Electrohydrodynamic Air Research Articles

Electrohydrodynamic air amplifier for low-energy airflow generation—An experimental proof-of-concept

With electrohydrodynamics (EHD), we can propel air in a low-energy fashion. EHD airflow, or ionic wind, arises when a high voltage gradient is applied to a set of electrodes. The air ionizes between electrodes via corona discharge and accelerates in an electric field, exchanging momentum with the surrounding air. While the ionization process is energy-efficient, reaching competitive flow rates remains challenging from a high-voltage engineering perspective. To increase EHD-generated flow rates, this study experimentally investigates a novel concept called EHD air amplification. The concept uses ionic wind as bleed flow to induce a more significant bulk flow by the air-amplifying Coanda effect. Due to the complex interactions between EHD and dielectric structures for air amplification, the conceptual EHD air amplifier device is designed stage-wise, starting with a simple emitter-collector electrode configuration. First, regular EHD flow was studied in a 150 × 150 × 500 mm3 channel. Then, a dielectric material was added to determine its influence on the electric field. The impact of a converging nozzle on the EHD-generated airflow was subsequently studied. Lastly, the converged nozzle airflow was used to create a bleed flow on a plate to facilitate air amplification of the surrounding air. We show the proof-of-concept for an EHD air amplification system. After a voltage threshold of 14 kV, amplified airstreams up to an amplification factor of 3 were measured. Maximum airflow rates of about 15 m3 h−1 were obtained shortly before electric breakdown at 22 kV. Compared to regular EHD, we achieved a higher aerodynamic performance for the same electric energy invested. The flow rate to electric power ratio increased to 66% in EHD air amplification compared to regular EHD. The proposed EHD air amplifier operates at atmospheric pressure. It lays the groundwork for further optimization studies to position EHD air amplification as a low-energy, low-maintenance, motor- and noiseless airflow generation technology.

An in-silico proof-of-concept of electrohydrodynamic air amplifier for low-energy airflow generation

Electrohydrodynamic (EHD) technology generates airflow without moving parts, making it a reliable solution for various low-energy applications. EHD-based airflow devices enhance airflow patterns, resulting in significant energy savings in air-moving systems. This airflow, also known as ionic wind, is created through Corona discharge, which accelerates electrically charged air molecules in a strong electric field. Currently, EHD's low electrical-to-mechanical energy conversion rate still limit its ability to generate large flow rates. The objective of this study is to enhance the flow rate of EHD-based devices, for applications where EHD can be used as an effective auxiliary technology with low pressure lift, to enhance airflow distribution and circulation. To this end, a novel bladeless air propulsion device is proposed that combines ionic wind with air amplification based on the Coanda phenomenon to amplify EHD-generated flow rates. We assess the performance of the bladeless air propulsion device to generate airflow by investigating fluid dynamics, electrostatics, and energy consumption. We demonstrate the proof-of-concept with an innovative fully-coupled simulation approach for corona discharge and EHD modeling. We explore different design parameters on the conceptual EHD air amplifier, such as the electric potential (10–30 kV) of the discharge electrode, the electrode spacing (5–25 mm), and the channel height (30–150 mm). The studies are performed on a 2D constrained channel flow and a 2D-axisymmetric open space design, respectively. In order to quantify the benefit of air amplification on EHD, the results are benchmarked to a regular EHD setup without amplifying vane as well as to a comparable commercial axial fan. We assess the performance in terms of flow rate per electric power input. Here, the EHD air amplifier in the constrained flow configuration increases the total flow rate by 59% compared to regular EHD and 48% compared to the axial fan for the same electrical energy input. Amplification factors of 16.5–19 are achieved for the constrained configuration and 5.5 to 6.4 for the open space configuration. The predicted energy consumption is 4–17.5 W for the open space configuration, resulting in flow rates up to 140 m3 h−1. These results show that EHD air amplification is a promising way to generate high flow rates with low pressure rise at a low electrical cost, by which it can provide a more sustainable alternative to conventional fans in specific applications..

Analysis of electrohydrodynamic air flow induced by DC corona field in wire-to-plane electrode system

Method of the electrohydrodynamic (EHD) air flow induced by DC corona field calculation is proposed. Computation based upon the finite-element method is performed using Comsol Multiphysics commercial program. EHD air flow velocities field distribution in inter-electrode space is presented. Two-dimensional numerical model for computation of the air flow induced by corona field in wire-to-plane electrode system is presented. Results have been obtained using mathematical model and compared with experimental ones. Results analyses consist of EHD flow distribution in inter electrode space and integrated total flow dependence from corona electrode voltage. Comparison of corona discharge electric and air flow mechanic powers is presented.

Performance and flow characteristics of miniature EHD air blowers for thermal management applications

Electrohydrodynamic (EHD) air blowers are receiving increasing attention as a thermal management cooling solution to overcome the restrictions of traditional rotary cooling systems used in small-scale consumer electronics. In this work, the performance and flow pattern characteristics of miniature EHD air blowers are evaluated for practical convective heat transfer applications, based on device size, operating voltage and power, and generated flow rate. For a range of blower heights up to 10 mm, two-dimensional (2D) and three-dimensional (3D) numerical models of a wire-to-plane EHD channel configuration are developed and validated against previous experimental data. Investigation of the influence of blower sidewalls, based on width parameter, on flow characteristics reveals that the 2D simulations for short and wide blower domains are valid to predict the generated flow rates effectively compared to that obtained by the means of 3D simulations. An optimized combined EHD blower is developed as a flow-controlled cooling system in thermal management applications, which minimizes the required operating voltages for specified flow rates. Comparisons against commercial rotary blowers demonstrate that the miniature EHD blowers are more competitive as cooling solutions for compact applications and extended heated surfaces based on transduction efficiency, blower size, flow production of uniform velocity profile, and power consumption.

