Scientists at GE Global Research are experimenting with thin jets of air to reduce turbulence along aircraft wings and wind turbine blades, and to improve efficiency. They are using devices the size of two stacked credit cards to speed up air that naturally slows down due to surface friction. Just a small decrease in drag could save millions of dollars for airlines alone.
The devices, called synthetic jet actuators (SJAs), have no moving parts and work like tiny bellows. They generate rapid pumping and sucking by applying electrical current across pieces of special ceramic material attached to the sides of two nickel plates separated in the middle by a narrow space. Electricity makes the ceramic vibrate slightly and the vibrations cause the gap between the plates to pull in and push out jets of air.
“This device works like our lungs, by expanding and contracting a chamber in such a way that air is sucked in and ejected through a single hole,” says Seyed Saddoughi, principal engineer in GE’s Aero-Thermal & Mechanical Systems lab. Saddoughi, who is leading the actuator’s development, says that devices eliminate the need for fans with moving parts. “The device is lightweight, very simple in operation, and with minimal power usage.”
Because of its low energy use, powerful air jet and silent operation, a version of the device is already beginning to be used for cooling consumer electronics and computers.
But Saddoughi says SJAs will realize their potential when rows of them start getting embedded in aircraft wings and turbine blades. His research team has also been running experiments with another version that can operate in water. Their experiments have shown that pumping high-powered water jets against the surface of boat hulls can change hydrodynamic flow and decrease drag.
“These devices energize the flow close to surfaces to reduce losses and increase the overall efficiency of the machines,” he says. “Synthetic jet actuators give us active control of flow over these surfaces. We can manipulate flow intelligently to gain better performance from our machines.”
Seyed Saddoughi inspects one of his creations, a propeller using miniature piezoelectric bellows designed to generate an air jet that can spin the arm attached to the device up 1,000 rotations per minute.