Nanosecond Pulsed Surface Dielectric Barrier Research Articles

Numerical simulation of streamer, pressure wave, and vortex induced by nanosecond pulsed surface dielectric barrier discharges

In this study, a two-dimensional fluid model is employed to simulate the streamer, pressure wave, and vortex in surface dielectric barrier discharge driven by nanosecond pulse voltage (ns-SDBD). It comprises a numerical model with two interconnected modules: discharge dynamics and gas flow dynamics. These modules are coupled through the physical variables including ‘EHD force’, ‘thermal source’, ‘velocity field’, ‘gas temperature’, and ‘gas pressure’. Our research primarily focuses on the underlying physical mechanisms of pressure waves and vortices for plasma-based flow control. The generation of pressure waves is attributed to the rapid gas heating by pulsed discharge, whereas the formation and development of the vortex are related to the ionic wind (EHD effect) provided by the plasma. To thoroughly understand and optimize flow control performance, an investigation into the effects of various discharge parameters, such as voltage amplitude and polarity, is conducted. Additionally, several SDBD modules are arranged in series, each featuring a dual three-electrode configuration. Subsequently, the dynamic behaviors of multiple streamers, pressure waves, and vortices, along with their interactions, are explored.

A Numerical Investigation of Supersonic Combustion Flow Control by Nanosecond-Pulsed Actuations

The efficiency of supersonic combustion is largely dependent on inlet and injection parameters. Additional energy input is required in some off-design conditions, and nanosecond discharge actuation can be a solution. In the present study, a phenomenological model of a nanosecond-pulsed surface dielectric barrier discharge (NS-SDBD) actuator was developed to analyze the combustion enhancement effect for a supersonic combustor with transverse H2 injection. A seven-reaction H2–air combustion model was adopted for the numerical simulation. Dynamic mode decomposition (DMD) was employed to acquire temperature perturbation in spatial and temporal domains. The results show that the actuator provides additional temperature-increment and species transportation through compression waves. The combustion enhancement effect is mainly attributed to the flow perturbation in the shear layer, which promotes the turbulent diffusion of fuel. Given the same power input, the combustion efficiency at the shockwave reflection point is increased by 17.5%, and the flame height is increased by 15.4% at its maximum.

Closed-Loop Control of Ionic Wind Speed Generated by Nanosecond Pulsed Surface Dielectric Barrier Discharge

Closed-Loop Control of Ionic Wind Speed Generated by Nanosecond Pulsed Surface Dielectric Barrier Discharge

Characteristics of a nanosecond pulsed dielectric barrier plasma actuator with a surface water film

Aircraft icing is one of the most serious hazards for airflight operations. The nanosecond pulsed surface dielectric barrier discharge (NSDBD) plasma actuator is recognized as an extremely promising anti-icing technology. In this paper, a multi-physics coupling simulation is used to study the plasma-discharge characteristics and responses of the air–water flow field generated by an NSDBD plasma actuator with a surface water film. The computational model describes air flows through an NSDBD plasma actuator with a water film at the center of two upper powered electrodes. The multi-physics model is solved using the drift-diffusion and energy-conservation equations for the plasma discharge and the mass, momentum, energy, and concentration equations for the air–water flow. The results show that, at the beginning of the voltage pulse, the surface water film has no effect on the plasma discharge. Then, during the pulse plateau time, the film leads to a longer plasma-discharge time and a larger plasma-discharge region. Furthermore, the film causes the plasma-actuator surface to develop a virtual positive electrode that would otherwise be absent and results in the plasma actuator generating more intense shock waves, higher gas temperatures, and larger heated regions.

Ice shape modulation with nanosecond pulsed surface dielectric barrier discharge plasma actuator towards flight safety

Ice accretion on aircraft wings seriously damage the aerodynamic performance and flight safety of an aircraft. To deal with this issue, a leading-edge ice shape modulation method using nanosecond pulsed surface dielectric barrier discharge (nSDBD) is proposed, featuring the merit of less energy consumption when compared to full-wing de-icing. A set of wind tunnel experiments are conducted for verification purposes. Results show that the dangerous continuous ice can be modulated into periodically segmented ice pieces by nSDBD, forming a wavy leading edge, and the energy consumption of ice shape modulation is less than 50% of that of complete deicing. In the case of NACA0012 airfoil, ice shape modulation can improve the lift noticeably at each angle of attack (0° to 22°), delay the stall angle by 2°, and reduce the drag coefficient by more than 50% compared to full ice condition. The duration of ice shape modulation with plasma actuators lasts for about 4 min to 6 min. For flow separation control, the coherent streamwise vortices generated by the wavy leading edge are able to enhance the mixing between the boundary layer and the freestream, resulting in an increase of the ability to resist the adverse pressure gradient above the airfoil. Since both ice shape modulation and flow separation control benefit the aerodynamic performance of icing airfoils, the flight safety is improved.

