Crack of the Snorkelers

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PyroJoe
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Re: Crack of the Snorkelers

Post by PyroJoe » Wed Apr 14, 2010 2:13 pm

Maybe by some means you could get a snorkeler to breathe more deeply and by doing so increase the thrust of a device,
This idea has legs and has already shown considerable results in the draft engines. Not only will it breath more deeply, it will nearly utilize the entire CC volume. Aerodynamic valving helps considerably in operation. Thrust was elusive, not so much anymore.

I should make up a drawing showing how a draft engine and snorkeler are closely related and why certain configurations are utilized.

Mark
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Re: Crack of the Snorkelers

Post by Mark » Wed Apr 14, 2010 2:21 pm

Another variation that might be fun to try instead of the dividing wall down the center of a snorkel is a slightly smaller diameter tube sleeved inside the larger. I wonder if the candle experiment would work with a tube within a tube, to convect air down to sustain a candle flame? In some Squid study with the Dynajet, the exhaust was seen to be choked down at the end of the cycle and while still having an outflow, inflow was occurring around the perimenter, flow in two directions at the same time for at least part of the period. It's really something to me to think about my piglet snorkeler when it is running so briskly, how that air is getting down there through the snorkel into the tank fast enough to sustain such lively combustion.
I wonder if some combination of a tube within a tube and a center dividing wall would be anything to try? I wonder too if the Enics drone twin exhausts both fire at the same time or if they are alternating? Not that the Enics engine is anything like a snorkeler, but the twin exhaust tubes are very much in form like single tube divided by a central plate, as in the candle experiment.
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Re: Crack of the Snorkelers

Post by Mark » Wed Apr 14, 2010 2:58 pm

PyroJoe wrote:
Maybe by some means you could get a snorkeler to breathe more deeply and by doing so increase the thrust of a device,
This idea has legs and has already shown considerable results in the draft engines. Not only will it breath more deeply, it will nearly utilize the entire CC volume. Aerodynamic valving helps considerably in operation. Thrust was elusive, not so much anymore.

I should make up a drawing showing how a draft engine and snorkeler are closely related and why certain configurations are utilized.
All of my draft engines seem to dampen thrust and feedback. In my experiments, even relatively small holes weaken amplitude compared to a sealed snorkeler. If there was some way to gate in fresh air from the combustion chamber while amplifying feedback, that would be nice. But simple holes in the combustion chamber didn't for me build a stronger feedback. Of course if you put tubes on the holes, you are once again back to an Enic. ha
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Re: Crack of the Snorkelers

Post by PyroJoe » Wed Apr 14, 2010 3:51 pm

even relatively small holes weaken amplitude
Very true, this is why there needs to be a certain length to the intake, otherwise the pressure bleeds away much to soon.

The Enic intakes probably bleed pressure (and fuel) in a copious fashion. There are some other things about the Enic that I considered flawed, but will refrain, for the engine probably does a fine job in the role it is intended.

The engine I would most like to see at the moment is Erics new one.

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Re: Crack of the Snorkelers

Post by PyroJoe » Wed Apr 14, 2010 9:56 pm

Here are the plans for the fuel test, not much different than the Kraken, just pointed skywards on the side of the snorkel. There is probably a optimum angle of the fuel pipe, will have to do some "trial by fire".
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Mark
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Re: Crack of the Snorkelers

Post by Mark » Thu Apr 15, 2010 2:10 am

One thing about fuel injection is that it keeps the fuel fresh, unlike my piglet snorkeler that eventually stops running and leaves just a bit of slosh in the bottom, probably methanol loaded with a high water content, for water is one of the by-products of methanol combustion. I think with my little jam jars that run for four or five minutes the same thing happens, the remaining fuel gets too watery. The battle then is not so much keeping the fuel at a proper level and the vessel cool, but more a battle with steam/water condensate. I wonder if some CaCl2 would help to absorb some of the water. Maybe it would impart a nice red flame to the fire. ha
http://assortedtips.blogspot.com/2008/0 ... ifier.html
http://www.flickr.com/photos/37388341@N ... et-214153/

