Popular Science

Description

Performers on DARPA's Instant Fire Suppression program evaluated an acoustic approach to suppressing flames. In this video, a flame is extinguished by an acoustic field generated by speakers on either side of the pool of fuel. Two dynamics are at play in this approach. First, the acoustic field increases the air velocity. As the velocity goes up, the flame boundary layer, where combustion occurs, thins, making it easier to disrupt the flame. Second, by disturbing the pool surface, the acoustic field leads to higher fuel vaporization, which widens the flame, but also drops the overall flame temperature. As the same amount of heat is spread over a larger area, combustion is disrupted.