metal jam jar experiments

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vturbine
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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 4:23 am

Time to resurrect this thread, maybe.

I think simple jam jars seem to have some important small characteristics. I'm not sure yet if these are all true. But I think they are on the basis of evidence of many posted experiences I've read. And if so, I'd like to use them.

1.)They need a stiff bottom and sides to reflect the pulse.
2.) They don't need a stiff top. In fact a flexible top may possibly help up to a small amount. It will however affect the needed orifice size, frequency and other system requirements.
3.) The thinner the metal surrounding the aperture, the better. This approaches the thin plate orifice ideal.
4.) A pipe tail has the effect of ejecting the exhaust in a directed line, while taking in air from all directions yielding a net thrust. reaction. This is similar to the action of pipes in a putt-putt toy steam boat motor. This same directing action on the outflow increases the "bark"

If 2 is true, then maybe I can use the top as a pseudo-valve. As well as a power diaphragm to take work out.

If the end of an external low pressure gas feed pipe nearly touches a flexible top it can still feed gas. If instead of a single aperture, five small holes are located outside and around the pipe diameter. the gas can enter those holes. If an explosion occurs in the jar, the top will be driven outward, cutting off the flow of gas, like a valve. When the pressure collapses in the jar, the valve is drawn away from the pipe and a mixture of air and gas is lip fed into the combustion chamber through the 5 holes.

With a gas, we need a source of ignition, unlike methanol, which remains burning in the bottom of the jar. Maybe a glow plug. Or, if the jar heats enough, that could do it. So we stop water cooling it and let it glow.
Yes?
ValvedJarCombustor.png
Schematic of valved jar combustor.
Last edited by vturbine on Thu Jul 16, 2009 5:33 am, edited 2 times in total.
No problem is too small or trivial if we can really do something about it.

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vturbine
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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 4:35 am

If this works, we can possibly throttle a jam jar, and also control mixture. If the pipe can be moved up or down while operating, we have a lot of control. Timing. Mixture, Throttle.

And the top may be a good place to take some power out of the system as a diaphragm. The exhaust stream could possibly be harnessed to amplify this.
No problem is too small or trivial if we can really do something about it.

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Bruno Ogorelec
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Re: metal jam jar experiments

Post by Bruno Ogorelec » Thu Jul 16, 2009 5:34 am

I'd say it is somewhat Quixotic to dabble at jam jars ith serious intentions without first studying the efforts of F.H. Reynst, the inventor of the jam jar 'engine' and the only man ever to have built it in industrial sizes and studied its functioning in a properly scientific manner.

One should try to see how far Reynst had progressed. Why reinvent the wheel? The Reynst pot may well have been the best pulsejet ever built. We are not likely to equal or surpass it very easily with amateur resources.

Someone should talk to ABB's Swiss HQ. ABB is the successor of Brown Boveri, for whom Reynst was a research and development engineer. The company must have plenty of Reynst stuff in its archives. It's all historical stuff; they will almost certainly be willing to share it.

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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 5:38 am

I am studying Reynst.

First time I ever was called quixotic for expressing an idea.
No problem is too small or trivial if we can really do something about it.

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Re: metal jam jar experiments

Post by Bruno Ogorelec » Thu Jul 16, 2009 5:43 am

No, no, expressing it is not Quixotic, of course. Reinventing the wheel would be. I am glad to hear that you are looking at Reynst. No one else seems to be doing it.

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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 5:46 am

What specific wheel did I reinvent?
No problem is too small or trivial if we can really do something about it.

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Re: metal jam jar experiments

Post by Bruno Ogorelec » Thu Jul 16, 2009 6:06 am

Aw, come on, man, relax. Whay are you so thin-skinned?

I did not say you did. I said devoting oneself to research of jam jars without studying Reynst would be reinventing the wheel. You said you did study Reynst. Good! You are nor reeinventing thewheel then. I commended you for that.

