Ionic Wind Velocity Research Articles

Ionic wind produced by volume corona discharges and surface dielectric barrier discharges: What role do streamers play?

The present study compares the ionic wind produced by volume DC and AC corona discharges, and by surface dielectric barrier discharges (DBD). On the one hand, in the case of a volume corona discharge ignited between a high-voltage needle and a grounded plate, our measurements highlight that the ionic wind velocity increases in the presence of positive breakdown streamers. On the other hand, in the case of a surface AC DBD, the ionic wind velocity decreases when streamers occur. Why such a difference? The answer is not easy and the debate remains open. However, one answer would be that the streamers occurring in a volume needle-to-plate discharge leave an abundance of positive ions in the inter-electrode space and that these ions drift because of the electric field, just after the streamer propagation. On the other hand, in the case of a surface DBD, the streamers can leave positive ions in their wake but their heads especially deposit positive ions at the location where they stop propagating, i.e. a few millimetres from the electrode (up to about 10–15 mm). Then this positive space charge deposited at a few millimetres from the active electrode edge on the dielectric surface acts as a screen against the electric field due to the applied high voltage, thus preventing the drift of the ions remaining on the surface of the dielectric, close to the electrode edge. Having said that, the reality is that this explanation is certainly very simplistic compared with the very complex phenomena taking place in these two discharges, particularly at the times when the streamers form and propagate.

Surface charge characteristics in a three-electrode surface dielectric barrier discharge

The surface charge characteristics in a three-electrode surface dielectric barrier discharge (SDBD) are experimentally investigated based on the Pockels effect of an electro-optical crystal. The actuator is based on the most commonly used SDBD structure for airflow control, with an exposed electrode supplied with sinusoidal AC high voltage, a grounded encapsulated electrode and an additional exposed electrode downstream supplied with DC voltage. The ionic wind velocity and thrust can be significantly improved by increasing DC voltage although the plasma discharge characteristics are virtually unaffected. It is found that the negative charges generated by the discharge of the three-electrode structure accumulate on the dielectric surface significantly further downstream in an AC period compared to the actuator with a two-electrode structure. The negative charges in the downstream region increase as the DC voltage increases. In addition, the DC voltage affects the time required for the positive charge filaments to decay. The positive DC voltage expands the ionic acceleration zone downstream to produce a greater EHD force. The amplitude of the DC voltage affects the electric field on the dielectric surface and is therefore a key factor in the formation of the EHD force. Further research on the surface charge characteristics of a three-electrode structure has been conducted using a pulse power to drive the discharge, and the same conclusions are drawn. This work demonstrates a link between surface charge characteristics and EHD performance of a three-electrode SDBD actuator.

Development and numerical optimization of a cylindrical wire-fin-type integrated ionic wind heat sink for cooling high-power LEDs

Light-emitting diodes (LEDs) are becoming increasingly high-power and compact, which makes rotary fans incompetent in some cooling situations. The ionic wind technique can compensate for the shortcomings of rotating fans, owing to its benefits of no moving parts and compact structure. Integrating the ionic wind generator with heat dissipation fins can effectively reduce the size of LED devices, but research in this area is still insufficient. In this study, an integrated ionic wind heat sink is designed for cooling LEDs. The multi-physical characteristics of discharge, flow, and heat transfer are numerically studied. The geometric parameters’ impact degree and mechanism on the multi-physical characteristics are analyzed. The performance optimization of the integrated heat sink is realized and verified. The fin length, flow channel center angle, and relative position of the fin have a large influence on the average velocity of ionic wind. The relative position of the wire electrode determines the electric field strength distribution, and it has the greatest influence on the ionic wind performance. The emitting electrode being placed at the inlet edge of the collecting electrode produces a high ionic wind flow rate. The integrated ionic wind heat sink designed in this study exhibits an outstanding cooling performance and temperature uniformity. This device can cool down the surface of a heat source with a power of 200 W to below 91 °C and make the average heat transfer coefficient reach 18.6 W/(m2·K). This study proposes a valuable method to optimize the integrated ionic wind heat sink for cooling high-power electronic devices.

