Fighting fire usually involves water or foam, but they can be messy and environmentally destructive. Engineers at Ohio State University have now developed handheld tools that cleanly extinguish fires with 'ionic wind’ and vortex rings.
If you’ve ever blown out a birthday candle, you’ll know that a quick burst of air can be enough to put out a flame. It works by separating the heat source from the fuel for long enough that it can’t reignite. Blowing on a campfire, however, won’t have the same effect – the heat source is too large, and all you’re really doing is adding oxygen.
The new device kind of scales up the birthday candle mechanism to fight larger fires. First it shoots a vortex ring of air, which creates a turbulent airflow that separates the heat and fuel. At the same time, that vortex is carrying conductive aerosol particles, which ionize the air and produce even more turbulence. Coarse copper leaf was chosen as the most conductive aerosol out of seven mixtures tested.
In practice, firefighters would aim the business end of a handheld cannon at a fire, and launch these ‘ionic wind’ vortex rings to put it out. That would reduce the expense, cleanup, collateral damage and environmental impact of using water or firefighting foam.
The team tested two prototypes of the device: one that generates vortices with bursts of compressed air through a cone-shaped muzzle, while the other fires air through a square-shaped muzzle using an elastic diaphragm at the back, which the firefighter pulls back and snaps like a big rubber band.
Both prototypes were found to successfully and consistently extinguish flames at a range of up to 2 m (6.6 ft), which would help firefighters stand at a safe distance from a fire. The compressed air version was found to be more efficient, and intriguingly the vortex rings alone seemed to do the job – the team saw no significant improvements when the conductive aerosols were used.
Much more work still needs to be done, however. For one thing, the devices were tested on arrays of candles, which might not accurately represent how they’d fare against a house or forest fire. Testing them against more realistic fires is a priority for future experiments. Still, the team is confident that the tech could eventually be used in the real world.
“The design of our Vortex Launcher is actually really simple in nature,” said John Simonis, co-author of a study describing the device. “One of the benefits of that simplicity is it’s also very scalable. It’s maneuverable in tight spaces so that you can walk through doors and indoor environments, but also large enough to have the practical benefits of generating those vortex rings.”
The research was published in the journal Technologies.
Source: Ohio State University
