Ion wind, also known as ionic wind, corona wind, or electric wind, is the airflow of charged particles induced by electrostatic forces linked to corona discharge arising at the tips of sharp conductors (such as points or blades) subjected to high voltage relative to ground. It is an electrohydrodynamic (EHD) phenomenon.
Mechanism
When a high voltage is applied between two asymmetric electrodes—one with a small radius of curvature (emitter) and one with a larger radius (collector)—the electric field concentrates around the sharp tip. When the electric field strength exceeds the corona discharge inception voltage, it ionizes the surrounding air molecules. The resulting ions, having the same polarity as the charged tip, are repelled and accelerated toward the collector. As these ions travel, they collide with neutral air molecules, transferring momentum and creating a bulk airflow known as ionic wind. A 2018 study found that electrons play a larger role than negative ions during the negative voltage period, leading to the suggestion that "electric wind" is a more accurate terminology than "ionic wind."
History
The earliest known report of electric wind was made by Francis Hauksbee, curator of instruments for the Royal Society of London, in 1709. In 1750, B. Wilson demonstrated the recoil force associated with corona discharge, a precursor to the ion thruster. Myron Robinson completed an extensive bibliography and literature review during the 1950s resurgence of interest in the phenomenon.
Applications
- Thermal management / Electronics cooling: Ionic wind generators are used for silent, compact, low-power cooling of LEDs, power chips, laptops, and other electronic devices. Heat transfer enhancements of 2 to 8 times compared with natural convection have been reported.
- Propulsion: In 2018, MIT researchers built and flew the first-ever solid-state plane (MIT EAD Airframe Version 2) propelled by ionic wind. Ionic thrusters can produce approximately 110 newtons of thrust per kilowatt, compared with a jet engine's 2 newtons per kilowatt.
- Food drying: Electrohydrodynamic drying uses ionic wind to dehydrate food products without heat damage.
- Flow control and drag reduction: Plasma actuators based on ionic wind are used to delay flow separation over aerodynamic surfaces, reducing drag.
- Electrostatic precipitation: Ionic wind influences particle collection in electrostatic precipitators.
Key characteristics
- Ionic wind velocities typically range from 1 to 10 m/s depending on electrode configuration and applied voltage.
- The phenomenon is silent, has no moving parts, responds rapidly, and consumes low power.
- Conversion efficiency from electrical to kinetic energy is typically in the range of 1–3%, though values up to 80% have been reported in specific configurations.
- Byproducts include ozone, which can be a health concern and limits some applications.
