Burning Propane Beautifully Illustrates How A Tesla Valve Works

When you hear the name “Tesla”, chances are good that thoughts turn instantly to the company that’s trying to reinvent the motor vehicle and every industry that makes it possible. While we applaud the effort, it’s a shame that they chose to appropriate the surname of a Serbian polymath as their corporate brand, because old [Nikola] did so many interesting things in his time, and deserves to be remembered in his own right.

Take the Tesla valve. In essence a diode for fluids, the Tesla valve uses a tortuous path to allow flow in one direction but severely restrict it in the other. Understanding how it works isn’t necessarily intuitive, though, which is why [NightHawkInLight] chose to demonstrate the Tesla valve principle with exploding propane. It’s not new territory to him; we’ve covered his propane-powered rifle in the past.

The swirling blue and green flame front in those experiments make burning propane the perfect working fluid to demonstrate how the Tesla valve works. The video below tells the tale, with high-speed footage showing the turbulence that restricts the reverse flow. The surprise discovery is that in the forward direction, the burning gas actually seems to accelerate as it moves down the valve; hypersonic Tesla plasma cannon, anyone?

We’ve seen Tesla valves before, including one made from a “Shrinky Dink”. That did a pretty good job of visualizing the flow patterns that make the valve work, but there’s a huge showmanship gap between tiny channels filled with colored water and the explosive decomposition of a fuel-air mix. It’s a bit riskier, and standard “don’t try this at home” disclaimers apply, but luckily [NightHawkInLight] still has his eyebrows, so he must be doing something right.

42 thoughts on “Burning Propane Beautifully Illustrates How A Tesla Valve Works

    1. Hahhahah!!! I remember as a kid playing with a bottle containing a very small amount of gasoline. I was dipping a stick in and then dripping small drops of gas on a fire. One time, I didn’t notice the stick was still on fire when I dipped it back into the bottle. It ignited, let out a funny “whooooooo” as it burned, shooting a nice flame out the top… and gone were my eyebrows.

      1. When I was a kid (rocks had just been invented, but dirt came later)…. They were building an extension onto the development/subdivision where we lived. The builders had lots of these metal containers of turpentine. When they were done with them, the got kicked out of the way for cleanup crews to deal with. We used to take the lids of one at a time and flick matches at them. The dimensions were something like 10” by 10” by 15”, as I recall. If you got the lit match close enough to the hole, the square sided can became a basketball and would land somewhere nearby. I was trying to get a match to light but was having difficulty. Unconsciously, I kept walking closer to the can and eventually it went off.

        I didn’t use brow pencil. Didn’t have to. I had red hair and you could hardly see them before that. It did leave me with a funny looking do, though.

  1. Very interesting. With the fact that the flame front accelerates down the channel, I wonder if this could be used in a gaseous fuel pulse jet design? No idea if it would be any better/worse than current pulse jet designs, but an interesting idea.

      1. Makes me wonder what a long tesla valve would sound like if you tried to play it like a tuba. Would certain tones be strongly dicouraged while others enhanced. What would sounds sound like listening through such a devices sound like, from either direction. :-)

    1. Last night I had a thought, what if we used a face plate of multiple tesla valves to replace the reed valves on a regular pulsejet, it would have the smaller size (and maybe weight) of a valved pulsejet but the lack of moving parts like a valveless pulsejet. It would just be a bitch making the face plate.

  2. The acceleration is (i think) because of the expanding gas behind the flame; you’re observing a cannon, with the unburnt gas as the projectile.

    That part is easy to experiment with; a few feet of clear water hose jammed on the end of a trigger type handheld propane torch will do. The ones with the peizio igniter. This rig is also great for launching beer cans.

    1. With the right gasses and tube diameters this can turn deflagration (perfectly normal flame front) into detonation (loud bang). Much fun was had demonstrating this with ethylene and air. Light a small bag of it with a blow torch and “whoomph”, bright orange/blue flame. Light the end of a 20″ hoes with the same size bag on the end and everybody jumps. Shreds the bag too.

        1. Apologies, I meant 20′, roughly 6m and not the 0.5m mentioned. More coffee has been consumed and not I can focus on the keyboard.

          The good thing is, if you start off with 20′ hoes, you can make many smaller hoes. One for any occasion. Should please friend :O)

    1. it could possibly augment the turbo as an afterburner between the exhaust manifold and output turbine but not as a direct replacement. maybe it could replace a reed valve in a 2 stroke engine.

  3. problem with this is your saturating a cavity with a gas, then igniting it sucking in air from the less restrictive side

    in reverse yes your correct, but its accelerating for the same reason your just burping vs farting

    neither of which really show why a tesla valve does what it does, it just shows fluid burning with more or less combustible air. if you want to show how a tesla valve works get a pearlescent visible fluid and pump it in slower than the speed of an explosion

    there’s of course shampoo, but a lot of options for PC water cooling that show flow patterns very clearly

  4. As impressive as the speed difference is between the two, I have to wonder if a straight tube would be even faster than the forward version of the Tesla valve. My intuition says that it would be, but I have to admit that my intuition doesn’t always agree with the universe.

    If the Tesla valve is indeed faster, then the question would be whether you could improve it further by adjusting the lengths of the loops, for example make them progressively longer or shorter.

    1. Straight tube can often encourage flame front to go supersonic. Complicated shapes can do this too (certain fuel pipe arrangements on aircraft that have to be left full of fuel as a way of preventing any possible flames). So while there may be a bit of variance, with a long enough system made of either type, expect a boom.

  5. Tesla is Rock and Roll Superstar of real Science. Im glad someone finally got around to naming something in his honor even if its an overpriced smug mobile. Though a part of me was secretly expecting and hoping that someone found plans to Tesla’s mythical electrical car that ran on a small chassis of tubes with a 6 foot antenna with unlimited range and without Wardenclyffe Tower. Knowing full well the usual group of criminals would never let that out; I put my real tin foil hat back in the drawer.
    To that I’ve yet to see anyone build a Tesla turbine. Supposedly of remarkable efficiency and to the valve sytem being expressed here was a component.
    It is a nice demo. Now show how to make it work.

    1. If you haven’t seen Tesla turbines maybe you should open your eyes, the internet is full of Tesla turbines projects. They aren’t remarkably efficient for general use – otherwise that design would be to standard.

      1. nope. Eyes wide shut. None that I’ve seen to date are anywhere near efficiencies reported in archives. Most are poor attempts at copying patent using conventional thinking and barely functional. Internet is full of it for sure.

  6. In this case, that tube in not filled with propane and is not sucking in air from one end. He is filling the tube with a well proportioned mix of propane and air from the torch.

    The torch draws in air at the base of the nozzle and mixes it with propane.

  7. I obviously know nothing about this subject but wonder what the effects or affects would be if the tubing was slowly narrowed as it passed through the length of the valve. Just curious.
    Ok, mock away…

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.