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The aim of this work is to investigate the effects of magnetic field and ionic wind on the ability of a wire-plate electrostatic precipitator (ESP) to trap fine particles. A theoretical model of multi-field coupling between gas flow field, particle dynamic field and electromagnetic field was established, and a grid model was built by GAMBIT software. The collection efficiency under different gas velocities was calculated in FLUENT software where the electric field force and the magnetic field force were introduced by User Defined Function (UDF). The numerical results indicate that both ionic wind and applied magnetic field can effectively improve the PM2.5 collection efficiency in a wire-plate ESP, and the smaller the particle size, the more obvious the improving effects are. With the increase of gas velocity, PM2.5 collection efficiency has a nonlinear declining trend, but the contribution of ionic wind or magnetic field to the collection efficiency increases. The trapping performance of the wire-plate ESP under the combined action of the two factors is better than that of considering one of them separately. The research results can open up a new design idea and direction for the performance upgrading of the wire-plate ESP.

Measurements of height-dependent electric field (E) and neutral wind (u) are important governing parameters of the Earth's upper atmosphere, which can be used to study, for example, how auroral currents close or how energy flows between the ionized and neutral constituents. The new EISCAT 3D (E3D) incoherent scatter radar will be able to measure a three-dimensional ion velocity vector (v) at each measurement point, which will allow less stringent prior assumptions about E and u to be made when estimating them from radar measurements. This study investigates the feasibility of estimating the three-dimensional electric field and neutral wind vectors along a magnetic field-aligned profile from E3D measurements, using the ion momentum equation and Maxwell's equations. The uncertainty of ion drift measurements is estimated for a time and height resolution of 5 s and 2 km. With the most favourable ionospheric conditions, the ion wind at E region peak can be measured with an accuracy of less than 1 m/s. In the worst case, during a geomagnetically quiet night, the uncertainty increases by a factor of around 10. The uncertainty of neutral wind and electric field estimates is found to be strongly dependent on the prior constraints imposed on them. In the lower E region, neutral wind estimates have a lower standard deviation than 10 m/s in the most favourable conditions. In such conditions, also the F region electric field can be estimated with uncertainty of about 1 mV/m. Simulated measurements of v are used to demonstrate the ability to resolve the field-aligned profile of E and u. However, they can only be determined well at the heights where they dominate the ion drift, that is above 125 km for E and below 115 km for u. At the other heights, the results are strongly dependent on the prior assumptions of smoothness. Elektrisk felt (E) og nøytralvind (uladd vind, u) er viktige og styrende parametre i Jordas øvre atmosfære. Målinger av u eller E kan brukes til å undersøke f.eks. lukking av elektriske nordlysstrømmer eller hvordan energi overføres mellom ladde og uladde bestanddeler av atmosfæren. Med den nye inkoherente spredningsradaren EISCAT3D (E3D) vil det bli mulig å måle alle tre komponentene av ionehastigheta (v) i hvert målepunkt. Dermed blir det mulig å estimere E og u fra radarmålinger med mindre strenge begrensninger enn i dag. I artikkelen undersøkes mulighetene for å estimere tredimensjonale elektriske felt- og nøytralvindvektorer i en lengdeprofil langs magnetfeltet ved å bruke bevegelsesligninga for ioner og Maxwells ligninger. Vi estimerer usikkerheta i målinger av ionedrifta med oppløsning på 5 s i tid og 2 km i avstand for ulike tilstander i ionosfæren. De gunstigste betingelsene gir bedre nøyaktighet enn 1 m/s for ionevinden der E-laget er på sitt sterkeste. Det verste tilfellet, ei geomagnetisk rolig natt, gir usikkerheter som er ti ganger så store. Usikkerheta i estimatene av E eller u viste seg å være svært avhengige av begrensningene de ble påført. I det nedre E-laget estimeres usikkerheta i u til lavere enn 10 m/s for de gunstigste betingelsene. I så fall kan også det elektriske feltet i F-laget bestemmes med ei nøyaktighet rundt 1 mV/m. Simulerte målinger av v brukes til å vise hvordan man kan finne estimater på E og u i en lengdeprofil langs magnetfeltet. Det viser seg at de kun kan bestemmes skikkelig i høydeområdet der de påvirker ionebevegelsen mest, dvs. over 125 km for E og under 115 km for u. Ellers påvirkes resultatene veldig mye av hvor sterke begrensninger som er satt.