On the other hand with my piglet snorkeler, it can be fussy to get it to sustain on certain days when the weather is not right or even when it is right. When it doesn't want to start the first try and I don't feel like intubating it and firing up my air compresser to air it out, I just put a loose fitting plastic cap over the top of the snorkel and try again later in the day or the next day, parking it in the shade somewhere. It's funny but the loose fitting cap will allow for it to air out after several hours of sitting for another zippy try. Sometimes the game will go on for several days. Then it will decide to start, and I suspect that this is because of two variables. One is the obvious hot day and sluggish starting and then slowing deciding it isn't going to run and chuff, chuff, chuff and it's out. You have to have a cool time of the year or try when the humidity is low.
The other variable is the perfectly cool day and ideal conditions for really perky combustion. In this case the snorkeler will hiss loudly and then flameout after a few very fast chuffs. Over and over again. So I give up and wait for the next day. Finally I think the methanol absorbs a bit of water from the air and that slows down the initial whoosh enough for it to catch. It may be that a small amount of water is beneficial to some designs, if you are using a lot of fuel that sloshes in the tank or other variables. Some days I would funnel all the fuel out and measure it to be sure there was still the same amount as from the initial try, to make sure it wasn't evaporating away. As you can see, my piglet snorkeler often requires some patience. But when it runs, it's something to behold - for its simplicity. "ha"
Last edited by Mark on Thu Apr 15, 2010 12:06 pm, edited 4 times in total.
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Re: Crack of the Snorkelers

Post by Mark » Thu Apr 15, 2010 2:23 am

PyroJoe wrote:Here are the plans for the fuel test, not much different than the Kraken, just pointed skywards on the side of the snorkel. There is probably a optimum angle of the fuel pipe, will have to do some "trial by fire".
That looks like a fun design if you are able to keep it running indefinitely. One thing though, as with my little Logan, I suspect some of the fuel will be spewed out without getting ingested or burned efficiently. Maybe later, you could design an internal fountain effect that would confine the fuel more inside the tank. If you get it to sustain for a long time, please make a video. Looks like a fun project to me. And the shape of the vessel seems promising too.
Maybe you could make a little car or boat out of it, a cute putt putt vehicle. It's every bit as interesting as a pulsejet to me.
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Re: Crack of the Snorkelers

Post by Mark » Thu Apr 15, 2010 3:34 am

One thing I was thinking about with holes in a draft engine is that the air might partially/softly dive in all around the edges of the hole and with a short snorkel of an intake of the Enics engine you not only get a little bit of a piston effect but also a more of a directional inertial throw of the gases, something more coherent.
I have tried in the past to think of a way to use a bunch or mesh of tiny holes and still get a good feedback to develop. It's such a tease to light a duct closed at one end and misted with methanol. You get such an impressive bark out of a straight tube, it's taunting to find a way to sustain that effect simply, in some new way.
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Re: Crack of the Snorkelers

Post by PyroJoe » Thu Apr 15, 2010 2:39 pm

Using a modifed metal lawn mower fuel tank to supply fuel. The brackets, heat shield etc. will require nearly as much construction time as building the jar. The thrust to weight ratio may be reasonable in a thin stainless steel version. When we become rich and shameless a thin walled titanium unit will do. :wink:


All of my draft engines seem to dampen thrust and feedback. In my experiments, even relatively small holes weaken amplitude compared to a sealed snorkeler.
This 3" dia CC draft engine has about the best thrust to weight ratio, and has been banished from indoor running. Earplug loud, very radical and has a tendency to shotgun blast on the first ignition. When I hold the tail pipe (with gloves) the CC will tend to push forward. This being said, the design can be improved considerably. It is the strongest of my methanol "fuel pool" engines.
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Mark
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Re: Crack of the Snorkelers