Numerical investigation of the sensible heat storage in novel electrostatic precipitators with liquid-filled collection electrodes

Heat recovery from flue gas holds significant potential for energy conservation. A strategy is proposed for recovering and storing heat in electrostatic precipitators by utilizing liquid-filled collection electrodes. In the prototype, the hollow collection electrode is connected to the heat storage tank. Convective heat transfer occurs between the gas stream and the liquid contained in the collection electrode. The heat storage mechanism is revealed by numerical simulation of corona discharge, flow and heat transfer processes in a simplified electrostatic precipitator. The results indicate that both the gas-side and liquid-side heat transfer coefficients reach steady values within approximately 100 s. The buoyancy-driven liquid flow results in a heat transfer coefficient that is 28 times higher than that for gas-side forced convection. Increasing the gas inlet temperature leads to a greater buoyancy force and, consequently, a higher heat transfer coefficient on the liquid side. Both ionic wind and inlet velocity affect the gas-side heat transfer. The ionic wind disturbs the thermal boundary layer, leading to a 27.9 % increase in the gas-side heat transfer coefficient at an inlet velocity of 0.5 m/s. Furthermore, this enhancement becomes more pronounced as the inlet velocity decreases. The flow pattern of liquid in the collection electrode and heat storage tank is crucial to the heat storage process. Additionally, installing the heat storage tank above the electrostatic precipitator provides added benefits. During the process of heat storage, the largest heat resistance is found on the gas side.

Enhancing fine particle removal by electrostatic precipitation from flue gas with a high PM concentration: Effect of various electrode configurations

Particle pollution has hazardous effects on air quality and human health, especially fine particle. However, the highly efficient removal of fine particles is an unsolved problem in electrostatic precipitators (ESPs). In this study, a transparent ESP was designed to investigate the effect of fine particles on the corona discharge performance and the role of ionic wind in particle migration. And five types of typical discharge electrodes were applied. The results showed that the presence of fine particles could weaken the corona current produced by electrode discharge. Among these electrodes, the spike electrode can reduce the adverse effect of the particle space charge. The maximum ionic wind velocity around the electrode tips and within the near-plate region could reached 5.67 m/s and 5.00 m/s under an applied voltage of 30 kV, respectively. Combining the effects of corona discharge and ionic wind, the collection efficiencies of fine particles decreased in the following order: spike electrode (medium needle) > spike electrode (longest needle) > arista electrode > spike electrode (shortest needle) > sawtooth electrode. In general, spike electrode discharge has better performance for particle charging and particle collection efficiency and is suitable for fine particle removal in ESPs. In addition, electrode configuration/arrangement optimization methods were proposed to enhance fine particle removal in ESPs.

The heat dissipation by the multi-needle electrode structure ionic wind generator

Ionic wind generated by atmospheric pressure discharge can be used for propulsion, heat dissipation, food drying, which shows the unique advantages of no mechanical parts and fast response. However, the wind speed and the energy efficiency of ionic wind generator are very low, which limit its application. In this paper, an ionic wind generator, constructed with needle-net electrode structure and powered by high-voltage positive dielectric current (DC) power supply, is built for cooling of a metal oxide semiconductor field effect transistor (MOSFET). The energy efficiency and wind speed of the ionic wind generator are optimized by adjusting the electrode structure and applied voltage amplitude. The results show that when the discharge spacing is fixed at 10 mm and the optimal needle spacing is 17.5 mm with 6 needles at 14 kV, the ionic wind velocity can reach a maximum value 3.20 m s−1 and the energy efficiency is 1.90%. Under optimal experimental conditions, the heat dissipation performance of MOSFET is significantly enhanced compared to using only a heat sink. With cooling by the ionic wind generator, the MOSFET junction temperature can be lowered by about 29 °C after 240 s operation.

