Reynst type propulsive duct

[Mike Everman]

Hey Bruno, anyone every actually make the Reynst style for a propulsion unit, or only for boiling water?

[larry cottrill]

Here's a stainless Reynst front end, for $32.00 by Coleman. I've seen them on sale in the sporting goods section at Wal-Mart. They look even better in real life than in the picture [a bit more tapered toward the top than what this shows]:

http://www.coleman.com/coleman/colemanc ... Percolator

L Cottrill

[hinote]

Hey Bruno, anyone every actually make the Reynst style for a propulsion unit, or only for boiling water?

Follow this train of thought:


1. Take one Reynst engine, in its classic form with slit and megaphone stack.

2. Add intake tuning in the form of an annular add-on, wrapped around the exhaust stack.

3, Now, substitute intake tubes of the same length and total cross-sectional area as the intake annulus had.

See below for the final result (already posted on the Off Topic Forum).

Bill H.
Acoustic propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."

[Viv]

Hey Bruno, anyone every actually make the Reynst style for a propulsion unit, or only for boiling water?

Follow this train of thought:


1. Take one Reynst engine, in its classic form with slit and megaphone stack.

2. Add intake tuning in the form of an annular add-on, wrapped around the exhaust stack.

3, Now, substitute intake tubes of the same length and total cross-sectional area as the intake annulus had.

See below for the final result (already posted on the Off Topic Forum).

Bill H.
Acoustic propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."

And that will lead you back to the Hinote point thread and the last discussions when we classified the engines in to rough types.

Logan, chinese, thermo, tharrat, pressure jet, all Reynsts as per Bens nice little drawing of an annuler chinese.

A pot type combustion chamber with a resonant exhaust and what ever takes your fancy for inlet geometry at the one third two thirds point (don't jump on me Larry:-)

Heres one of my old ones from the vault:-) circa 2000

Viv

[Mike Everman]

No no no! The Reynst is similar acoustically, except for limited resonant behavior of the intake tract. It is different in that the intake is always drawing in, even when the CC is exhausting.
Reynst documented the strong vacuum draw available in the intake manifold, and not just during injestion.
I was playing with a PVC tee fitting last night as a simulator, and you can blow like hell down the straight, and squat comes out the branch hole.

I'd like to ask Mark to consider putting a tee at the base of one of his snorkeler stacks, with a ball valve on it. I believe that you could put a carburetor there without trouble for true Reynst type breathing.

I shalange you to prove this is not so! ;-) Ha ha!

[Viv]

No no no! The Reynst is similar acoustically, except for limited resonant behavior of the intake tract. It is different in that the intake is always drawing in, even when the CC is exhausting.
Reynst documented the strong vacuum draw available in the intake manifold, and not just during injestion.
I was playing with a PVC tee fitting last night as a simulator, and you can blow like hell down the straight, and squat comes out the branch hole.

I'd like to ask Mark to consider putting a tee at the base of one of his snorkeler stacks, with a ball valve on it. I believe that you could put a carburetor there without trouble for true Reynst type breathing.

I shalange you to prove this is not so! ;-) Ha ha!

Yes yes yes the derivative engines just add this resonant intake to the basic Reynst.

They are derivates of the Reynst:-)

Viv

[Mike Everman]

No no no, the derivatives are flow reversing inlets with all the attendant fueling grief!

[larry cottrill]

I was playing with a PVC tee fitting last night as a simulator, and you can blow like hell down the straight, and squat comes out the branch hole.

This is essentially steady flow. For it to have suction [not just neautrality], make the tee smaller and use a reducer before and after the tee, and you should get a suction measurable with a sensitive manometer [say a straw in a glass of water]. The static pressure in a simple tee is virtually constant under constant mass flow.

The latest little mini-compressor I bought has a diffuser to inflate air mattresses - AND, a little venturi to pull them back down quickly. Very neat.

I'd like to ask Mark to consider putting a tee at the base of one of his snorkeler stacks, with a ball valve on it. I believe that you could put a carburetor there without trouble for true Reynst type breathing.

I shalange you to prove this is not so! ;-) Ha ha!

Since his snorkelers use straight pipes, this would be very nice if the stack pipe could be seven times as long as the distance from the bottom of the "pig" to the tee, putting the Reynst Point at L/8. Could be a real performer, in a low frequency kind of way.

As Graham alluded to, broadening the stack into a big cone profoundly affects where the ideal Reynst Point will be found. On the classic Reynst Pot, it's practically L/3 !!! But this is because the stack is so massive and breathes so well that it stays practically cool compared to the chamber. I note that on the diagram you posted at the beginning of the thread, it's closer to L/4, due to the stack being significantly narrower than in the classic design. The better re-filling of the stack you have, the cooler it will be internally, and the slower the waves will run to bring low pressure back to where you need it to aspirate the engine. On most well-developed straight-pipe designs, L/8 is apparently pretty good; on crudely designed engines like my Elektra I, it's more like L/12 [at least, if the intake impedance is kept low].

I am convinced that the placement of the Reynst Point is 100% dependent on how well the engine does at replacing the tail slug with cool air. This, of course, can be affected by several factors in the design. Even a little flare at the tail end will have a noticeable impact.

