggering mechanism in tokamak plasmas

    SciTech Connect

    Dong, J.Q.; Mou, Z.Z.; Long, Y.X.; Mahajan, S.M.

    2004-12-01

    Sheared flow layers driven by magnetic energy, released in tearing-reconnection processes inherent in dissipative magnetohydrodynamics, are proposed as a triggering mechanism for the creation of the internal transport barrier (ITB) in tokamak plasmas. The double tearing mode, mediated by anomalous electron viscosity in configurations with a nonmonotonic safety factor, is investigated as an example. Particular emphasis is placed on the formation of sheared poloidal flow layers in the vicinity of the magnetic islands. A quasilinear simulation demonstrates that the sheared flows induced by the mode have desirable characteristics (lying just outside the magnetic islands), and sufficient levels required for ITB formation. A possible explanation is also proffered for the experimental observation that the transport barriers are preferentially formed in the proximity of low-order rational surfaces.

  11. [Study on Chemical Kinetic Effect of Dielectric Barrier Discharge Plasma].

    PubMed

    Zrang, Peng; Hong, Yan-ji; Shen, Shuang-yan; Ding, Xiao-yu; Ma, Di

    2015-03-01

    To reveal the mechanism of plasma (assisted the ignition process of methane/air further, schematic of dielectric barrier discharge plasma system with atmospheric air was designed and set up, the emission spectrum of dielectric barrier discharge plasma with atmospheric air was measured, and the active particles produced by the interaction of dielectric barrier discharge plasma with atmospheric air were analyzed with the spectrum technology, the ignition model and calculation methods of sensitivity analysis and reaction path analysis were given, effects of NO and O3 on the ignition delay time were simulated, and the chemical kinetics mechanism of NO and O3 assisted ignition was revealed via sensitivity analysis and reaction path analysis. The results show that main excited particles of N2 and O3 are generated via effect of plasma on the atmospheric air, which are converted into active particles of NO(ξ) and O3 in the end, the life of which are longer than any other active particles, effects of plasma on the ignition is simplified as effects of NO(ξ) and O3 on the ignition; NO and O3 could reduce the ignition delay time significantly, but the amplitude decrease with increase of the initial temperature, this is because the rate of ignition is decided by the oxidation rate of CH3, the oxidized pathway of CH3 is R155 and R156 for auto-ignition and their rates are slower when temperature is low, so the ignition delay time of methane/air is longer; NO could reduce the ignition delay time significantly because of the oxidized pathway of CH3 is changed to R327 CH3O2 + NO = CH3O + NO2, R328 CH3 + NO2 = CH3O + NO for NO(ξ) (assisted ignition process from R155 and R156 for auto-ignition; and the chemical kinetic effect is the dominating factor of O3 on the ignition and which change the reaction path. PMID:26117883

  12. Numerical simulations of tokamak plasma turbulence and internal transport barriers

    NASA Astrophysics Data System (ADS)

    Thyagaraja, A.

    2000-12-01

    A wide variety of magnetically confined plasmas, including many tokamaks such as the JET, TFTR, JT-60U, DIII-D, RTP, show clear evidence for the existence of the so-called `internal transport barriers' (ITBs) which are regions of relatively good confinement, associated with substantial gradients in temperature and/or density. A computational approach to investigating the properties of tokamak plasma turbulence and transport is developed. This approach is based on the evolution of global, two-fluid, nonlinear, electromagnetic plasma equations of motion with specified sources. In this paper, the computational model is applied to the problem of determining the nature and physical characteristics of barrier phenomena, with particular reference to RTP (electron-cyclotron resonance heated) and JET (neutral beam heated) observations of ITBs. The simulations capture features associated with the formation of these ITBs, and qualitatively reproduce some of the observations made on RTP and JET. The picture of plasma turbulence suggested involves variations of temperature and density profiles induced by the electromagnetic fluctuations, on length scales intermediate between the system size and the ion Larmor radius, and time scales intermediate between the confinement time and the Alfvén time (collectively termed `mesoscales'). The back-reaction of such profile `corrugations' (features exhibiting relatively high local spatial gradients and rapid time variations) on the development and saturation of the turbulence itself plays a key role in the nonlinear dynamics of the system. The corrugations are found to modify the dynamical evolution of radial electric field shear and the bootstrap current density, which in turn influence the turbulence. The interaction is mediated by relatively long wavelength, electromagnetic modes excited by an inverse cascade and involving nonlinear instabilities and relaxation phenomena such as intermittency and internal mode locking.

  13. Influence of geometrical parameters on performance of plasma synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Zong, Hao-hua; Wu, Yun; Jia, Min; Song, Hui-min; Liang, Hua; Li, Ying-hong; Zhang, Zhi-bo

    2016-01-01

    Plasma synthetic jet actuator (PSJA) has shown wide and promising application prospects in a high speed flow control field, due to its rapid response, high exhaust velocity, and non-moving components. In this paper, the total pressure profile of a plasma synthetic jet (PSJ) is measured and a new method is developed to evaluate the pulsed thrust of the PSJA. The influence of geometrical parameters including the electrode distance, the orifice diameter, and the throat length on PSJA performance is analyzed based on the pulsed thrust, the discharge characteristics, and the schlieren images. When varying the electrode distance, the dominant factor determining the jet intensity is the heating volume instead of the discharge energy. For the arc discharge, the electrode distance should be extended to increase both the jet velocity and the jet duration time. The design of the orifice diameter should be based on the controlled flow field. A large orifice diameter produces a strong perturbation with short time duration, while a small orifice diameter induces a lasting jet with low mass flux. In order to obtain better high frequency performance, the throat length should be shortened on the condition that the structural strength of the PSJA is maintained, while there is almost no influence of the throat length on the single cycle performance of the PSJA. Once the discharge energy is fixed, the pulsed thrust remains almost unchanged with different orifice diameters and throat lengths. These three geometrical parameters are independent to some extent and can be optimized separately.

  14. Coherent structures in plasma-actuator controlled supersonic jets: Axisymmetric and mixed azimuthal modes

    NASA Astrophysics Data System (ADS)

    Gaitonde, D. V.; Samimy, M.

    2011-09-01

    High-fidelity simulations are employed to study the effect of eight localized arc filament plasma actuators placed around the periphery of a Mach 1.3 converging-diverging nozzle exit. Emphasis is placed on understanding the coherent structures generated by axisymmetric (m = 0), flapping or first mixed (m = ±1) and second mixed (m = ±2) modes, which are excited at the jet column-mode frequency corresponding to a Strouhal number based on jet diameter of 0.3. Baseline (no control) and constant excitation (actuators on continuously) cases are also simulated. Comparisons with experimental results indicate that the computational model reproduces the main features induced by the actuators. Furthermore, the mean flow exhibits many similarities with the theoretical predictions of Cohen and Wygnanski [J. Fluid Mech. 176, 221 (1987)]. Overall, the results indicate a complex coherent structure generation, evolution, and disintegration process. For m = ±1, the phase-averaged flow reveals successive distorted elliptic vortex rings with axes in the flapping plane but alternating on either side of the jet axis. This generates a chain of structures each of which interacts with its predecessor on one side of the major plane and its successor on the other. Through self and mutual induction, the leading segment of each loop is pinched and passes through the previous ring before rapidly breaking up. The m = ±2 mode yields elliptic structures with major axes of successive rings being aligned with the two symmetry planes, which are orthogonal to each other. The minor axis side is pulled downstream faster than the rest of the structure because of the higher velocity near the jet centerline and self-induced effects, yielding a horse-shoe shape when viewed in profile. The m = 0 mode exhibits axisymmetric roll-up events, with vortex ribs in the braid regions connecting successive large coherent structures. The constant excitation (with largest energy input) and baseline cases are similar

  15. Characteristics of dielectric barrier discharge plasmas in atmospheric humid air

    NASA Astrophysics Data System (ADS)

    Fukuda, Y.; Fukui, K.; Iwami, R.; Matsuoka, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2012-10-01

    Atmospheric pressure plasmas have a great advantage for industrial applications such as surface modifications, sterilization and film preparation. In particular, reactive plasmas including OH radicals can be generated in humid air. On the other hand, it is known that dielectric barrier discharge (DBD) plasmas in air are strongly affected by humidity. In this study, a twisted pair sample is used as a DBD electrode. The twisted pair consists of two enameled wires, and it is installed in a climate chamber to control ambient temperature and humidity. Repetitive impulse voltage pulses were applied to the twisted pair to produce DBD plasmas. Light emission, electromagnetic wave and current pulses were used to detect discharge activities. The discharge inception voltage (DIV) is basically determined by Paschen curve in air, however, the DIV was decreased by increasing the humidity. In addition, it was found that there were largely scattered data of DIV at the low humidity condition. After the pre-discharges, the DIV reached to the steady state value. On the other hand, there was no scattering of the observed DIV at the high humidity condition. Measurements of surface potential of the sample after the discharge show these behaviors could be explained by surface charge accumulation on the enameled wire. It is noted that there was no fluctuation in the DIV data in the case of unipolar voltage pulse.

  16. Plasma and ion barrier for electron beam spot stability

    SciTech Connect

    Kwan, T.J.T.; Snell, C.M.

    1999-04-01

    The concept of a self-biased target to spatially confine the ions generated by the bombardment of intense electron beams on bremsstrahlung conversion targets has been predicted by computer simulation and further verified by experiments at the Integrated Test Stand for DARHT at Los Alamos National Laboratory. This technical article reports an alternative method of containing the plasmas and ions from the bremsstrahlung conversion target if the energy density of the electron beam is below a certain threshold. With the proposed changes of the electron beam parameters of the second axis of DARHT, the authors are able to show that a thin (0.5 mm) metallic barrier such as pure beryllium, or boron carbide with desirable thermal properties, is sufficiently transparent to the 20 MeV DARHT beam and at the same time able to confine the ions between the target and the barrier foil. The temperature rise in the foil due to energy deposited by the electron beam is expected to be below the melting point of the materials for the first three pulses. More important, they have shown in their time dependent particle-in-cell simulations that the deployment of a barrier situated 1 to 2 cm away from the converter target can achieve the ion confinement needed for the stability of the electron beam spot.

  17. Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate

    SciTech Connect

    Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

    2014-12-09

    This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

  18. Efficiency of plasma actuator ionization in shock wave modification in a rarefied supersonic flow over a flat plate

    NASA Astrophysics Data System (ADS)

    Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

    2014-12-01

    This paper describes experimental and numerical investigations focused on the shock wave modification, induced by a dc glow discharge, of a Mach 2 flow under rarefied regime. The model under investigation is a flat plate equipped with a plasma actuator composed of two electrodes. The glow discharge is generated by applying a negative potential to the upstream electrode, enabling the creation of a weakly ionized plasma. The natural flow (i.e. without the plasma) exhibits a thick laminar boundary layer and a shock wave with a hyperbolic shape. Images of the flow obtained with an ICCD camera revealed that the plasma discharge induces an increase in the shock wave angle. Thermal effects (volumetric, and at the surface) and plasma effects (ionization, and thermal non-equilibrium) are the most relevant processes explaining the observed modifications. The effect induced by the heating of the flat plate surface is studied experimentally by replacing the upstream electrode by a heating element, and numerically by modifying the thermal boundary condition of the model surface. The results show that for a similar temperature distribution over the plate surface, modifications induced by the heating element are lower than those produced by the plasma. This difference shows that other effects than purely thermal effects are involved with the plasma actuator. Measurements of the electron density with a Langmuir probe highlight the fact that the ionization degree plays an important role into the modification of the flow. The gas properties, especially the isentropic exponent, are indeed modified by the plasma above the actuator and upstream the flat plate. This leads to a local modification of the flow conditions, inducing an increase in the shock wave angle.

  19. Improving thrust by pulse-induced breakdown enhancement in AC surface dielectric barrier discharge actuators for airflow control

    NASA Astrophysics Data System (ADS)

    Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng

    2016-07-01

    The characteristics of a plate-to-plate AC surface dielectric barrier discharge (SDBD) actuator using the pulse-induced breakdown enhancing method are experimentally investigated. The encapsulated electrode is supplied with a sine high AC voltage, while the exposed electrode is feed by a synchronized pulse voltage. Based on the thrust force and power consumption measurements, a parametric study was performed using a positive pulse applied at the trough phase of the AC cycles in which the thrust force was observed to increase by about 100% to 300% and the efficiency up to about 100% compared with the AC-only supply conditions for different AC voltages within the tested range. The pulse-induced breakdown effect was analyzed from the electrical and light emission waveforms to reveal the underlying mechanism. The surface potential due to the charge deposition effect was also measured using a specially designed corona-like discharge potential probe. It is shown that the pulse-induced breakdown was able to cause a temporarily intensified local electric field to enhance the glow-like discharge and meanwhile increase the time-average surface potential in the region further downstream. The improvement in the force by the enhancement in the pulse-induced breakdown was mainly due to enhancements in the glow-like discharge and the surface potential increment, with the latter being more important when the AC voltage is higher.

  20. MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM

    SciTech Connect

    V.K. Mathur

    2003-02-01

    In the past decade, the emission of toxic elements from human activities has become a matter of great public concern. Hg, As, Se and Cd typically volatilize during a combustion process and are not easily caught with conventional air pollution control techniques. In addition, there is no pollution prevention technique available now or likely be available in the foreseeable future that can prevent the emission of these trace elements. These trace elements pose additional scientific challenge as they are present at only ppb levels in large gas streams. Mercury, in particular, has attracted significant attention due to its high volatility, toxicity and potential threat to human health. In the present research work, a non-thermal plasma dielectric barrier discharge technique has been used to oxidize Hg{sup 0}(g) to HgO. The basic premise of this approach is that Hg{sup 0} in vapor form cannot be easily removed in an absorption tower whereas HgO as a particulate is amiable to water scrubbing. The work presented in this report consists of three steps: (1) setting-up of an experimental apparatus to generate mercury vapors at a constant rate and modifying the existing non-thermal plasma reactor system, (2) solving the analytical challenge for measuring mercury vapor concentration at ppb level, and (3) conducting experiments on mercury oxidation under plasma conditions to establish proof of concept.

  1. Plasma chemistry in CO2 dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Brehmer, F.; Welzel, S.; van de Sanden, M. C. M.; Engeln, R.

