Reynst Pot test rig

tufty · Post by **tufty** » Wed Dec 24, 2003 6:13 pm

Hi all.

I'm a new member, although a relatively longterm lurker, primary interest here is valveless pulsejets in general, and Reynst combustors in general.

As a followup to my post on the eGroups (well, Yahoo!Groups, these days ;-) pulsejets forum here, some more thoughts and a proposed design. I'd like some feedback as to the validity of this approach.

The attached drawing covers the combustor chamber part of my proposed test rig - this will be a piece of straight steel pipe, honed on the interior to take a piston, and threaded at one end to take varying shapes of combustion chamber 'ends'. These ends will have large holes, the orifices being variable using detachable 'orifice plates'.

Welded to the main chamber will be lengths of threaded rod to hold in place the orifice plates and allow adjustment of piston depth.

After the orifice plate comes a fuel feed system (basically, a 'closed' annular feed of fuel/air mix attached to an air metering system, and then the 'exhaust'. This will be of steel pipe, cut to 'binary' lengths and threaded to fit one into the other, allowing the exhaust length to be adjusted arbitrarily.

The air metering system will be a large, volumetrically indicated, glass belljar, floating in water, feeding from the top and counterbalanced so as to provide air at atmospheric pressure.

I'm thinking liquid fuel, maybe standard unleaded or plain methanol to avoid having to preheat, and I can knock together an atomiser from one of the old (car) carbs I have floating around, or maybe buy a needle jet assembly intended for a large model A/C engine.

Basically, the plan is to have something that can be adjusted (almost) infinitely for a given combustion chamber diameter, to see what effect varying the various parts has. I intend to blag a DV camera that does timecode from somewhere to record test runs and then analyse the results and see if I can come up with something concrete linking variables to results.

I have a bunch of old brake pistons of various sizes lying about (from little tiddly scooter brakes to big truck models) so should be able to vary diameter as well as the other variables, access to steel of useful sizes allowing.

Thoughts?

Simon
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Post by **Mike Everman** » Wed Dec 24, 2003 6:58 pm

Hey, Simon. How's the Alpine weather?
I like the approach, and the potential data to come out of it. Initially, I would run it vertically like a jamjar and just drip fuel in a small port in the orifice plate. It'll be great to see the dependence of frequency on orifice size and volume, or as compared to diameter/length or surface/volume. If you've got a load cell, it would be nice to have impulse data, though now that I think about it, you're recording the sounds digitally, so maybe you could just mount a whistle somewhere near the exhaust, and you'll get comparitive implulse data after doing a transform on the sound.
Mark'll probably chime in on this one, he's the JamJar king, among other things. What I've learned from him, and my own very recent experiments is that:
Sealing is very important (you'll need an 0-ring on the piston, or a really good honing job)
Humidity is bad for your fuel and operation.
Orifice quality is important, and a good starting point is 12mm for chambers of 50-100mm dia.
Also a good starting point volume is 1:3 diameter to length.
Too much pooled fuel will hurt operation.
Temperature of chamber is a variable, and hot engines can be hard to start again until they cool. (so if you really want to do it right, you should water cool the chamber and monitor the water temp.)
Whenever you change orifices, it would be nice to chamfer the hole on the exit side and re-run, or have another that is chamfered, to see if there is any effect of thick orifice material.

That's all I can think of for now.

Mark · Post by **Mark** » Wed Dec 24, 2003 8:25 pm

Yea, I would orientate the combustion pointing up and use methanol. Varying the combustion chamber is a good way to get around a lot of guess work, just as trombone lengths of pipe on a pulsejet exhaust tube do the same. It's a lot of trial and error when fishing for the right dimentions. Some days I get kind of cranky, when nothing works, but that's the way it's going to be when you toy with the unknown.
Mark

Nick · Post by **Nick** » Wed Dec 24, 2003 9:05 pm

Hi,

last year i made a small reynst pot with a water cooling jacket which runs for as long as you want to keep putting fuel in and can keep the temp steady, i use a 1 litre bottle as a temp syphon system but it needs bigger for longer runs of 3 minutes or more as it will boil the water pretty rapidly.
fuel is fed via a small pipe and ball valve, gravity ensures that the pressure going in is slightly more than the high pressure fluctuations inside the pot, but it is a temperamental set up and needs refining.
i can do a little film of it running and a sound file if you wish.

Nick

Post by **Mike Everman** » Wed Dec 24, 2003 11:40 pm

I'd like to see and hear it Nick! Hey, I wonder if a camera iris might be rigged up to make a variable diameter one could change while the engine is running? Uh, oh, another camera bites the dust for parts....

Nick · Post by **Nick** » Tue Dec 30, 2003 8:57 pm

Hi all,

as requested i have made a short film of the little reynst poyt running, however when i tried to attach it to this message i got a error saying that the forum does not support windows media files .wmv extn so i cant post it here. if someone has software to change the format to quicktime or whatever let me know and i will email it to you, its about 3.8mb.