Ionic wind and ozone generation in a single magnetic fluid dielectric barrier discharge plasma actuator with different electrode configurations

Plasma actuators are compact wind power generators without mechanical power mechanisms. Plasma actuators have been investigated and developed. In a previous study of the authors, a single dielectric barrier discharge (DBD) plasma actuator using magnetic fluid (MF), termed “MF-DBD plasma actuator,” was proposed for application to fanless air purification devices that can collect low-resistive particulate matter, such as diesel particulate, by electrostatic force without re-entrainment. The fundamental characteristics of the MF-DBD plasma actuator, such as ionic wind, temperature distribution, and ozone and ion concentrations, were investigated in the previous study. The advantage of an MF-DBD plasma actuator is that the position and shape of the MF electrode can be controlled using a magnetic field. In view of this advantage, in this study, ionic wind and ozone generation in a single MF-DBD plasma actuator with different electrode configurations is investigated for the future development of MF-DBD plasma actuators and their application in fanless air purification. In these experiments, the width of the insulated electrode and the distance between the exposed and insulated electrodes are varied. As a result, in the case of a constant applied voltage, the ionic wind velocity and ozone concentration depend only on the overlap between the magnetic fluid and the insulated electrode, and these values increase as the overlap increases. It is clarified that a large overlap between the MF and insulated electrodes can generate an efficient ionic wind in terms of wind velocity and energy consumption.

Experimental and numerical study on transportation performance of ionic wind generator with distributed auxiliary heat source

Ionic wind technology can be used to achieve directional airflow transportation and local heat and mass transfer enhancement, which are suitable in the field of food drying. Ionic wind can be coupled with medium- and low-temperature heat sources to achieve collaborative heat and mass transfer while satisfying the requirements of efficient drying and maintaining food quality. However, the distributed heat source introduces ambient temperature gradients. Notably, different ambient temperature gradients of the generator exert obvious effects on the local molecular number as well as particle energy; this can affect the gas transportation performance of the generator, which has not been clarified thus far. Herein, the gas transportation performance of a wire-mesh ionic wind generator operating at different heat-source temperatures is experimentally and numerically investigated. The experimental results show that ionic wind generators operating at normal atmospheric temperature are more beneficial to obtaining a high mass flow rate and local velocity of ionic wind. Additionally, continuously increasing the heat source temperature can improve the transportation performance of ionic wind generators. In the simulation, an electrohydrodynamic (EHD) force is introduced to indicate ionic wind strength. The simulated EHD force reaches the highest value without a temperature difference between the two electrodes. The variation trend of the simulation results is consistent with that of the experimental results. The simulation results emphasize the combined effects of particle energy and air molecule number on ionic wind strength, which can explain the phenomena observed in the experiments. This study thus provides a theoretical guideline for the design and combined application of ionic wind generators and distributed auxiliary heat sources.

Experimental investigation of a new solar panels cleaning system using ionic wind produced by corona discharge

This paper aims to study a new solar panels cleaning device based on the ionic wind produced by corona discharge plasma. The device comprises a high-voltage electrode composed of a series of parallel sharp needles and a grounded frame electrode. The system is moved using two driven wheels fixed at its extremities, and is placed at a few millimetres above the solar panel surface at. The cleaning operation is done by moving the dust particles from the surface using the ionic wind coming out through a 5 mm-width opening located at the bottom of the device. The study was carried out by measuring the wind velocity and the cleaning efficiency as a function of the device movement speed and the applied voltage level. The results obtained using Algerian Sahara sand dust allowed to obtain an ionic wind velocity of about 2 m/s and a cleaning efficiency that reaches 95% with a consumed power of about 20 W.

Ionic wind generation through coplanar discharge: A plasma actuator without exposed electrodes

This study demonstrates the successful induction of a unidirectional ionic wind by adding an embedded electrode in a coplanar discharge, thus breaking the generation of a symmetrical electric field. The strategy for the ionic wind generation is based on separating the ionization process and the charged-particle acceleration process. Conventional plasma actuators used to induce an ionic wind typically incorporate exposed electrodes that pose a risk of unexpected airflow disturbance and reduce durability due to oxidation. However, the coplanar discharge-based, exposed-electrodeless plasma actuator developed in this study overcomes these issues. The coplanar discharge generates a diffused and uniform surface discharge, a desirable attribute for plasma actuators. The ionic wind velocity generated by this coplanar discharge plasma actuator is comparable to that generated by conventional plasma actuators when applying a square-waveform bias voltage to the additional electrode. Furthermore, this study emphasizes the significance of the phase difference between the repetitive pulses for generating coplanar discharge and the square-waveform voltage for accelerating the charged particles.