The kinetic energy transfer of ions in non-uniform electric field causes the flow of fluids called an ionic wind. This study investigates ionic wind velocity by the multi-stage configuration of corona discharge electrodes and installation of accelerating electrodes. Ionic wind velocity can be improved, independent of the increase in the applied voltage being limited by the breakdown voltage. The amount of ion generation is increased and overlapped by the multi-stage configuration that considers reverse ionization and the movement distance of ions. This study shows the shape of accelerating electrodes that minimize traps occurred during ion movement. Ultimately, the ionic wind velocity was improved by 142.3% and the energy efficiency was improved by 5.1 times compared to the single-stage ionic wind generator.

Conventional compression refrigeration systems generate considerable noise and vibration. The noise results in serious, negative impacts on people. Thermoelectric refrigeration technologies are considered a potential way to overcome these challenges. A novel thermoelectric refrigeration system, wherein thermoelectric chips are coupled with ionic wind fans, is proposed. Its performance was experimentally investigated and compared with theoretical results. The actual operating noise of the thermoelectric refrigeration system is only 4.2 dB(A), which is much lower than the maximum noise value that does not affect sleep. From experiments under different operating conditions, the optimal operating voltage of the thermoelectric chip is 5.5 V at 283.15 and 313.15 K on the cold and hot sides. The maximum coefficient of performance (COP) values reaches 0.28 and 0.31, which are equivalent to those of a system coupled with mechanical fans. Additionally, an ionic wind fan has an optimal operating voltage of 10.8 kV to maximize its air supply efficiency. Notably, such an operating voltage might be distinguished from the optimal voltage that achieves maximum operational performance for the new system. When the operating voltage of the thermoelectric chip is 5 V, the optimal operating voltage to obtain a maximum COP of 0.31 is 11.1 kV. Moreover, the experimental refrigeration capacity is greater than 8 W. The new system shows the ultra-quiet ability to operate at a large refrigeration capacity, and has good potential in applications, such as advanced refrigeration, building air-conditioning and ventilation systems.

Surface dielectric barrier discharges (SDBDs) at atmospheric pressure can be achieved by direct air discharge. It can produce reactive species without expensive vacuum chambers as well as generate the ionic wind to control the airflow or accelerate actuators. For the purpose of extending the discharge zone to satisfy the larger area treatment of materiel or enhance the electrohydrodynamic (EHD) force, an efficient way is to arrange several single modules of SDBDs in series. In this article, several kinds of SDBDs with different geometries and voltage polarities of multi-electrode are studied to investigate the discharge dynamical characteristics, such as the discharge uniformity, the streamer length, the number of streamers, and the EHD force during the discharge. The spatial distribution of the electric field (or potential gradient) established by the electrode array is crucial to determine the discharge behaviors.

Purpose This paper aims to investigate the effects of a dielectric barrier discharge (DBD) plasma actuator (PA) qualitatively on aerodynamic characteristics of a 3 D-printed NACA 4412 airfoil model. Design/methodology/approach Airflow visualization study was performed at a Reynolds number of 35,000 in a small-scale open-loop wind tunnel. The effect of plasma actuation on flow separation was compared for the DBD PA with four different electrode configurations at 10°, 20° and 30° angles of attack. Findings Plasma activation may delay the onset of flow separation up to 6° and decreases the boundary layer thickness. The effects of plasma diminish as the angle of attack increases. Streamwise electrode configuration, in which electric wind is produced in a direction perpendicular to the freestream, is more effective in the reattachment of the airflow compared to the spanwise electrode configuration, in which the electric wind and the free stream are in the same direction. Practical implications The Reynolds number is much smaller than that in cruise aircraft conditions; however, the results are promising for low-velocity subsonic airflows such as improving control capabilities of unmanned aerial vehicles. Originality/value Superior efficacy of spanwise-generated electric wind over streamwise-generated one is demonstrated at a very low Reynolds number. The results in the plasma aerodynamics literature can be reproduced using ultra-low-cost off-the-shelf components. This is important because high voltage power amplifiers that are frequently encountered in the literature may be prohibitively expensive especially for resource-limited university aerodynamics laboratories.

Effect of DC electric field on lean premixed biogas turbulent flame structure at low and medium turbulence intensity was studied experimentally using OH-PLIF. OH signal distribution, turbulent burn...