Jesus, I should really steer away from this place. Once in a few months is obviously too often.

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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 6:18 am

???
No problem is too small or trivial if we can really do something about it.

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Jutte
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Re: metal jam jar experiments

Post by Jutte » Thu Jul 16, 2009 10:23 am

Hey V,
Somewhere here someone has tried the valved idea that you drew a picture of.
If I remember rightly it didn't go that good. However - in saying that there are heaps of us
here that have lost eyebrows etc to the Jam Jar beasties so give it a whirl dude.
Bang in "Reynst" or "Jam Jar" into the search engine and you will have a couple of hours reading.
Bruno - I always enjoy your comments - how about a Reynst Jam Jar Jet pack...LOL!!

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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 12:56 pm

Thanks Jutte, I have great respect for Mr. Ogorolec myself. I've enjoyed reading his comments, and he's extremely knowledgeable, and quite helpful to people here. I'm glad that he has singlehandedly brought Reynst to greater attention, since it is obviously deserved.

I have read all the the jam jar posts and threads I could uncover, as well as the Reynst posts. I've downloaded the Reynst book, unpacked it, and have been studying all those little jpegged pages for 3 days now. It's fascinating reading, and I'm obviously very excited by all of these topics. I apologize if that enthusiasm appears to jump the gun, but it is difficult to contain.

I would particularly like to read the reference you mention to someone trying out a version of what I mentioned above. That would be really helpful and interesting. There may be some differences in approach, or application that would be interesting in relation to what I'm focusing on.

One thing I'm not trying to do is create a "better" jar than Reynst did. I am trying to demonstrate something to myself, not save the world . . .and working with a very specific set of simple requirements. I'm also, like most people here, out to have fun doing it.
No problem is too small or trivial if we can really do something about it.

Richard Feynman

PyroJoe
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Re: metal jam jar experiments

Post by PyroJoe » Thu Jul 16, 2009 1:40 pm

Didn't have luck with valveing a flexible lid:
viewtopic.php?f=2&t=4467&st=0&sk=t&sd=a

The lid becomes heated and stays bowed outward. ha
Joe
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Re: metal jam jar experiments

Post by tufty » Thu Jul 16, 2009 1:47 pm

vturbine wrote:With a gas, we need a source of ignition, unlike methanol, which remains burning in the bottom of the jar.
Nope. There's enough burning / hot gas already in the chamber, and being pulled back in, to keep it going, just like any gas-fed pulse combustor. Don't worry about ignition.

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Re: metal jam jar experiments

Post by vturbine » Thu Jul 16, 2009 2:15 pm

Hi Joe!
A couple of things (and again apologies if this has already been answered by others, including Reynst) maybe the spring rate of the diaphragm wasn't enough in your design? You'd need a valve spring partly also because the direction of inflow is radial and outflow is axial. Net result is outward. Hitting the seat damps it to a fixed seating.

Don't know if the one I sketched would act the same.

"Different valves, different strokes." (Dugald Clerk in a private conversation with Nicolaus Otto at a cocktail party). :)

EDIT: Joe just read your valve thread . That first diaphragm was very large and made from aluminum, which is a pretty dead material, particularly at temperature. So you really had almost no spring bias to an open position. The smaller washer shaped valve worked better, but that was aluminum, too.
No problem is too small or trivial if we can really do something about it.

Richard Feynman

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Re: metal jam jar experiments

Post by ace_fedde » Thu Jul 16, 2009 3:27 pm

Bruno,
Ja mislim da je to sve bilo nesporazum malo prije. Izgleda da je tip i svatio da je malo zajebao.
Fedde
Your scepticism is fuel for my brain.

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Re: metal jam jar experiments

Post by PyroJoe » Thu Jul 16, 2009 5:50 pm

Yeah, my dabblings aren't the best approach in many circumstances. I was trying to keep the mass of valve material as light as possible.
Joe

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