Ionic Wind Generator Research Articles

Experimental study of heat transfer enhancement with point-to-ring corona discharge

In this study, we experimentally inquire into the mechanism of the electric field for heat transfer enhancement by a point-to-ring corona gas discharge with either positive or negative applied voltage. We use a self-assembly 2D2C particle imaging velocimetry system to visualize and record the flow field. Results show that in our configuration the onset voltage of positive corona discharge is only slightly higher than that of the negative corona as a relatively large ring electrode is used. The current-voltage relationship follows Townsend's quadratic equation. The electrode distance has a slight effect on the current-voltage relationship. The time-averaged velocity demonstrates that the positive corona produces a faster and thinner jet compared to the negative one, and the region of the ionic wind is limited at low corona voltage. In addition, it is observed that the ionic wind can dramatically enhance heat transfer by ∼ 200%, and the enhancement effect of the positive discharge is more significant than that of the negative one. Furthermore, the proposed ionic wind generator has low power consumption, and therefore it is energy efficient.

Surface-charge control strategy for enhanced electrohydrodynamic force in dielectric barrier discharge plasma actuators

A relationship between electric potential distribution on a dielectric surface and electrohydrodynamic (EHD) force generation is experimentally investigated to improve the performance of dielectric-barrier-discharge (DBD) plasma actuators. Direct current (DC) biased repetitive pulses are applied to the DBD plasma actuator, which has two or three electrodes. Although the additional downstream exposed electrode has little effect on the electrical and optical characteristics of the DBD plasma actuator, the electric potential distribution strongly depends on the presence of the additional exposed electrode. Moreover, the saturation time of the surface charge is hundreds of milliseconds when the pulse repetition frequency is , showing a large difference in the time scale of surface DBD. We also demonstrated a significant improvement in the generation of ionic wind by adding an additional downstream exposed electrode owing to the prevention of the electric field screening. A concept that separates the ionization process and the acceleration process works properly for improving the performance of the DBD plasma actuators, but at the same time, the dynamics of the surface charge should be controlled so that a strong electric field is generated rather than the electric field being screened by surface charge.

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.

LED chip cooling system using ionic wind induced by multi-wire corona discharge

• A T-shaped multi-wire ionic wind pump is developed for cooling a high-power LED chip. • Relationship between air flow in the pump and its electrode configuration is revealed. • Increasing the wire-plate gap in the outlet channel strengthens the reverse discharge effect. • Arranging electrodes in the outlet channel further improves the performance of the T-shaped EHD pump. The high temperature of a light-emitting diode (LED) chip reduces its luminous output and lifetime and can even cause catastrophic damage to the chip. In recent years, ionic wind generators have shown great potential for LED chip cooling owing to their noiselessness, low energy consumption, and compact structure. However, the heat transfer and flow characteristics of ionic wind generated by multi-wire electrodes for LED cooling have not been sufficiently investigated. In this study, a T-shaped multi-wire ionic wind pump, in which each wire electrode corresponds to a pair of parallel plates, was designed for heat dissipation of a 24 W high-power LED chip. The relationship between the air flow characteristics inside the ionic wind pump and the electrode configuration was revealed through numerical simulations. Then, an optimized ionic wind pump was fabricated to test the cooling performance of the LED chip. The results show that each pair of plate electrodes has a critical length, and the average velocity at the pump inlet becomes independent of the plate length when it exceeds this critical value. For fixed wire electrodes in the outlet channel, when their operating voltage remains constant, increasing the wire-plate distance reduces the charge density around these wires, thus strengthening the reverse discharge effect and reducing the average velocity at the pump inlet. When only the wire in the inlet channel discharges electricity at a fixed voltage of 18 kV, the ionic wind pump can stabilize the LED case temperature below its safe temperature (LED operating voltage: 36 V). If all wires discharge electricity at a fixed voltage of 18 kV, the LED case temperature can be further reduced to 74 °C, which is lower than the maximum rated case temperature of 85 °C. In conclusion, when designing multi-wire ionic wind pumps, the electrodes inside them should be elaborately configured to reduce mutual interference and maximize the ionic wind flow rate. The designed ionic wind pump can serve as a noiseless thermal management equipment for high-power LED illumination devices.

Plasma-jet sterilization enhanced by ion wind

This work demonstrates that a needle-ring discharge device combined with an ion-wind generator can realize a plasma-jet system of self-inlet gas, replacing huge, unportable carrier-gas systems. First, a needle-ring atmospheric-pressure plasma-jet device is designed and manufactured. The effects of a dielectric tube and the discharge voltage on the jet characteristics are analyzed. The results show that a needle-ring discharge device with a dielectric tube can produce a long, stable plasma jet under a high DC applied voltage. Second, such a device and a 10-stage ion-wind device are combined into an integrated device, and the discharge characteristics are studied. The results show that an ion wind with a speed of 2.62 m/s can be generated when a DC voltage of −13 kV is applied to the ion-wind device. The plasma jet produced by the integrated device is longer and brighter when the ion wind is included. Finally, the ion wind is found to enhance the sterilization effect of the jet and greatly increase the sterilization range.

