FWE engine for valveless testing and valveless pulsejet calc

[Eric]

When the engine produced loud bangs the entire rig would jump ahead a little bit, when a loud bang was followed by self sustaining the rig would jump and then move for a fraction of a second at constant velocity. I guess the loud bangs break the static friction and then the rig is free to move a bit at a lower level of friction. For some reason I thought I used a peice of the 12" ibeam but just to clarify, Its more along 8 or 9 inch. I guess if I put the rig back the way I had it I could do a realatively accurate pull test to determine about how much thrust it has.

It would be interesting to see if this engine could be converted into a psuedo-pulse detonation engine of sorts. If a sparkplug were used with some sort of timing unit, and these large bangs could be reproduced at high frequency, then there would be a large increase in thrust without a doubt.

I definately agree with you that the engine has really high tail suction. As soon as a rain drop hit the tail pipe and turned to steam, even if it was 6 or 8 inches down the pipe it would get sucked back parrallel to the pipe and a take an amazingly sharp turn, about 1 inch radius, all in one cycle of the engine. You just see these puffs of steam form, accelerate, and vanish in the blink of an eye


The piece of I beam gets very warm all over, and near the combustion chamber it gets down right hot. Its nice to be able to warm your hands and roast marshmellows in the raidiant heat of a jet engine :), I keep forgetting to pick up a bag. I will definatley be able to corner the pulsejet powered toaster oven market.

Eric

[Eric]

Oh yea Mike, I definately believe I have nailed what you would call a unified pulsejet theory, wether it be valved or valveless. I now need to build a massive valveless engine to see if the equations still hold true. I have also been itching to build a full size argus V-1 engine :)... I wonder if i could get away with useing something thinner than 3mm steel for the tailpipe, 3mm would make things expensive. I wonder if we could get some kind of group effort going to design and build something tremendously big and loud.

[Mark]

If you made a giant pulsejet, you could take it to remote snowy mountain regions and set off avalanches. I came across some interesting terminology refering to shock and detonation waves, it was termed "avalanche ionization." Anyway somewhere I saw a twin-tubed device about 10 or 12 feet tall, mounted on the slopes, that used propane and it was for creating avalanches at a ski resort. I think I saw the show on TV. It didn't run but merely created a sudden pulse of sound. Kind of like a valveless pulsejet without the machine gun effect, more of a hollow tube effect.
Mark

[pezman]

That avalanche control thing was a cool tip. Found some references to a "gaz-ex" or "gazex", which is a giant version of the torch pop-gun that I've been using to evaluate how geometry of tubes etc. influences pulse behavior.

[Eric]

I wonder if a running pulsejet could have the same effect on clouds. Every time it is very cloudy out and I start a pulsejet up it immediately starts to rain. It could be that the sound waves cause the water vapor to suddenly condense, or it could just be that I have really bad luck when it comes to weather.

[Mike Everman]

I wonder if a running pulsejet could have the same effect on clouds. Every time it is very cloudy out and I start a pulsejet up it immediately starts to rain. It could be that the sound waves cause the water vapor to suddenly condense, or it could just be that I have really bad luck when it comes to weather.

Ah, pulsejets as Chaos drivers... to hell with butterflies, give the chaotic system a real kick in the rear! A rain cloud must need such a small bounce to start dumping... hmmm... Faaaascinating.

[tufty]

That avalanche control thing was a cool tip. Found some references to a "gaz-ex" or "gazex", which is a giant version of the torch pop-gun that I've been using to evaluate how geometry of tubes etc. influences pulse behavior.

If we ever get any snow so the the season here can start, I'll have a word with the pisteurs and see if I can dig up some gazex docs. We use it.

Simon

[Tom]

If you can get anything on the Avalauncheur, I would be very interested...

Tom

[larry cottrill]

I guess if I put the rig back the way I had it I could do a realatively accurate pull test to determine about how much thrust it has.

Eric -

I doubt that this would be very accurate, and would almost certainly err on the side of exaggerating the thrust. My reasoning is that, with the engine running, the vibration probably alleviates much of the static friction between the beam and the blocks, making it move a lot more easily than you would think - or than you would measure in a static pull.

Of course, it would probably be somewhere "in the ballpark", possibly off by no more than a factor of two or some such. So it would give us a sort of "order of magnitude" measurement.

L Cottrill

[NanoSoft]

Eric can't wait for you calc 1.5 to come out. I really want to build a big FWE like yours but don't know how to calculate the dims so I will wait for you calc.

Nanosoft

PS. if you need some else to test your calc out tell me and I will gladly build a FWE scaled up.

[tufty]

If you can get anything on the Avalauncheur, I would be very interested...

Okay, here's the rundown on a few avalanche triggering techniques:

1: Direct intervention. Basically, the pisteurs stand above the area to trigger, and lob dynamite onto it. This is bloody dangerous, especially when you consider that this is normally done at about 5-6AM, off-piste, in bad conditions. The main danger with this, and all of the explosive techniques, is misfires - misfire == pisteurs go down onto avalanche risk area and dig out live explosives...