Ionic wind velocity and energy efficiency improvement in needle-net ionic wind generator by electrical field optimization

Ionic wind produced by high voltage discharge has been proved as a promising technique in heat dissipation, food drying, electrostatic precipitation and air propulsion. On the other hand, the low wind velocity and the low energy efficiency of the ionic wind generators limit their performance in practical industrial applications. To improve this, a single needle-net electrode structure ionic wind generator driven by positive DC voltage is constructed and the effects of the applied voltage and electrode structure on the discharge characteristics and the converting efficiency from electric energy to kinetic energy have been investigated. The results show that with the increase of the applied voltage from 4 kV to 11 kV, the discharge shows four stages, burst pulse, streamer corona, glow corona and spark discharge, and the wind velocity increases monotonously and reach 1.90 m/s at 11 kV. At the same applied voltage, the shorter needle-net distance leads to the larger wind velocity. At 15 mm needle-net distance, the needle-net electrode structure ionic wind generator shows a maximum energy efficiency value of 2.19%. A metal circular plate is attached on the needle electrode to change the spatial electric field distribution, increase the field intensity of the discharge gap, and promote the particle collision. It is found that the wind velocity and energy efficiency can be improved from 1.90 m/s to 2.35 m/s, and 1.87% to 3.14%, at same applied voltage and needle-net distance. The cooling experiment shows that the ionic wind generator with metal circular plate needle-net electrode has better heat dissipation effect.

IONIC WIND FLOW CHARACTERISTICS OF A MAGNETIC-FIELD-ENHANCED SOLID-STATE FAN AND ITS PERFORMANCE IN LIGHT-EMITTING DIODE COOLING APPLICATIONS

Solid-state fans (SSFs) have distinct advantages over traditional cooling fans in the thermal management of high-power electronics. In this work, a magnetic-field-enhanced SSF is proposed, and the physical model of negative corona discharge superimposed by an electromagnetic field is established. A computational model is used to calculate and analyze the effect of the magnetic field on the ionic wind distribution. The magnetic flux density and permanent magnet position distribution in the SSF are optimized experimentally, and the optimized SSF is applied to LED chip cooling. The findings show that adding a magnetic field encourages electrons to collide with neutral gas molecules and enhances the driving force of charged particles. The ionic wind velocity and mean driving force at the SSF's outlet will grow as magnetic flux density rises, and the ionic wind flow distribution will show apparent divergence. When the permanent magnet spacing is 15 mm, the highest ionic wind velocity is 2.82 m/s, and the mean driving force of SSF increases by 30.2%. The magnetic-field-enhanced SSF has a better LED-chip cooling effect, the maximum junction temperature drop is 11.6°C, and the cooling efficiency is higher. This research introduces a novel way of improving the cooling of electronics.

Ionic Wind Driven Fog Collection in Windless Environment

Fog collection is a promising technique to harvest water from the atmosphere. However, the fog collection in the windless environment is still a challenge. An ionic wind-driven fog collector was numerically designed. Numerical results demonstrated that the discharge electrode location significantly influenced the ionic wind flow pattern and fog collection rate. The fog collection rate corresponding to a nearly unidirectional flow pattern was several times of that corresponding to the vortices dominant flow pattern. An enhancement of 6.7 times in the fog collection rate was realized by increasing the input power. The fog collection rate increased linearly with the liquid water content under a fixed power consumption. A fog collector prototype was fabricated. The measured ionic wind velocity and fog collection rate supported the numerical design. In a windless foggy environment with a liquid water content of 0.62 g m–3, a collection rate of 0.46 L h–1 was achieved.