Flow separation control in S-shaped ∼inlet with a nanosecond pulsed surface dielectric barrier discharge plasma actuator

A nanosecond pulsed surface dielectric barrier discharge (nSDBD) plasma actuator is proposed to eliminate the complex 3D flow separation in an S-shaped ∼engine inlet. A set of wind tunnel experiments based on pressure measurements are conducted to verify the flow control effectiveness and obtain the influence laws of actuation voltage, pulse frequency, actuator layout and coverage area. The results show that nSDBD can effectively eliminate flow separation, leading to a noticeable improvement in the total pressure distribution at the outlet, manifested as a reduction in the low-pressure zone and an extension of the high-pressure zone. The spanwise layout nSDBD delivers a better flow control effect compared to the streamwise layout. For the same geometrical layout, the flow control effect improves with increasing voltage, and the optimal actuation frequency corresponds to a Strouhal number of approximately F + = 0.5. In particular, with a spanwise array of nSDBD plasma actuators operating at V p-p = 10 kV and F + = 0.5, the flow separation region is completely suppressed. The mechanism of flow separation with nSDBD can be ascribed to the mixing enhancement between the boundary layer and the main flow, which improves the boundary layer’s ability to resist the adverse pressure gradient.

Numerical verification of the two-spike-current behavior in the initial stage of plasma formation in a pulsed surface dielectric barrier discharge

Nanosecond pulsed surface dielectric barrier discharge (SDBD) is a hot topic in many fields, but the mechanisms of discharge evolution and micro-channel propagation are still not clearly understood. In this paper, a plasma fluid model of nanosecond pulsed SDBD is established, and the deductions of the two current spikes are verified and improved by simulation. The two current spikes correspond to the two stages of the discharge: the ionization wave propagation and the repeated re-ignition in the gap between the ionization wave and the dielectric surface. In the first stage, the ionization wave develops rapidly at first and propagates very slowly in the end, which produces the first current spike with a very short rise time and a tailing falling edge. The curve profile of the ionization wave velocity is very similar to that of the first current spike. A certain distance is maintained between the bottom of the ionization wave and the dielectric surface in this stage, which forms the gap for the next stage. In the second stage, the charged particle cloud induced by the quasi-uniform electric field in the middle of the gap and the new micro-channel from the edge of the high-voltage electrode propagate at first, and then merge together to establish a new discharge channel. The reverse electric field in the gap induced by the accumulated charges on the dielectric surface restricts the expansion velocity of the second discharge channel, which results in a longer rise time and falling time of the second current spike.

Surface ionization wave propagation in the nanosecond pulsed surface dielectric barrier discharge: the influence of dielectric material and pulse repetition rate

In this work, the propagation of the surface ionization wave (SIW) in the nanosecond pulsed surface dielectric barrier discharge with different dielectric materials and pulse repetition rates is investigated. The current waveforms at different locations along the route of the SIW propagation are obtained, based on a specially designed ground strip array geometry. The temporal evolution and spatial distribution of the electric field during the SIW propagation are measured by using the electric field induced second harmonic generation method. The distribution of the residual surface potential after the discharge is mapped with a Kelvin electrostatic probe, which verifies both the existence of the residual electric field and its opposite direction to that during the SIW propagation. It is found that with the dielectric material on which the surface charges decay faster, there are the well-pronounced primary and secondary SIWs with a higher velocity on the voltage rising edge and both the peak current and the peak electric field are also higher, with a less spatial attenuation along the SIW propagation route. It is demonstrated that the residual surface charges with the same polarity as the high-voltage pulse suppress the development of the SIW.