    2013-09-01

    Plasma-assisted gas phase conversion in non-thermal environments is increasingly being considered as promising technology for fuel production from CO2 and hydrogen containing sources. Particularly the rate-limiting activation of CO2 is suggested to be tackled in plasmas at (sub-)atmospheric pressure conditions without the admixture of carrier gases. Therefore CO2 dielectric barrier discharges were studied to assess conversion yields and reaction mechanisms. The CO2 discharges were resonantly excited at around 100 kHz in a flow-tube lab-scale reactor designed to facilitate time-resolved in-situ optical emission and infrared laser absorption spectroscopy. Complementary analysis of the gas phase constituents using ex-situ FT-IR spectroscopy and a thorough electrical characterisation were carried out. The CO conversion yields were typically below 5% and hence in-line with similar studies. The energy efficiency can be uniformly described for different external plasma parameters (e.g. flow rate, power input, excitation frequency) as function of the specific energy input. Special attention was paid to the non-negligible formation of by-products such as O3 and O2 which suggests an inefficient recycling of atomic oxygen in secondary CO2 dissociation reactions.

  2. Superior Thermal Barrier Coatings Using Solution Precursor Plasma Spray

    NASA Astrophysics Data System (ADS)

    Jordan, E. H.; Xie, L.; Gell, M.; Padture, N. P.; Cetegen, B.; Ozturk, A.; Ma, X.; Roth, J.; Xiao, T. D.; Bryant, P. E. C.

    2004-03-01

    A novel process, solution precursor plasma spray (SPPS), is presented for depositing thermal barrier coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting coatings microstructure has three unique features: (1) ultra fine splats (1 µm), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) coatings. The conductivity of SPPS coatings is lower than EB-PVD coatings and higher than the best APS coatings. Manufacturing cost is expected to be similar to APS coatings and much lower than EB-PVD coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.

  3. Extremum Seeking Adaptive Separation Control on a Wing with Plasma Synthetic Jet Actuator

    NASA Astrophysics Data System (ADS)

    Ogawara, Kakuji; Kojima, Ryota; Matsumoto, Shoji; Shingin, Hidenori

    Plasma synthetic jet actuator (PSJA) is a flow control device which has structure that insulator is tucked with electrode pair. It generates electrohydrodynamic (EHD) effect and induces a flow. The experiment was held to investigate the effect of flow control using extremum seeking with PSJA placed on the surface of NACA0012 wing installed in the wind tunnel. Frequency of the input signal to PSJA is modulated to maximize the effect of PSJA in flow control. The wake velocity fluctuation is one of indexes on separation control effect. The wake velocity is minimized over the input frequency by employing extremum seeking. The seeking algorithm calculates the correlation of the modulation frequency and wake velocity fluctuation. The modulation signal frequency where the correlation changes from negative to positive minimizes the wake velocity fluctuation. To detect a local minimum of the wake velocity fluctuation by extremum seeking, it is necessary to change the modulation signal frequency with time. Sine and square waves change the modulation signal frequency to PSJA. The wind tunnel speed was changed as an external factor. The experimental results show that the modulation signal frequency can track the optimum value when the wind tunnel speed is changed. This paper shows that adaptive flow control to optimize the modulation signal frequency with PSJA using extremum seeking enables to suppress turbulence on the flow field of wings.

  4. Efficient global optimization applied to wind tunnel evaluation-based optimization for improvement of flow control by plasma actuators

    NASA Astrophysics Data System (ADS)

    Kanazaki, Masahiro; Matsuno, Takashi; Maeda, Kengo; Kawazoe, Hiromitsu

    2015-09-01

    A kriging-based genetic algorithm called efficient global optimization (EGO) was employed to optimize the parameters for the operating conditions of plasma actuators. The aerodynamic performance was evaluated by wind tunnel testing to overcome the disadvantages of time-consuming numerical simulations. The proposed system was used on two design problems to design the power supply for a plasma actuator. The first case was the drag minimization problem around a semicircular cylinder. In this case, the inhibitory effect of flow separation was also observed. The second case was the lift maximization problem around a circular cylinder. This case was similar to the aerofoil design, because the circular cylinder has potential to work as an aerofoil owing to the control of the flow circulation by the plasma actuators with four design parameters. In this case, applicability to the multi-variant design problem was also investigated. Based on these results, optimum designs and global design information were obtained while drastically reducing the number of experiments required compared to a full factorial experiment.

  5. Diagnostics of Argon Inductively Coupled Plasma and Dielectric Barrier Discharge Plasma by Optical Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-liang; Yu, Shi-ji; Ma, Teng-cai; Deng, Xin-lu

    2001-08-01

    An experimental setup was built up to carry out radio frequency (RF) inductively coupled plasma (ICP) and dielectric barrier discharge (DBD), and to depict the optical emission spectra (OES) of the discharges. OES from argon ICP and DBD plasmas in visible and near ultraviolet region were measured. For argon ICP, the higher RF power input (higher than 500 W for our machine), the higher degree of argon plasma ionization. But that doesn't mean a higher mean electron energy. With the increase in the power input, the mean electron energy increases slightly, whereas the density of electron increases apparently. Or, the contrary, argon DBD discharge behaves in the manner of a pulsed DC discharge on optical emission spectroscopy and V-I characteristics. DBD current is composed of a series of pulses equally spaced in temporal domain. The kinetics of DBD emission strength is mainly governed by the frequency of the current pulse.

  6. Effect of dielectric and liquid on plasma sterilization using dielectric barrier discharge plasma.

    PubMed

    Mastanaiah, Navya; Johnson, Judith A; Roy, Subrata

    2013-01-01

    Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ≥ 6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ≥ 6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C-66 °C (for FR4) and 20 °C-49 °C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

  7. Effect of Dielectric and Liquid on Plasma Sterilization Using Dielectric Barrier Discharge Plasma

    PubMed Central

    Mastanaiah, Navya; Johnson, Judith A.; Roy, Subrata

    2013-01-01

    Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ≥6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ≥6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C–66°C (for FR4) and 20°C–49°C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

  8. Control of a shock wave-boundary layer interaction using localized arc filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Webb, Nathan Joseph

    Supersonic flight is currently possible, but expensive. Inexpensive supersonic travel will require increased efficiency of high-speed air entrainment, an integral part of air-breathing propulsion systems. Although mixed compression inlet geometry can significantly improve entrainment efficiency, numerous Shock Wave-Boundary Layer Interactions (SWBLIs) are generated in this configuration. The boundary layer must therefore develop through multiple regions of adverse pressure gradient, causing it to thicken, and, in severe cases, separate. The associated increase in unsteadiness can have adverse effects on downstream engine hardware. The most severe consequence of these interactions is the increased aerodynamic blockage generated by the thickened boundary layer. If the increase is sufficient, it can choke the flow, causing inlet unstart, and resulting in a loss of thrust and high transient forces on the engine, airframe, and aircraft occupants. The potentially severe consequences associated with SWBLIs require flow control to ensure proper operation. Traditionally, boundary layer bleed has been used to control the interaction. Although this method is effective, it has inherent efficiency penalties. Localized Arc Filament Plasma Actuators (LAFPAs) are designed to generate perturbations for flow control. Natural flow instabilities act to amplify certain perturbations, allowing the LAFPAs to control the flow with minimal power input. LAFPAs also have the flexibility to maintain control over a variety of operating conditions. This work seeks to examine the effectiveness of LAFPAs as a separation control method for an oblique, impinging SWBLI. The low frequency unsteadiness in the reflected shock was thought to be the natural manifestation of a Kelvin-Helmholtz instability in the shear layer above the separation region. The LAFPAs were therefore placed upstream of the interaction to allow their perturbations to convect to the receptivity region (near the shear layer origin

  9. Dielectric barrier discharge plasma induced degradation of aqueous atrazine.

    PubMed

    Feng, Jingwei; Jiang, Lin; Zhu, Dan; Su, Kuizu; Zhao, Dayong; Zhang, Jibiao; Zheng, Zheng

    2016-05-01

    Degradation of herbicide atrazine in aqueous solution was investigated using a plate type dielectric barrier discharge (DBD) plasma reactor. DBD plasma was generated at the gas-liquid interface of the formed water film. At discharge time of 14 min, atrazine was degradated effectively with a degradation rate of 99 % at the discharge power of 200 W. The experimental data fitted well with first-order kinetics and the energy efficiency for 90 % degradation of atrazine (G value) was calculated, obtaining a rate constant of 0.35 min(-1) and a G value of 1.27 × 10(-10) mol J(-1) (98.76 mg kW(-1) h(-1)) at a discharge power of 200 W, respectively. The addition of Fe(2+) increased the rate constant and G value dramatically, and a significant decrease of the rate constant and G value was observed with the addition of radical scavengers (tert-butyl alcohol, isopropyl alcohol, or Na2CO3). The generated aqueous O3 and H2O2 were determined, which promoted the degradation of herbicide atrazine. Dechlorination was observed and the experimentally detected Cl(-) was 1.52 mg L(-1) at a discharge time of 14 min. The degradation intermediates of atrazine were detected by means of liquid chromatography-mass spectrometry; dechlorination, hydroxylation, dealkylation, and alkyl oxidation processes were involved in the degradation pathways of atrazine. PMID:26832879

  10. Enhanced Design of Turbo-jet LPT by Separation Control Using Phased Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Ashpis, David (Technical Monitor); Corke, Thomas C.; Thomas, Flint O.

    2003-01-01

    This work deals with the documentation and control of flow separation that occurs over turbine blades in the low-pressure turbine stage at low Reynolds numbers that exist at high altitude cruise. We utilize a specially constructed linear cascade that is designed to study the flow field over a generic LPT cascade consisting of Pratt & Whitney 'Pak B' shaped blades. This facility was constructed under a previous one-year NASA Glenn RC initiative. The center blade in the cascade is instrumented to measure the surface pressure coefficient distribution. Optical access allows two-component LDV measurement for boundary layer profiles. Experimental conditions have been chosen to give a range of chord Reynolds numbers from 10 to 100K, and a range of free-stream turbulence levels from u'/U(sub infinity)= 0.08 to 3 percent. The surface pressure measurements were used to define a region of separation and reattachment that depend on the free-stream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, reattachment location was very sensitive to the turbulence level and Reynolds number. Excellent agreement was found between the measured pressure distributions and predictions from Euler and RANS simulations. Two-component LDV measurements are presently underway to document the mean and fluctuating velocity components in the boundary layer over the center blade for the range of experimental conditions. The fabrication of the plasma actuator is underway. These are designed to produce either streamwise vortices, or a downstream-directed wall jet. A precursor experiment for the former approach was performed with an array of vortex generators placed just upstream of the separation line. These led to reattachment except for the lowest Reynolds number. Progress has also been made on the proposed concept for a laterally moving wake. This involved constructing a smaller wind tunnel and molding an array of symmetric airfoils

  11. Micronucleus formation induced by dielectric barrier discharge plasma exposure in brain cancer cells

    NASA Astrophysics Data System (ADS)

    Kaushik, Nagendra K.; Uhm, Hansup; Ha Choi, Eun

    2012-02-01

    Induction of micronucleus formation (cytogenetic damage) in brain cancer cells upon exposure of dielectric barrier discharge plasma has been investigated. We have investigated the influence of exposure and incubation times on T98G brain cancer cells by using growth kinetic, clonogenic, and micronucleus formation assay. We found that micronucleus formation rate directly depends on the plasma exposure time. It is also shown that colony formation capacity of cells has been inhibited by the treatment of plasma at all doses. Cell death and micronucleus formation are shown to be significantly elevated by 120 and 240 s exposure of dielectric barrier discharge plasma.

  12. Plasma Surface Modification of Polymer Backsheets: Origins of Future Interfacial Barrier/Backsheet Failure

    SciTech Connect

    Pankow, J. W.; Glick, S. H.

    2005-11-01

    Flexible polymer substrates coated with inorganic oxide moisture barriers are a potential replacement for glass backsheets in thin film PV modules. Silicon oxynitride (SiOxNy) deposited by PECVD on polyethylene terephthalate (PET) represents one potential new backsheet candidate. Barrier deposition runs at NREL have typically included a nitrogen-rich plasma pretreatment prior to actual barrier deposition with the intention of cleaning the PET surface as well as enhancing adhesion of the SiOxNy barrier film to PET; however, test coupons of PET/barrier/EVA/TPE failed after damp heat exposure. PET substrates exposed to plasma conditions similar to those used in pre-treatment were examined by X-ray photoelectron spectroscopy (XPS) to reveal new low molecular weight PET fragments are created which are volatile upon heating and water soluble. Failure analysis of the coupons determined that the moisture barrier is, in fact, transferred to the encapsulant side.

  13. Plasma diagnostic techniques in thermal-barrier tandem-mirror fusion experiments

    SciTech Connect

    Silver, E.H.; Clauser, J.F.; Carter, M.R.; Failor, B.H.; Foote, J.H.; Hornady, R.S.; James, R.A.; Lasnier, C.J.; Perkins, D.E.

    1986-08-29

    We review two classes of plasma diagnostic techniques used in thermal-barrier tandem-mirror fusion experiments. The emphasis of the first class is to study mirror-trapped electrons at the thermal-barrier location. The focus of the second class is to measure the spatial and temporal behavior of the plasma space potential at various axial locations. The design and operation of the instruments in these two categories are discussed and data that are representative of their performance is presented.

  14. In-situ formation of multiphase air plasma sprayed barrier coatings for turbine components

    DOEpatents

    Subramanian, Ramesh

    2001-01-01

    A turbine component (10), such as a turbine blade, is provided which is made of a metal alloy (22) and a base, planar-grained thermal barrier layer (28) applied by air plasma spraying on the alloy surface, where a heat resistant ceramic oxide overlay material (32') covers the bottom thermal barrier coating (28), and the overlay material is the reaction product of the precursor ceramic oxide overlay material (32) and the base thermal barrier coating material (28).

  15. Fatigue testing of plasma-sprayed thermal barrier coatings, volume 2

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Nagy, A.; Popelar, C. F.

    1990-01-01

    A plasma sprayed thermal barrier coating for diesel engines were fatigue tested. Candidate thermal barrier coating materials were fatigue screened and a data base was generated for the selected candidate material. Specimen configurations are given for the bend fatigue tests, along with test setup, specimen preparation, test matrix and procedure, and data analysis.