Viewed in one way, the classic Reynst Pot is unbeatable - it is practically a cold air pump driven directly by explosive combustion! [Of course, this is probably a slight exaggeration, since I've never actually seen one in action ... but probably just slight.]

L Cottrill

[Mike Everman]

hi Larry. The diagram at the beginning of this thread I believe to be a cartoon, and I suspect it has never been built. Someone must do this! How many times has it popped up, whether annular or otherwise and no one tries it? Wish I had time.

[Mike Everman]

This is essentially steady flow. For it to have suction [not just neautrality], make the tee smaller and use a reducer before and after the tee, and you should get a suction measurable with a sensitive manometer [say a straw in a glass of water]. The static pressure in a simple tee is virtually constant under constant mass flow.

As to that, the Reynst CC exit is of smaller dia than the stack opening, so it will draw fuel/air mix into the stack in the exhaust phase. This could be eliminated by making the two diameters similar or the same. Depends on what you want to happen; this may be a good thing, kind of like afterburning.
My point was not necessarily to draw in in this phase as in a venturi, that is already handled by the vacuum created in the CC, it will draw in both stack and intake because of this.

The chinese style is tantamount to blowing in the branch of the tee, whereas the Reynst is more blowing down the length of the tee. Very different. When injesting, they are virtually the same thing, as a vacuum draws omni-directionally.

The Reynstish approach eliminates the need for pressurized fuel for the most part, other than for your need to pull hi G's. ;-)

I can just hear Bruno yelling "THAT'S WHAT I'VE BEEN SAYING!!!"

[Mark]

Mike,
Those sketches came out of the something something Symposium on Pulsating Combustion I have. There is an actual photograph of the rooster headed one with the wacky rectifier. I think I could find a picture the double branching one too on some test stand.
I think these designs were conceived without proper parenting skills, and might be bastardly.
Mark

[Mike Everman]

Viv, Bill, giving up just like that? I'm whipping myself into a burning need (ha ha, unintentional pun) to make a snorkeler with a pipe T in its neck and fuel feed in the branch. Surely Nick would build one, too...

[Mark]

I've drilled a small hole in my snorkelers, at the base of the tube where it joins the tank or canister on the canister sizes. In my studies, it was a complete no-no. First you have this up and down motion, a burning need as you say, and then you throw air into the resonant effect, in my case it dampened and killed the effect most notably.
Maybe if you could catch the wave, introduce the secondary flow at a friendly angle and at the right node and moment of pause and effect. A 90 degree angle of inflow just wrecks havoc, yet seems to be fine for the side port Logan but you do not have more than one channel contending at the confluence.
In the first place the snorkel is building a piston effect and if you open a side port to that, it bleeds off pressure. Maybe by making a long enough small secondary tube , the escaping gases would sense a block and not try to escape prematurely out your secondary channel.
I haven't thought much about this topic, I am just shooting from the hip, telling you what happened to me. I didn't try a whole lot of variables or positions.
Mark

[hinote]

Viv, Bill, giving up just like that? I'm whipping myself into a burning need (ha ha, unintentional pun) to make a snorkeler with a pipe T in its neck and fuel feed in the branch. Surely Nick would build one, too...

I'm here (sort of).

One of the interesting nuances of the Reynst is that the intake slit can be shaped and proportioned so the exhaust outflow pressure can be roughly balanced by the Bernoulli effect. The result is that fuel does NOT flow during the 1st part of the outflow--a desirable effect since it would result in unburned fuel going out the stack.

After the pressure drops a bit, the Bernoulli effect becomes stronger than the outflow pressure and the fuel begins to flow. The fuel/air slug which partially fills the stack during the remainder of the outflow cycle is rammed back into the comb. chamber, and supplemented by additional fuel during the inflow cycle.

So the slit design is critical.

Reynst mentions intake tuning as a refinement of his concept, but I don't see any evidence he ever tried it.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

[Mark]

I used the TLAR method and a lot of trial and error. It's funny, the 1 inch pipe and the 1 1/14 inch pipe both work well. I tried some 1 1/2 inch pipe but it wouldn't sustain. I put short lengths of 3 inches on the tank and it runs well that way too. And too, I can just screw in an adapter plug in the top with an inner threaded hole and it then works like a jam jar lid.
I tried variable diameter snorkels and a whole lot of other sizes though, it wasn't a cake walk with the longer snorkels.
I also experimented with a short snorkel and a long snorkel side-by-side, kind of the Chinese approach, since my tank has female 2 inch, 1 inch, and 1/2 inch fittings in the top. If you can imagine me screwing in one fitting after another, TLARing, there's alot of combinations and no luck as of yet. I tried opening/unplugging the two tiny side ports of 1/8th fittings on opposite sides. No luck there. Funny a tiny hole destroyed the snorkeling like you wouldn't believe.
Then I tried opening up holes in the opposite end of the tank, I got some horrible cannon fire, the rumbling echo kind. I didn't think the neighbors should be subjected to that so I discontinued toying with exponential burning.
It's an ideal tank for experimentation, I already had several pipe fittings and it has 7 places to screw in lengths of pipe. It's facinating to me it can breath so deeply down the snorkel and still run robustly. To see it run is a treat. I can start it up and go inside the house for a few minutes and then return to still see it running steady as can be.
Mark