Characterization of the single nanosecond pulsed surface dielectric barrier plasma actuator: Geometric and electric effects

AbstractThe influence of the electrode length and the voltage pulses on the discharge characteristics of the surface dielectric barrier discharge actuators were investigated numerically by using the plasma kinetic model. The governing equations including the coupled continuity plasma discharge equation, drift‐diffusion equation, electron energy equation, Poisson's equation, and Navier–Stokes equation were solved in quiescent air at atmospheric pressure. The results show that the shorter pulse rising time results in higher discharge characteristics, more intense discharge, and bigger discharge region. Differently, the compared discharge characteristics for the electrodes with different lengths prove that the length of the powered and ground electrodes has little effect on the surface dielectric barrier discharge driven by nanosecond pulsed voltage.

Monte Carlo simulation of negative ion kinetics in air plasmas in a time-varying electric field

The kinetics of and O− ions was addressed in air plasma in a rapidly time-varying electric field that is typical for nanosecond pulsed surface dielectric barrier discharges. Self-consistent sets of cross-sections for these ions in collisions with O2 and N2 molecules were developed. The Monte Carlo technique was used to calculate ion energy distribution, mean ion energy and reaction rate coefficients in a time-varying electric field at air pressures from 0.1 to 1 atm. Simulations showed that the ion characteristics followed the instantaneous values of the electric field at atmospheric pressure, whereas these characteristics evolved with a noticeable delay at lower pressures. As a result, the rates of electron detachment and ion charge exchange were much lower than those corresponding to the instantaneous values of the electric field at the leading edge of the voltage pulse. The reverse effect was observed for the rates of ion–molecule reactions at the trailing edge of the voltage pulse. Here, the reaction rates decreased with some delay in comparison with electric field variation. An approach was suggested to describe ion rate coefficients in time-varying electric fields on the basis of the Monte Carlo calculation of these coefficients under steady electric field conditions, and the calculation of the mean ion energy in unsteady electric fields.

Numerical Investigation on the Effects of Dielectric Barrier on a Nanosecond Pulsed Surface Dielectric Barrier Discharge.

In order to understand the impacts of dielectric barrier on the discharge characteristics of a nanosecond pulsed surface dielectric barrier discharge (NS-DBD), the effects of dielectric constant and dielectric barrier thickness are numerically investigated by using a three-equation drift–diffusion model with a 4-species 4-reaction air chemistry. When the dielectric constant increases, while the dielectric barrier thickness is fixed, the streamer propagation speed (V), the maximum streamer length (L), the discharge energy (), and the gas heating () of a pulse increase, but the plasma sheath thickness (h), the fast gas heating efficiency , and the charge densities on the wall surface decrease. When the dielectric barrier thickness increases, while the dielectric constant is fixed, V, L, , and of a pulse decrease, but h, , and the charge densities on the wall surface increase. It can be concluded that the increase of the dielectric constant or the decrease of the dielectric barrier thickness results in the increase of the capacitance of the dielectric barrier, which enhances the discharge intensity. Increasing the dielectric constant and thinning the dielectric barrier layer improve the performance of the NS-DBD actuators.

Performance and mechanism analysis of nanosecond pulsed surface dielectric barrier discharge based plasma deicer

Ice accretion on aircraft surfaces, especially on wings, may do harm to the aerodynamic performance and safety of an aircraft. In this work, de-icing experiments on an NACA0012 airfoil model were conducted in an icing wind tunnel using nanosecond pulsed surface dielectric barrier discharge (nSDBD) actuator under typical glaze icing conditions. The spatial-temporal distribution of the temperature and the dynamic process of de-icing on the surface of the airfoil were obtained and analyzed. Accreted ice with an average thickness of 3 mm can be removed within 4 s by nSDBD, and then the ice never appeared again on the plasma-protected zone. In the whole de-icing process, the ice on the plasma-protected zone was “cut” and the adhesion force between the ice layer and airfoil surface was reduced by the heat generated by the plasma actuator. The “cut” ice layer was blown downstream by aerodynamic force of the incoming flow. It can be concluded that both the thermal effects of the nSDBD actuator and the aerodynamic force of the incoming flow contribute to the de-icing performance.

