Ionic Wind Characteristics Research Articles

Study on the Influence of Central Hole Diameter in a Wire Mesh Electrode on Ionic Wind Characteristics.

Ionic wind, which is generated by a corona discharge, is a promising field that offers significant advantages by directly converting electrical energy into kinetic energy. Because of the electrical characteristics of ionic wind, most studies aiming to improve the performance of ionic wind generators have focused on modifying the geometry of electrode configurations. A mesh-type electrode is one of the electrodes used as a collecting electrode in an ionic wind generator. Using a mesh electrode results in decreased momentum of the ionic wind and increased pressure drop due to frictional loss of the flow. In this study, to minimize the reduction in momentum, a mesh electrode with a central hole was proposed and investigated. Experiments were conducted with the configuration of a needle and mesh with the central hole. These experiments analyzed the effect of the central hole diameter and the distance between the needle and the mesh electrodes on the electrical and physical characteristics of the ionic wind. The addition of the central hole led to a higher average velocity and lower current, thus resulting in increased energy conversion efficiency. The presented configuration offers a simple geometry without electrical and physical interference from complex configurations, and it is considered to have the potential to improve energy conversion efficiency and optimize ionic wind flow.

Physical mechanism of electrode coatings to suppress wire particle’s firefly motion under DC stress and selecting criterion for in situ applications

The Wire metal particles in gas-insulated equipment such as GIS (Gas-Insulated Substation) and GIL (Gas-Insulated transmission lines) under DC stress present a special firefly motion behaviour, namely a long-term levitation on the surface of conductors. However, the electrode coating, as a key device available to suppress the movement of particles, lacks of a theoretical basis as well as an effective selecting criterion to suppress wire particle’s firefly. In this paper, a test platform is established to obtain the charge dynamics and ionic wind characteristics of the wire particles on the coated electrodes. Experimental results illustrate that, the polarity alternation of wire particle charge due to the space charge accumulation near the wire particles as well as the ionic wind generated by the wire particles, is the key impact factor upon firefly motion. The coated electrodes will reduce the surface conduction current and thereby suppress the particle corona discharge, consequently suppressing the firefly motion by limiting the charge acquisition and ionic wind speed of the wire particles. Based on the above research, a selecting criterion of electrode coating material is further proposed. Electrode coatings is primarily expected to increase the corona onset voltage of the wire particles on the coating surface, so as to lower the ionic wind at the end of the particles less than 1 m s−1. Regarding the high voltage conductor, the coating material with relatively large conductivity is recommended, while for the grounded enclosure, the coating material with smaller conductivity is preferable as to constrain the particles adhere to the enclosure, thereby preventing the firefly motion of wire particle. Both the clarified physical mechanism and the proposed selecting criterion of electrode coating presents theoretical and quantitative guidance for DC GIL design from a specific point of view in suppressing the firefly motion.

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.

Effects of Magnetic Field Configuration on Ionic Wind Characteristics

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.

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.

Convective heat transfer enhancement of ionic wind under variable air pressures

Presently, limited studies are available in understanding the ionic wind's behaviour under restricted or extreme environmental conditions. Thus, this study aims to investigate ionic wind characteristics and its convective heat transfer enhancement under the influence of varying air pressures. Here, an ionic wind generated from a cone to mesh configuration was used. Results showed that the discharge current (which translates to power consumption) and velocity of the ionic wind behaved in opposing manners at pressures above and below atmospheric pressure. Increasing the pressure above the atmospheric pressure led to a decrease in velocity for both positive and negative ionic wind, while the wind velocity was relatively constant at air pressures below atmospheric pressure. On the other hand, the power consumption was also seen to be consistent for positive ionic wind, while the negative ionic wind showed a power consumption decline with increasing air pressure. The highest power consumption was observed for the negative ionic wind at the lowest air pressure. Further investigations on the convective heat transfer showed a maximum achievable enhancement of 17% over natural convection for both positive and negative ionic wind. The optimum performance, which is defined as the heat transfer enhancement ratio over power consumption of the ionic wind, was found to be at just beneath the atmospheric pressure at 0.9 bar for both positive and negative ionic wind, with the positive ionic wind superseding the efficiency of negative ionic wind by 17%.

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.

Separation Flow Control of a Generic Ground Vehicle Using an SDBD Plasma Actuator

Quiescent flow and wind tunnel tests were performed to gain additional physical insights into flow control for automotive aerodynamics using surface dielectric barrier discharge plasma actuators. First, the aerodynamic characteristics of ionic wind were studied, and a maximum induced velocity of 3.3 m/s was achieved at an excitation voltage of 17 kV. Then, the optimal installation position of the actuator and the influence of the excitation voltage on flow control at different wind speeds were studied. The conclusions drawn are as follows. The effect of flow control is better when the upper electrode of the actuator is placed at the end of the top surface, increasing the likelihood of the plasma generation region approaching the natural separation location. The pressure on top of the slanted surface is primarily affected by airflow acceleration at a low excitation voltage and by the decrease of the separation zone at a high excitation voltage. The maximum drag reduction can be realized when the maximum velocity of ionic wind reaches 1.71 m/s at a wind speed of 10 m/s and 2.54 m/s at a wind speed of 15 m/s. Moreover, effective drag reduction can be achieved only by continuing to optimize the actuator to generate considerable thrust at a high wind speed.