  16. Improving plasma actuator performance at low pressure, and an analysis of the pointing capabilities of cubeSats using Plasmonic Force Propulsion (PFP) thrusters

    NASA Astrophysics Data System (ADS)

    Friz, Paul Daniel

    This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites. The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried electrodes produced 26% more thrust overall and 34% more thrust at low pressure than the standard 15 mm design. The second half details work done modeling small satellite attitude and reaction control systems in order to compare the use of Plasmonic Force Propulsion thrusters with other state of the art reaction control systems. The model uses bang bang control algorithms and assumes the worst case scenario solar radiation pressure is the only disturbing force. It was found that the estimated 50-500 nN of thrust produced by PFP thrusters would allow the spacecraft which use them extremely high pointing and positioning accuracies (<10-9 degrees and 3 pm). PFP thrusters still face many developmental challenges such as increasing specific impulse which require more research, however, they have great potential to be an enabling technology for future NASA missions such as the Laser Interferometer Space Antenna, and The Stellar Imager.

  17. Ideal MHD stability of double transport barrier plasmas in DIII-D

    NASA Astrophysics Data System (ADS)

    Li, G. Q.; Wang, S. J.; Lao, L. L.; Turnbull, A. D.; Chu, M. S.; Brennan, D. P.; Groebner, R. J.; Zhao, L.

    2008-01-01

    The ideal MHD stability for double transport barrier (DTB or DB) plasmas with varying edge and internal barrier width and height was investigated, using the ideal MHD stability code GATO. A moderate ratio of edge transport barriers (ETB) height to internal transport barriers (ITBs) height is found to be beneficial to MHD stability and the βN is limited by global low n instabilities. For moderate ITB width DB plasmas, if the ETB is weak, the stability is limited by n = 1 (n is the toroidal mode number) global mode; whereas if the ETB is strong it is limited by intermediate-n edge peeling-ballooning modes. Broadening the ITB can improve stability if the ITB half width wi lsim 0.3. For very broad ITB width plasmas the stability is limited by stability to a low n (n > 1) global mode.

  18. Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation

    NASA Astrophysics Data System (ADS)

    Kang, Chen; Hua, Liang

    2016-02-01

    Plasma flow control (PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle (UAV) by nanosecond discharge plasma aerodynamic actuation (NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge (30 A) is much bigger than that for millisecond discharge (0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation (MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control. Project supported by the National Natural Science Foundation of China (Grant Nos. 61503302, 51207169, and 51276197), the China Postdoctoral Science Foundation (Grant No. 2014M562446), and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2015JM1001).

  19. Plasma Surface Modification of Polymer Backsheets: Origins of Future Interfacial Barrier/Backsheet Failure (Poster)

    SciTech Connect

    Pankow, J. W.; Glick, S. H.

    2006-05-01

    Flexible polymer substrates coated with inorganic oxide moisture barriers are a potential replacement for glass backsheets in thin-film PV (photovoltaic) modules. Silicon oxynitride (SiO{sub x}N{sub y}) deposited by plasma enhanced chemical vapor deposition (PECVD) on polyethylene terephthalate (PET) represents one potential new backsheet candidate. Barrier deposition runs at NREL have included a nitrogen-rich plasma pretreatment prior to barrier deposition with the intention of cleaning the PET surface and enhancing adhesion of the SiO{sub x}N{sub y} barrier film to PET; however, test coupons of PET/barrier/EVA/TPE failed after damp-heat exposure. (EVA is ethylene vinyl acetate and TPE is Tedlar{reg_sign}-PET-EVA). PET substrates exposed to plasma conditions similar to those used in pretreatment were examined by X-ray photoelectron spectroscopy (XPS) to reveal that new low molecular weight PET fragments were created at the PET surface. These fragments are responsible for barrier/PET interfacial failure and barrier transfer to the EVA encapsulant side following damp heat exposure.

  20. Miniaturized Argon Plasma: Neutral Gas Characteristics in Dielectric Barrier Discharge

    NASA Astrophysics Data System (ADS)

    Ashraf, Farahat

    2015-10-01

    Plasma-neutral gas dynamics is computationally investigated in a miniaturized microthruster that encloses Ar and contains dielectric material sandwiched between two metal plates using a two-dimensional plasma mode. Spatial and temporal plasma properties are investigated by solving the Poisson equation with the conservation equations of charged and excited neutral plasma species using the COMSOL Multiphysics 4.2b. The microthruster property is found to depend on the secondary electron emission coefficient. The electrohydrodynamic force (EHD) is calculated and found to be significant in the sheath area near the dielectric layer and is found to affect gas flow dynamics including the Ar excimer formation and density. The effects of pressure and secondary emission coefficient are discussed. The plasma characteristics are affected by small changes in the secondary electron emission coefficient, which could result from the dielectric erosion and aging, and is found to affect the electrohydrodynamic force produced when the microthruster is used to produce thrust for a small spacecraft.

  1. Feasibility study of plasma sprayed Al2O3 coatings as diffusion barrier on CFC components

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Zhao, Lidong; Kopp, Nils; Warda, Thomas

    2012-12-01

    Carbon fibre reinforced carbon (CFC) materials are increasingly applied as sample carriers in modern furnaces. Only their tendency to react with different metals at high temperatures by C-diffusion is a disadvantage, which can be solved by application of diffusion barriers. Within this study the feasibility of plasma sprayed Al2O3 coatings as diffusion barrier was studied. Al2O3 coatings were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure, bonding to CFC substrates and thermal stability. The results showed that Al2O3 could be well deposited onto CFC substrates. The coatings had a good bonding and thermal shock behavior at 1060°C. At higher temperature of 1270°C, crack network formed within the coating, showing that the plasma sprayed Al2O3 coatings are limited regarding to their application temperatures as diffusion barrier on CFC components.

  2. Development of a stable dielectric-barrier discharge enhanced laminar plasma jet generated at atmospheric pressure

    SciTech Connect

    Tang Jie; Li Shibo; Zhao Wei; Wang Yishan; Duan Yixiang

    2012-06-18

    A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N{sub 2} and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions and electrons.

  3. Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma

    NASA Astrophysics Data System (ADS)

    Pu, Sichuan; Chen, Jierong; Wang, Gang; Li, Xiaoyong; Ma, Yun

    2013-05-01

    The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

  4. Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma

    SciTech Connect

    Pu, Sichuan; Chen, Jierong; Wang, Gang; Li, Xiaoyong; Ma, Yun

    2013-05-13

    The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

  5. Tunable one-dimensional plasma photonic crystals in dielectric barrier discharge

    SciTech Connect

    Fan Weili; Dong Lifang

    2010-07-15

    A tunable one-dimensional plasma photonic crystal is obtained by using a dielectric barrier discharge with two liquid electrodes. It is formed by the self-organization of the filaments, rather than that in an artificial array of electrodes. The dispersion relations of the plasma photonic crystals are calculated by solving the Helmholtz equation using a method analogous to Kronig-Penney's problem. The photonic band diagrams of the plasma photonic crystals are studied when changing the filling factor, the lattice constant, and the electron density, based on the experimental results. The critical electron density is given, beyond which the plasma photonic crystal will have a remarkable band structure.

  6. Capillary Dielectric Barrier Discharge: Transition from Soft Ionization to Dissociative Plasma.

    PubMed

    Klute, Felix David; Michels, Antje; Schütz, Alexander; Vadla, Cedomil; Horvatic, Vlasta; Franzke, Joachim

    2016-05-01

    A capillary He dielectric barrier discharge was investigated with respect to its performance as a soft or dissociative ionization source. Spatiotemporal measurements of the plasma emission showed that in one voltage duty cycle the plasma evolved from a soft to dissociative ionization source. At the earliest time, the soft plasma was generated between the electrodes as well as outside the capillary forming the plasma jet. It was characterized by significant radiation arising only from He and N2(+), which are known to be important in the process of the soft ionization of the analyte. Later in time, the plasma capable of dissociating molecules develops. It is characterized by appreciable radiation from analyte dissociation products and is restricted to the interelectrode region in the capillary. Thus, for the soft ionization purposes, it is feasible to introduce the analyte exclusively in the plasma jet. For elemental analysis, the interelectrode plasma is appropriate. PMID:27032869

  7. Transport barriers with and without shear flows in a magnetized plasma

    SciTech Connect

    Martinell, Julio J.

    2014-01-14

    Different ways of producing a transport barrier in a toroidal magnetized plasma are discussed and the properties of the barriers are analyzed. The first mechanism is associated with the presence of a sheared plasma flow that is present in a limited region of the plasma, which creates a zonal flow. In contrast to the usual paradigm stating that the sheared flow reduces the turbulence correlation length and leads to suppression of the fluctuation driven transport in the region of highest shear, it is shown that from the perspective of chaotic transport of plasma particles in the fluctuation fields, the transport barrier is formed in the region of zero shear and it can be destroyed when the fluctuation level is high enough. It is also shown that finite gyroradius effects modify the dynamics and introduces new conditions for barrier formation. The second mechanism considers a method in which radio-frequency waves injected into the plasma can stabilize the drift waves and therefore the anomalous transport is reduced, creating a barrier. This process does not involve the presence of sheared flows and depends only on the effect of the RF wave field on the drift waves. The stabilizing effect in this case is due to the nonlinear ponderomotive force which acts in a way that offsets the pressure gradient destabilization. Finally, a mechanism based on the ponderomotive force of RF waves is described which produces poloidal plasma rotation around the resonant surface due to the asymmetry of induced transport; it creates a transport barrier by shear flow stabilization of turbulence.

  8. Atmospheric pressure resistive barrier air plasma jet induced bacterial inactivation in aqueous environment

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, Magesh; Sarani, Abdollah; Gonzales, Xavier

    2013-03-01

    An atmospheric pressure resistive barrier air plasma jet is designed to inactivate bacteria in aqueous media in direct and indirect exposure modes of treatment. The resistive barrier plasma jet is designed to operate at both dc and standard 50-60 Hz low frequency ac power input and the ambient air at 50% humidity level was used as the operating gas. The voltage-current characteristics of the plasma jet were analyzed and the operating frequency of the discharge was measured to be 20 kHz and the plasma power was measured to be 26 W. The plasma jet rotational temperatures (Trot) are obtained from the optical emission spectra, from the N2C-B(2+) transitions by matching the experimental spectrum results with the Spectra Air (SPECAIR) simulation spectra. The reactive oxygen and nitrogen species were measured using optical emission spectroscopy and gas analyzers, for direct and indirect treatment modes. The nitric oxides (NO) were observed to be the predominant long lived reactive nitrogen species produced by the plasma. Three different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and Neisseria meningitidis (Gram-negative) were suspended in an aqueous media and treated by the resistive barrier air plasma jet in direct and indirect exposure modes. The results show that a near complete bacterial inactivation was achieved within 120 s for both direct and indirect plasma treatment of S. aureus and E. coli bacteria. Conversely, a partial inactivation of N. meningitidis was observed by 120 s direct plasma exposure and insignificant inactivation was observed for the indirect plasma exposure treatment. Plasma induced shifts in N. meningitidis gene expression was analyzed using pilC gene expression as a representative gene and the results showed a reduction in the expression of the pilC gene compared to untreated samples suggesting that the observed protection against NO may be regulated by other genes.

  9. Investigation on the suitability of plasma sprayed Fe Cr Al coatings as tritium permeation barrier

    NASA Astrophysics Data System (ADS)

    Fazio, C.; Stein-Fechner, K.; Serra, E.; Glasbrenner, H.; Benamati, G.

    1999-08-01

    Results on the fabrication of a tritium permeation barrier by spraying Fe-Cr-Al powders are described. The sprayed coatings were deposited at temperatures below the Ac1 temperature of the ferritic-martensitic steel substrate and no post-deposition heat treatment was applied. The aim of the investigation was the determination of the efficiency of the coatings to act as tritium permeation barrier. Metallurgical investigations as well as hydrogen isotope permeation measurements were carried out onto the produced coatings. The depositions were performed on ferritic-martensitic steels by means of three types of spray techniques: high velocity oxy fuel, air plasma spray and vacuum plasma spray.

  10. Plasma-Sprayed Ceramic Coatings for Barrier Applications Against Molten Uranium Corrosion

    NASA Astrophysics Data System (ADS)

    Ananthapadmanabhan, P. V.; Chakravarthy, Y.; Chaturvedi, Vandana; Thiyagarajan, T. K.; Pragatheeswaran, A.

    2015-07-01

    Ceramic coatings are applied on engineering components for protecting them from large thermal load and hot corrosion. Choices of coating material for protection against hot corrosion by uranium are few, because of its high reactivity. Yttrium oxide has a high melting temperature and is inert towards uranium. Therefore, yttrium oxide coatings are effective as a barrier against hot corrosion by uranium and its alloys. This paper gives a summary of the developmental work on plasma-sprayed yttria coatings for corrosion barrier applications against molten uranium. Results show that plasma-sprayed yttria coatings offer a long-term solution to hot corrosion problems.

  11. Technical note - Plasma-sprayed ceramic thermal barrier coatings for smooth intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Doychak, J.

    1992-01-01

    A new approach for plasma spray deposition of ceramic thermal barrier coatings directly to smooth substrates is described. Ceramic thermal barrier coatings were directly applied to substrates that had been coated with low-pressure plasma sprayed NiCrAlY bond coats and then centerless ground to simulate a smooth oxidation-resistant substrate. As the high-temperature oxidation behavior of NiAl+Zr is superior to that of MCrALY alloy, the bond coat is not required for oxidation resistance.

  12. PIV analysis of the homogeneity of energy deposition during development of a plasma actuator channel

    NASA Astrophysics Data System (ADS)

    Glazyrin, F. N.; Znamenskaya, I. A.; Mursenkova, I. V.; Naumov, D. S.; Sysoev, N. N.

    2016-01-01

    Nonstationary velocity fields that arise during the development of flows behind shock (blast) waves initiated by pulsed surface sliding discharge in air at a pressure of (2-4) × 104 Pa have been experimentally studied by the particle image velocimetry (PIV) technique. Plasma sheets (nanosecond discharges slipping over a dielectric surface) were initiated on walls of a rectangular chamber. Spatial analysis of the shape of shock-wave fronts and the distribution of flow velocities behind these waves showed that the pulsed energy deposition is homogeneous along discharge channels of a plasma sheet, while the integral visible plasma glow intensity decreases in the direction of channel propagation.