Technological processes of electro-gas dynamics of dispersed systems are based on charging and transporting dispersed raw material particles in a strong electric field of a corona discharge. It is accompanied by turbulent gas motion caused by momentum transfer of ions to gas molecules. This accompanying motion is called electric wind. It must be considered when calculating the trajectories of particles and devices design. In recent years, equipment is being developed, the operation of which is based on the direct use of electric wind. In most cases these studies are based on experimental research and empirical calculation formulas, therefore, to make the design and construction of this equipment science oriented, it is necessary to develop mathematical models and methods for calculating this phenomenon. The object of the research is a unipolar electric corona discharge of direct current between a negative corona wire and a flat electrode in the form of a mesh. The calculation of a turbulent jet of an electric wind is considered both within the framework of the boundary layer theory and in a full-scale formulation using the k- и k- turbulence models in the Comsol program. Two new solutions for the velocity field of a submerged flat jet of electric wind are found and compared. They are an analytical solution based on the boundary layer theory and a numerical solution in a full-scale formulation based on the Reynolds equation integration. The novelty of the solutions is that they are applied for a two-dimensional problem and consider the turbulent motion of gas. The phenomenon of electric wind is widely applied in modern technologies that allow electric and gas cleaning, disinfection, and water purification from organic impurities, as well as treatment and disinfection of surfaces and air which is especially important recently. In the case of jet spread of electric wind in a closed channel, the boundary layer approximation conditions are satisfied, and a self-similar solution can be used. In the case of an open jet, the calculation should be carried out in a full-scale formulation of the problem based on the numerical solution of the Reynolds equation.

Ionic wind has been widely used in the fields of flow control, heat cooling, thruster, and so on. In this work, an investigation of ionic wind under different magnetic field configurations is processed. By changing the position relationship between the electrode and the magnetic field, the magnetic field configuration in the discharge region is modified. With the injection of different magnetic field configurations to the discharge region, the amplitude of Trichel pulse is decreased, and the pulse frequency is increased. Besides, the ionic wind velocities’ distribution is deflected and the electrical-to-kinetic energy conversion efficiency is enhanced. The mechanism is analyzed by considering the movement path of particles in the ionization region and drift region under different magnetic field configurations. These results illustrate that the magnetic field configuration would be a method to adjust the direction and improve the electrical-to-kinetic energy conversion efficiency of ionic wind. This method provides a feasible way to regulate the performance of ionic wind without additional energy consumption.

Impinging gas jets can induce depressions in liquid surfaces, a phenomenon familiar to anyone who has observed the cavity produced by blowing air through a straw directly above a cup of juice. A dimple-like stable cavity on a liquid surface forms owing to the balance of forces among the gas jet impingement, gravity and surface tension1,2. With increasing gas jet speed, the cavity becomes unstable and shows oscillatory motion, bubbling (Rayleigh instability) and splashing (Kelvin-Helmholtz instability)3,4. However, despite its scientific and practical importance-particularly in regard to reducing cavity instability growth in certain gas-blown systems-little attention has been given to the hydrodynamic stability of a cavity in such gas-liquid systems so far. Here we demonstrate the stabilization of such instabilities by weakly ionized gas for the case of a gas jet impinging on water, based on shadowgraph experiments and computational two-phase fluid and plasma modelling. We focus on the interfacial dynamics relevant to electrohydrodynamic (EHD) gas flow, so-called electric wind, which is induced by the momentum transfer from accelerated charged particles to neutral gas under an electric field. A weakly ionized gas jet consisting of periodic pulsed ionization waves5, called plasma bullets, exerts more force via electrohydrodynamic flow on the water surface than a neutral gas jet alone, resulting in cavity expansion without destabilization. Furthermore, both the bidirectional electrohydrodynamic gas flow and electric field parallel to the gas-water interface produced by plasma interacting 'in the cavity' render the surface more stable. This case study demonstrates the dynamics of liquids subjected to a plasma-induced force, offering insights into physical processes and revealing an interdependence between weakly ionized gases and deformable dielectric matter, including plasma-liquid systems.

Electrostatic precipitators (ESPs), which remove particles from a flue gas by corona discharge, are widely used in industry. In this work, numerical investigations were carried out to explore the multi-physical characteristics of a wire-plate ESP with different collecting electrodes. By employing the COMSOL Multiphysics simulation tool, the multi-physical fields of ESPs were properly coupled. The effects of different types of collecting electrodes on electric filed, ionic wind, particle transport, and collection efficiency were investigated. The results show the ionic wind induced by corona discharge has a great influence on flow behaviors in ESP. In addition, simulation results indicate the existence of uneven collecting plates could have an impact of suppression on the flow near the plates, which would be beneficial for reducing the re-entrainment dust particles. Compared with C-type plate, the collection efficiency with triangle plate is found 6.87% higher for 5 μm particles, and 10.37% for 10 μm particles.