Static and dynamic stall control by NS SDBD actuators

In the last two decades, nonequilibrium plasmas have demonstrated the ability to affect a variety of flows of aeronautical interest, including mitigation of stall on steady airfoils as it is a nonintrusive, active control method. Plasma actuation also shows promise to address dynamic stall in rotorcraft because of the absence of moving parts, extremely lightweight and flexible assembly, extremely fast turn-on time and wide range of actuation frequency. In this paper, we summarize the recent advances in flow control both for static and dynamic flow separation control using nanosecond pulsed surface dielectric barrier discharge plasma devices. Topics of discussion include the mechanism of NS plasma actuation, results of experiments at different Reynolds and Mach numbers, dynamics of flow reattachment, and boundary layer separation control on a pitching airfoil. The common issue of retreating blade stall, as experienced in helicopters, was also considered in this study by experimenting with a reverse flow over an airfoil. Increases in lift are demonstrated for separated flows for reduced frequencies up to k = 0.05, angle of attack up to 32°. Instantaneous increase in lift with plasma control was demonstrated to be up to 55%. The 20% integral lift force increase of a helicopter model in hover mode using a constant engine power is also demonstrated with NS SDBD actuation of the flow on the rotating blades.

Effect of rise time on nanosecond pulsed surface dielectric barrier discharge actuator

Nanosecond pulsed surface dielectric barrier discharge (ns-SDBD) actuator is a novel technology for active flow control due to its high control capability and low power consumption. The electrical, and aerodynamic, characteristics of ns-SDBD actuator with different rise times are investigated by electrical measurement system, Schlieren optical system, and particle image velocimetry (PIV) system. Experimental results show that the short rise time leads to a high current amplitude and a diffuse-like plasma layer. The deposited energy reaches its maximum (9.26 mJ) at a rise time of 50 ns, and then declines, finally, slight changes occur when the rise time is increased from 150 ns to 500 ns. Furthermore, a circular arc wave and a plane wave are produced due to the localized heating. The intensity of the circular arc wave increases when the rise time decreases and the propagation distance of induced pressure waves in the vertical direction increases in a quasi-linear manner. In addition, due to the greater ability to transmit output energy to the surroundings, and the stronger tangential acceleration ability in the case of a short rise time, the area of action for the starting vortex is larger when rise time decreases and two vortexes are formed, which is conducive to mixing with the airflow and improving flow control capability.

Numerical investigation on the effects of discharge conditions on a nanosecond pulsed surface dielectric barrier discharge

In order to understand the impacts of discharge conditions on the discharge characteristics of a nanosecond pulsed surface dielectric barrier discharge, the effects of gas pressure, temperature, and velocity are numerically investigated by using a three-equation drift-diffusion model with a 4-species 4-reaction air chemistry. The scaling laws of plasma morphology and gas heating on pressure are obtained for further reduced modeling in the flow-control application. Theoretical discussions on the scaling laws are carefully conducted. When the pressure increases in the studied range, while the temperature is fixed, the streamer propagating velocity (V), the plasma sheath thickness (h), the maximum streamer length (L), the total discharge energy (QD_ei), and the gas heating (QGH) decrease. The plasma morphology and the gas heating have different scalings on the pressure according to V∼ep, h∼p−0.8, L∼p−0.8, QD_ei∼p−0.5, and QGH∼p−0.5. When the temperature decreases in the investigated range, while the pressure is kept constant, V, h, L, QD_ei, and QGH also decrease. When the gas velocity increases from 0m/s to 258m/s, while the pressure and the temperature are kept fixed, V and h increase. The total QD_ei and QGH increase by 4.3% and 4.6%, respectively. It is concluded that, on the one hand, the discharge characteristics are mainly dominated by the gas number density, which can be equivalently changed by the gas pressure and temperature. On the other hand, when the gas pressure and temperature are kept constant, the uniform gas velocity has weak effects on the discharge characteristics.

Fast gas heating of nanosecond pulsed surface dielectric barrier discharge: spatial distribution and fractional contribution from kinetics

The effect of heat release in reactions with charged and electronically excited species, or so-called fast gas heating (FGH), in nanosecond surface dielectric barrier discharge (nSDBD) in atmospheric pressure air is studied. Two-dimensional numerical simulations based on the PArallel Streamer Solver with KinEtics code are conducted. The code is based on the direct coupling of a self-consistent fluid model with detailed kinetics, an efficient photoionization model, and Euler equations. The choice of local field approximation for nSDBD modeling with simplified kinetics is discussed. The reduced electric field and the electron density are examined at both polarities for identical high-voltage pulses 24 kV in amplitude on a high-voltage electrode and 20 ns full width at half maximum. The distribution of the FGH energy and the resulting gas temperature field are studied and compared with findings in the literature. The input of different reactions to the appearance of hydrodynamic perturbations is analyzed.