  13. Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.; Argarwal, P.; Duderstadt, E. C.

    1984-01-01

    The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.

  14. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  15. Plasma and ion barrier for electron beam spot stability

    SciTech Connect

    Kwan, Thomas J. T.; Snell, Charles M.

    2000-03-01

    High-current electron beams of small spot size are used for high-resolution x-ray radiography of dense objects. Intense energy deposition in the bremsstrahlung target causes generation of ions which can propagate upstream and disrupt the electron beam. We have investigated the use of a thin beryllium foil placed 1-2 cm in front of the target, which serves as a barrier for the ions but is essentially transparent to the incoming electron beam. Analysis and computer simulations confirm that this confinement method will halt ion propagation and preserve the spot size stability of the electron beam. (c) 2000 American Institute of Physics.

  16. Dielectric barrier plasma dynamics for active control of separated flows

    SciTech Connect

    Roy, Subrata; Singh, K.P.; Gaitonde, Datta V.

    2006-03-20

    The dynamics of separation mitigation with asymmetric dielectric barrier discharges is explored by considering the gas flow past a flat plate at an angle of attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the fluid. The charge separation and concomitant electric field yield a time-averaged body force which is oriented predominantly downstream, with a smaller transverse component towards the wall. This induces a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several geometric and electrical operating parameters is elucidated.

  17. The Effect of Air Plasma on Sterilization of Escherichia coli in Dielectric Barrier Discharge

    NASA Astrophysics Data System (ADS)

    Hu, Miao; Guo, Yun

    2012-08-01

    In this work, a Dielectric Barrier Discharge (DBD) air plasma was used to sterilize Escherichia coli (E. coli) on the surface of medical Polyethylene Terephthalate (PET) film. The leakage of cellular DNA and protein by optical absorbance measurement at 260 nm and 280 nm, together with transmission electron microscopy (TEM) about cell morphology were performed after sterilization to analyse inactivation mechanisms. The results indicated that the DBD air plasma was very effective in E. coli sterilization. The plasma germicidal efficiency depended on the plasma treatment time, the air-gap distance, and the applied voltage. Within 5 min of plasma treatment, the germicidal efficiency against E. coli could reach 99.99%. An etching action on cell membranes by electrons, ions and radicals is the primary mechanism for DBD air plasma sterilization, which leads to the effusion of cellular contents (DNA and protein) and bacterial death.

  18. Electron dynamics and plasma jet formation in a helium atmospheric pressure dielectric barrier discharge jet

    SciTech Connect

    Algwari, Q. Th.; O'Connell, D.

    2011-09-19

    The excitation dynamics within the main plasma production region and the plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet operated in helium was investigated. Within the dielectric tube, the plasma ignites as a streamer-type discharge. Plasma jets are emitted from both the powered and grounded electrode end; their dynamics are compared and contrasted. Ignition of these jets are quite different; the jet emitted from the powered electrode is ignited with a slight time delay to plasma ignition inside the dielectric tube, while breakdown of the jet at the grounded electrode end is from charging of the dielectric and is therefore dependent on plasma production and transport within the dielectric tube. Present streamer theories can explain these dynamics.

  19. Deactivation of A549 cancer cells in vitro by a dielectric barrier discharge plasma needle

    SciTech Connect

    Huang Jun; Chen Wei; Li Hui; Wang Xingquan; Lv Guohua; Wang Pengye; Khohsa, M. Latif; Guo Ming; Feng Kecheng; Yang Size

    2011-03-01

    An inactivation mechanism study on A549 cancer cells by means of a dielectric barrier discharge plasma needle is presented. The neutral red uptake assay provides a quantitative estimation of cell viability after plasma treatment. Experimental results show that the efficiency of argon plasma for the inactivation process is very dependent on power and treatment time. A 27 W power and 120 s treatment time along with 900 standard cubic centimeter per minute Ar flow and a nozzle-to-sample separation of 3 mm are the best parameters of the process. According to the argon emission spectra of the plasma jet and the optical microscope images of the A549 cells after plasma treatment, it is concluded that the reactive species (for example, OH and O) in the argon plasma play a major role in the cell deactivation.

  20. Compact High-Velocity Atmospheric Pressure Dielectric Barrier Plasma Jet in Ambient Air

    NASA Astrophysics Data System (ADS)

    Annette, Meiners; Michael, Leck; Bernd, Abel

    2015-01-01

    In this paper, a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted. In the present technological approach, the employment of air poses a significant challenge. The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime. The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient. In this way, the electron density and in turn the density of reactive species is increased. In addition, the plasma jet assembly is equipped with a short electrode. This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species. The plasma jet is formed within and emitted by a small conical nozzle. A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle. In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma. The range of short-lived active plasma species is in turn considerably enhanced. The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment. Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume.

  1. Inactivation of Spoilage Bacteria in Package by Dielectric Barrier Discharge Atmospheric Cold Plasma - Treatment Time Effects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to investigate the effect of treatment time of dielectric barrier discharge atmospheric cold plasma (DBD-ACP) on inactivation of spoilage bacteria, Pseudomonas fluorescens and Macrococcus caseolyticus. P. fluorescens and M. caseolyticus were isolated from spoiled chicken carcasses ...

  2. Sintering and Interface Strain Tolerance of Plasma-Sprayed Thermal and Environmental Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Leissler, George W.; Miller, Robert A.

    2003-01-01

    Ceramic thermal and environmental barrier coatings will be more aggressively designed to protect gas turbine engine hot section SiC/SiC Ceramic Matrix Composite (CMC) components in order to meet future engine higher fuel efficiency and lower emission goals. A coating system consisting of a zirconia-based oxide topcoat (thermal barrier) and a mullite/BSAS silicate inner coat (environmental barrier) is often considered a model system for the CMC applications. However, the coating sintering, and thermal expansion mismatch between the zirconia oxide layer and the silicate environmental barrier/CMC substrate will be of major concern at high temperature and under thermal cycling conditions. In this study, the sintering behavior of plasma-sprayed freestanding zirconia-yttria-based thermal barrier coatings and mullite (and/or barium-strontium-aluminosilicate, i.e., BSAS) environmental barrier coatings was determined using a dilatometer in the temperature range of 1200-1500 C. The effects of test temperature on the coating sintering kinetics were systematically investigated. The plasma-sprayed zirconia-8wt.%yttria and mullite (BSAS) two-layer composite coating systems were also prepared to quantitatively evaluate the interface strain tolerance of the coating system under thermal cycling conditions based on the dilatomentry. The cyclic response of the coating strain tolerance behavior and interface degradation as a function of cycle number will also be discussed.

  3. Barriers to diffusion of plasma membrane proteins form early during guinea pig spermiogenesis.

    PubMed Central

    Cowan, A E; Nakhimovsky, L; Myles, D G; Koppel, D E

    1997-01-01

    The plasma membrane of the mature guinea pig sperm is segregated into at least four domains of different composition. Previous studies have shown that some proteins localized within these domains are free to diffuse laterally, suggesting that barriers to protein diffusion are responsible for maintaining the nonuniform distribution of at least some surface proteins in mature sperm. The different membrane domains appear sequentially during sperm morphogenesis in the testis and during later passage through the epididymis. To determine when diffusion barriers become functional during sperm development, we examined the diffusion of two proteins that are expressed on the cell surface of developing spermatids and become segregated to different plasma membrane domains during the course of spermiogenesis. Both proteins exhibited rapid lateral diffusion throughout spermiogenesis, even after they become localized to specific regions of the surface membrane. These results suggest that barriers to membrane diffusion form concomitantly with membrane domains during spermiogenesis. Images FIGURE 1 FIGURE 2 PMID:9199813

  4. Ion internal transport barrier in neutral beam heated plasmas on HL-2A

    NASA Astrophysics Data System (ADS)

    Yu, D. L.; Wei, Y. L.; Liu, L.; Dong, J. Q.; Ida, K.; Itoh, K.; Sun, A. P.; Cao, J. Y.; Shi, Z. B.; Wang, Z. X.; Xiao, Y.; Yuan, B. S.; Du, H. R.; He, X. X.; Chen, W. J.; Ma, Q.; Itoh, S.-I.; Zhao, K. J.; Zhou, Y.; Wang, J.; Ji, X. Q.; Zhong, W. L.; Li, Y. G.; Gao, J. M.; Deng, W.; Liu, Yi; Xu, Y.; Yan, L. W.; Yang, Q. W.; Ding, X. T.; Duan, X. R.; Liu, Yong; HL-2A Team

    2016-05-01

    Ion internal transport barriers (iITBs) are first observed in neutral beam injection (NBI) heated plasmas at the HL-2A tokamak. The position of the barrier foot, in the stationary state, coincides with the q  =  1 surface within its uncertainty of measurement. iITBs can develop more easily at the beginning of NBI heating. Also, iITBs are unstable for the sawtooth plasma. Simulations reveal that the thermal diffusivity of ions (χ i) inside the barrier can be as low as the neoclassical level. It is observed that the flow shear in the stationary iITB state reaches the level required for suppressing the ion temperature gradient mode instability, which indicates the important role of flow shear in sustaining the iITB.

  5. Non-thermal dielectric-barrier discharge plasma damages human keratinocytes by inducing oxidative stress

    PubMed Central

    KIM, KI CHEON; PIAO, MEI JING; HEWAGE, SUSARA RUWAN KUMARA MADDUMA; HAN, XIA; KANG, KYOUNG AH; JO, JIN OH; MOK, YOUNG SUN; SHIN, JENNIFER H.; PARK, YEUNSOO; YOO, SUK JAE; HYUN, JIN WON

    2016-01-01

    The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2′,7′-dichlorodihydro-fluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components. PMID:26573561

  6. Non-thermal dielectric-barrier discharge plasma damages human keratinocytes by inducing oxidative stress.

    PubMed

    Kim, Ki Cheon; Piao, Mei Jing; Madduma Hewage, Susara Ruwan Kumara; Han, Xia; Kang, Kyoung Ah; Jo, Jin Oh; Mok, Young Sun; Shin, Jennifer H; Park, Yeunsoo; Yoo, Suk Jae; Hyun, Jin Won

    2016-01-01

    The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components. PMID:26573561

  7. Permeation barrier coating and plasma sterilization of PET bottles and foils

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Deilmann, Michael; Bibinov, Nikita; Awakowicz, Peter

    2009-10-01

    Modern packaging materials such as polyethylene terephthalate (PET) offer various advantages over glass or metal containers. Beside this they only offer poor barrier properties against gas permeation. Therefore, the shelf-live of packaged food is reduced. Additionally, common sterilization methods like heat, hydrogen peroxide or peracetic acid may not be applicable due to reduced heat or chemical resistance of the plastic packaging material. For the plasma sterilization and permeation barrier coating of PET bottles and foils, a microwave driven low pressure plasma reactor is developed based on a modified Plasmaline antenna. The dependencies of important plasma parameters, such as gas mixture, process pressure, power and pulse conditions on oxygen permeation through packaging foil are investigated. A residual permeation as low as J = 1.0 ±0.3 cm^3m-2day-1bar-1 for 60 nm thick silicon oxide (SiOx) coated PET foils is achieved. To discuss this residual permeation, coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrate. A defect density of 3000 mm-2 is revealed responsible for permeation. For plasma sterilization, optimized plasma parameters based on fundamental research of plasma sterilization mechanisms permit short treatment times of a few seconds.

  8. Generation of dusty plasmas in supercritical carbon dioxide using surface dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Matsubayashi, Yasuhito; Urabe, Keiichiro; Stauss, Sven; Terashima, Kazuo

    2015-11-01

    Dusty plasmas are a class of plasmas that not only have repercussions for many branches of plasma science and technology, but also thermodynamics and statistical mechanics. However, in ground-based experiments, gravity influences the dynamics and formation of plasma crystals, and the realization of zero-gravity dusty plasmas in space is very costly and time-consuming. To overcome some of these limitations, we propose dusty plasmas in supercritical fluids as a means for realizing ground-based experiments under pseudo-microgravity conditions, to study the formation and self-organization of plasma crystals. Dusty plasmas were realized by using surface dielectric barrier discharges (DBDs) generated in supercritical carbon dioxide (\\text{scC}{{\\text{O}}2} ), and the motion of fine particles above the electrode surface was studied by high-speed imaging. The plasmas deposited charge on the particles, and the particles formed a self-organized structure above the surface DBD reactor. The particle charge estimated from the analysis of particle motion was on the order of  -104 to -105 e C, and the estimation of the Coulomb coupling parameter of the charged particles with a value of 102 to 104 confirmed the formation of strongly coupled plasmas.

  9. A hypersonic plasma bullet train traveling in an atmospheric dielectric-barrier discharge jet

    SciTech Connect

    Shi Jianjun; Zhong Fangchun; Zhang Jing; Liu, D. W.; Kong, M. G.

    2008-01-15

    An experimental observation of fast-moving plasma bullets produced in an atmospheric dielectric-barrier discharge jet is reported in this paper. Nanosecond imaging suggests that the atmospheric discharge jet consists of a plasma bullet train traveling at a hypersonic speed from 7.0 km/s to 43.1 km/s. Yet on a millisecond scale, the bullet train appears as a plasma jet of several centimeters long. The plasma bullets are produced through several possible mechanisms, the most likely of which is related to the ionization wave. Time and space resolved optical emission spectroscopy show that reactive plasma species can be delivered to different spatial sites with varying quantities.

  10. Measurement of plasma parameter in Dielectric Barrier Discharge (DBD) by Moiré deflectometry technique

    NASA Astrophysics Data System (ADS)

    Salimi Meidanshahi, Fatemeh; Madanipour, Khosro; Shokri, Babak; Khani, Mohammad Reza; Borzoki, Hamid Razavi

    2015-05-01

    In this work it is shown that the refractive index and temperature distribution of atmospheric Dielectric Barrier Discharge (DBD) plasmas are measured by Moiré deflectometry. Fringe analysis is used to calculate Moiré deflection and to evaluate refractive index in different points of plasma. By Sa-Ha equation and considering the first ionization, the dependence of refractive index and temperature, electrons, ions and molecules number densities of DBD plasma is obtained. By knowing this relation between plasma parameters, the spatial distributions of the plasma refractive index and temperature are evaluated. The advantages of this method are: simplicity, non-contact, non-destructive measurement, low cost, high accuracy and direct measurement of refractive index gradient.