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.

Influence of dielectric thickness and electrode structure on the ion wind generation by micro fabricated plasma actuators

Surface dielectric barrier discharges are investigated in order to explore the combined effects of barrier thickness and microstructure of the exposed electrode on the ion wind generation. Actuators with straight and structured high voltage electrodes with characteristic sizes of 200 and 250 µm and dielectric thicknesses of 0.5, 1 and 2 mm are compared. It is observed that: i) actuator efficiency of ion wind generation strongly depends on the applied voltage amplitude; ii) operation voltage depends on the dielectric thickness logarithmically; iii) electrode microstructure slightly increases the dynamic pressure (few percent in maximum), however the effect decreases with thicker dielectrics and smaller electrode structures; iv) the pattern of the most intensive discharge parts as well as the dielectric erosion repeats the regular structure of the electrodes down to 200 µm. Several identical samples are tested during different days to estimate the impact of the air humidity and the degradation of the dielectric. The microscale precision of the sample manufacture was accomplished by a commercial facility for printed circuit boards.

Comparison of the generation characteristics and application performance of nanomaterials-enhanced ionic wind

Ionic wind technology is a right candidate for the thermal management of electronic devices. However, some highly-oxidizing substances are produced during corona discharge, which can destroy the electrode and shorten its service life. In the present work, nanomaterials were coated on the surfaces of needles, which act as emitting electrodes. The generation characteristics of ionic wind and the working durability of an ionic wind generator (IWG) were compared experimentally. The generator modified by nanomaterials was subsequently used to cool high-power LED chips, and the changes in the optical properties of the chips were studied. The results indicate that the electric field intensity and corona current increased after the application of the nanomaterials. The nanomaterials-decorated IWG performed better in operating durability than the original prototype. When the nanomaterials-decorated IWG was applied to cool LEDs, the case temperature at a discharge power of 3 W was reduced by 5.8 °C compared with the original generator. The luminous flux output increased by 28 lm and took less time to reach a stable working state. The ionic wind velocity and the energy conversion efficiency of the system were also greatly improved. This study provides a potential solution for the efficient thermal management of electronic devices.

Enhanced Cooling of LED Filament Bulbs Using an Embedded Tri-Needle/Ring Ionic Wind Device

Improving the heat dissipation ability for light-emitting diode (LED) filament bulb is very difficult. A tri-needle/ring ionic wind generator was developed to improve the heat dissipation condition of bulbs. The operation characteristics of the ionic wind generator, such as the electrode gap, inception voltage, and discharge current with regard to the operation voltage, were studied by experiments. The ionic wind velocity within the bulb was investigated under different electrode gaps and applied voltages. The temperature drop achieved by the ionic was were tested with the consideration of many operation parameters for analysis. The experiments showed that ionic wind can provide efficient and stable cooling effect for LED filament bulbs. The temperature drop of LED junction can reach 30 °C at best. Good stability and adjustability of the ionic wind generator were demonstrated by tracing the temperature history of LED filaments in long-term tests. Finally, the light efficiency of LED filament bulbs with ionic wind cooling was studied. The experimental results showed that light efficiency was improved by 7.3% under the best cooling case. The experimental results indicate that the embedded ionic wind generator can provide an effective solution for cooling LED filament bulbs.

침대 링형 구조에서 다단 가속전극 적용에 따른 이온풍 발생 특성

침대 링형 구조에서 다단 가속전극 적용에 따른 이온풍 발생 특성

유도 전극과 가속 전극의 형태와 조합에 따른 EHD 특성 연구

The electrodynamics(EHD) ionic wind cooling system is very efficient in cooling of electronics, compared to the standard cooling systems. However, standard ionic wind generator is only composed of a corona electrode and an induction electrode, to be limited in improving the ionic wind velocity. In order to improve the ionic wind velocity, we applied accelerating electrode to a conventional ionic wind generator. and investigated the effect of change in shapes of induction and accelerating electrode pairs. Applying accelerating (mesh or ring) electrodes to a shape of corona (needle) electrodes and induction (mesh or ring) electrodes in an ionic wind generator increase the ionic wind velocity according to application of voltage to the accelerating electrodes. Also, increase rate of ionic wind velocity was higher when the induction electrodes were rings and the accelerating electrodes were mesh.