Breezes conjured at the flick of a switch could power aircraft, make vehicles more efficient and smooth our path to green energy, says Ben Skuse

Electric fields are useful for enhancing stability limits of flames, increasing the overall burning rate and reducing soot emissions. The electric body force has been known as a key element behind the aforementioned augmentation, and recent studies have provided clear picture for the resulted flow modification. In this study, we investigate the effects of pressure on an ionic wind by applying transverse electric fields to methane premixed jet flames in a pressurized chamber up to 2 atm. We investigated the voltage-current response by varying the pressure, the equivalence ratio of the mixture, and the flow rate. We found that the saturated current for lean and stoichiometric mixtures was not affected by the pressure, while the saturated current of rich premixed flames changed significantly. We developed a model to predict the voltage-current behavior and the ion-production rate, which we validated using experimental results. Based on our flow field measurements, we found that elevated pressure conditions enhanced ionic wind-driven mass transport. These results support the use of electric fields in a high-pressure environment.

In this research, a combination of reactive force field (ReaxFF) and electron force field (eFF) molecular dynamics (MD) simulations is constructed to reveal the fundamental mechanisms for the influence of the electric field on ethanol oxidation reactions at atomic and subatomic scales. In total, 21 ReaxFF MD simulations and 35 eFF MD simulations have been conducted. ReaxFF MD results indicate that the ethanol oxidation reaction is a two-stage process where the electric field plays varied roles in each stage. The first stage features the decomposition of ethanol molecules, in which the electric field influences the decomposition reaction rate by changing the kinetic energy of carbon-containing molecules/radicals on the order of 100–1000 kJ/mol and altering the molecular conformation and thereby the bond dissociation energy. At the second stage where oxygen molecules participate in the reaction, the electric field affects reactions by modifying the reaction pathways. The application of the eFF MD simulations, for the first time, extends our understanding of the electric field effects on ethanol oxidation reaction to subatomic scales. The results indicate that the electric field modifies the electron energy on the order of 10–100 kJ/mol. The present study also offers interpretation of previous findings on electric field effects on reaction pathways and fluorescence experimental observations, and provides support for both “ionic wind” and chemistry-driven hypotheses. This research provides unprecedented insight into reactions aided by the electric field, which potentially can facilitate the design of realistic field-assisted combustion systems.

Central recirculation zone (CRZ) is commonly formed in the near field of the injector exit by the vane swirler and used to stabilize the flame. In our experiment, a CRZ induced by the DBD plasma actuation was observed in the low swirl burner configuration for the first time, which clearly demonstrated that the mechanism of the combustion control by the plasma swirler is mainly through the aerodynamic effect. Three dielectric barrier discharge (DBD) actuators are placed in a circular array around the axis to generate ionic wind in the circumferential direction of the injector. Characteristics of the flow field have been measured using Laser Doppler Anemometry. It is found that a central recirculation zone with the shape of an ellipsoid is formed in the non-reacting flow field with the plasma actuation. The position of the upstream stagnation point was determined by the strength of the actuation. Although the CRZ disappears in the reacting flow field as the result of combustion heat release, the influence of the discharge on the flame lift-off height is noticeable. The results demonstrate that swirl enhancement by the plasma swirler is feasible, flexible and effective as a non-intrusive measure for flow control.

An experimental study of the velocity field in a three-electrode arrangement of a plasma-chemical surface dielectric barrier discharge (SDBD) reactor designed for plant seed’s treatment was carried out. The effect of polarity and magnitude of the extraction voltage (potential of the third electrode), configuration of the SDBD system (5- and 10-mm distances between the strips were observed) and the permeability for gas flow of the third electrode (in the form of a plate or a grid) on the magnitude of the extraction ion current, and induced gas flow structure were analyzed. It is shown that the most uniform flow in the direction of the third electrode, necessary for uniform seed treatment, is achieved in the case of a permeable third electrode under positive displacement potential, opposing a surface discharge electrodes with a distance between the strips much less than the gap dimensions (5 mm between the strips with 10 mm between the third electrode and the barrier surface).