  11. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2010-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  12. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2008-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  13. Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Koban, Ina; Matthes, Rutger; Hübner, Nils-Olaf; Welk, Alexander; Meisel, Peter; Holtfreter, Birte; Sietmann, Rabea; Kindel, Eckhard; Weltmann, Klaus-Dieter; Kramer, Axel; Kocher, Thomas

    2010-07-01

    Because of some disadvantages of chemical disinfection in dental practice (especially denture cleaning), we investigated the effects of physical methods on Candida albicans biofilms. For this purpose, the antifungal efficacy of three different low-temperature plasma devices (an atmospheric pressure plasma jet and two different dielectric barrier discharges (DBDs)) on Candida albicans biofilms grown on titanium discs in vitro was investigated. As positive treatment controls, we used 0.1% chlorhexidine digluconate (CHX) and 0.6% sodium hypochlorite (NaOCl). The corresponding gas streams without plasma ignition served as negative treatment controls. The efficacy of the plasma treatment was determined evaluating the number of colony-forming units (CFU) recovered from titanium discs. The plasma treatment reduced the CFU significantly compared to chemical disinfectants. While 10 min CHX or NaOCl exposure led to a CFU log10 reduction factor of 1.5, the log10 reduction factor of DBD plasma was up to 5. In conclusion, the use of low-temperature plasma is a promising physical alternative to chemical antiseptics for dental practice.

  14. Ultrafast thermal plasma physical vapor deposition of yttria-stabilized zirconia for novel thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Huang, Heji; Eguchi, Keisuke; Kambara, Makoto; Yoshida, Toyonobu

    2006-03-01

    This research aims to develop advanced thermal plasma spraying technology for the next-generation thermal barrier coatings (TBCs) with a high power hybrid plasma spraying system. By using thermal plasma physical vapor deposition (TP-PVD), various functional structured yttria-stabilized zirconia (YSZ) coatings were deposited. Parameters, such as powder feeding rate, hydrogen gas concentration, and total mass flow rate of the plasma gas, were optimized, and their influences on the evaporation of YSZ powder were investigated. Ultrafast deposition of a thick coating was achieved at a rate of over 150 μm/min. The deposited porous coating has a low thermal conductivity of 0.7W/mK and the dense coating with interlaced t' domains possesses a high nanohardness of 27.85 GPa and a high reflectance. These characteristics show that the TP-PVD technique is a very valuable process for manufacturing novel TBCs.

  15. Study of non-thermal plasma jet with dielectric barrier configuration in nitrogen and argon

    NASA Astrophysics Data System (ADS)

    Choo, C. Y.; Chin, O. H.

    2014-03-01

    Dielectric barrier discharge (DBD) is advantageous in generating non-thermal plasma at atmospheric pressure, as it avoids transition to thermal arc and dispenses with costly vacuum system. It has found useful applications in treating heat-sensitive materials such as plastics and living tissue. In this work, the discharge formed between the Pyrex glass layer and the ground electrode is extruded through a nozzle to form the non-thermal plasma jet. The DBD characteristics were investigated in terms of charge transferred and mean power dissipated per cycle when operated in nitrogen and argon at various flow rates and applied voltages. These characteristics were then correlated to the dimension of the plasma jet. The mean power dissipated in the DBD was below 7 W giving an efficiency of 17 %. The length of the plasma jet was greatly limited to below 1 cm due to the configuration of the DBD system and nozzle.

  16. Carbon dioxide splitting in a dielectric barrier discharge plasma: a combined experimental and computational study.

    PubMed

    Aerts, Robby; Somers, Wesley; Bogaerts, Annemie

    2015-02-01

    Plasma technology is gaining increasing interest for the splitting of CO2 into CO and O2 . We have performed experiments to study this process in a dielectric barrier discharge (DBD) plasma with a wide range of parameters. The frequency and dielectric material did not affect the CO2 conversion and energy efficiency, but the discharge gap can have a considerable effect. The specific energy input has the most important effect on the CO2 conversion and energy efficiency. We have also presented a plasma chemistry model for CO2 splitting, which shows reasonable agreement with the experimental conversion and energy efficiency. This model is used to elucidate the critical reactions that are mostly responsible for the CO2 conversion. Finally, we have compared our results with other CO2 splitting techniques and we identified the limitations as well as the benefits and future possibilities in terms of modifications of DBD plasmas for greenhouse gas conversion in general. PMID:25641832

  17. Detection of hydroxyl radicals during regeneration of granular activated carbon in dielectric barrier discharge plasma system

    NASA Astrophysics Data System (ADS)

    Tang, Shoufeng; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

    2013-03-01

    To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (•OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of •OH. Oxygen atmosphere and a suitable GAC water content were contributed to •OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.

  18. Generation of tunable plasma photonic crystals in meshed dielectric barrier discharge

    SciTech Connect

    Wang, Yongjie; Dong, Lifang Liu, Weibo; He, Yafeng; Li, Yonghui

    2014-07-15

    Tunable superlattice plasma photonic crystals are obtained in a meshed dielectric barrier discharge. These plasma photonic crystals are composed of thin artificial lattices and thick self-organized lattices, and can be tuned easily by adjusting the applied voltage. A plasma photonic crystal with self-organized hexagonal lattice coupled to artificial square lattice is first realized. The dispersion relations of the square sublattices with different radii, which are recorded by an intensified charge-coupled device camera, are calculated. The results show that the thick square sublattice has the higher band edge frequencies and wider band widths. Band gaps of superlattice plasma photonic crystals are actually temporal integrations of those of transient sublattices.

  19. Field emission microplasma actuation for microchannel flows

    NASA Astrophysics Data System (ADS)

    Sashank Tholeti, Siva; Shivkumar, Gayathri; Alexeenko, Alina A.

    2016-06-01

    Microplasmas offer attractive flow control methodology for gas transport in microsystems where large viscous losses make conventional pumping methods highly inefficient. We study microscale flow actuation by dielectric-barrier discharge (DBD) with field emission (FE) of electrons, which allows lowering the operational voltage from kV to a few hundred volts and below. A feasibility study of FE-DBD for flow actuation is performed using 2D particle-in-cell method with Monte Carlo collisions (PIC/MCC) at 10 MHz in nitrogen at atmospheric pressure. The free diffusion dominated, high velocity field emission electrons create a large positive space charge and a body force on the order of 106 N m‑3. The body force and Joule heat decrease with increase in dielectric thickness and electrode thickness. The body force also decreases at lower pressures. The plasma body force distribution along with the Joule heating is then used in the Navier–Stokes simulations to quantify the flow actuation in a microchannel. Theoretical analysis and simulations for plasma actuated planar Poiseuille flow show that the gain in flow rate is inversely proportional to Reynolds number. This theoretical analysis is in good agreement with the simulations for a microchannel with closely placed actuators under incompressible conditions. Flow rate of FE-DBD driven 2D microchannel is around 100 ml min‑1 mm‑1 for an input power of 64 μW mm‑1. The gas temperature rises by 1500 K due to the Joule heating, indicating FE-DBD’s potential for microcombustion, micropropulsion and chemical sensing in addition to microscale pumping and mixing applications.

  20. Dielectric-barrier-discharge vortex generators: characterisation and optimisation for flow separation control

    NASA Astrophysics Data System (ADS)

    Jukes, Timothy N.; Choi, Kwing-So

    2012-02-01

    We investigated the use of dielectric-barrier-discharge plasma actuators as vortex generators for flow separation control applications. Plasma actuators were placed at a yaw angle to the oncoming flow, so that they produced a spanwise wall jet. Through interaction with the oncoming boundary layer, this created a streamwise longitudinal vortex. In this experimental investigation, the effect of yaw angle, actuator length and plasma-induced velocity ratio was studied. Particular attention was given to the vortex formation mechanism and its development downstream. The DBD plasma actuators were then applied in the form of co-rotating and counter-rotating vortex arrays to control flow separation over a trailing-edge ramp. It was found that the vortex generators were successful in reducing the separation region, even at plasma-to-free-stream velocity ratios of less than 10%.

  1. Isothermal and cyclic oxidation of an air plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.; Rigney, E.D.

    1996-08-01

    Thermogravimetric methods for evaluating bond coat oxidation in plasma-sprayed thermal barrier coating (TBC) systems were assessed by high-temperature testing of TBC systems with air plasma-sprayed (APS) Ni-22Cr-10Al-1Y bond coatings and yttria-stabilized zirconia top coatings. High-mass thermogravimetric analysis (at 1150{sup degrees}C) was used to measure bond coat oxidation kinetics. Furnace cycling was used to evaluate APS TBC durability. This paper describes the experimental methods and relative oxidation kinetics of the various specimen types. Characterization of the APS TBCs and their reaction products is discussed.

  2. Oxidation and degradation of a plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.

    1996-04-01

    The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

  3. Cold pulse experiments in plasma with an electron internal transport barrier on LHD

    NASA Astrophysics Data System (ADS)

    Inagaki, S.; Ida, K.; Tamura, N.; Shimozuma, T.; Kubo, S.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Ohkubo, K.; LHD Experimental Group

    2004-05-01

    Transient transport experiments are performed in LHD plasma with electron internal transport barrier (e-ITB). Evidence for a reduction of electron heat diffusivity inside the ITB is observed from cold and heat pulse propagations. The observed enhancement of the cold pulse peak is explained by the temperature dependent electron heat diffusivity. The heat diffusivity inside the ITB decreases with an increase in the electron temperature in LHD. A preliminary version of this study was presented in the 29th EPS Conf. on Plasma Phys. and Control. Fusion (Montreux, Switzerland, 17 21 June 2002) [1].

  4. A dielectric-barrier discharge enhanced plasma brush array at atmospheric pressure

    SciTech Connect

    Li Xuemei; Zhan Xuefang; Yuan Xin; Zhao Zhongjun; Yan Yanyue; Duan Yixiang; Tang Jie

    2013-07-15

    This study developed a large volume cold atmospheric plasma brush array, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel. A platinum sheet electrode was placed in the middle of the discharge chamber, which effectively reduced the breakdown voltage and working voltage. Emission spectroscopy diagnosis indicated that many excited argon atoms were distributed almost symmetrically in the lateral direction of the plasma. The concentration variations of reactive species relative to the gas flow rate and discharge current were also examined.

  5. Nanocapsules for drug delivery through the skin barrier by tissue-tolerable plasma

    NASA Astrophysics Data System (ADS)

    Lademann, J.; Patzelt, A.; Richter, H.; Lademann, O.; Baier, G.; Breucker, L.; Landfester, K.

    2013-08-01

    For many years, several attempts have been made to enhance skin penetration by chemical, physical or mechanical manipulation to reduce the barrier function of the skin. The present study demonstrates the possibility of penetration enhancement for 400 nm sized nanocapsules loaded with a model drug consisting of a fluorescent dye by the application of tissue-tolerable plasma (TTP). Therefore, the stability of the nanocapsules and their penetration through the skin barrier prior to and in combination with TTP application was evaluated. The results revealed that the penetration of the nanocapsules could be effectively enhanced when applied in combination with TTP, hence delivering the model drug unaffected by plasma into deeper skin layers. The stability testing showed no significant structural changes of the nanocapsules after contact with TTP. Thus, the present study introduces a new strategy for the penetration enhancement of substances by the combined utilization of nanocapsules and TTP.

  6. Non-thermal plasma remediation of SO2/NO using a dielectric-barrier discharge

    NASA Astrophysics Data System (ADS)

    Sun, Wanming; Pashaie, Bijan; Dhali, Shirshak K.; Honea, Frank I.

    1996-04-01

    Here we report the experimental and simulation results of removal of SO2 and NO from a simulated coal combustion gas using a dielectric-barrier discharge. A Monte Carlo calculation is done to determine the transport properties of the flue gas. Following this, a detailed plasma chemistry calculation is done which takes into account the pulsed nature of the dielectric-barrier discharge. The computed results are in good agreement with the experimental data. We find that in low concentrations (400 ppm for SO2 and 100 ppm for NO) the dielectric-barrier discharge was capable of removing 99% of the SO2 and NO. Due to temperature dependence of the heavy particle reactions, there is a decrease in NO removal as the energy density is increased past an optimum value.

  7. Skeletal cell differentiation is enhanced by atmospheric dielectric barrier discharge plasma treatment.

    PubMed

    Steinbeck, Marla J; Chernets, Natalie; Zhang, Jun; Kurpad, Deepa S; Fridman, Gregory; Fridman, Alexander; Freeman, Theresa A

    2013-01-01

    Enhancing chondrogenic and osteogenic differentiation is of paramount importance in providing effective regenerative therapies and improving the rate of fracture healing. This study investigated the potential of non-thermal atmospheric dielectric barrier discharge plasma (NT-plasma) to enhance chondrocyte and osteoblast proliferation and differentiation. Although the exact mechanism by which NT-plasma interacts with cells is undefined, it is known that during treatment the atmosphere is ionized generating extracellular reactive oxygen and nitrogen species (ROS and RNS) and an electric field. Appropriate NT-plasma conditions were determined using lactate-dehydrogenase release, flow cytometric live/dead assay, flow cytometric cell cycle analysis, and Western blots to evaluate DNA damage and mitochondrial integrity. We observed that specific NT-plasma conditions were required to prevent cell death, and that loss of pre-osteoblastic cell viability was dependent on intracellular ROS and RNS production. To further investigate the involvement of intracellular ROS, fluorescent intracellular dyes Mitosox (superoxide) and dihydrorhodamine (peroxide) were used to assess onset and duration after NT-plasma treatment. Both intracellular superoxide and peroxide were found to increase immediately post NT-plasma treatment. These increases were sustained for one hour but returned to control levels by 24 hr. Using the same treatment conditions, osteogenic differentiation by NT-plasma was assessed and compared to peroxide or osteogenic media containing β-glycerolphosphate. Although both NT-plasma and peroxide induced differentiation-specific gene expression, neither was as effective as the osteogenic media. However, treatment of cells with NT-plasma after 24 hr in osteogenic or chondrogenic media significantly enhanced differentiation as compared to differentiation media alone. The results of this study show that NT-plasma can selectively initiate and amplify ROS signaling to enhance

  8. Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

    PubMed Central

    Arjunan, Krishna Priya; Friedman, Gary; Fridman, Alexander; Clyne, Alisa Morss

    2012-01-01

    Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm–2 had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm–2 plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization. PMID:21653568

  9. Skeletal Cell Differentiation Is Enhanced by Atmospheric Dielectric Barrier Discharge Plasma Treatment

    PubMed Central

    Zhang, Jun; Kurpad, Deepa S.; Fridman, Gregory; Fridman, Alexander; Freeman, Theresa A.

