An ionic or electric wind is a bulk air movement induced by electrohydrodynamic (EHD) phenomena in a gas discharge. Because they are silent, low power, respond rapidly, and require no moving parts, ionic wind devices have been proposed for a wide range of applications, ranging from convection cooling and food drying to combustion management. The past several decades have seen the area grow tremendously leading to a number of new actuation strategies and devices that can be incorporated into various applications. In this review, we discuss the physics of ionic winds and recent developments of the past five years that have pushed the field forward, focusing on the development on bulk air-moving devices we term EHD pumps. We then highlight the ongoing challenges with transitioning ionic wind technologies to the market place, from issues that affect robustness to practical implementation, and point to areas where future research could have an impact on the field.

https://iopscience.iop.org/article/10.1088/1361-6595/aa88e7/pdf

Recent advances in electrohydrodynamic pumps operated by ionic winds: a review

Three-dimensional analysis of electrohydrodynamic flow in a spiked electrode-plate electrostatic precipitator

The application of the ionic wind in the fields of aerodynamic control and heat transfer is limited by its low velocity and small active area. This paper deals with the experimental and theoretical analysis of the ionic-wind velocity in serial-staged electrohydrodynamic gas pumps under a negative corona discharge in air. Each stage consists of a pair of needle array-to-ring or needle array-to-mesh electrodes. It was observed that the active area of the gas pump can be enlarged by using a needle array electrode where the negative corona discharge started simultaneously and that the needle array-to-mesh electrode can generate a higher ionic wind velocity compared to that of the needle array-to-ring electrode. The flow velocity of the ionic wind is dependent on both the number of serial stages and the pressure loss. A maximum average flow velocity of 7.39 m/s, volumetric flow rate of 140 L/min, and energy conversion efficiency of 0.8% were achieved experimentally in this paper.

The Velocity Characteristics of a Serial-Staged EHD Gas Pump in Air

Kilowatt-level narrow-linewidth SM ytterbium fiber laser operating in high-repetition-rate QCW regime was used to obtain 700 W average power at 532 nm with single-mode beam quality and wall-plug efficiency of over 23 %. To the best of our knowledge, this is ~60 % higher power than previously reported for single-mode green lasers based on other platforms, and also is ~30 % increase comparing to the previous result obtained by our group on the base of similar fiber laser platform. We have also experimentally proved that the same type of fiber laser can be used for generating of world-record levels of power at other wavelengths of visible and UV spectral ranges by employing cascaded non-linear frequency conversion. Thus, utilizing frequency tripling in 2 LBO crystals, we achieved over 160 W average power of nearly single-mode UV light at 355 nm with THG efficiency of more than 25 %. As far as we know, this is the highest output power ever reported for UV laser with nearly diffraction limited beam quality. We also conducted some preliminary experiments to demonstrate suitability of our approach for generating longer wavelengths of the visible spectrum. By pre-shifting fundamental emission wavelength in fiber Raman converter, followed by frequency doubling in NCPM LBO, we obtained average powers of 36 W at 589 nm and 27 W at 615 nm. These proof-of-concept experiments were performed with low-power pump laser and were not fully optimized with respect to frequency conversion. Our analysis indicates that employing kW-level QCW ytterbium laser with optimized SRS and SHG converters we can achieve hundreds of Watts of average power in red and orange color with single-mode beam quality.

High average power quasi-CW single-mode green and UV fiber lasers

In this paper, particle velocity fields inside three electrostatic precipitators (ESPs) are investigated experimentally using particle image velocimetry (PIV). The reference case is a typical wire-to-plane ESP under negative and positive dc high voltages. The two other ESPs use an ac high voltage to generate a dielectric barrier discharge (DBD) in wire-to-plane and plane-to-plane configurations. The main objective of this paper is to analyze the effect of the ionic wind on the particle collection efficiency in such systems. The high voltage magnitude and the frequency are the major parameters taken into account. With the wire-to-plane ESPs, PIV results show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and viscous forces. With this configuration, the particle trajectory is 3-D. In the case of the plane-to-plane ESP, a 2-D analysis of the time-averaged flow can be accepted. The time-averaged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of the ionic wind on the primary flow in such a configuration is negligible. The correlation between the electrohydrodynamic flow and the collection efficiency shows that increasing the ionic wind magnitude did not improve necessarily the electrostatic precipitation effectiveness of submicrometer particles, particularly using DBD precipitators.