Enhancement of thrust force of an atmospheric pressure positive corona discharge by DC superimposed AC high voltage

The ability of corona discharge as an electrohydrodynamic propulsion system has been considered by many physicists and aerospace researchers. The results show that the most important factor in increasing the thrust force and thrust effectiveness is increasing the momentum transmission frequency in other words reduction of ion mobility that leads to a reduction of the average velocity. By configuring the wire-cylinder in atmospheric conditions, in an experimental study, using a new strategy in generating corona discharge, and without changing the system configuration, the thrust force is increased by increased of exciting species and reducing the ion mobility. DC superimposed AC (AC-DC) voltage source was utilized to achieve higher thrust force efficiency. Results show that the thrust force generated by the AC-DC source is increased by 4–2 times, with the applied voltage range of 10–20 kV compared to the DC source, respectively; while the thrust effectiveness has also been increased. A theory is introduced to calculate the thrust force due to ionic wind generation in the corona discharge regime. Accordingly, a relation is obtained for calculating thrust force and ion mobility using the average vertical ionic wind velocity on the side of the grounded electrode to support experimental results.

음의 가속전계 형성에 따른 이온풍 추력 특성

This study is a basic research on the ionic wind propulsion technique, and the thrust characteristics of the ionic wind propulsion device of a two-stage series structure with an acceleration electrode applied with a negative voltage are studied based on various theoretical equations suggested in previous studies. Experimental results show that the current measured at the acceleration electrode increased as the amount of corona current decreased as the negative voltage applied to the accelerating electrode increased. The ionic wind velocity increased as the negative voltage applied to the acceleration electrode increased, and the thrust increased by up to 72.9%. In the condition of the applied voltage with the maximum thrust, the thrust efficiency decreased rapidly, but the kinetic energy efficiency decreased less.

Study on vehicle drag reduction simulation based on Suzen–Huang model

In the past numerical simulation of plasma and fluid coupling, the usually used Suzen numerical simulation model has the defect that the error increases with the increase in excitation voltage. The static test of the ionic wind is used to modify the parameters of the Suzen simulation model, and it applied the modified Suzen model to the flow control of the automobile external flow field, which shows good consistency with the wind tunnel test results. Results show that the Suzen model modified by the static test results of the ionic wind is suitable for different excitation voltage conditions. The corrected body force and charge density distribution conform to the change trend of plasma discharge, and the error between the maximum ionic wind velocity obtained by simulation and the test result is within 4%; the modified Suzen model is successfully applied to the plasma flow control of automobile aerodynamic drag reduction. The results show that the exciter suppresses the generation of periodic separation vortices in the tail of the model, which makes the vorticity in the wake significantly decrease, thereby reducing the energy dissipation and the aerodynamic drag of the model. Through the research in this paper, the modified Suzen model reduces the simulation error. Plasma flow control technology is applied to the field of automobile aerodynamic drag reduction, which has accumulated important experience methods and data foundation for the engineering application of this technology. It also provides new methods for improving vehicle aerodynamic performance and fuel economy.

Magnetic field enhanced ionic wind for environment-friendly improvement and thermal management application

High heat flux electronics have encountered difficulties in thermal management. There are some shortcomings in traditional cooling methods. Ionic wind cooling technology based on electrohydrodynamic (EHD) has unique advantages. There are by-product hazards and speed raising limits in the reported ionic wind generators. An electromagnetic field and nanomaterials improved ionic wind cooling system is designed for environment-friendly improvement and thermal management application. The proposed cooling system is optimized experimentally to increase the ionic wind intensity and reduce ozone generation. The results indicate that adding a magnetic field changes the movement trajectory of charged particles and thus regulates the distribution of the flow field. In the macroscopic sense, the ionic wind intensity is also improved, and the greater the magnetic flux density is, the more obvious the effect is. A maximal improvement of 58.6% was obtained. The ionic wind velocity increases by 0.71 m/s due to the synergistic effect of a magnetic field. Meanwhile, the O3 concentration decreased by more than 95% using both the magnetic field and the carbon nanotubes. When the cooling system is applied to a high-power light-emitting diode (LED) chip for thermal management, the cooling effect is remarkable. The results provide an important theoretical basis for the application of EHD technology in the thermal management of electronic devices.