    2013-01-01

    Enhancing chondrogenic and osteogenic differentiation is of paramount importance in providing effective regenerative therapies and improving the rate of fracture healing. This study investigated the potential of non-thermal atmospheric dielectric barrier discharge plasma (NT-plasma) to enhance chondrocyte and osteoblast proliferation and differentiation. Although the exact mechanism by which NT-plasma interacts with cells is undefined, it is known that during treatment the atmosphere is ionized generating extracellular reactive oxygen and nitrogen species (ROS and RNS) and an electric field. Appropriate NT-plasma conditions were determined using lactate-dehydrogenase release, flow cytometric live/dead assay, flow cytometric cell cycle analysis, and Western blots to evaluate DNA damage and mitochondrial integrity. We observed that specific NT-plasma conditions were required to prevent cell death, and that loss of pre-osteoblastic cell viability was dependent on intracellular ROS and RNS production. To further investigate the involvement of intracellular ROS, fluorescent intracellular dyes Mitosox (superoxide) and dihydrorhodamine (peroxide) were used to assess onset and duration after NT-plasma treatment. Both intracellular superoxide and peroxide were found to increase immediately post NT-plasma treatment. These increases were sustained for one hour but returned to control levels by 24 hr. Using the same treatment conditions, osteogenic differentiation by NT-plasma was assessed and compared to peroxide or osteogenic media containing β-glycerolphosphate. Although both NT-plasma and peroxide induced differentiation-specific gene expression, neither was as effective as the osteogenic media. However, treatment of cells with NT-plasma after 24 hr in osteogenic or chondrogenic media significantly enhanced differentiation as compared to differentiation media alone. The results of this study show that NT-plasma can selectively initiate and amplify ROS signaling to enhance

  10. A model for residual stress evolution in air-plasma-sprayed zirconia thermal barrier coatings

    SciTech Connect

    Nair, B. G.; Singh, J. P.; Grimsditch, M.

    2000-02-28

    Ruby fluorescence spectroscopy indicates that residual stress in air-plasma-sprayed zirconia thermal barrier coatings is a function of the local interface geometry. The stress profile of a simulated rough interface characterized by ``peaks'' and ``valleys'' was modeled with a finite-element approach that accounted for thermal mismatch, oxide scale growth, and top coat sintering. Dependence of the stress profile on interface geometry and microstructure was investigated, and the results were compared with measured stresses.

  11. Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo; Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 ; Choi, Hagyoung; Lee, Sanghun; Jeon, Heeyoung; Jeon, Hyeongtag; Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791

    2013-11-07

    In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 × 10{sup −4} gm{sup −2}day{sup −1} and 1.2 × 10{sup −3} gm{sup −2}day{sup −1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

  12. Gene Transfection Method Using Atmospheric Pressure Dielectric-Barrier Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Sasaki, Shota; Kanzaki, Makoto; Kaneko, Toshiro

    2013-09-01

    Gene transfection which is the process of deliberately introducing nucleic acids into cells is expected to play an important role in medical treatment because the process is necessary for gene therapy and creation of induced pluripotent stem (iPS) cells. However, the conventional transfection methods have some problems, so we focus attention on promising transfection methods by atmospheric pressure dielectric-barrier discharge (AP-DBD) plasmas. AP-DBD He plasmas are irradiated to the living cell covered with genes. Preliminarily, we use fluorescent dye YOYO-1 instead of the genes and use LIVE/DEAD Stain for cell viability test, and we analyze the transfection efficiency and cell viability under the various conditions. It is clarified that the transfection efficiency is strongly dependence on the plasma irradiation time and cell viability rates is high rates (>90%) regardless of long plasma irradiation time. These results suggest that ROS (Reactive Oxygen Species) and electric field generated by the plasma affect the gene transfection. In addition to this (the plasma irradiation time) dependency, we now investigate the effect of the plasma irradiation under the various conditions.

  13. Degradation of triclosan in aqueous solution by dielectric barrier discharge plasma combined with activated carbon fibers.

    PubMed

    Xin, Lu; Sun, Yabing; Feng, Jingwei; Wang, Jian; He, Dong

    2016-02-01

    The degradation of triclosan (TCS) in aqueous solution by dielectric barrier discharge (DBD) plasma with activated carbon fibers (ACFs) was investigated. In this study, ACFs and DBD plasma coexisted in a planar DBD plasma reactor, which could synchronously achieve degradation of TCS, modification and in situ regeneration of ACFs, enhancing the effect of recycling of ACFs. The properties of ACFs before and after modification by DBD plasma were characterized by BET and XPS. Various processing parameters affecting the synergetic degradation of TCS were also investigated. The results exhibited excellent synergetic effects in DBD plasma-ACFs system on TCS degradation. The degradation efficiency of 120 mL TCS with initial concentration of 10 mg L(-1) could reach 93% with 1 mm thick ACFs in 18 min at input power of 80 W, compared with 85% by single DBD plasma. Meanwhile, the removal rate of total organic carbon increased from 12% at pH 6.26-24% at pH 3.50. ACFs could ameliorate the degradation efficiency for planar DBD plasma when treating TCS solution at high flow rates or at low initial concentrations. A possible degradation pathway of TCS was investigated according to the detected intermediates, which were identified by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) combined with theoretical calculation of Gaussian 09 program. PMID:26421625

  14. Manipulation of a grid-generated mixing with an active honeycomb dielectric barrier plasma discharge

    NASA Astrophysics Data System (ADS)

    Benard, N.; Mizuno, A.; Moreau, E.

    2015-12-01

    This study defines and characterizes an active system for turbulent and scalar mixing enhancement. This system is made of an active grid composed of 121 holes where the gas flows. A high voltage is applied between printed electrodes and embedded ground electrodes in order to produce a non-thermal surface discharge at the hole exits. The goal is to modify the flow downstream of the active grid. First, electrical and optical characterizations of the actuator are proposed. Second, it is shown that the discharge strongly modifies the flow distribution of the multi-jet exhaust, and the flow change depends on the high voltage applied to the active plasma grid. A minimization of the potential core by 40% is reported when discharge frequency corresponds to jet column mode instability.

  15. The cold and atmospheric-pressure air surface barrier discharge plasma for large-area sterilization applications

    SciTech Connect

    Wang Dacheng; Zhao Di; Feng Kecheng; Zhang Xianhui; Liu Dongping; Yang Size

    2011-04-18

    This letter reports a stable air surface barrier discharge device for large-area sterilization applications at room temperature. This design may result in visually uniform plasmas with the electrode area scaled up (or down) to the required size. A comparison for the survival rates of Escherichia coli from air, N{sub 2} and O{sub 2} surface barrier discharge plasmas is presented, and the air surface plasma consisting of strong filamentary discharges can efficiently kill Escherichia coli. Optical emission measurements indicate that reactive species such as O and OH generated in the room temperature air plasmas play a significant role in the sterilization process.

  16. Internal Transport Barrier Broadening through Subdominant Mode Stabilization in Reversed Field Pinch Plasmas.

    PubMed

    Lorenzini, R; Auriemma, F; Fassina, A; Martines, E; Terranova, D; Sattin, F

    2016-05-01

    The reversed field pinch (RFP) device RFX-mod features strong internal transport barriers when the plasma accesses states with a single dominant helicity. Such transport barriers enclose a hot helical region with high confinement whose amplitude may vary from a tiny one to an amplitude encompassing an appreciable fraction of the available volume. The transition from narrow to wide thermal structures has been ascribed so far to the transport reduction that occurs when the dominant mode separatrix, which is a preferred location for the onset of stochastic field lines, disappears. In this Letter we show instead that the contribution from the separatrix disappearance, by itself, is marginal and the main role is instead played by the progressive stabilization of secondary modes. The position and the width of the stochastic boundary encompassing the thermal structures have been estimated by applying the concept of a 3D quasiseparatrix layer, developed in solar physics to treat reconnection phenomena without true separatrices and novel to toroidal laboratory plasmas. Considering the favorable scaling of secondary modes with the Lundquist number, these results open promising scenarios for RFP plasmas at temperatures higher than the presently achieved ones, where lower secondary modes and, consequently, larger thermal structures are expected. Furthermore, this first application of the quasiseparatrix layer to a toroidal plasma indicates that such a concept is ubiquitous in magnetic reconnection, independent of the system geometry under investigation. PMID:27203329

  17. Spatially resolved spectroscopic measurements of a dielectric barrier discharge plasma jet applicable for soft ionization

    NASA Astrophysics Data System (ADS)

    Olenici-Craciunescu, S. B.; Müller, S.; Michels, A.; Horvatic, V.; Vadla, C.; Franzke, J.

    2011-03-01

    An atmospheric pressure microplasma ionization source based on a dielectric barrier discharge with a helium plasma cone outside the electrode region has been developed for liquid chromatography/mass spectrometry and as ionization source for ion mobility spectrometry. It turned out that dielectric barrier discharge ionization could be regarded as a soft ionization technique characterized by only minor fragmentation similar to atmospheric pressure chemical ionization (APCI). Mainly protonated molecules were detected. In order to characterize the soft ionization mechanism spatially resolved optical emission spectrometry (OES) measurements were performed on plasma jets burning either in He or in Ar. Besides to spatial intensity distributions of noble gas spectral lines, in both cases a special attention was paid to lines of N 2+ and N 2. The obtained mapping of the plasma jet shows very different number density distributions of relevant excited species. In the case of helium plasma jet, strong N 2+ lines were observed. In contrast to that, the intensities of N 2 lines in Ar were below the present detection limit. The positions of N 2+ and N 2 distribution maxima in helium indicate the regions where the highest efficiency of the water ionization and the protonation process is expected.

  18. Internal Transport Barrier Broadening through Subdominant Mode Stabilization in Reversed Field Pinch Plasmas

    NASA Astrophysics Data System (ADS)

    Lorenzini, R.; Auriemma, F.; Fassina, A.; Martines, E.; Terranova, D.; Sattin, F.

    2016-05-01

    The reversed field pinch (RFP) device RFX-mod features strong internal transport barriers when the plasma accesses states with a single dominant helicity. Such transport barriers enclose a hot helical region with high confinement whose amplitude may vary from a tiny one to an amplitude encompassing an appreciable fraction of the available volume. The transition from narrow to wide thermal structures has been ascribed so far to the transport reduction that occurs when the dominant mode separatrix, which is a preferred location for the onset of stochastic field lines, disappears. In this Letter we show instead that the contribution from the separatrix disappearance, by itself, is marginal and the main role is instead played by the progressive stabilization of secondary modes. The position and the width of the stochastic boundary encompassing the thermal structures have been estimated by applying the concept of a 3D quasiseparatrix layer, developed in solar physics to treat reconnection phenomena without true separatrices and novel to toroidal laboratory plasmas. Considering the favorable scaling of secondary modes with the Lundquist number, these results open promising scenarios for RFP plasmas at temperatures higher than the presently achieved ones, where lower secondary modes and, consequently, larger thermal structures are expected. Furthermore, this first application of the quasiseparatrix layer to a toroidal plasma indicates that such a concept is ubiquitous in magnetic reconnection, independent of the system geometry under investigation.

  19. Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Ganvir, Ashish; Curry, Nicholas; Markocsan, Nicolaie; Nylén, Per; Joshi, Shrikant; Vilemova, Monika; Pala, Zdenek

    2016-01-01

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  20. Laser-assisted plasma coating at atmospheric pressure: production of yttria-stabilized zirconia thermal barriers

    NASA Astrophysics Data System (ADS)

    Ouyang, Zihao; Meng, Liang; Raman, Priya; Cho, Tae S.; Ruzic, D. N.

    2011-07-01

    A laser-assisted plasma-coating technique at atmospheric pressure (LAPCAP) has been investigated. The electron temperature, electron density and gas temperature of the atmospheric-pressure plasma have been measured using optical emission spectroscopy (OES). LAPCAP utilizes laser ablation of 3 mol% yttria-stabilized zirconia into an atmospheric helium/nitrogen plasma to deposit thermal barrier coatings on a nickel-based substrate. The deposited film shows columnar structures similar to films prepared by high-vacuum deposition methods, such as physical vapour deposition and conventional pulsed-laser deposition. However, the LAPCAP films have smaller columns and higher porosity, compared with the films deposited by other techniques. The morphology and characteristics of the films have been analysed by scanning electron microscope, focused ion beam and x-ray diffraction.

  1. Direct current dielectric barrier assistant discharge to get homogeneous plasma in capacitive coupled discharge

    SciTech Connect

    Du, Yinchang; Li, Yangfang; Cao, Jinxiang; Liu, Yu; Wang, Jian; Zheng, Zhe

    2014-06-15

    In this paper, we propose a method to get more homogeneous plasma in the geometrically asymmetric capacitive coupled plasma (CCP) discharge. The dielectric barrier discharge (DBD) is used for the auxiliary discharge system to improve the homogeneity of the geometrically asymmetric CCP discharge. The single Langmuir probe measurement shows that the DBD can increase the electron density in the low density volume, where the DBD electrodes are mounted, when the pressure is higher than 5 Pa. By this manner, we are able to improve the homogeneity of the plasma production and increase the overall density in the target volume. At last, the finite element simulation results show that the DC bias, applied to the DBD electrodes, can increase the homogeneity of the electron density in the CCP discharge. The simulation results show a good agreement with the experiment results.

  2. Fluid modelling of a packed bed dielectric barrier discharge plasma reactor

    NASA Astrophysics Data System (ADS)

    Van Laer, Koen; Bogaerts, Annemie

    2016-02-01

    A packed bed dielectric barrier discharge plasma reactor is computationally studied with a fluid model. Two different complementary axisymmetric 2D geometries are used to mimic the intrinsic 3D problem. It is found that a packing enhances the electric field strength and electron temperature at the contact points of the dielectric material due to polarization of the beads by the applied potential. As a result, these contact points prove to be of direct importance to initiate the plasma. At low applied potential, the discharge stays at the contact points, and shows the properties of a Townsend discharge. When a high enough potential is applied, the plasma will be able to travel through the gaps in between the beads from wall to wall, forming a kind of glow discharge. Therefore, the inclusion of a so-called ‘channel of voids’ is indispensable in any type of packed bed modelling.

