A recently completed research program by the Department of Defense looks at the possibility of extinguishing fires using sound.
The Defense Advanced Research Projects Agency, a division of the DOD, launched the Instant Fire Suppression program in 2008, completed Phase II in December and released the results last week.
In military settings, fire in ship holds, aircraft cockpits and ground vehicles can jeopardize the lives of both soldiers and firefighters.
In order to find a safer way to battle such blazes, the agency tested the theory that by using physics rather than combustion chemistry, it could be possible to manipulate and extinguish flames.
Through the program, DARPA researchers sought to understand and quantify the interaction of electromagnetic and acoustic waves with the plasma in flames.
One of the flame-suppression systems used in Phase I explored used a handheld electrode sheathed in ceramic glass to suppress small methane gas and liquid fuel fires.
The electric field created an ionic wind that blew out the flame.
Researchers also evaluated the use of acoustic fields to suppress flames.
In one test, a flame was extinguished by an acoustic field generated by speakers on either side of the flames.
The acoustic field increased the air velocity, caused the flame boundary layer to thin and led to higher fuel vaporization.
The speakers essentially blasted sound at specific frequencies that extinguish the flame.
While there was some success putting out relatively small flames, researchers noted that it was not clear how to effectively scale the approaches to put out fires.
"We have shown that the physics of combustion still has surprises in store for us," DARPA Program Manager Matthew Goodman said in a statement. "Perhaps these results will spur new ideas and applications in combustion research."