Numerical Analysis and Optimization of Miniature Electrohydrodynamic Air Blowers

As the demand for advanced microelectronic devices of small form factor and high power density has increased, the capability of the miniaturized mechanical solutions for effective cooling has become critical. Electrohydrodynamic (EHD) air blowers have great potential as alternative cooling solutions over the traditional mechanical systems to meet the thermal management requirements with flexible design and considerable flow production for effective heat removal. In this paper, a numerical analysis and optimization of wire-to-plane EHD air blowers are performed based on 2-D developed models validated against previous data. For a range of blower heights from 2 to 10 mm, the location and length of the collecting plane located at the blower walls apart from the emitter wire electrode are investigated and optimized based on pumping efficiency using the ranges of fixed operating powers and voltages. Simple relations for each optimization method are presented to determine the optimal blower configuration. Results of flow rate and static pressure obtained by each optimized blower show good agreement with those predicted by EHD scaling laws previously presented.

The effect of the electric wind on the spatial distribution of chemical species in the positive corona discharge

The electrohydrodynamic air flow generated by a positive corona discharge, and its effect on the spatial distribution of chemical species within a wire-plate corona reactor, have been numerically simulated. The computational model is based on the solutions of the Navier–Stokes equation and the continuity equation of each chemical species generated by the electrical discharge. A simplified analytical expression of the electric force density, which only requires the current density as the input parameter, has been used in the Navier–Stokes equation to obtain the velocity field. For the solution of the continuity equations, a plasma chemistry model that includes the most important reactions between electrons, atoms and molecules in air has been used. Similar to the electric force, the electron density distribution has been approximated by using a semi-analytical expression appropriate for the electrode geometry. The results of the study show that the spatial distribution of chemical species can be very different, and depends on the interplay between the electrohydrodynamic flow, the chemical kinetics of the species and its characteristic lifetime.

Numerical modelling of electrohydrodynamic airflow induced in a wire-to-grid channel

Electrohydrodynamic (EHD) airflows provide a means of generating air motion by a gas discharge across two electrodes without the need for moving parts. A two-dimensional numerical model for a wire-to-grid EHD air blower is developed, validated against previous data, and used to investigate the influence of key design parameters on blower efficiency, including the emitter wire diameter, the blower height, the locations of the collecting surfaces and grid wires, and the collecting grid density. The optimal locations of both collectors from the corona wire are determined based on blower efficiency at a fixed operating power, resulting in improvements in the average outlet velocity between 9% and 15%, depending on blower thickness. The presence of the grid has a strong influence on the electric field distribution and increases the blower performance, with higher flow, lower operating voltage and reduced blower size. An investigation into the effect of grid density reveals that using coarse collecting grids is generally beneficial, leading to higher efficiency with lower pressure losses.

Numerical Analysis of Electric Wind in Corona Field

Two-dimensional digital model for analysis of direct current corona field and induced electrohydrodynamic air flow field in wire-to-plane electrode system is presented. The model based on the finite-difference method in polar coordinate system for corona field computation is suitable to use in usual personal computers. Results of computation of current-voltage discharge characteristic are compared with experimental one. The digital model of electrohydrodynamic air flow field consists of finite-difference approximation of the Navier-Stokes equation and the continuity equation in Cartesian coordinates. Digital velocity values are checked experimentally. Ill. 10, bibl. 7 (in English; abstracts in English and Lithuanian). http://dx.doi.org/10.5755/j01.eee.116.10.871

Microfluidic blood plasma separation via bulk electrohydrodynamic flows.

An effective mechanism for rapid and efficient microfluidic particle trapping and concentration is proposed without requiring any mechanically moving parts. When a voltage beyond the threshold atmospheric ionization value is applied on a sharp electrode tip mounted at an angle above a microfluidic liquid chamber, the bulk electrohydrodynamic air thrust that is generated results in interfacial shear and, hence, primary azimuthal liquid surface recirculation. This discharge driven vortex mechanism, in turn, causes a secondary bulk meridional liquid recirculation, which produces an inward radial force near the bottom of the chamber. Particles suspended in the liquid are then rapidly convected by the bulk recirculation toward the bottom, where the inward radial force causes them to spiral in a helical swirl-like fashion toward a stagnation point. In particular, we show that these flows, similar to Batchelor flows occurring in a cylindrical liquid column between a stationary and rotating disk, can be used for the separation of red blood cells from blood plasma in a miniaturized device.

Computation of Electric Wind Parameters in Direct Current Corona Field

Digital model for analysis of two-dimensional direct current corona field and induced electrohydrodynamic air flow field in wire-to-plane electrode system is discussed. Finite-difference method in polar coordinate system is used for corona field computation. Results of computation of corona field are checked by comparison of digital and experimental data of current-voltage characteristics. Maximum difference of these values of linear current density is 150 µA/m corresponding to the voltage value of 7 kV. The digital model of EHD air flow field consists of finite-difference approximation of the Navier-Stokes equation and the continuity equation in Cartesian coordinates. Check of digital velocity values by comparison of these values with the experimental ones is only qualitative because of the distortion of corona field and air flow field by the probe of hot-wire anemometer. Ill. 6, bibl. 6 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.110.4.275