Two Typical Charge Transportation Characteristics in Nanosecond-Pulse Surface Dielectric Barrier Discharge

Charge transportation expressed as a Lissajous figure usually is a standard method for the analysis of discharge power and energy in surface dielectric barrier discharge (SDBD). In this paper, the charge transportation characteristics under different parameters of power supply and actuator configurations are investigated, and the mechanisms of two typical Lissajous figures are discussed theoretically. Experimental results show that when the plasma distribution is quasi-diffuse mode, the Lissajous figure is almond shape correspondingly, while the plasma distribution looks like separated-channel mode, the Lissajous figure presents a parallelogram shape. Based on an improved time-varying lumped-element circuit model, two equivalent circuits of SDBD under two plasma distributions are built, and the Lissajous figures are calculated theoretically. Calculations and analysis results indicate that the two kinds of Lissajous figures under different plasma distribution modes are due to the current pulse durations and equivalent dielectric capacitances caused by plasma distributions acting together. The protrusions of Lissajous figures are caused by the current narrow pulses in the characteristics of separated-channel mode, while Lissajous figures under quasi-diffuse mode have no protrusions.

Control of Shock-Wave/Boundary-Layer Interaction Using Nanosecond-Pulsed Plasma Actuators

Nanosecond-pulsed surface dielectric barrier discharge plasma actuators are used to control shock-wave/boundary-layer interactions. Characterization of the separation region without plasma actuation is conducted to understand the interaction based on measurements of pressure distribution, schlieren imaging, and velocimetry by the femtosecond laser electronic excitation tagging technique. The results show a weak separation due to the interaction. Three types of plasma actuators are applied to control the separation. Schlieren images are taken by a high-speed camera to evaluate the magnitude of the interaction. It is shown that the plasma actuators affect the flow in two different ways: heat generation in the boundary layer, and generation of vorticity near the surface. When the first effect is dominant, the shock-wave/boundary-layer interaction becomes stronger and the size of the separation bubble increases. If the vorticity generation prevails, it suppresses the separation due to the momentum transfer from the main flow to the boundary layer. The experimental results of the three actuator’s geometries provide the design guidelines for nanosecond-pulse-driven electrodes to control the interaction. An optimal actuation frequency is found through an investigation of the frequency response of the flow.

Regeneration of Sooty Surface Using Nanosecond Pulsed Dielectric Barrier Discharge

In this paper, the regeneration of sooty surface by using nanosecond pulsed surface dielectric barrier discharge type reactor is investigated experimentally. The goal is to characterize the regeneration process as a function of the applied voltage magnitude and pulse polarity. The reactor is composed of two electrodes separated by a dielectric and are arranged asymmetrically. The power supply system provides high voltage pulses with the following characteristics: voltage up to ±10 kV; rise and decay time less than 50 ns; and a frequency of 2 kHz. The main results show that the regeneration performance increases with the applied voltage magnitude and the duration of treatment. Furthermore, depending on the polarity and the magnitude of the applied voltage pulse, the cleaned surface area can be either more uniform along the active electrode (negative pulses) or extended on the dielectric surface (positive pulses). The regeneration mechanism remains not very well understood, but it seems that the soot particle size is reduced mainly due to the interaction with ozone molecules and oxygen radicals generated by the discharge.

Investigation of the electrode surface geometry effects driven by nanosecond-pulsed surface dielectric barrier discharge

Nanosecond-pulsed surface dielectric barrier discharge (NS-DBD) plasma actuations with powered electrodes of different surface geometries were investigated numerically by solving the coupled plasma discharge equations, electron energy equations and the Navier–Stokes equations in quiescent air at atmospheric pressure. The plasma discharge characteristics and the air flow features were simulated numerically using a simple chemical kinetics plasma model for three powered electrodes with serrated, rectangular and semicircular surfaces, respectively. The results show that the reduced electric field of the serrated electrode is globally the strongest, while that of the rectangular electrode the second strongest, and that of the semicircular electrode the weakest. The maximum values of the reduced electric field, the mean electron energy and the electron density are found to occur immediately near the right upper tips of the powered electrodes, and the streamers of the mean electron energy and electron density in the serrated electrode case are larger in size and higher in value than in the rectangular and semicircular electrode cases. On the other hand, the pressure wave in the serrated electrode case is more intensive, and propagates slightly faster than in the other two electrode cases. Besides, the heated region in the serrated electrode case is greater with a higher temperature than in the other two electrode cases. The comparison results indicate that the performance of NS-DBD plasma actuators depends significantly on the powered electrode surface geometry, and the serrated surface design is a very promising means of flow control.