March 28, 2011 at 4:06 PM ET
Last updated 10:15 p.m. ET:
Researchers say they've found a new way to snuff out flames using an electric field-generating wand — and the seemingly magical technique just might be put to use in future fire rescues.
"What we are excited about is that this presents a new capability in the control of flames," Harvard researcher Ludovico Cademartiri told me today.
Cademartiri presented a report on the flame-quenching method on Sunday at a national meeting of the American Chemical Society in Anaheim, Calif. He has been working on the technique as a member of Harvard Professor George M. Whitesides' research group, along with Penn State's Kyle Bishop.
The technology sounds a bit like the fictional flame-freezing charm or the Aguamenti spell mentioned in J.K. Rowling's series of Harry Potter books, and the fact that it's done with a wand-like electrode makes the story even better. "The best geometry of the electrode is in the form of a thin wire, which journalists creatively labeled a wand," Cademartiri said.
For two centuries, scientists have known that electric fields can interact with flames, but the effect from a continuous DC electric field was too small to have practical applications. "By applying oscillating fields, the effect was much, much larger," Cademartiri said.
In the lab, researchers set up a 600-watt amplifier — with about the same power as a high-end car stereo system — and hooked it up to the wand. Then they pointed the wand at the base of a methane-fueled flame emanating from the orifice of a burner. Cademartiri said the wand's electric field disrupted the flame and snuffed it out, even when the flame was cranked up to a height of 20 inches (50 centimeters).
"The electric field interacts with the charged particles in the flame — the electrons, ions and soot particles — and this collective motion of the charges in the electric field can lead to movement of the gas within the flame," Cademartiri explained. "The mechanics of suppression is that the flame gets detached from the fuel source, so it gets pushed away. This is somewhat different from blowing on the flame."
Bishop said that the flame-taming effect isn't all that noticeable at low voltages. "The one thing that is new is the ability to use large, time-varying electric fields. ... It's only been recently that the high-voltage power supplies that make this kind of perturbation possible have become commercially available," he told me.
In their most successful experiments, the researchers turned the dial up to 40,000 volts, Bishop said.
The research could eventually lead to the development a new gizmo for the firefighter's toolbox, in addition to tried-and-true methods such as water from fire hoses, powder from a fire extinguisher and flame-suppressing foam from a tank. In contrast with those methods, the electro-blaster does not need to put any material in contact with the flames themselves. Cademartiri imagines that such gizmos could be attached to the walls or ceilings of buildings or ships, or carried by a firefighter in a backpack. Electric wands could help fire crews open an escape path for people trapped in an enclosed space. However, Cademartiri noted that the system wouldn't be as suitable for quelling flames in open spaces, such as in the midst of a forest fire.
The Pentagon's Defense Advanced Research Projects Agency and the U.S. Department of Energy have been funding this research for a couple of years now, but the flame-freezing wand isn't ready for prime time yet.
"We want to really completely understand this interaction," Cademartiri said. "It's a novel thing. People have not seen it before, and it's really complex. ... The second thing is that we are starting to look at how these effects scale with the size of the flame."
Bishop said he and his colleagues were already getting ready to submit research papers to a number of scientific journals. "There should be publications forthcoming within the next six months," he said.
In the longer term, the technology could be applied not only to future rescues, but also to industrial applications ranging from better welding torches to more efficient automotive engines and power plants. "Ninety percent of our energy comes from combustion," Cademartiri noted.
All things considered, it sounds like a technology worth waiting for. Making combustion more controllable would add to a long list of advances that go all the way back to, well, the mastery of fire itself.
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