Another variant of a valveless pulsejet. COMMENTS???

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Anthony Colette
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Another variant of a valveless pulsejet. COMMENTS???

Post by Anthony Colette » Sun Jan 11, 2004 10:18 pm

Gentlemen,

I am looking for your thoughts, comments or criticisms on the attached power point drawing. It is a more mild variation of what is commonly seen for valveless pulsejets. I am looking for what your thoughts are on the viability or possible effectiveness or pitfalls of this configuration. The objective is to maintain torroidal vortex momentum in an area that would not be detrimental to inlet or tailpipe flow. It would also have the advantage of axisymmetry and slightly reduced over all length.

Tony
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Mike Everman
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Post by Mike Everman » Mon Jan 12, 2004 12:15 am

Anthony-
I like it. I've been talking similar things with Mark of late, submerged "snorkels" that is.. I got to a similar place, but with the intake concentric and outside of the exhaust tube (annular intake, tubular exhaust.
I think these approaches have merit, but oh, where to begin on volumes, etc?? the more our whacky ideas differ from the known, the more frustration is in store, as Bruno points out.
Greetings from 90 miles north, by the way! You'll have to come up and check my robotics and other stuff sometime. Perhaps you could be one of the (loosely affiliated) California Flaming Pulsators (working title! ) ;-P
Mike
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Bruno Ogorelec
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Post by Bruno Ogorelec » Wed Jan 14, 2004 12:54 am

I like it a lot. It's an inversion of the Thermojet, with the intakes and exhaust nearly transposed in function and position.

Somehow, it reminds me of Gary Robinson's black beast. Anyone remember that one? Anyone remember our Gary, the Pulse of the Outback?
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Post by Mike Everman » Wed Jan 14, 2004 1:05 am

Man, I just got a junk propane tank for that very idea, but I'm scared!
Mike
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Post by Mark » Wed Jan 14, 2004 2:57 am

Mike Everman wrote:Man, I just got a junk propane tank for that very idea, but I'm scared!
No need for fear, just use a very long ignition wire or have it positioned around the corner of your house or other protective structures, just in case. I have blasted my ears before by a super powerful hissing when lighting a constricted hole.
I use a piezo sparker with a long wire so that I don't have to be next the object in question. Just load that tank up with methanol and stand back! I don't know if I would have the $**#@ to light a 3/4 inch pipe threaded tank hole which holds 5 or 7 gallons is it? I've done a 2.5 gallon tank and with torch in one hand, I press my finger against my ear closest to the combustion.
Go for it and report back, ha ha.
Mark

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Post by Mike Everman » Wed Jan 14, 2004 5:04 am

No way, not me. I'll be far away for sure, with a lot more snorkel than that!
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Post by Mark » Wed Jan 14, 2004 4:00 pm

Mike Everman wrote:No way, not me. I'll be far away for sure, with a lot more snorkel than that!
I have a barrel that is about 20 inches tall and 18 inches diameter or so, and it has a substantial stiff ring that clamps the top to the upper lip by way of a screw on the clamp that pulls/locks the two ends together.
Anyway, I have wondered about making a jam jar out of it, and if the hole should be less or more than the 1/5 diameter recommended for the jelly jar size.
I have tried soup cans and the top and bottom flex out of sync and I haven't been able to get them to keep running for more than a few seconds, a stiff vessel eliminates that variable. I don't even know if a 10 or 15 gallon drum would work no matter the hole size. If a peak pressure of 10 psi developed for some reason, maybe by confining the exhaust, and/or by errant thought processes, it would put something in the neighborhood of a ton of force on the bottom of the drum, I wonder if it would hold together?
If the barrel/drum didn't work as a jam jar, it probably would make a good smoke ring shooter or even a fire ring shooter if it had a fat snorkel just above the bottom to aspirate or "suck" a layer of fuel off the bottom when fired.
With only a steel pint-sized canister and 1/2" X 6" water pipe snorkel/straw you can throw a nice green fire ring which spreads to several feet across about 10 feet downrange of the snorkel/barrel. Or what I did when I first was experimenting with the pint-sized contraption in my garage, I lit my ceiling on fire unexpectedly when the alcohol was ejected straight up out of the pint canister I set on the floor. This ordinarily wouldn't be so bad but if it had shot up where there is no decking/ceiling, the attic may have taken fire.
There is a thrill you get when you learn by doing. Fire ring throwing is probably best as an outdoor experiment.
Mark

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Post by Bruno Ogorelec » Wed Jan 14, 2004 4:08 pm

I have the impression that this type of the jet, involving unconventional positioning of the ports, requires a lot of separate study. They don't behave like the conventionsl intake-chamber-exhaust engines. Each may well be a law unto its own, just like the Reynst.

A lot of thought must go into the way the flows will change over the duration of the cycle, how eddies in one part will affect flows in another etc. This is what I am talking about when I say (as I do very often) that pulsejets are incredibly complex inside, despite being mostly a simple assembly consisting of a tin can and two pipes.

Well-educated people tend to dismiss the idea of complexity, but they are often wrong. I remember the case of the bicycle, whose mechanism of stability was for ages assumed to be the gyroscopic effect. It was only relatively recently that someone debunked the idea and offered the real explanation, which was a bit more complex than that.

Gary Robinson's Black Beast should have shook the Antipodes when he fired it up, but it only produced benign, lethargic whooshes. Ajustment of the position of the exhaust tube did not help. He made it easy to slide the pipe up and down but it produced no visible difference.

The problem may have been in the incorrect ratios between the intake and exhaust port areas; I don't know. Gary had to abandon the project temporarily due exigencies of everyday life and later never really found time to return to it, but it certainly proved unexpectedly complex. He and I both expected the thing to work well right off, especially given its impressive dimensions. Big pulsejets are always easier to get to work than small ones.

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Post by vhautaka » Thu Jan 15, 2004 9:07 am

Yep, even a couple of drops ether in a plastic bottle give enough blast to hurt human ears. :)

My most successful "potato gun" type experiment was a thick-walled plastic bottle with a trigger-type stove/barbecue lighter through the bottom, and a tight-fitting cardboard tube glued to the bottle mouth. After the first launch I was soft of afraid to hold the thing in my hands, but the Finnish plastic return bottles seem to hold together well enough.

That's one of the reasons pulsejets appeal to me; I always wanted to make a thing like that fire machine-gun style, with or without projectiles... Just couldn't figure out how to ventilate it fast enough without a compressor or something.

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