No Moving Parts, 1-Way Valve

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Swamper
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No Moving Parts, 1-Way Valve

Post by Swamper » Fri Aug 14, 2015 3:35 am

Hello Pulseheads,
I'm just starting to learn about pulsejets, and hope to build a small array this winter for eventual mounting on my small boat. I'll likely use some plans for a reed valve engine, but I was thinking about ways to modify common designs. I read about the failures of rotary valve engines and think that there is another valve option which solves all of these problems. Has anybody heard of Tesla's "valvular conduit". It is a tangle of channels which allows fluids to flow quickly in one direction, and impeded in the opposite direction. Initial research seems to indicate that the effect is increased when this channel is smaller, and the pressure is increased. I'm not sure what pressures a hobby sized jet runs at, but I wonder if an array of valvular conduits can act effectively enough to exclude the combustion gasses from exiting the intake. I was thinking that 100 or so of these conduits could be etched in a 1/8inch plate at 1/16 inch deep. Repeated a dozen times and sandwiched together you should essentially get a 1-way air filter for the intake on your engine. There would be no timing issues like the rotary valves, no worn reed valves, and the mass of the metal filter should provide great heat resistance. I look forward to hearing what you folks think.
Cheers

Ryan Blake
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Re: No Moving Parts, 1-Way Valve

Post by Ryan Blake » Fri Aug 14, 2015 4:37 am

This has been explored before, as detailed under Essential Reading in the Valveless section of this forum. It is about 1/3 of the way through the document.

"Few people will be surprised to hear that the amazingly prolific and spectacularly inventive researcher
of things electrical, Nikola Tesla, also turned his mind to the problem of pulsating combustion. He
wanted to have a good gas generator for his neat smooth-disk rotor turbine that used the viscosity of
the working fluid to transfer energy to a rotating shaft. He immediately saw that mechanical valves
would not offer the simplicity and reliability he had sought. So, he studied the ways to rectify the gas
flow aerodynamically. Eventually he came up with arguably the best aerodynamic ‘valve’ ever. Its
cross section is shown below.

At first glance, it looks like another serrated passage, but if you take a closer look, you can see that it
does not really employ either baffles or dead air pockets. Instead, it just changes the direction of the
gas and turns it upon itself. At each turn, a side blast of gas will push the main flow towards the side
passage that eventually turns backwards. The harder you blow into that tube, the harder it will resist.

While undoubtedly ingenious, the ‘valvular conduit’, as Tesla called it, never found practical application
to the best of my knowledge. Tesla himself probably did not have time or inclination to pursue its
development after applying for patent, being busy with his experiments in electromagnetism, and the
patent was mostly forgotten. As the inventor has recently become the center of a cult following, his
modern disciples have revived the idea. A few have been built, but I have not been able to find data
on their performance."

If you are looking to do away with the problems that come from valve wear, etc. a valveless engine may be better. They have less power for their length, are difficult to run on liquid fuel, but are easier to fabricate and don't have the wear issues.

Swamper
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Re: No Moving Parts, 1-Way Valve

Post by Swamper » Fri Aug 14, 2015 12:09 pm

Thanks for the information. Sorry to waste space on the board. As for my personal boat, I'm not too worried about the valves wearing. My friend works for a cnc shop, so I'm sure he could cut a whole roll of springsteel for me.

Swamper
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Re: No Moving Parts, 1-Way Valve

Post by Swamper » Fri Aug 14, 2015 1:09 pm

Ok, I read the article mentioning these baffled methods. I am not surprised that the figure showing the valvular conduit failed. It is far too large a diameter to effectively impede blowback. As I mentioned, the conduits function best at smaller scales and higher pressures. It does not appear that anybody has tested a massive array of minuscule channels. I'm not putting a lot of eggs in this basket, but I might make a small "1-way filter" of my design just to fiddle with. Might not even hook it to an engine, but I would like to see how it performs with so much more frictional air resistance than a few larger conduits can provide. While my idea might not be novel, I'm hoping my approach is.

Mark
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Re: No Moving Parts, 1-Way Valve

Post by Mark » Mon Aug 17, 2015 2:06 pm

There was Foa in "Elements of Flight Propulsion" (1950s) who said this after trying several flow rectifiers. "So far, no rectifier for pulsejets has been found more effective than a simple intake duct of adequate length."
While I can't claim any expertise in the topic, there are a few things that come to mind. He mentioned things being a tradeoff, good breathing vs. good mixing. It seems like there's something about what you gain in one direction you lose in the other. I once thought about using a bunch of small pinhole intakes that were flat on one side and countersunk on the outer intake side to maybe favor inflow. But if you had too much "play", it could be that the various channels wouldn't stay coherent and then dampen feedback or fail for other reasons.
I have some of those espresso stainless steel cups/filters with very tiny pinholes in the bottom. If you press your mouth against it and blow into the cup of one kind no sound is produced but if wetted and then removed from water and shaken dry the cup will make the most unusual whistling/whining sound for a time as the air passes through the holes when you blow into it. Somehow the wet edges of the holes creates this sound as air is forced through, lasting perhaps 10 seconds before the traces of water dissipate. It would be nice if you could think of a way to admit air as quickly as possible and confine it as suddenly too. Maybe some sort of surface tension use of fuel in pinhole intakes properly timed would be something to fiddle with - "waterboarding" a pulsejet.
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