Double lockwood blast compression proposed design

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steve
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Double lockwood blast compression proposed design

Post by steve » Sun Jun 06, 2004 6:52 pm

This was an idea I had awhile back as a way to maximize the pressure in the combustion chamber. If it works like I think it should, all the air being sucked in as well as exaust returning from the tailpipe should impact violently at nearly the same time in the middle of the combustion chamber. I'm pretty sure it wouldn't run because of some obscure detail that I overlooked but the idea is interesting nonetheless (at least to me). If someone has built something similar I'd love to hear about it
and now, the pictures:
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Mike Everman
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Post by Mike Everman » Sun Jun 06, 2004 8:23 pm

You of course must build it and see! Half of your concept engine is what I've been wanting to do, kind of a concentric Thermojet. Graham and Nick can tell you about the trials you will go through with BCVP, but I sincerely hope you make this your next thing. Few riddles in this world are as fascinating to my eye.

The LH areas and lengths are a good starting point, though it gets fuzzy in my mind as to CC length. I was thinking

I never want to discourage someone from trying something like this. I do however feel that it is unstable, rewarding a weak pulse with a weak ingestion, and so on, moving the sweet spot toward one end, a few cycles to flame out. This needs to be addressed I think. It may not be the case. Perhaps the "pop locus" moving toward an end after a weak pop at that end would make for a stronger ingestion? I can argue both.
Mike Often wrong, never unsure.
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Rossco
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Post by Rossco » Sun Jun 06, 2004 11:46 pm

Very tricky one!

Ive envisaged all sorts of things along the same theory. BUT
Central combustion is a headache! As Mike has said, balance is too critical in this design. Well, very hard to achieve anyway! For this design, i would suggest, with no suggestions of method, a self regulator (balancer).

I have many designs for a similar EP chinese style engine, but come to no conclusion on auto balancing, so went no further with it.

What i did diverge to from this is a comon duel combuster idea. Where the blast from one end is used to compress and ignite the other. This then is not balanced in the middle, rather bouncing from one end to the other. This also has some balancing issues, as all PJ's do, and CC length is what i get all screw headed on too! But i think less than similtanious motion.

Ill stick some of my scribles in here for you, as ideas only, they by no means run, or have been built, or for that matter even are of solid theory.

These configerations also lend themselfs to well to mixing plenum chambers, rynest style. In fact they are all renyst style.

These arnt all the designs that i have come up with along these lines! Just most of the other ones crashed and burned with the last computer brain fart!

Rossco
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Post by Bruno Ogorelec » Mon Jun 07, 2004 10:53 am

I have considered the idea a lot. For a number of reasons, this is a very exciting idea to me. It offers a great number of possibilities in many directions.

Mind you, I am talking of a two-sided combustor, not about teh tailpipe entering the combustion chamber. I am not sure about the latter. gary Robinson built a big, big, huge pulsejet in that configuration, but couldn't get it to sustain. I think he may have had too short an exhaust -- or maybe teh configuration simply isn't any good.

But, without the tailpipe up its... er... mouth, what you have shown is a Reynst combustor that has another Reynst combustor instead of the simple closed bottom. Reynst thought it possible, and had some weird ideas about possible performance, but apparently never tried it in practice. If he did, he did not publish the results.

If one Reynst works, a double should be able to do it, too. But, what if one vortex descending one side of the combustor interferes badly with the vortex descending the opposite side when they meet in the middle?

What if the thing works only if both inflows are perfectly symmetrical? I would really, really want someone to try this. If it does work, I have a perfect design of a pulse ramjet that will work at all speeds from zero to Mach 1. I showed it to Bill Hinote at some point early last year, but he was skeptical about such a combustor working.

Please try it and let us all know if it works.

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Post by Bruno Ogorelec » Mon Jun 07, 2004 10:55 am

Rossco,

Yes, your sketches are very close to some of the layouts I have been thinking about. You and I seem to be getting remarkably similar ideas. First the inverted intake and now this. Weird.