스마트대전력 및 고전압기술] 가속전극의 적용에 따른 이온풍 발생 특성

Currently, the devices to generate ion winds in air are mainly composed of corona electrodes and induction(ground) electrodes, of which the corona electrodes mainly use needles or wires as electrodes and the induction electrodes use plate electrodes of ring or mesh type. Ion winds can be effectively generated through a diverse combination of corona electrodes and induction electrodes mentioned above. However, only changing the form and structure of corona electrodes and induction electrodes has a limit in raising the speed of ion winds. This paper conducted a study on the characteristics of ion wind generation by additionally installing acceleration electrodes in addition to corona electrodes and induction electrodes to increase the speed of ion winds.

Insights into the role of ionic wind in honeycomb electrostatic precipitators

Electrostatic precipitators (ESPs) separate particles from flue gas by corona discharge and accompany by the generation of ionic wind. In this work, a Computational Fluid Dynamics model was presented to investigate the effects of ionic wind on flow field and particle precipitation in a honeycomb ESP in terms of the coupled processes among corona discharge, gas flow, particle charging and transport. Results indicated that the electric field and ion charge density around the needle tips were highest and respectively reach 2.5 × 106 V/m and 0.164 C/m3 in the gas without suspended particles, which played a key role in corona-electrostatic field. The maximum velocity of ionic wind could reach 13.81, 11.74 and 9.42 m/s under the applied voltage of 27, 21 and 15 kV, and ionic wind velocity sharply decreased away from the needle tip. Meanwhile, the flow field could be divided into three regions (ionic wind affected region, vortex and back flow region) according to the direction of gas flow velocity. When the electrically neutral particles with a spherical shape were injected into ESP at the entrance, the charged particles were transported by drag force and electric force, and inhomogeneous distribution of the deposited particle has occurred because of ionic wind. More intense vortices were formed with the increase in applied voltage, and promoting the particle precipitation process. Moreover, higher applied voltage enhanced the aggregation of particles in the upstream, and reduced the dead zone of deposited particles in the downstream.

Successively accelerated ionic wind with integrated dielectric-barrier-discharge plasma actuator for low-voltage operation

Electrohydrodynamic (EHD) force is used for active control of fluid motion and for the generation of propulsive thrust by inducing ionic wind with no moving parts. We propose a method of successively generating and accelerating ionic wind induced by surface dielectric-barrier-discharge (DBD), referred to as a DBD plasma actuator with multiple electrodes. A conventional method fails to generate unidirectional ionic wind, due to the generation of a counter ionic-wind with the multiple electrodes DBD plasma actuator. However, unidirectional ionic wind can be obtained by designing an applied voltage waveform and electrode arrangement suitable for the unidirectional EHD force generation. Our results demonstrate that mutually enhanced EHD force is generated by using the multiple electrodes without generating counter ionic-wind and highlights the importance of controlling the dielectric surface charge to generate the strong ionic wind. The proposed method can induce strong ionic wind without a high-voltage power supply, which is typically expensive and heavy, and is suitable for equipping small unmanned aerial vehicles with a DBD plasma actuator for a drastic improvement in the aerodynamic performance.

Enhanced ionic wind generation by graphene for LED heat dissipation

Enhanced ionic wind generation by graphene for LED heat dissipation

Numerical and experimental study of heat-transfer characteristics of needle-to-ring-type ionic wind generator for heated-plate cooling

Ionic wind generators have shown significant application potential in devices for cooling, air actuation, and flow control. In this study, a needle-to-ring electrode ionic wind generator with optimized parameters was employed to cool a heated copper plate. A three-dimensional numerical simulation was conducted to obtain the electric, flow, and temperature fields of the ionic wind generator. To verify the ionic wind generator's capacity to cool the heated plate, an ionic wind generator prototype was fabricated and experimentally tested. The temperature distribution of the plate heated by a uniform distributed heat flux and non-uniform heat flux with a local hot spot was analyzed. Results show that the applied voltage should be less than the threshold voltage of spark discharge to ensure effective and stable operation of the ionic wind generator. When the plate is heated by a uniform heat flux, the temperature distribution in most areas around the center of the plate is relatively uniform. If a hot spot exists, the temperature of the central plate is higher than that of the surrounding areas, and the radial temperature difference gradually increases with the increase of the hot-spot heat flux. Moreover, the high-temperature area in the center of the plate gradually expands with increasing hot-spot radius. Besides, the increase in the copper plate thickness has little influence on the final temperature distribution. The heated plate with a uniform heat flux below 2 kW/m2 could be cooled to below 80 °C by the ionic wind generator at an applied voltage of 11 kV. When the plate is heated by a non-uniform heat flux with a hot spot, compared with the experimental results of natural convection, ionic wind can effectively reduce the temperature of the plate (a temperature drop of at least 45 °C was observed). This study provides a potential solution for commercial chip cooling with needle-to-ring-type ionic wind generators.