Control of boundary layer by ionic wind for heat transfer

In this study, local convection heat transfer technology was investigated using ionic wind. The characteristics of ionic wind using wire and plate electrodes are studied by experiment and numerical method. A particle image velocimetry (PIV) test was conducted in a wind tunnel to observe the flow behavior by the ionic wind on the heated surface. A new boundary layer was formed on the heated surface which was controlled by the ionic wind, regardless of the Reynolds number of bulk flow. The surface averaged heat transfer coefficient with the ionic wind increased by 11% at low Reynolds number (100–200) and decreased by 19% at high Reynolds number (2500–3500). It was also found that the zigzag type of wire arrangement enhanced the heat transfer coefficient by 40% compared with the single wire. It is thus concluded that ionic wind can be used for enhancing the convection heat transfer rate or insulating the local surface according to its operating condition.

Effects of magnetic field intensity on ionic wind characteristics

The characteristics of ionic wind under the magnetic field are studied by using a needle-to-mesh electrode. With the increasing of magnetic field intensity, the amplitude of Trichel pulse decreases and the pulse frequency increases significantly; the ionic wind speed clouds in the yOz plane shift from concentric circle to eccentric ellipse, and the ionic wind profiles along y-axis gradually transfer from a symmetrical distribution to a biased state; the maximum wind speed value and the corresponding electrical-to-kinetic energy conversion efficiency are also increased. These results illustrate that the magnetic field could adjust the ionic wind.

Experimental study of high power LEDs heat dissipation based on corona discharge

High power light-emitting diodes (LEDs) consume most of the applied power as heat, which leads to a high junction temperature; thus, an efficient cooling device is needed. Most of the developed cooling systems face constraints such as cost, consumption, and noise, leading to low work efficiency. In this study, a needle-to-net type ionic wind generator based on corona discharge is suggested for high power LED cooling. The LEDs' junction temperature was calculated by measuring the case temperature, which is called the pin-temperature measurement method. The characteristics of ionic wind in various electrode arrangements or electrical parameters were analyzed, and the case temperature changes induced by ionic wind were measured under various conditions for analysis. The experimental results indicate that the designed ionic wind generator had good cooling performance close to cooling fan, coupled with lower energy consumption and less mechanically induced noise. The maximum ionic wind velocity was measured to be 2.97m/s at a 15 mm discharge distance and 17 kV applied voltage.

Basic Study on Flow Control by Using Plasma Actuator

The airflow induced by corona discharge is called ionic wind, and it could be applied for flow control with its advantages of no moving parts and simple construction. This paper introduces ionic wind characteristics on a flat plate by discharge voltage of 5 kV.

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

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

Characteristics of ionic wind in needle-to-ring corona discharge

Abstract The characteristics of ionic wind of DC corona discharge are investigated in needle-to-ring configuration. The effects of the discharge parameters including the voltage polarity, the overvoltage and the electrode gap are studied experimentally. The results show that the ionic wind has a velocity of several m/s. The ionic wind in the center increases linearly with the overvoltage due to the larger Coulomb force obtained from the electric field and the slope of velocity–overvoltage plot depends on the electrode gap. The ionic wind in the positive corona has a larger velocity in the central part while the ionic wind in negative corona distributes more homogeneously. But the voltage polarity has little influence on the conductance of the discharge channel. A theoretical description is deduced from the basic physics and can express well the correlations between the ionic wind velocity and the discharge parameters.

The Characteristics of Ionic Wind and Its Effect on Electrostatic Precipitators

The ionic wind and turbulent flow field formed in a nonconservative electric force field have long been recognized to have a significant effect on an electrostatic precipitator (ESP). To simulate the flow field in an ESP, one should include the electric force term in the momentum equation. We considered the flow field in an ESP to be a turbulent flow and applied two- and three-dimensional models of k-e-A and k-e-E to close turbulence. The SIMPLE-C numerical scheme was applied to investigate the characteristics of the ionic wind and its influence on an ESP. The collecting efficiency of an ESP for a particle diameter of each grade was calculated to understand how the ionic wind interferes with the collecting efficiency. The results indicate that under normal operating conditions the effect of ionic wind is not pronounced. However, as the flow velocity becomes smaller, especially when the flow velocity is <0.6 m/s, the ionic wind becomes pronounced and has a significant influence on the flow field and the co...