2: Helicopter intervention. The same as direct intervention, but for areas where it's not easily possible to get to the zone. This has the same problems with having to recover misfires, plus it's bloody expensive, plus you have to fly a helicopter about in the dark when there are pylons and cables all over the place. There was a fatal crash last year in Chamonix doing exactly this.

3: Avalancheur. This is a static 'firing' post, which is equipped with a big-ass airgun. Literally. The cannon is fired using pressurised nitrogen, and shoots a big explosive dart into the mountain. Range is over 2km. The darts contain a 2-part explosive, inert until mixed, which explode on contact with the snow. Unless they don't, in which case we're back to digging out explosives (or manually triggering). The explosive used is Nitroroc S.8.48 in most cases (all cases here in France, I believe), which obviates the need for digging out in many cases as it goes inert 8 hours after mixing. Basically, it depends where the arrow ends up.

4: Gazex. This is a static installation which can only act in one place, as opposed to the above which can be deployed anywhere. It's a big tube with a downward-pointing end, it's filled with a propane/air mixture aand ignited. The blast triggers the avalanche.

5: Avalhex. This is again a static installation, it uses a big balloon filled with a hydrogen-air mixture, but otherwise similar to Gazex. The reason for the big balloon is that the shock wave hits more snow at once, thus in theory triggering more reliably.

No matter what methods of triggering are used, most resorts also have methods 1/2 as fallback for areas that can't be reached or triggered otherwise.

Simon

[larry cottrill]

I definitely agree with you that the engine has really high tail suction. As soon as a rain drop hit the tail pipe and turned to steam, even if it was 6 or 8 inches down the pipe it would get sucked back parrallel to the pipe and a take an amazingly sharp turn, about 1 inch radius, all in one cycle of the engine. You just see these puffs of steam form, accelerate, and vanish in the blink of an eye

If you get a good run in the sunshine, video this against a dark background, using a garden hose as a rain source. I think this would be worth a bit of study, if you can capture it. It would be interesting to see what the action is up at the intake, too, if it's visible there. You need to set up a dark background and brightly lit water droplets. Another possibility would be smoke, from a little pile of pipe tobacco or burning incense on top of the pipe.

I think that was a really sharp observation! There's just so much you can do [once you have an engine running] that might be of interest. The action of air near a running pulsejet is important to know, although it will never be complete without moving tests, of course.

L Cottrill

[Eric]

It is officially back to winter again. It was down to about 20 this evening, probably lower now. I didnt bother trying to run the big engines in the cold but I finished up the small FWE so I decided to try that out quick. It was still too cold to get it to self sustain, got some good bursts with the shop vac. When I turned up the fuel all the way and had the leafblower up to it, it wouldnt resonate but it did make nice explosions about as loud as 308 at a few hundred per minute.

Eric

[larry cottrill]

Eric -

Why don't you grab a picture of that one [indoors] and post it so we can see what it looks like?

(Remember - always show your work ;-)

L Cottrill

[Eric]

You people! :) My digital camera burns the pictues directly to cd, and for some reason when I got the new service pack for windows, my computer wont read the cds until they are finalized. Before I could just put in a cd and it would read the pictures, but now I have to finalize the cd essentially turning it into a coaster with a few pics on it. So now I usually take a bunch of pictures at once, and then finalize it, until I figure out how to un-service pack the certian components of my computer. And anyway the engine is still up in the shop. But either way I was going to take a bunch of pictures of all the engines lined up on their stands tomorrow. Fear not.

The engine basically looks like the one you and steve made. I made some modifications, like flaring the exhaust pipe, and flaring the intake pipe instead of rolling a cone. The intake flare seems to be quite substantial. If its warm out hopefully I can get a few of them started and get some video. I really need to move to southern california. Have you or steve tried making the engine with various levels of intake constriction as well as various levels of protrusion into the combustion chamber? If you can heat your electrical conduit up hot enough, perhaps with an oxy torch if you have to, it is quite simple to make a very large and smooth flowing flare without splitting the welded seam. Also instead of welding a joint in the intake you could also make a smooth bend. This would make prototyping a lot quicker. Oh yea the normal size FWE is 2 pounds exactly made from 18 gauge steel, and bike tubing, as well as including the spark plug and 2 stainless propane injectors.

I was trying to get onto the focus website but it seems to be down, dont know if it was a temporary glitch or what. I dont know if you made multiple paint drawings depicting the same engine. But for some reason when I printed the one out, the intake lenght before the bend measured out to be 5.25 or so inches by your scale in the corner. Perhaps my printer is screwed up and streached part of it. If you want I could make up a really nice 3 view / isometric autodesk inventor drawing and then JPEG it, you could do with it as you wish, either keep it or have it posted to kenneths list of engines. There really needs to be more well documented valveless designs put onto the site here.

I noticed you have my PJC 1.4 down for the next version of jetzilla, I dont remember if I ever sent you the full article I wrote up about it. I think I still have the stuff floating around here somewhere.

Eric