Experimental investigation on flow characteristics of ionic wind induced by wire electrode

ABSTRACT The idea of applying ionic wind cooling technology without moving parts to portable electronic devices is becoming a reality. In this study, the wire-wire type and wire-mesh type ionic wind generators reported in a few references are investigated while copper wire is used as the emitter electrode. The flow characteristics of ionic wind are qualitatively described under a variety of structural parameters, and quantitatively analyzed by calculating the correlations defining relationships between flow field and electric field. The results of u-V relation indicate that the square of the ionic wind velocity is proportional to the voltage. Moreover, the optimal parameters of single-stage generators are presented, such as electrode gap, electrode angle, electrode polarity, wind velocity and efficiency. Finally, the results of multi-stage structures with wire-mesh electrode show that superimposing multi-stage electrode pairs can enhance the wind velocity and the three-stage structure is optimal with a velocity increase of 26.8% over the single-stage structure, but the practicality will be limited due to low efficiency.

Heat dissipation of electronic components by ionic wind from multi-needle electrodes discharge: Experimental and multi-physical analysis

High temperature during electronic components operation can cause the failure of PN junctions of chips, and it can even damage the entire component. Ionic wind is a promising technique for heat dissipation due to its noiseless, compact structure and flexible design. In this study, needle-ring-type ionic wind devices with multi-needle electrodes connected in parallel are developed for cooling an electronic component. The effects of the number of needles, needle electrode material (tungsten and stainless steel), inter-electrode distance on the device output velocity and cooling performance are experimentally studied for a cylindrical heat sink mounted with a heating film. A full three-dimensional multi-physical numerical method, in which the coupled effects of the electric field, air flow, and heat transfer are considered, is also established. Mutual interference of the electric fields is identified between needle electrodes. The ionic wind velocity is determined by electric field strength and the angle between the ring axis and the line that connects the needle tip and the upper edge of the ring. The wind velocity first decreases and then increases with continuously increasing inter-electrode distance. Although the electrode material has an obvious effect on the ionic wind velocity of the free flow state, the heating film surface temperature is not sensitive to the needle material, whereas it is sensitive to the inter-electrode distance and the number of needles. The output wind velocity of the four-needle layout is larger than that of the three-needle layout despite backflow inside the ring. The heating film surface temperature is below 55 °C for the two designed electrode layouts, which is lower than the safety temperature of 70 °C. This study can serve as a guideline for developing multi-electrode ionic wind cooling systems.

Study on the electrical response of small ethanol‐air diffusion flame under the uniform electric field

Ethanol is a renewable alternative fuel in many application areas. The external electric field is applied to assist the small ethanol diffusion flame in this study. The electrical response of flame under the uniform electric field is discussed. A reduced chemical mechanism of ethanol is used to establish a numerical model corresponding to the experimental system. The characteristics of current-electric field strength, equivalent resistance, distribution of charged species, velocity field, and reaction rate are studied. The results show that the electric field brings significant effects on the combustion and electrical characteristics of flame. As the electric field strength increases, the current through the circuit and the equivalent resistance of the flame show a three-stage variation. The current increases first (0-40 kV/m), then stabilizes (40-70 kV/m) and then continues to increase (70-100 kV/m) with the increase of the electric field strength. It shows that the flame has certain electric resistance characteristic. The number density of charged species in the flame increases, and the distributions of charged species tend to move upstream by the effect of electric field. When the electric field strength is high as 100 kV/m, the charged species density increases by 10%. Meantime, the gas velocity near the flame front is accelerated and the chemical reaction rate also increases by the effect of electric field. When the electric field strength reaches 100 kV/m, the corresponding reaction rate and the corresponding flow velocity are increased by about 40% and 20%, respectively, compared with those without electric field. The calculated ionic wind velocity increases greatly with the electric field strength and shows a nearly linear increasing trend. The combined effects of the enhanced ionic wind effect, the intensified chemi-ionization process, and the increase of the concentration of charged species are considered as the main reason for the effect of electric field.