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Post by steve » Mon Jun 07, 2004 10:14 pm

It just occured to me that the airflow in the cc is the slowest of any part of the engine. that means that even if the vorticies and airflow inside the cc were stabilized with fins or something (by the way, has anyone tried that?) and gotten it to run, the two masses of air/exaust would not collide with enough force to produce the pressures I intended the design to generate. Correct me If I am wrong (and that is most of the time) but in hindsight this layout seems pointless and unessarily complicated if not kind of cool looking in a rube goldberg sort of way.
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Post by Bruno Ogorelec » Mon Jun 07, 2004 11:09 pm

steve wrote:It just occured to me that the airflow in the cc is the slowest of any part of the engine. that means that even if the vorticies and airflow inside the cc were stabilized with fins or something (by the way, has anyone tried that?) and gotten it to run, the two masses of air/exaust would not collide with enough force to produce the pressures I intended the design to generate. Correct me If I am wrong (and that is most of the time) but in hindsight this layout seems pointless and unessarily complicated if not kind of cool looking in a rube goldberg sort of way.
Steve, why do you want high flow speed? What you need the most is pressure. For the given volume, the lower the speed, the higher the pressure. You should _want_ low speed. tht's why all subsonic jet engines have diffusers up front -- to slow down the flow and convert the speed to pressure.

If you are talking the energy of the two charges that will collide, it stays the same. The speed falls of but the pressure rises. Instead of two masses colliding at high speed but low pressure, you get the same two masses colliding at low speed but high pressure.

What you failed to see is the real beauty of the concept. It is symmetrical. That means that the impulses coming into the chamber for the opposing sides are equal. If further means that those impulses are converted to pressure to the greatest possible extent, generating teh greatest possible pressure from the available energy.

In asymmetrical designs, an impulse (say, a pressure wave or mass flow) coming in does one good thing but spoils another. For instance, the fact that in a Lockwood one port is shorter than the other means that the process of expansion is interrupted too soon by the start of suction at the shorter end. The pressure thus never gets as low as it might. As a result, the suction is also weaker than it could be. Valve-equipped engines are even worse in that respect, but fortunately they have other virtues that keep them performing comparably well.

So, don't dismiss a potentially good idea offhand.

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Post by steve » Mon Jun 07, 2004 11:40 pm

the lower the speed, the higher the pressure.
you're right, I completely forgot about our friend bernoulli.
So If its true what you say and the turbulence in the cc can be stabilized so the engine will run, then It would be a pretty powerful design.
you mentioned earlier that the collision of the vorticies inside the cc could make combustion unstable. In a reynst engine these vorticies are bennificial if not essential for proper mixing, but in a double lockwood they wouldn't be necessary right? <probably wrong> If they are not essential then would it be possible to reduce or eliminate them with a series of fins running the length of the cc (sort of like the way an aircraft's wingtip vorticies can be reduced with winglets) When I get some spare time I'll have to draw what I'm talking about
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Post by Bruno Ogorelec » Mon Jun 07, 2004 11:59 pm

steve wrote:
the lower the speed, the higher the pressure.
you're right, I completely forgot about our friend bernoulli.
So If its true what you say and the turbulence in the cc can be stabilized so the engine will run, then It would be a pretty powerful design.
you mentioned earlier that the collision of the vorticies inside the cc could make combustion unstable. In a reynst engine these vorticies are bennificial if not essential for proper mixing, but in a double lockwood they wouldn't be necessary right? <probably wrong> If they are not essential then would it be possible to reduce or eliminate them with a series of fins running the length of the cc (sort of like the way an aircraft's wingtip vorticies can be reduced with winglets) When I get some spare time I'll have to draw what I'm talking about
Steve, I am talking theoretical, what I learned from others. You have to have vortices to get good mixing. Without it, the poor mixture will cause bad running or no running at all.

You can try to get laminar flow instead of turbulent, but then you'll face a tough task of mixing in fuel into such a tidy flow. Very, very difficult. I know of only one engine design in the entire history of pulsejet development that used laminar flow. Everyone else uses turbulence.

What Reynst did is, he replaced a lot of small chaotic vortices (that you find in most pulsejets) with one big one (or a train of a few big ones). In this way, he kept the mixture moving in a common direction, rather than dissipating the momentum.

Whether you can replace the bottom of his combustor with another combustor turned towards the opposite side is anyone's guess. If you can get the two incoming charges to collide in the center more or less symmetrically, well, great! I'm just not certain that it can be done neatly. I don't know anyone who has tried that.

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Post by Mark » Tue Jun 08, 2004 12:13 pm

I wonder if there is a Reynst museum of sorts somewhere, some remaining relics of his work?
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Post by Bruno Ogorelec » Wed Jun 09, 2004 6:52 am

I strongly doubt it. maybe his grandchildren are holding onto some memorabilia and that's that. He's a relatively obscure figure. Only the people interested in pulsating combustion get to know about him and -- let's face it -- they are few and far between.

Who was it -- Mike Kunz? -- that located a copy of his book in a university library a few years ago and found out that in 57 years the book had been on the shelves, he was its first reader ever.

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