Post by Mark » Sat Apr 17, 2010 12:05 am

I should say when I tested my snorkelers with holes in the combustion chamber, they didn't like it. And I shouldn't have referred to them as draft engines really as the proportions of a draft engine are different. When I put a 3 foot length of big 2 inch diameter plumbing pipe on my piglet snorkeler, it gives the gases more freedom. I never got it to sustain in snorkel mode but it did make some very loud cannon noises and I worried about the police coming to visit. ha
The thing about "fuel pooled" engines is that you can't have extreme combustion or else the fuel will fly about too wildly and destroy any steady state fueling. Another thing about "fuel pooled" snorkelers and draft engines is that the thrust is not really very functional as a toy unless you are hot air ballooning or spinning tennis balls. ha
(I should say it would be nice to have them run as well in the horizontal as they do in the vertical.)
I remember putting a large washer in the front end of some of my typical homemade plumbing pipe pulsejets with typical Dynajet proportions. The washer would if you primed the engine and lit the front end, would go off like a gunshot, the flat face acting as some kind of reflector. Long ago I made a growly valveless/draft engine of sorts out of a 4 inch sphere with a long piece of pipe threaded into one end and the opposite side of the sphere just a hole. When "fuel pooled" and held at a 45 degree angle with the tail up it, the arrangement would rev up to a high speed but it was weak in thrust.
I have a 3 foot length of titanium tubing about 1.75 inches in diameter and another of the same lenght 2.5 inches in diameter. And I also have some 1 inch diameter and a few pieces in the 1/2 inch size, one piece is 6 feet long I think. Then I have a small bundle of 1/4 inch titanium tubing too. The 1.75 inch diameter stuff is an amazing .020ths thickness so it is very light. And I suppose since titanium is kind of reactive with very hot air, a snorkeler would be a better choice than a pulsejet. But I have no way to transition the pieces or weld some toy of sorts together. I think titanium would be ideal for a cooler running snorkeler if you needed something light that could fly or propel itself along.
"Titanium burns in air when heated to 1,200 °C (2,190 °F) and in pure oxygen when heated to 610 °C (1,130 °F) or higher, forming titanium dioxide.[7] As a result, the metal cannot be melted in open air as it burns before the melting point is reached, so melting is only possible in an inert atmosphere or in a vacuum." "It is also one of the few elements that burns in pure nitrogen gas..."
http://en.wikipedia.org/wiki/Titanium

I ran across this tidbit on flue gas stacks, perhaps vaguely of interest.
http://en.wikipedia.org/wiki/File:Chimney_effect.svg
http://en.wikipedia.org/wiki/Flue_gas_stack

Titanium cooling.
"Cooling was carried out by cycling fuel behind the titanium surfaces at the front of the wings (chines)."
http://en.wikipedia.org/wiki/SR-71_Blackbird

PS
"When we become rich and shameless a thin walled titanium unit will do."
Maybe one day. Oh!
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Re: Crack of the Snorkelers

Post by PyroJoe » Sat Apr 17, 2010 7:15 am

If time permits, will someday further develop that 3" engine, it likes turbulence on the surface of the pool, and there is plenty of surface area for the pool to create enough vapor. The front of the CC is very lax,(longish) but if I modify it to a better design it will out run the fuel pool and go lean.
At full zest it will stack most of the pool up near the intake.

Starting to find solutions to this problem. Ever notice how some engines produce more thrust from the intake while others produce more from the tail? If a engine where perfectly balanced the fuel pool may have a chance of remaining reasonably stable in a horizontal orientation.

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Re: Crack of the Snorkelers

Post by PyroJoe » Tue Apr 27, 2010 2:31 pm

Continuing work on the 6" Jar with the side flare snorkel. The flare is welded, the inside transition of the flare is filed & sanded smooth. Need to drill a hole in the flare and construct a support for the fuel pipe on the snorkel.

