Fighting Fires With Beams of Electricity

cylonlover writes "It's certainly an established fact that electricity can cause fires, but a group of Harvard scientists have presented their research on the use of electricity for fighting fires. In a presentation at the 241st National Meeting & Exposition of the American Chemical Society, Dr. Ludovico Cademartiri told of how they used a unique device to shoot beams of electricity at an open flame over one foot tall. Almost immediately, he said, the flame was extinguished. 'Such a device could be used, for instance, to make a path for firefighters to enter a fire or create an escape path for people to exit, he said. The system shows particular promise for fighting fires in enclosed quarters, such as armored trucks, planes, and submarines.'"

Anyone have any idea how it works?

[IICV]

Anyone have any idea how this thing actually works?

The best I could come up with is based on a very small part of the article:

But how does it work? Cademartiri acknowledged that the phenomenon is complex with several effects occurring simultaneously. Among these effects, it appears that carbon particles, or soot, generated in the flame are key for its response to electric fields. Soot particles can easily become charged. The charged particles respond to the electric field, affecting the stability of flames, he said.

So I guess what happens is that the electrical field charges the soot and other light carbony things generated in the fire, which causes them to disperse sort of like what happens with this toy [thinkgeek.com]? How does that help extinguish the fire, though? Wouldn't the outward motion of the carbon particulates just bring in more oxygen?

What other effects are going on?

Re:Anyone have any idea how it works?

[Anonymous Coward]

At http://cosmiclog.msnbc.msn.com/_news/2011/03/28/6362578-fight-fire-with-a-magic-wand was a small statement that helped me wrap my head around this a lot better: "By applying oscillating fields, the effect was much, much larger"

Usually this type of thing would be picked up by mainstream media long after technical papers have been written, but in this case the article says they're still 6 months or more away from understanding it well enough to write papers about it.

Some idea

[dackroyd]

Flames are ionised (i.e. charged) particles. If you have a strong enough electric field (which is really not the same as 'shooting electricity' as per the article) when the charged particles move through the electric field there will be a force on them perpendicular to their motion and to the field i.e. the flame will curve over into spiral.

If you could get this to happen on a large enough scale, the flame would suppress itself as instead of the flame moving away from the fuel it would hang around - stopping oxygen from reaching the fuel.

If this all sounds really unlikely, that's because it is. Here it a video showing an electric field affecting a small candle:

http://www.youtube.com/watch?v=6fKGeV4NrrA&feature=mfu_in_order&list=UL [youtube.com]

It looks like you need an electric field on the order of 10keV per 5cm to get this effect. So if you wanted to do it on a fire that was say 5 meters across you'd need an electric field in the order of 1MV which while obtainable is not exactly an easy thing to setup - particularly when there's a fire going on.

Electric and magnetic field confused

[PeterM from Berkeley]

Sir,

    You have electric and magnetic fields confused with each other. If you have a MAGNETIC FIELD, when charged particles move across (NOT along) it, there is a force on them perpendicular to their motion (and to the field, incidentally).

    In an electric field, the force on the charged particle depends on the orientation of the electric field, not on the orientation of the charged particle's momentum.

    I refer you to the Lorentz equation, which goes like this:
F = q (E + V cross B)
where capital letters denote vector quantities and "cross" is the cross-product operator. As you can see, the force from the electric field (q times E) is parallel to E. The force from the magnetic field (q V cross B) is perpendicular to both the magnetic field and the particle's velocity.

    I'm not sure whether the rest of your explanation holds water--when you have a rapidly changing electric field it is accompanied by a magnetic field, which WILL curve particles like you say. In fact, when you have both, you have what is called an "E cross B" drift, in which charged particles have a motion perpendicular to both the E and the B field. (Is that what you meant?)

And yes, IAAP.

--PeterM