Nick

Viv · Post by **Viv** » Wed Dec 31, 2003 2:03 am

Nick it may be just as easy to ask Kenneth if he can allow .wmv's to be uploaded?

Viv

Stephen H · Post by **Stephen H** » Wed Dec 31, 2003 8:44 am

nick send it to me and i will host it then give everyone a link...

tufty, when the piston on your test stand moves the volume of air in the pot will increase... this would probibly notr be to bigger problim but it would effect the results...

Stephen

George · Post by **George** » Wed Dec 31, 2003 12:13 pm

Hi !

Searching informations about reynst pots, i find a site where a man called Marc de Piolenc says that he have a reynst book... maybe someone can contact him to have a copy or informations ?

The mail:
piolenc@reporters.net

The site:
http://www.repp.org/discussion/gasifica ... 00155.html

The reynst book:

Reynst, F.H.: "The collected works of F.H. Reynst; Thring, M.W.; editor; Pergamon New York 1961

Nick · Post by **Nick** » Wed Dec 31, 2003 3:06 pm

Ok, i have sent the film to Stephen as above, hopefully he will post the link soon so you can all have a gander at it.
The film is just a very small part of three or four films Viv and I did on the 30th Dec 03, there is about 150mb of it in all and many types of shots showing the everything from the water boiling up the exit tube to the engine revving in response to fuel being injected etc so if anyone has any requests, i will do some more. The editing was done with microsoft movie maker which is free with XP- its much better than i would have thought!.but it only (unsurprisingly) lets you save .wmv files.

Nick

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Dec 31, 2003 7:32 pm

George wrote:Searching informations about reynst pots, i find a site where a man called Marc de Piolenc says that he have a reynst book...

Well several people on the forum have the book. I have it, too.

My caveat concerns the fuel supply. You don't want a jam jar, but a Reynst combustor. There's a difference.

A jam jar has fuel pooled on the bottom and basically works only to burn the fuel in the pulsating fashion. A Reynst combustor sucks fuel in from the perimeter of the combustor mouth and atomizes it by the intense intake turbulence. It works in a much more powerful fashion and at greater frequency.

Reynst used fuel supply into the 'pot' only on ignition. As soon as the thing started pulsating, he would stop the fuel feed and adjust the air intake slit between the 'pot' and the exhaust tube to very narrow. This created great draft in the slit (high air speeds). The passing air picked up liquid fuel from a narrow circular 'trough' milled around the combustor mouth. Fuel was kept in it mostly by surface tension.

See the attached picture. It shows the combustor mouth pointing upwards to blow into the exhaust diffuser above it. You can also see the fuel 'trough' around the mouth, fed through the supply tube on the left.

As you can see, the air slit is very narrow and air blows through it at great speed. The suction generated is very strong (see Bernoulli law) and picks up droplets of fluid from the trough. The vortex generated in the pot on induction is so strong that it managed to atomize even heavy diesel fuel perfectly, so that it burned without smoking.

Note also that Reynst used bigger volume on ignition. As the engine started, he would push the piston up to make the chamber smaller, because it was more efficient with smaller volume.

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Dec 31, 2003 7:36 pm

Simon,

Do you plan to experiment with the internal diffuser, too? You can see its top inside the combustor on the picture I have posted. It is rather important for a proper Reynt combustor, for it helps create the toroidal swirl inside the 'pot' that makes the Reynst such an efficient combustor.

Nick · Post by **Nick** » Wed Dec 31, 2003 8:08 pm

just a note to say that the little Reynst pot featured in the film has an internal duct or diffuser fitted, this does make it run much better than it did before.
As regards fuel, currently it enters the pot via a tiny 0.7mm i/d pipe just about at the level of the duct, some further experimentation with a pipette indicates that droplets of fuel placed just at the edge of the intake also let the beast run long after the initial pool of meths has been consumed. In short even at this greatly reduced size the pot could be fuelled in the same way as the full size version. Experiments continue.

Nick

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Dec 31, 2003 8:28 pm

Nick, old friend, have a Happy New Year. You're the first cop I have ever known not to be after me, and a great guy to boot. How funny our first tries with BCVP look now! Pioneering times indeed. I'm proud to have been with you back then.

marksteamnz · Post by **marksteamnz** » Wed Dec 31, 2003 9:58 pm

I bought a copy from Marc. No problems with the transaction. It is a sharp photo copy that you can have Marc bind as you wish.
I posted a link on the old forum and my review of the book which resulted in an agree to dissagree thread developing.

George wrote:Hi !

Searching informations about reynst pots, i find a site where a man called Marc de Piolenc says that he have a reynst book... maybe someone can contact him to have a copy or informations ?

The mail:
piolenc@reporters.net

The site:
http://www.repp.org/discussion/gasifica ... 00155.html

The reynst book:

Reynst, F.H.: "The collected works of F.H. Reynst; Thring, M.W.; editor; Pergamon New York 1961

www.pulse-jets.com

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