A one-way water valve with no moving parts invented over 100 years ago by Nikola Tesla could be adapted to pump fluids around motors using otherwise wasted energy.
Tesla patented his “valvular conduit” in 1920. It is essentially a pipe with an intricate internal design that forces fluid moving in one direction to loop back on itself at various points along its length. When water flows into the mouths of the loops, it becomes turbulent and slows down, halting the flow. But if you run water in the other direction, it doesn’t enter the loops and flows freely.
Leif Ristroph at New York University and his colleagues built a 30-centimetre-long version of the valve, following Tesla’s original plan, and measured the flow in both directions at a variety of pressures.
Although Tesla claimed in his patent that the valve could make water flow 200 times slower in one direction than the other, the researchers found that their version only made it two times slower. “He was a very imaginative guy,” says Ristroph. “It’s a little unclear whether he actually made and tested it. I suspect so, but there’s no documentation of that.”
Although the effect was much lower than Tesla claimed, the valve is still a useful design, says Ristroph, especially as it has no moving parts so could be maintenance-free.
“It has been known about and has been used in some applications, or at least proposed for use. But no one had ever really done the thorough hydrodynamics work on it to figure out how it works, how well it works,” says Ristroph.
The team found that there was no difference in resistance between forward and reverse at low flow rates. Instead the valve abruptly activates above flows of around 1 centimetre per second and significantly resists reverse flow.
Ristroph believes that Tesla, who also had a patent for an AC to DC electrical converter, conceived of the valvular conduit to do the same thing for fluid currents. AC electricity sees electrons constantly reverse their direction, but when converted to DC they effectively flow in a loop. His team made a ring of Tesla’s water valves to mimic Tesla’s electrical converter and found that it successfully took oscillating water sloshed back and forth by a piston and converted it into a steady flow of water in one direction – effectively turning it into a pump.
The team believes that the design could harness the vibrations in engines and other machinery to pump fuel, coolants, lubricants and other gases and liquids.
“Imagine if you had those fluid pump systems basically take the vibration from the motor that’s there anyway, and have that circulate it. It has no moving parts. There’s nothing to break,” says Ristroph.
Journal reference: Nature Communications, DOI: 10.1038/s41467-021-23009-y
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