Rotary valves do not work.

[Rocket Man]

Test have proven that rotary valves do not work. The #1 problem is, NO pulse jet engine runs at an EXACT same frequency all the time. Test have proven the pulse frequency of the engine varies by as much as 14 Hz. The test engine runs at about 200 Hz, the frequency goes up and down 5 to 7 Hz all the time and some times as much as 14 Hz.

It was learned that no mechanical devices and electronic device can open and close the valves at a speed that matches the exact speed of the engine.

A variable speed DC motor rotary valve system was built and set to run at 200 Hz to match the 200 Hz engine. The engine tries to run but it will not run on its own. The valves must open and close at the exact same speed as the engine. If the valve is off by 1 HZ the engine will fire with the valve open.

Combustion chamber pressure is about 18 psi. This pressure was used to operate a mechanical valve system that was never able to keep up with the same frequency of the 200 Hz engine.

If it were possible to make a pulso run at exactly 200 Hz all the time a valve system could be made to run at a matching speed.

[nitro]

I think any idea for Poppet Valves or Rotary valves must have the valve opened or shut by the internal pressure alown.As your PJ gets bigger new design ideas open up more.

[sockmonkey]

You might get away with rotary or other externally actuated valves if it were a very large pulsejet since the bigger ones operate at much lower frequencies.

[Swamper]

The benefits of a rotary valve would be to reduce valve wear as seen in other designs, no? Why not use the only one-way valve with no moving parts? Tesla's valvular conduit?

[sockmonkey]

Oh, what if the fuel injector was controlled by the rotary valve? Then the timing of the explosion would have to match the valve's opening and closing because that's when the fuel would show up.

[paxpgc]

Actually, rotary valves do work. Check out this link:
https://www.researchgate.net/publicatio ... _Combustor

[Mike Everman]

Well, sure, with a ball valve and a big motor to drive it in a lab. I think the point has usually been "practical use in a flight unit".
That paper is a good read, though, thanks!

[paxpgc]

The work described in this paper was a first crack at a rotary valve. It is a prototype. Definitely not envisioned as something that could fly. However, there is a community that is looking to utilize pulse-jets (aka, pulse combustors) in applications requiring operation for thousands of hours. Reed valves will never allow that. Something 'rotary-like' might. This particular unit has run for many hours. Plus, there are many ways to shrink or lighten a rotary valve. It's probably true that this is impractical for model aircraft. But for other applications, maybe.

[Mike Everman]

I think there is a popular misconception that valveless motors are less gutsy. Not true, BTW. Nothing beats a proper valveless, if your goal is run-forever. And I think I am safe in saying that no mechanical valve can come in at less weight than flappers.

My own efforts made this little motor:
https://www.pulse-jets.com/phpbb3/viewt ... 390#p53993
3.5 lb thrust, with the 1.2x scale up of it (still smaller than a red-head) getting 5.2
https://www.pulse-jets.com/phpbb3/viewt ... 270#p61600
They were designed to take augmenters that can double the thrust, which is why they have straight pipe exits, for high exit velocity. I still haven't done the augmenters, or the two engine RC model for it, but will someday!

[metiz]

My own efforts made this little motor:

[Mike Everman]

Ha ha!
Time so flies, dunt it?