Have spent considerable time in preparing the fuel tank. The tank is from a Briggs&Stratton 3.5hp engine. The leg supports allow the height to be adjusted for various applications, also the slotted angle is easy to attach to a thrust stand. Cut a plate to cover the opening left from the carburetor, finished cutting a cork/rubber gasket last night. The thickness of the original carb flanges were thick, and the replacement plate was rather thin, this created a condition in which the original mounting screws bottomed out in the threaded mounting holes. Had to grind some length off the fastners and clean the threads.

Cut a hole through the plate and into the tank to route the fuel line, previously welded a cradle into the rear bracket to clamp the copper fuel line.

Need to cut a few more braces for the lower supports.
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Re: Crack of the Snorkelers

Post by PyroJoe » Tue May 04, 2010 7:29 pm

Attached the fuel pipe/cradle to the side of the snorkel, via welding a bolt to the side of the snorkel. The depth of the pipe can be easily adjusted, and by bending the two rods on the cradle the angle can be adjusted.

Need more methanol fuel, but is very near to testing time.
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PyroJoe
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Re: Crack of the Snorkelers

Post by PyroJoe » Mon May 10, 2010 2:36 pm

After considerable adjustment, it is becoming apparent that the sluggish response of the fuel system is a problem. I shortened the circuit by several inches, but the response is not quick enough. Fuel flow appears to be occuring at the last half of the intake cycle, and continues briefly into the beginning of the exhaust cycle. I can see a nice little cloud of fuel droplets just inside the flare at times. Most runs either ended by the cycle becoming shallow or by a rich condition.

I think two parameters need to be improved:

#1. the fuel line needs to be routed to the bottom of the fuel tank, so the circuit doesn't have a "line empty" condition on startup.

#2. The intake fuel air path needs to be shortened, as a few weak cycles will tend to shallow the depth of the intake charge and the cycle will "shallow up" within the CC and cease.

It would be nice to have flow regulation of some type as the initial whoosh, will often setup a high fuel flow condition.

Mark
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Re: Crack of the Snorkelers

Post by Mark » Tue May 11, 2010 2:04 am

I remember when I went with some "jumbo" silicone tubing for a fuel line/bigger fuel tank for my little Logan, the effect was a hammer fuel feed where it would rev up and down at an extremely high rate. Much has been said about how a pulsejet will stop if it misses a beat but the little Logan would squeal and nearly die over and over again in an erratic fashion skipping and instantly hopping from high to low in a blink, so funny the sound that it was almost something you'd want to design for. (My tubing was the fuel tank, since the Logan was so small I could get away with that philosophy). Even though the tubing was a relatively wide diameter, the final injection point was reduced/necked down to a very tiny, thin stem of copper tubing, about the diameter of a large syringe needle. I bought it in foot lengths from some hobby shop, as a straight hollow rod, not coiled, almost like capillary tubing.
I wonder if you used as thin a line as possible if it would correct some of the sponginess of the fuel flow or if a metal fuel line would work better than a flexible silicone fuel line for your snorkeler? On the Logan you could see the silicone fuel line pulse or twitch with the sudden quirks in fuel flow. The jet would respond like a scalded duck quacking with a high pitched whine and then choking and coughing and sometimes nearly dying before squealing again all the while the tubing twitching with the pressure fluctuations swingly wildly, constantly forming new stacatto arrangements.
So anyway, I was just wondering about the lag effect you are getting and if you could somehow use some of the pressure from your snorkeler to drive fuel to your engine in some fashion like my Logan, using a thin fuel line to avoid a mild hammer effect.
I once tried a very tiny duckbill one-way valve you put inside silicone fuel lines but only for pressurizing a fuel tank. Sadly after the fuel tank built up too much pressure bled off the engine, the little Logan stopped running and the fuel still kept spewing out from the head of pressure still in the tank - anything that can go wrong will. ha
Last edited by Mark on Tue May 11, 2010 2:18 pm, edited 2 times in total.
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