New research by DARPA’s IFS Program presents the potential for novel advancements in firefighting methods using electricity & sound.
For nearly 50 years no significant advancements for extinguishing or manipulating fire were developed despite the severity of the threat from fire. In 2008, DARPA launched the Instant Fire Suppression (IFS) program to develop a fundamental understanding of fire with the aim of transforming approaches to firefighting.
Most fire suppression techniques focus on the chemical reactions involved in combustion. According to physics, however, flames are cold plasmas. This means that the flames in a fire contain mildly ionized gas – a gas where a few molecules have an electromagnetic charge. Based on this, DARPA decided to experiment with physics rather than combustion chemistry.
One of the technologies the IFS explored was a novel flame-suppression system that used a handheld electrode to suppress small fires from methane gas and liquid fuel. In the video below, performers sweep an electrode over the ignited burner and progressively extinguish the gas flame. Since the electrode is sheathed in ceramic glass, there’s no worry of an exposed electrically charged material. The basic idea is that an oscillating field created by the wand creates jets in the gas which move the combustion from it’s source. It’s like an ionic wind putting out the flame.
Another neat technique they developed is the use of acoustic fields (sound waves) to suppress flames. In the video below, an acoustic field generated by speakers on either side of a pool of fuel extinguishes flames. Two processes are at play here. First, the acoustic field increases the air velocity. This thins the flame boundary layer, where combustion occurs, making it easier to disrupt the flame. Second, by disturbing the pool surface, the fuel evaporates at a higher rate, which widens the flame & drops the overall flame temperature. As you can see, this eventually extinguishes the flame.
Although these experiments were successful on the scale they were applied to, it was not clear from the research how to effectively scale these approaches to the levels required for defense applications. DARPA remains optimistic. Matthew Goodman, DARPA program manager, 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.” For example, the data collected by the experiments conducted by the IFS could potentially be applied to the opposite scenario: increasing the efficiency of combustion. Such technology could be very beneficial to defense technologies that employ small combustion engines.
It looks like your trucks & crews will be using water & chemicals for the foreseeable future. However, the future of firefighting may look very different than it does now.