Numerical and experimental investigation on configuration optimization of the large-size ionic wind pump

An ionic wind pump is an energy-saving device that can produce a volume flow when electrodes are applied with high voltage. Compared to the traditional methods, ionic wind pumps possess the advantages of low energy consumption, no moving parts, compact structure and flexible design. In this study, a large-size ionic wind pump, consisting of many single regular hexagonal needle-ring ionic wind generators, was developed as the preliminary model. However, its experimental performance was not as good as our expectations. In order to improve this preliminary model, a simulation method was used to investigate the configuration factors of the single ionic wind pump. In the optimized model, mesh gap is 6 mm, eccentricity is 0.26, section area is 238.44 mm2 and needle electrode number is 3. In subsequent experiments, the final optimized large-size ionic wind pump showed a great promotion in velocity, and the maximum average velocity of the optimized pump was higher than the preliminary model by 13.3%. Our numerical simulation and experiment results have practical significance in designing ionic wind pumps.

Influencing Factors of Flow Field of Ionic Wind Induced by Corona Discharge in a Multi-Needle-to-Net Electrode Structure Under Direct-Current Voltage

The morphologies and velocity of ionic wind induced by direct-current (DC) corona discharge were experimentally measured. DC voltage was applied to short air gaps of high-voltage electrode-needle electrode and grounding electrode-net electrode to generate coronas, so as to allow the generation of ionic wind induced by corona discharge. The purpose of the study is to optimise the multi-needle-to-net electrode structure to improve the velocity of the ionic wind and keep it in a relatively stable state. For this purpose, the influences of various parameters on the velocity of the ionic wind were explored. The research results showed that the side length of meshes and the distribution mode of needles significantly affected the velocity of the ionic wind. The maximum velocity of the ionic wind, when the side length of meshes was 0.85 mm was 3 and 1.28 times those when the side lengths of the meshes were 2 and 0.425 mm, respectively. This indicated that there was an optimal side length that can maximise the velocity of the ionic wind. Increasing the number of needles and optimising the distribution mode of needles can effectively improve the velocity, that is, the improvement of the number and distribution uniformity of needles was conducive to increase the velocity of the ionic wind. Increasing the voltage amplitude can increase the velocity of the ionic wind, however, it was possible that noise was significant and in this case, the corresponding voltage cannot be considered as the working voltage of the ionic wind generator.

Dynamic responses of counterflow nonpremixed flames to AC electric field

Although ionic wind has been observed to play important roles in the effects of electric fields on flames, there is a lack of systematic quantification of ionic wind that allows interpretation of a flame's responses to electric fields. Here, we report on various responses of nonpremixed flames, such as the flame's dynamic responses and the generation of bidirectional ionic wind, in relation to the applied voltage and frequency of an alternating current (AC) in a counterflow burner. We find that although the Lorentz force acting on charged molecules initiates related effects, each effect is both complex and different. When the applied voltage is in the sub-saturated regime (small) as determined by the voltage-current behavior, flame movements and flow motion are minimally affected. However, when the applied voltage is in the saturated regime (large), flame oscillation occurs and a bidirectional ionic wind is generated that creates double-stagnation planes. The flame's oscillatory motion could be categorized in the transport-limited regime and in the oscillatory decaying regime, suggesting a strong dependence of the motion on the configuration of the burner. We also observed bidirectional ionic wind in visibly stable flames at higher AC frequencies. We present detailed explanations for flame behaviors, electric currents, and flow characteristics under various experimental conditions.

Electrohydrodynamic drying of multiple food products: Evaluating the potential of emitter-collector electrode configurations for upscaling

Electrohydrodynamic (EHD) drying is a promising, non-thermal drying technology, based on ionic wind generation between an emitter and a collector electrode. This simulation-based study evaluates impact of various emitter-collector configurations for EHD drying in order to assess their potential towards industrial upscaling. The conventional wire-to-plate configuration, which creates impinging flow, is found not to be an optimal solution for EHD drying of multiple food products in a fast and uniform way. With a single wire (emitter), it is found that the products placed more downstream dry slower due to the progressive loading of the air with water vapor. With multiple emitters, up to a threefold increase in drying time of the food products is found, compared to a single wire. This increase is caused by the recirculation of most air. To avoid water vapor accumulation in the drying zone, a wire-to-mesh configuration is proposed. The mesh collector minimizes interference of neighboring airflows and avoids recirculation of moist air in the drying zone. As such, the wire-to mesh configuration provides more uniform drying between adjacent products, but also within a product, as it can dry from all its surfaces. An increase in emitter density for the wire-to-mesh configuration leads to an overall increase in air speed, but, surprisingly, not to increased product drying rates. The reason is that the high-speed EHD airflow is always generated very locally in the vicinity of the emitter and collector. Thereby the convective drying process is not affected so much by the emitter density.