20.07.12

DARPA fights fire with loudspeakers

AUTHOR: Inavate

A US military agency is harnessing acoustic frequencies in a fire-fighting push after admitting that previous research into fire suppression techniques lacked innovation. The US Defense Advanced Research Project Agency (DARPA) has established that the technique can extinguish small flames with a demonstration shown in the following video. However, the agency concedes that it has doubts regarding real-world application.

DARPA embarked on the research in 2008 in response to concerns about the high cost and danger of fire in enclosed military environment such as ship holds, aircraft cockpits and ground vehicles. "For nearly 60 years, despite the severity of the threat from fire, no new methods for extinguishing or manipulating fire were developed," says the agency.

In a recent phase of the research acoustic fields were analysed and a pair of speakers were used to successfully extinguish a flame.

According to Darpa, the acoustic field increases air velocity which thins the flame boundary layer, where the combustion occurs, making it easier to disrupt the flame.

"Second, by disturbing the pool surface, the acoustic field leads to higher fuel vaporisation, which widens the flame, but also drops the overall flame temperature," continues DARPA.

"Combustion is disrupted as the same amount of same amount of heat is spread over a larger area. Essentially in this demonstration the performers used speakers to blast sound at specific frequencies that extinguish the flame."

Matthew Goodman, programme manager at DARPA, said: "We have shown that the physics of combustion still has surprises in store for us. Perhaps these results will spur new ideas and applications in combustion research."