how does the valve of a valved pulse jet work?

[dikkebillenman]

how does the valve of a valved pulse jet work?

[dikkebillenman]

i mean it can't be some piece some piece of metal that opens to let the air in and then closed because of the pressure of the explosion 50 times per second... right?

[NickC]

actually that's exactly what it does....

[Dang911]

And its more like 200+ times per seccond!!!!

[dikkebillenman]

hmm... seems pretty difficult to me to build something like that, i think i'll start with building valveless pj.

[NickC]

difficult to build? it's basically a metal flap bolted to a piece of aluminum with a hole in it. The only thing valved pulsejets have going for them is that they can draw in their own fuel, like a carburetor. Valveless pulsejet TSFCs have gotten pretty low and they don't use up reed valves.

[Mark]

I remember our northern friends Viv and Luc made a Chinese valveless that drank fuel from a container.
I was thinking today the best way to describe a pulsejet no matter what kind, is to use the caveats if, and, or, and but.
All things considered, I don't think a valved pulsejet is any harder to make than a valveless. Each will have some problem to solve. Each will have advantages and disadvantages.
Mark

[NickC]

really? that's pretty cool! where's the thread?

[Mike Everman]

...use the caveats if, and, or, and but.
Mark

That's priceless, Mark.

[NanoSoft]

I took my Laird Chinese out today to test my new ignition setup and had it sucking its own fuel out of a container as well. It can run on gas, diesel, and methanol. So valveless pulsejets can definitely suck their own fuel out of a container as well as valved ones, so no advantage there.

mikhail jones

[NickC]

how do you have the "flowjector" deisgned?

[NanoSoft]

My injector is just a piece of brake tubing that protrudes into the intake perpendicular to the flow. It comes up flush to the inside of the intake tube. It is approximately 1 inch away from the end of the flare, although I think it needs to be moved farther back because a lot of fuel is blown out of the intake on the exhaust portion of the cycle. Hopefully tomorrow I will finish my thrust stand and be able to get not only some good numbers but also be able to tune the injector placement for optimal power. My thrust stand is going to just be a board with roller blade wheels lifting a container of water. I have found that the simpler is definitely better when it comes to pulsejets.

mikhail jones

[Mike Everman]

Hey, Mikhail, long time no speak. Hope all is well.
Good to hear you're getting some deflagration in.

[Mark]

I remember my little Logan when I used a very thin piece of copper tubing, like that of a large syringe needle. I put it right flush on the outside lip of the side port of my little Logan. While it would run fine like that, it spewed out a horredous amount of methanol wasting more than it drank.
It comes to mind a time I put/made a little washer with a reed over the hole, a single flapper valve that I installed in the front of the little Logan, whilst still having the side port in place. Imagine something like the little Craftjet, a single flapper valved engine with a side port thrown in. The Logan then reved up nicely using both the reed port and the valveless side port. So continuing on this theme, it seems interesting to try to employ a very small flap valve, a one-way gate, on a valveless to admit air and fuel into a region more inclined to digest all the fuel.
The Russian book outlines some pressure taps and fueling tricks by bleeding pressure off of an engine. Depending on the direction the little valve was installed you could either pull a vacuum or pressurize a fuel tank, they had a manometer showing the results.
Another time I strung a silicone tubing fuel line full of fuel,(it acted as a 15 second gas tank), from the nose of the Logan over to the side port where the fuel was ingested. The pressure from the combustion chamber was higher than the inside of the side port so it drank fuel that way, the fuel pushed along and over to the side port. But one time I tried using fatter tubing to increase the fuel tank size. This time I was able to drill a hole in the side of the side port and get the fuel to get drawn in instead of pushed back down the line when the engine reved up.
The most interesting thing occurred with with the fatter tubing, a hammer effect developed in the fuel line causing the Logan to go into seizures as the fuel squirted into the side port. It was so funny, hearing it go from near silence to full grease and up and down all over the place, as erratic as could be. It was the most wacky, comically entertaining sound, something a clown or special effects person might like.
Mark