In natural clouds, water droplets grow by condensation in a supersaturated environment. Under subsaturated conditions, water droplets normally keep evaporating until they eventually disappear. In this article, we study the effect of corona discharge on water droplet growth under both supersaturated and subsaturated conditions. It is shown that the formation of mist visible to the naked eyes could be induced by direct current (dc) corona discharge under supersaturated conditions. Furthermore, we find that corona discharge could promote the growth of water droplets even under subsaturated conditions. Possible mechanisms are discussed, and the results suggest that the droplet growth enhancement is supported by the synergetic effects of droplet surface charge, external electric field, and ionic wind generated by the corona discharge.

We have investigated experimentally the cooling of a heated plate playing the role of a grounded electrode by a narrow intense ionic wind jet produced by a needle electrode and directed along the normal at the plate center. For a fixed average temperature of the heater, we have obtained the dependence of the heat power removed with the wind on the electric power spent for sustaining the corona discharge for various interelectrode distances and voltages. It is shown that a small ionic wind jet can effectively cool a massive plate, removing up to 23 W of heat power for a spent electric power of up to 0.7 W. We have also studied experimentally the structure of ionic wind in the electrode system considered. A laser anemometry setup was used for visualizing the flow and for obtaining velocity distributions. The velocities in the central jet of ionic wind reached 8–9 m/s. The jet was narrower and faster for the positive polarity of the corona discharge. However, the efficiency of cooling for positive and negative polarities was approximately the same.

To satisfy the demand for thrust control on solid rocket motors and solid ramjet engines, numerical simulation of the effect of high-voltage electric fields on the combustion characteristics of polymethyl methacrylate (PMMA) under lateral inflow was undertaken. The mechanism of the effect of electric fields on the regression rate and mass flow rate of PMMA was analyzed. The results show that PMMA mass flow rate can increase by about 54% when subjected to positive voltages. The PMMA mass flow rate can not only increase by about 5.5% but also decrease by about 14% under the action of negative voltages. When the oxygen mass fraction is 54.5% at 0.101 MPa, the effect of electric fields on PMMA mass flow is weakened as the lateral velocity increases. When the inflow velocity is 1.95 m s−1 and oxygen mass fraction is 23.2%, the effect of electric fields on PMMA mass flow is decreased as the pressure rises. The effect of electric fields on PMMA regression rate is mainly due to the electric-field-induced volumetric body force. It will result in large-scale bulk flow movement, known as ionic wind, which changes the distribution of species and affects the heat of reaction, thus causing the changes in flame temperature, finally altering the thermal feedback to the solid phase.

The aim is to comprehensively and further explore the thawing characteristics and mechanism of frozen beef in high voltage electric field (HVEF). In this paper, the frozen beef was thawed under blocking ionic wind and changing voltage, electrode distance in the high voltage electric field system. The thawing characteristics, quality parameters and microstructure of beef during thawing were measured. The results showed that compared with the control, high voltage electric field could significantly shorten the thawing time of beef. During the thawing process, the influence of the high voltage electric field in the beef center temperature range from -5 °C to 0 °C on the thawing characteristics is larger than the control. Electrode distance and voltage have significant influence on color, loss rate and quality parameters. The experimental results of blocking ionic wind showed that ionic wind and non-uniform electric field have different effects on the characteristic parameters, quality parameters and microstructure of beef. Both the ionic wind and non-uniform electric field played a significant role in thawing process. This study provides theoretical basis and practical guidance for further understanding of the parameter characteristics and thawing mechanism of high voltage electric field thawing technology.

In this work, the effect of electrodynamic flow (EHD) on particle motion behavior is studied numerically on the basis of the single needle–plate electrode configuration. The interaction between primary–secondary flow and the trajectory of particles in a 3D environment is presented. In addition, the effects of the needle-shaped discharge electrode structure on the electric field and the flow field distribution are explored. Results show that the sharp surface of the needle tip causes high-intensity discharge that creates high-speed ion wind near this tip. The maximum velocity of the ionic wind can reach 9.028 m/s at applied voltage and inlet velocity of −60 kV and 1 m/s, respectively. This high-speed ion wind generated near the needle tip can increase the migration speed of particle. Moreover, the phenomenon that 90% of 1 µm particles penetrate the outlet surface indicates that the EHD flow negatively affects the capture of fine particles. The relationship among the injection position, residence time, and escape velocity of the particles further confirms that secondary flow seriously affects fine-particle capture. These results can help improve and optimize an electrode structure that reasonably uses high-speed ion wind to capture particles and prevent fine particles from escaping.