DARPA Creates Fire Extinguisher Made of Sound
Firefighting technology hasn't changed much in recent history and fire in enclosed areas can cause a lot of damage and potentially threaten lives. Now, the Defense Advanced Research Projects Agency (DARPA) - the innovations arm of the U.S. Department of Defense - has pioneered a new way to extinguish flames using sound.
As part of its Instant Fire Suppression initiative, the agency tested the ability to approach extinguishing fire from a physics standpoint, instead of trying to disrupt chemical combustion, which is how water puts out a fire. From a physics perspective, flames are cold plasmas. DARPA theorized that by using physics techniques rather than combustion chemistry, it might be possible to manipulate and extinguish flames, reports IT World. They successfully use a sound wall blasting at a specific frequency to put out a fire by placing speakers on either side of the fuel feeding a flame.
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The acoustic field increases air velocity, which thins out the flame boundary layer where combustion occurs. The sound disrupts the flame as well as the surface of the pool of fuel, resulting in a wider flame and higher fuel vaporization. It also drops the overall temperature of the fire. As the same amount of fire spreads over a larger area, the flame fizzles out.
"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," said DARPA program manager Matthew Goodman, according to Phys.org.
They also tested electrodes as potential fire extinguishers. A handheld electrode, which could be useful in containing small methan and liquid fuel fires, can be swept across a burner with flames spewing out and will extinguish the gas flame. The oscillating field produced by the electrode creates a rapid series of jets that disrupt combustion happening at the fuel source. The electric field pumped out by the electrode creates an ionic wind that essentially blows out the flame.
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