EHD Flow and Collection Efficiency of a DBD ESP in Wire-to-Plane and Plane-to-Plane Configurations

EHD flow measured by 3D PIV in a narrow electrostatic precipitator with longitudinal-to-flow wire electrode and smooth or flocking grounded plane electrode

The increasing demands for miniaturization and better functionality of electronic components and devices have a significant effect on the requirements facing the printed circuit board (PCB) industry. PCB manufactures are driving for producing high density interconnect (HDI) boards at significantly reduced cost and reduced implementation time. The interconnection complexity of the PCB is still growing and today calls for 50/50 μm or 25/25 μm technology are real. Existing technologies are unable to offer acceptable solution. Recently the Laser Direct Imaging (LDI) technology is considered as an answer for these challenges. LDI is a process of imaging electric circuits directly on PCB without the use of a phototool or mask. Our laboratory system for Laser Direct Imaging is designed for tracks and spaces on PCB with minimum width distance of 50/50 μm. In comparison with conventional photolithography method, this technology is much better for 50/50 μm track and spaces. In our research we used photoresist with resolution 50 μm, but in case of using laser photoresists with better resolution (e.g. 25 μm) it will be possible to image tracks in super-fine-line technology (25/25 μm). The comparison between two technology of creating mosaic pattern tracks on PCB proved that laser imaging is promising technology in high density interconnects patterns, which are widely use in multilayered PCB and similar applications.

Laser direct imaging of tracks on PCR covered with laser photoresist

Ice accumulation on wind turbine blades due to the impact of supercooled water droplets can be reduced by the application of surfaces with anti-icing properties. Hydrophobic surfaces are considered as a promising solution because of their water repellent behavior. In recent years, short-pulsed laser technologies have been developed as an efficient technique to modify the surface properties of materials. However, the anti-icing properties of such surfaces have not yet been validated. In this work, a hybrid modification of polyester resin-based gelcoats was adopted. Laser patterning (LP) was used to produce periodic surface structures on modified unsaturated polyester resin (UPR) substrates. One of the innovations of this research is the utilization of novel purpose-made chemical modifiers for gelcoats. The implementation of linear polymethylhydrosiloxane (PMHS) as a building block is a key improvement in terms of durability and functionality of the coating, since there is an option of introducing not only groups bonding in the polyester into one molecule, but also groups that increase hydrophobicity. The other novelty is a successfully conducted experiment combining such chemical modification with laser texturization of the surface. The influence of the laser energy, pattern shape, and spatial periods on the topographical characteristics and hydrophobicity as well as the anti-icing properties of the produced surfaces were investigated. To characterize the surface topography of the produced structures, scanning electron microscopy (SEM) and profilometer were utilized. Measurements of the wettability parameters (static contact angle and contact angle hysteresis) on the treated surfaces allowed the identification of the influence of wetting behavior and laser parameters on the investigated materials. Anti-icing properties were characterized by ice adhesion (IA) and freezing delay time (FDT) tests. It was found that hybrid modification of unsaturated polyester resin by chemical modifiers and laser treatment increased the hydrophobic and anti-icing properties of polyester gelcoats.

/pdf/hydrophobic-and-anti-icing-behavior-of-uv-laser-treated-535ybcpva9.pdf

Hydrophobic and Anti-Icing Behavior of UV-Laser-Treated Polyester Resin-Based Gelcoats

The results of 3{dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) ∞ow patterns in a narrow electrostatic precipitator (ESP) are presented in this paper. The ESP was an acrylic parallelepiped with a wire discharge electrode and two plane collecting electrodes. In contrary to typical ESPs the wire electrode was placed along the gas ∞ow, in the ESP centre, in the halfway between collecting electrodes. Either two smooth stainless steel plates or two stainless steel meshes with nylon ∞ocks were used as the collecting electrodes. They were placed on the top and bottom of the ESP. The PIV measurements were carried out in two parallel planes, placed perpendicularly to the collecting electrodes and parallel to the wire electrode. The obtained results showed some similarities and difierences of a 3D particle ∞ow in the ESP with plate or ∞ocking electrodes.

https://www.imp.gda.pl/fileadmin/old_imp/struktura/o3/z3/093-CzechJPhys-2006.pdf

3D PIV measurements of the EHD flow patterns in a narrow lectrostatic precipitator with wire-plate or wire-flocking electrodes

A system for cooling electronic components where the liquid coolant flow is forced with ion-drag type EHD micropumps was tested. For tests we used isopropyl alcohol as the coolant and CSD02060 diodes in TO-220 packages as cooled electronic elements. We have studied thermal characteristics of diodes cooled with EHD flow in the function of a coolant flow rate. The transient thermal impedance of the CSD02060 diode cooled with 1.5 ml/min EHD flow was 7.8°C/W. Similar transient thermal impedance can be achieved by applying to the diode a large RAD-A6405A/150 heat sink. We found out that EHD pumps can be successfully applied for cooling electronic elements.

http://iopscience.iop.org/article/10.1088/1742-6596/494/1/012010/pdf

R. Barbucha

Papers

EHD flow measured by 3D PIV in a narrow electrostatic precipitator with longitudinal-to-flow wire electrode and smooth or flocking grounded plane electrode

Laser direct imaging of tracks on PCR covered with laser photoresist

Hydrophobic and Anti-Icing Behavior of UV-Laser-Treated Polyester Resin-Based Gelcoats

3D PIV measurements of the EHD flow patterns in a narrow lectrostatic precipitator with wire-plate or wire-flocking electrodes

A System for Cooling Electronic Elements with an EHD Coolant Flow