  3. Surface treatment of para-aramid fiber by argon dielectric barrier discharge plasma at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Gu, Ruxi; Yu, Junrong; Hu, Chengcheng; Chen, Lei; Zhu, Jing; Hu, Zuming

    2012-10-01

    This paper is focused on influence of argon dielectric barrier discharge (DBD) plasma on the adhesive performance and wettability of para-aramid fibers and three parameters including treated power, exposure time and argon flux were detected. The interfacial shear strength (IFSS) was greatly increased by 28% with 300 W, 60 s, 2 L min-1 argon flux plasma treatment. The content of oxygen atom and oxygen-containing polar functional groups were enhanced after the argon plasma treated, so as the surface roughness, which contributed to the improvement of surface wettability and the decrease of contact angle with water. However, long-time exposure, exorbitant power or overlarge argon flux could partly destroy the prior effects of the treatment and damage the mechanical properties of fibers to some degree.

  4. Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in Airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Gao, Wei; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Volume diffuse dielectric barrier discharge (DBD) plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra (OES), the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap. supported by National Natural Science Foundation of China (No. 51437002)

  5. Development of barrier coatings for cellulosic-based materials by cold plasma methods

    NASA Astrophysics Data System (ADS)

    Denes, Agnes Reka

    Cellulose-based materials are ideal candidates for future industries that need to be based on environmentally safe technologies and renewable resources. Wood represents an important raw material and its application as construction material is well established. Cellophane is one of the most important cellulosic material and it is widely used as packaging material in the food industry. Outdoor exposure of wood causes a combination of physical and chemical degradation processes due to the combined effects of sunlight, moisture, fungi, and bacteria. Cold-plasma-induced surface modifications are an attractive way for tailoring the characteristics of lignocellulosic substrates to prevent weathering degradation. Plasma-polymerized hexamethyldisiloxane (PPHMDSO) was deposited onto wood surfaces to create water repellent characteristics. The presence of a crosslinked macromolecular structure was detected. The plasma coated samples exhibited very high water contact angle values indicating the existence of hydrophobic surfaces. Reflective and electromagnetic radiation-absorbent substances were incorporated with a high-molecular-weight polydimethylsiloxane polymer in liquid phase and deposited as thin layers on wood surfaces. The macromolecular films, containing the dispersed materials, were then converted into a three dimensional solid state network by exposure to a oxygen-plasma. It was demonstrated that both UV-absorbent and reflectant components incorporated into the plasma-generated PDMSO matrix protected the wood from weathering degradation. Reduced oxidation and less degradation was observed after simulated weathering. High water contact angle values indicated a strong hydrophobic character of the oxygen plasma-treated PDMSO-coated samples. Plasma-enhanced surface modifications and coatings were employed to create water-vapor barrier layers on cellophane substrate surfaces. HMDSO was selected as a plasma gas and oxygen was used to ablate amorphous regions. Oxygen plasma

  6. Comparison Between Dielectric Barrier Discharge Plasma and Ozone Regenerations of Activated Carbon Exhausted with Pentachlorophenol

    NASA Astrophysics Data System (ADS)

    Qu, Guangzhou; Liang, Dongli; Qu, Dong; Huang, Yimei; Li, Jie

    2014-06-01

    In this study, two regeneration methods (dielectric barrier discharge (DBD) plasma and ozone (O3) regeneration) of saturated granular activated carbon (GAC) with pentachlorophenol (PCP) were compared. The results show that the two regeneration methods can eliminate contaminants from GAC and recover its adsorption properties to some extent. Comparing the DBD plasma with O3 regeneration, the adsorption rate and the capacity of the GAC samples after DBD plasma regeneration are greater than those after O3 regeneration. O3 regeneration decreases the specific surface area of GAC and increases the acidic surface oxygen groups on the surface of GAC, which causes a decrease in PCP on GAC uptake. With increasing regeneration cycles, the regeneration efficiencies of the two methods decrease, but the decrease in the regeneration efficiencies of GAC after O3 regeneration is very obvious compared with that after DBD plasma regeneration. Furthermore, the equilibrium data were fitted by the Freundlich and Langmuir models using the non-linear regression technique, and all the adsorption equilibrium isotherms fit the Langmuir model fairly well, which demonstrates that the DBD plasma and ozone regeneration processes do not appear to modify the adsorption process, but to shift the equilibrium towards lower adsorption concentrations. Analyses of the weight loss of GAC show that O3 regeneration has a lower weight loss than DBD plasma regeneration.

  7. Surface modification of polypropylene non-woven fabric using atmospheric nitrogen dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Wang, Kunlei; Wang, Wenchun; Yang, Dezheng; Huo, Yan; Wang, Dezhen

    2010-09-01

    In this paper, a dielectric barrier discharge operating in nitrogen at atmospheric pressure has been used to improve the surface hydrophilic property of polypropylene (PP) non-woven fabric. The changes in the hydrophilic property of the modified PP samples are investigated by the contact angle measurements and the variation of water contact angle is obtained as a function of the energy density; micrographs of the PP before and after plasma treatment are observed by scanning electron microscopy (SEM) and the chemical composition of the PP surface before and after plasma treatment is also analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the surface hydrophilic property of the PP samples is greatly improved with plasma treatment for a few seconds, as evidenced by the fact that the contact angle of the treated PP samples significantly decreases after plasma treatment. The analysis of SEM shows that the surface roughness of the treated PP samples increases due to bonding and etching in plasma processing. The analyses of FTIR and the C1s peak in the high-resolution XPS indicate that oxygen-containing and nitrogen-containing polar functional groups are introduced into PP surface in plasma processing. It can be concluded that the surface hydrophilic property of the modified PP samples has been obviously improved due to the introduction of oxygen-containing and nitrogen-containing polar groups and the increase of the surface roughness on the PP surface.

  8. Plasma Filaments in Dielectric Barrier Discharges Penetrating into High Aspect Ratio Cracks for Sterilization

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu.; Kushner, Mark J.

    2012-10-01

    The ability of surface-hugging-plasmas, as produced in dielectric barrier discharges (DBDs), to penetrate into crevices, turn corners and navigate geometrical obstructions, is important in plasma-wound healing and sterilization. In this talk, we discuss results from a computational investigation of the plasma filaments produced in an air DBD and impinging on and penetrating into deep, high aspect ratio cracks in the bottom dielectric. The model used in this work, nonPDPSIM, is a plasma hydrodynamics model in which continuity, momentum and energy equations are solved for charged and neutral species with solution of Poisson's equation for the electric potential, concurrent with radiation transport. A Monte Carlo simulation is used to obtain ion energy distributions (IEDs) to surfaces. Cracks are 1 mm deep and 3 μm to 250 μm wide (aspect ratios of 333 to 4). We found that when impinging onto the cracked dielectric, the plasma filament conformally spreads over the surface. The conductive plasma transfers the applied potential to the opening of the crack. The width of the crack, w, then determines the penetration of the plasma. If w is large compared to the filament, the penetration is surface hugging. If w is commensurate with the filament, the plasma fills the crack. If the Debye length is about w or larger, there is not significant penetration. For the conditions investigated, penetration occurred for w > 5-6 μm. IEDs onto the surfaces of the trenches produce transient pulses of ions with energies >150 eV.

  9. Mechanisms and dynamics of the external transport barrier formation in non-linear plasma edge simulations

    NASA Astrophysics Data System (ADS)

    Chôné, L.; Beyer, P.; Sarazin, Y.; Fuhr, G.; Bourdelle, C.; Benkadda, S.

    2015-07-01

    L-H transition features are reproduced using three-dimensional first-principles plasma edge turbulence simulations. A transport barrier is observed to form spontaneously above a threshold of the input power. The physical mechanism relies on the coupling between the equilibrium pressure gradient and the poloidal flow, through both the radial force balance and the neoclassical friction. Accounting for the actual radial profile and time evolution of the latter is key to the barrier formation. It is found that neoclassical friction acts as an energy source for the flow, which largely overcomes the sink due to the turbulent Reynolds stress during the whole barrier lifetime. Importantly, experimentally reported dynamical features are recovered during the formation and lifetime of the barrier. This includes dithering of the radial electric field, which is reminiscent of experimentally observed limit-cycle oscillations and quasi-periodic relaxation oscillations showing similarities with type-III ELMs. These rich dynamics emerge from interplay between turbulence, turbulence-driven flows and the equilibrium flow governed by force balance.

  10. Failure of PVD/plasma sprayed thermal barrier coatings during thermal cycling

    SciTech Connect

    Teixeria, V.; Andritschky, M.; Gruhn, H.; Mallener, W.; Buchkremer, H.; Stoever, D.

    1995-12-31

    ZrO{sub 2}7Y{sub 2}O{sub 3} plasma sprayed coatings (PS top coating) were applied on high temperature Ni-based alloys precoated by Physical Vapor Deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by Atmospheric Plasma Spraying (APS) and Inert gas Plasma Spraying (IPS at 2 bar) for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1,000 C and 1,150 C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables the authors to calculate the transient thermal strains and stresses which contribute to a better understanding of the failure mechanisms of the TBC during thermal cycling. They have also studied experimentally the adherence and failure modes of these coating systems during this high temperature testing. The TBC failure mechanism during thermal cycling is discussed in the light of coating transient stresses and substrate oxidation.

  11. Failure of physical vapor deposition/plasma-sprayed thermal barrier coatings during thermal cycling

    NASA Astrophysics Data System (ADS)

    Teixeira, V.; Andritschky, M.; Gruhn, H.; Malléner, W.; Buchkremer, H. P.; Stöver, D.

    2000-06-01

    ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS) and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1000 and 1150 °C. The temperature gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady heat transfer program. This modeling enables calculation of the transient thermal strains and stresses, which contributes to a better understanding of the failure mechanisms of the TBC during thermal cycling. The adherence and failure modes of these coating systems were experimentally studied during the high-temperature testing. The TBC failure mechanism during thermal cycling is discussed in light of coating transient stresses and substrate oxidation.

  12. High performance reversed shear plasmas with a large radius transport barrier in JT-60U

    NASA Astrophysics Data System (ADS)

    Fujita, T.; Hatae, T.; Oikawa, T.; Takeji, S.; Shirai, H.; Koide, Y.; Ishida, S.; Ide, S.; Ishii, Y.; Ozeki, T.; Higashijima, S.; Yoshino, R.; Kamada, Y.; Neyatani, Y.

    1998-02-01

    The operation of reversed shear plasmas in JT-60U has been extended to the low-q, high-Ip region keeping a large radius transport barrier, and a high fusion performance has been achieved. Record values of deuterium-tritium (DT)-equivalent power gain in JT-60U have been obtained: QDTeq = 1.05, τE = 0.97 s, nD(0) = 4.9 × 1019 m-3 and Ti(0) = 16.5 keV. A large improvement in confinement resulted from the formation of an internal transport barrier (ITB) with a large radius, which was characterized by steep gradients in electron density, electron temperature and ion temperature just inside the position of qmin. Large negative shear regions, up to 80% of the plasma minor radius in the low-qmin regime (qmin~2), were obtained by plasma current ramp-up after the formation of the ITB with the pressure and current profiles being controlled by adjustment of plasma volume and beam power. The ITB was established by on-axis beam heating into a low density target plasma with reversed shear that was formed by current ramp-up without beam heating. The confinement time increased with the radius of the ITB and the decrease of qmin at a fixed toroidal field. High H factors, up to 3.3, were achieved with an L mode edge. The effective one fluid thermal diffusivity χeff had its minimum in the ITB. The values of H/q95 and βt increased with the decrease of q95, and the highest performance was achieved at q95 ~3.1 (2.8 MA). The performance was limited by disruptive beta collapses with βN~2 at qmin~2.

  13. Experimental investigation of electron transport across a magnetic field barrier in electropositive and electronegative plasmas

    NASA Astrophysics Data System (ADS)

    Thomas, M. B.; Rafalskyi, D.; Lafleur, T.; Aanesland, A.

    2016-08-01

    In this paper we experimentally investigate the \\mathbf{E}× \\mathbf{B} drift of electrons in low temperature plasmas containing a magnetic field barrier; a plasma configuration commonly used in gridded negative ion sources. A planar Langmuir probe array is developed to quantify the \\mathbf{E}× \\mathbf{B} drift of electrons over the cross-section of the ion-extraction region of an ion–ion plasma source. The drift is studied as a function of pressure using both electropositive plasmas (Ar), as well electronegative plasmas (Ar and SF6 mixtures), and is demonstrated to result from an interaction of the applied magnetic field and the electric fields in the sheath and pre-sheath near the transverse boundaries. The drift enhances electron transport across the magnetic field by more than two orders of magnitude compared with simple collisional transport, and is found to be strongly dependant on pressure. The lowest pressure resulted in the highest influence of the drift across the extraction area and is found to be 30%.

  14. Patterning of graphene for flexible electronics with remote atmospheric-pressure plasma using dielectric barrier

    NASA Astrophysics Data System (ADS)

    Kim, Duk Jae; Park, Jeongwon; Geon Han, Jeon

    2016-08-01

    We show results of the patterning of graphene layers on poly(ethylene terephthalate) (PET) films through remote atmospheric-pressure dielectric barrier discharge plasma. The size of plasma discharge electrodes was adjusted for large-area and role-to-role-type substrates. Optical emission spectroscopy (OES) was used to analyze the characteristics of charge species in atmospheric-pressure plasma. The OES emission intensity of the O2* peaks (248.8 and 259.3 nm) shows the highest value at the ratio of \\text{N}2:\\text{clean dry air (CDA)} = 100:1 due to the highest plasma discharge. The PET surface roughness and hydrophilic behavior were controlled with CDA flow rate during the process. Although the atmospheric-pressure plasma treatment of the PET film led to an increase in the FT-IR intensity of C–O bonding at 1240 cm‑1, the peak intensity at 1710 cm‑1 (C=O bonding) decreased. The patterning of graphene layers was confirmed by scanning electron microscopy and Raman spectroscopy.

  15. High-speed sterilization technique using dielectric barrier discharge plasmas in atmospheric humid air

    NASA Astrophysics Data System (ADS)

    Miyamae, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2010-11-01

    The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma produced by an ac voltage application of 1 kHz in atmospheric humid air was investigated in order to develop low-temperature, low-cost and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where the air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of Bacillus atrophaeus spores was found to be dependent strongly on the humidity, and was completed within 15 min at a relative humidity of 90 % and a temperature of 30 C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. It is considered that reactive species such as hydroxyl radicals that are effective for the inactivation of Bacillus atrophaeus spores could be produced by the DBD plasma in the humid air. Repetitive micro-pulsed discharge plasmas in the humid air will be applied for the sterilization experiment to enhance the sterilization efficiency.

  16. Surface treatment of aramid fiber by air dielectric barrier discharge plasma at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Jia, Caixia; Chen, Ping; Liu, Wei; Li, Bin; Wang, Qian

    2011-02-01

    Aramid fiber samples are treated by air dielectric barrier discharge (DBD) plasma at atmospheric pressure; the plasma treatment time is investigated as the major parameter. The effects of this treatment on the fiber surface physical and chemical properties are studied by using surface characterization techniques. Scanning electron microscopy (SEM) is performed to determine the surface morphology changes, X-ray photoelectron spectroscopy (XPS) is analyzed to reveal the surface chemical composition variations and dynamic contact angle analysis (DCAA) is used to examine the changes of the fiber surface wettability. In addition, the wetting behavior of a kind of thermoplastic resin, poly(phthalazinone ether sulfone ketone) (PPESK), on aramid fiber surface is also observed by SEM photos. The study shows that there seems to be an optimum treatment condition for surface modification of aramid fiber by the air DBD plasma. In this paper, after the 12 s, 27.6 W/cm3 plasma treatment the aramid fiber surface roughness is significantly improved, some new oxygen-containing groups such as C-O, Cdbnd O and Odbnd C-O are generated on the fiber surface and the fiber surface wettability is greatly enhanced, which results in the better wetting behavior of PPESK resin on the plasma-treated aramid fiber.

  17. Plasma From Patients With HELLP Syndrome Increases Blood–Brain Barrier Permeability

    PubMed Central

    Tremble, Sarah M.; Owens, Michelle Y.; Morris, Rachael; Cipolla, Marilyn J.

    2015-01-01

    Circulating inflammatory factors and endothelial dysfunction have been proposed to contribute to the pathophysiology of hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. To date, the occurrence of neurological complications in these women has been reported, but few studies have examined whether impairment in blood–brain barrier (BBB) permeability or cerebrovascular reactivity is present in women having HELLP syndrome. We hypothesized that plasma from women with HELLP syndrome causes increased BBB permeability and cerebrovascular dysfunction. Posterior cerebral arteries from female nonpregnant rats were perfused with 20% serum from women with normal pregnancies (n = 5) or women with HELLP syndrome (n = 5), and BBB permeability and vascular reactivity were compared. Plasma from women with HELLP syndrome increased BBB permeability while not changing myogenic tone and reactivity to pressure. Addition of the nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester caused constriction of arteries that was not different with the different plasmas nor was dilation to the NO donor sodium nitroprusside different between the 2 groups. However, dilation to the small- and intermediate-conductance, calcium-activated potassium channel activator NS309 was decreased in vessels exposed to HELLP plasma. Thus, increased BBB permeability in response to HELLP plasma was associated with selective endothelial dysfunction. PMID:25194151

  18. Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows

    NASA Technical Reports Server (NTRS)

    Sammy, Mo

    2010-01-01

    Active flow control is often used to manipulate flow instabilities to achieve a desired goal (e.g. prevent separation, enhance mixing, reduce noise, etc.). Instability frequencies normally scale with flow velocity scale and inversely with flow length scale (U/l). In a laboratory setting for such flow experiments, U is high, but l is low, resulting in high instability frequency. In addition, high momentum and high background noise & turbulence in the flow necessitate high amplitude actuation. Developing a high amplitude and high frequency actuator is a major challenge. Ironically, these requirements ease up in application (but other issues arise).

  19. Fabrication of metallic single electron transistors featuring plasma enhanced atomic layer deposition of tunnel barriers

    NASA Astrophysics Data System (ADS)

    Karbasian, Golnaz

    The continuing increase of the device density in integrated circuits (ICs) gives rise to the high level of power that is dissipated per unit area and consequently a high temperature in the circuits. Since temperature affects the performance and reliability of the circuits, minimization of the energy consumption in logic devices is now the center of attention. According to the International Technology Roadmaps for Semiconductors (ITRS), single electron transistors (SETs) hold the promise of achieving the lowest power of any known logic device, as low as 1x10-18 J per switching event. Moreover, SETs are the most sensitive electrometers to date, and are capable of detecting a fraction of an electron charge. Despite their low power consumption and high sensitivity for charge detection, room temperature operation of these devices is quite challenging mainly due to lithographical constraints in fabricating structures with the required dimensions of less than 10 nm. Silicon based SETs have been reported to operate at room temperature. However, they all suffer from significant variation in batch-to-batch performance, low fabrication yield, and temperature-dependent tunnel barrier height. In this project, we explored the fabrication of SETs featuring metal-insulator-metal (MIM) tunnel junctions. While Si-based SETs suffer from undesirable effect of dopants that result in irregularities in the device behavior, in metal-based SETs the device components (tunnel barrier, island, and the leads) are well-defined. Therefore, metal SETs are potentially more predictable in behavior, making them easier to incorporate into circuits, and easier to check against theoretical models. Here, the proposed fabrication method takes advantage of unique properties of chemical mechanical polishing (CMP) and plasma enhanced atomic layer deposition (PEALD). Chemical mechanical polishing provides a path for tuning the dimensions of the tunnel junctions, surpassing the limits imposed by electron beam

  20. Antimicrobial Efficacy of Two Surface Barrier Discharges with Air Plasma against In Vitro Biofilms

    PubMed Central

    Matthes, Rutger; Bender, Claudia; Schlüter, Rabea; Koban, Ina; Bussiahn, René; Reuter, Stephan; Lademann, Jürgen; Weltmann, Klaus-Dieter; Kramer, Axel

    2013-01-01

    The treatment of infected wounds is one possible therapeutic aspect of plasma medicine. Chronic wounds are often associated with microbial biofilms which limit the efficacy of antiseptics. The present study investigates two different surface barrier discharges with air plasma to compare their efficacy against microbial biofilms with chlorhexidine digluconate solution (CHX) as representative of an important antibiofilm antiseptic. Pseudomonas aeruginosa SG81 and Staphylococcus epidermidis RP62A were cultivated on polycarbonate discs. The biofilms were treated for 30, 60, 150, 300 or 600 s with plasma or for 600 s with 0.1% CHX, respectively. After treatment, biofilms were dispensed by ultrasound and the antimicrobial effects were determined as difference in the number of the colony forming units by microbial culture. A high antimicrobial efficacy on biofilms of both plasma sources in comparison to CHX treatment was shown. The efficacy differs between the used strains and plasma sources. For illustration, the biofilms were examined under a scanning electron microscope before and after treatment. Additionally, cytotoxicity was determined by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cell line. The cell toxicity of the used plasma limits its applicability on human tissue to maximally 150 s. The emitted UV irradiance was measured to estimate whether UV could limit the application on human tissue at the given parameters. It was found that the UV emission is negligibly low. In conclusion, the results support the assumption that air plasma could be an option for therapy of chronic wounds. PMID:23894661

  1. Mechanisms of degradation and failure in a plasma deposited thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Demasi-Marcin, Jeanine T.; Sheffler, Keith D.; Bose, Sudhangshu

    1989-01-01

    Failure of a two layer plasma deposited thermal barrier coating is caused by cyclic thermal exposure and occurs by spallation of the outer ceramic layer. Spallation life is quantitatively predictable, based on the severity of cyclic thermal exposure. This paper describes and attempts to explain unusual constitutive behavior observed in the insulative ceramic coating layer, and presents details of the ceramic cracking damage accumulation process which is responsible for spallation failure. Comments also are offered to rationalize the previously documented influence of interfacial oxidation on ceramic damage accumulation and spallation life.

  2. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-05-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

  3. Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

    2016-07-01

    The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

  4. Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying

    SciTech Connect

    Helminiak, M A; Yanar, N M; Pettit, F S; Taylor, T A; Meier, G H

    2012-10-01

    The high-temperature behavior of high-purity, low-density (HP-LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The high purity yttria-stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as-processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP-LD coatings is compared with that of state-of-the-art electron beam physical vapor deposition TBCs.

  5. Decomposition of trifluoromethane in a dielectric barrier discharge non-thermal plasma reactor.

    PubMed

    Gandhi, M Sanjeeva; Mok, Y S

    2012-01-01

    The decomposition of trifluoromethane (CHF3) was carried out using non-thermal plasma generated in a dielectric barrier discharge (DBD) reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF3 with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF3 gradually increased with the addition of O2 up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF3 were found to be COF2, CF4, CO2 and CO although the COF2 and CF4 disappeared when the plasma were combined with alumina catalyst. PMID:23513444

  6. Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition.

    PubMed

    Majumdar, Abhijit; Hippler, Rainer

    2007-07-01

    Cost effective and a very simple dielectric barrier discharge plasma processing apparatus for thin film deposition and mass spectroscopic analysis of organic gas mixture has been described. The interesting features of the apparatus are the construction of the dielectric electrodes made of aluminum oxide or alumina (Al(2)O(3)) and glass and the generation of high ignition voltage from the spark plug transformer taken from car. Metal capacitor is introduced in between ground and oscilloscope to measure the executing power during the discharge and the average electron density in the plasma region. The organic polymer films have been deposited on Si (100) substrate using several organic gas compositions. The experimental setup provides a unique drainage system from the reaction chamber controlled by a membrane pump to suck out and remove the poisonous gases or residuals (cyanogens, H-CN, CH(x)NH(2), etc.) which have been produced during the discharge of CH(4)N(2) mixture. PMID:17672789

  7. Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

    2014-10-01

    This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

  8. Effects of Dielectric Barrier Discharge Plasma Treatment on Pentachlorophenol Removal of Granular Activated Carbon

    NASA Astrophysics Data System (ADS)

    Ji, Puhui; Qu, Guangzhou; Li, Jie

    2013-10-01

    The pentachlorophenol (PCP) adsorbed granular activated carbon (GAC) was treated by dielectric barrier discharge (DBD) plasma. The effects of DBD plasma on the structure of GAC and PCP decomposition were analyzed by N2 adsorption, thermogravimetric, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and gas chromatography mass spectrometry (GC-MS). The experimental data of adsorption kinetics and thermodynamics of PCP on GAC were fitted with different kinetics and isotherm models, respectively. The results indicate that the types of N2 adsorption isotherm of GAC are not changed by DBD plasma, while the specific surface area and pore volume increase after DBD plasma treatment. It is found that the weight loss of the saturated GAC is the highest, on the contrary, the weight loss of DBD treated GAC is the least because of reduced PCP residue on the GAC. The XPS spectra and SEM image suggest that some PCP on the GAC is removed by DBD plasma, and the surface of GAC treated by DBD plasma presents irregular and heterogeneous morphology. The GC-MS identification of by-products shows that two main dechlorination intermediate products, tetrachlorophenol and trichlorophenol, are distinguished. The fitting results of experimental data of adsorption kinetics and thermodynamics indicate that the pseudo-first-order and pseudo-second order models can be used for the prediction of the kinetics of virgin GAC and DBD treated GAC for PCP adsorption, and the Langmuir isotherm model fits better with the data of adsorption isotherm than the Freundlich isotherm in the adsorption of PCP on virgin GAC and DBD treated GAC.

  9. Barrier-free paths of directed protein motion in the erythrocyte plasma membrane.

    PubMed Central

    Boal, D H; Boey, S K

    1995-01-01

    A model is presented for the steric interaction between a plasma membrane protein and the membrane cytoskeleton in the human erythrocyte. The cytoskeleton is treated as a network of polymer chains attached to a flat bilayer, and the membrane protein is a hemisphere of effective radius R(e) with center on the bilayer edge. The simulation is used to investigate the barrier-free path L for linear guided motion of a protein in the bilayer plane. It is shown that the barrier-free paths of small proteins can be used to extract the effective in-plane diameter of cytoskeletal components. For example, the in-plane diameter of an ankyrin attachment site is found to be approximately 12 nm in the simulation, or twice the computational spectrin diameter. The barrier-free paths of large proteins (R(e) > 23 nm) vanish when the proteins are corralled by the cytoskeleton. For intermediate size proteins, L decreases approximately as L is directly proportional to S-1.4 where S is proportional to the sum of the protein and cytoskeleton chain radii. Images FIGURE 1 PMID:8527650

  10. Physical and plasmachemical aspects of diffuse coplanar barrier discharge as a novel atmospheric-pressure plasma source

    NASA Astrophysics Data System (ADS)

    Cernak, M.; Kovacik, D.; Zahoranova, A.; Rahel, J.

    2008-07-01

    Collaborating Czech and Slovakian university teams have recently developed an innovative plasma source, the so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD), which has the potential to move a step closer to the industry requirement for in-line treatment of low-added-value materials using a highly-nonequlibrium ambient air plasma (Simor et al. 2002, The idea is to generate a thin (on the order of 0.1 mm) layer of highly-nonequlibrium plasma with a high power density (up to 100 W/cm^3) in the immediate vicinity of the treated surface and bring it into a close contact with the treated surface. Comparing to atmospheric-pressure glow discharge, volume dielectric barrier discharge, and plasma jet plasmas, such a diffuse plasma layer is believed to provide substantial advantages in energy consumption, exposure time, and technical simplicity. A brief outline of physical mechanism and basic properties of DCSBD will given using the results of emission spectroscopy, high-speed camera, and spatially resolved cross-correlation spectroscopy studies. The presentation will review also a current state of the art in in-line plasma treatment of low-cost materials and opportunities for the use of the so-called Diffuse Coplanar Surface Dielectric Barrier Discharge (DCSBD). The results obtained on the ambient air plasma treatments of textile, paper, wood, and glass illustrate that DCSBD offers outstanding performance with extremely low energy consumption for large area, uniform surface modifications of materials under continuous process conditions.