www.pulse-jets.com

Well I made a little removeable test stand for the first all stainless FWE prototype and started it up today when it was 5 degrees out. I waited until dark and started it up again at -3 degrees F !!!!!!!!!!

I made the intake 5/8" ID with a small lockwood type flare rounded back. The intake tapers from about 1" from the intake all the way to the CC. There is no spark plug, it starts up easy just by having the CC heated.

I figured I would use this engine on some kind of remote / control line craft and had a very high probablilty of crashing and ruining the engine, so I didnt spend a lot of time making the welds look nice.

The engine is made from 24 gauge stainless, with fuel injector weights 1 pound 1 ounce, without removable test stand. I will probably put this engine up on ebay once I start my pulsejet yard sale.

Eric

Eric wrote:
I made the intake 5/8" ID with a small lockwood type flare rounded back. The intake tapers from about 1" from the intake all the way to the CC. There is no spark plug, it starts up easy just by having the CC heated.

Eric

Nice job, Eric!

Would you please quote the location of the output end of the fuel probe, as a percentage of the length of the intake?

For example "the end of the probe extends into the intake approx. 20% of its length".

Also, do you consider the current location of the fuel probe to be optimum? For example, can you throttle the engine over a reasonable range of flow rates?

Thanks in advance for your information.

Bill H.
Acoustic Propulsion Concepts

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

On all the valveless engines I have built it seems that the best place for the end of the fuel probe is exactly even with the edge of the intake.

I tested the FWE engines with a sliding fuel probe (the brake line vaporizer coil that could be slid back and forth and spun side to side), and this is the spot where it is easiest to start, runs the smoothest, and can be throttled the most. Having the fuel probe lined up right in the middle of the intake and perfectly straight gives the best results.

When you have the fuel injector set up going through the side of the pipe like the Chinese design (I seriously wonder why they had the fuel port at that position unless it was supposed to be for liquid fuel), you are relying entirely on the incoming air to mix the gas, and a lot goes right out the intake and makes a big flame contributing squat to thrust.

With the fuel pointing into the engine it sucks in a lot more air, mixes better, and gives probably a 10% boost in thrust, as well as a disproportional improvement in fuel efficiency. I made a little propane nozzle with a tiny little hole, I forget exactly what size, it was a small dynajet metering jet size drill hole. I shaped the nozzle so that the speeding gas would draw in more air, and I got engine to run very very low. It throttled down to practically zero thrust, and barely any fuel. At that level of fuel consumption it probably would of run 12++(conservative estimate) hours on a 20 pound tank. At full thrust the engine runs about an hour or two on a 20 lb tank

Eric

Eric wrote:On all the valveless engines I have built it seems that the best place for the end of the fuel probe is exactly even with the edge of the intake.

Eric--thanks for your reply.

There are some historic examples to support your claim about the location of the fuel entry. The Chinese PJ requires the longest "fuel mixing lengths" due to the various complications arising from the folded engine configuration.

Bill H.
Acoustic Propulsion Concepts

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

Heres a clip of video, the radiant heat barely made my hands feel warm. I was pretty suprised at how well the enging ran at these temps.

Very nice work eric. When can we expect a FWE calculator? Can't wait. I have made my own calculator for regular valved pulse jets that seems to get very close results to running jets. Once again congrats and can't wait to see more!

Nanosoft

Eric wrote:On all the valveless engines I have built it seems that the best place for the end of the fuel probe is exactly even with the edge of the intake.

Eric, do you mean that the tip of the probe is aligned with the inner and of the intake -- the place where the intake transitions into the chamber? This is the traditional French positioning. Escopette and Ecrevisse both had that.

Eric wrote:When you have the fuel injector set up going through the side of the pipe like the Chinese design (I seriously wonder why they had the fuel port at that position unless it was supposed to be for liquid fuel), you are relying entirely on the incoming air to mix the gas, and a lot goes right out the intake and makes a big flame contributing squat to thrust.

The original drawing of the Chinese by Don Laird has the probe sticking into the intake, aligned with the intake tube centerline, just as you describe it. If I am not mistaken, the side location of the injector, perpendicular to the intake axis, was used by someone in the forum. It is not the original placement as far as I know.

Eric -

Congratulations, once again! It looks like this may be the best running FWE yet, and is probably the best looking one so far, though it strikes me as weird without a plug mount. Nice weight, too. Did you build this one shorter, or to the original length?

Eric wrote:I made the intake 5/8" ID with a small lockwood type flare rounded back. The intake tapers from about 1" from the intake all the way to the CC. There is no spark plug, it starts up easy just by having the CC heated.

Tapered down to what? It doesn't look quite as tight at the CC end as I would have tried, but seems to start and run wonderfully. How about a simple drawing [even if not to scale] with the complete final dimensions?

The engine is made from 24 gauge stainless, with fuel injector weights 1 pound 1 ounce, without removable test stand. I will probably put this engine up on ebay once I start my pulsejet yard sale.

Hey - I might want to make an offer first ...

Again, very nice work, Eric!

L Cottrill

Eric -

Just had a look at the video, and I wonder if running so cold whether this is a typical run. If it is, you've finally accomplished what I always wanted - no perceptible mass ejection from the intake [even though wave emergence must still be there]. Amazing. I'd love to know if that will hold true in normal weather.

It may not be so surprising that this version handles the cold well, especially since you're heating up the chamber to start it. Stainless holds a lot more heat before radiating it away than mild steel, and I'll bet that has a lot to do with it.

Please publish all dimensions, in some form. I just realized that what I said before about the intake not being squished as much as I expected was from forgetting that you said this was smaller intake tube [5/8 -inch ID] rather than the original sized tube. I think I have ruined mine by pinching it too much, but I want to change it to approx. 3/4-inch ID tubing anyway before trying the venturi and liquid fuel again.

Eric, send me a quote for what you would need to send me one set of stainless parts, especially if you can fabricate the big pieces from even smaller gauge sheet material! I would want the intake tubing uncut, but with the flare done for me. All the rest could be left unwelded. If it is type 304 or 316, I should be able to weld it with oxyacetylene and Chromalloy flux and the filler rod I have.

L Cottrill

Nano,
I dont know when I will have time to make a FWE calculator, sorry :)

Bruno,
The fuel probe is positioned so that a sheet of paper can be slid between the flare of the intake, and the edge of the fuel probe. It is right even with the edge of the intake flare, not the intake cc junction.

I tried the escopette position and it didnt start, just lots of bangs and pops. The way gas flows is definately different from an escopette or the likes.

Oh yea you might be interested in my attempts to photograph the gas flow in my lockwood. I took wet silica casting sand and coated the interior of the engine, unfortunately the flash of the camera at night time didnt show the shiny little sand grains as I hoped, but it did turn the engine into a sand blaster. I probably need some sort of strobe light connected to the camera, and behind the gasflow.

With the chinese, at least the one I downloaded, It has a small fuel probe sticking through the side wall, and then a starting air attachment in the position that i have my fuel probe set up. It may well be a multi purpose engine such that you could start it on propane with that injector, and then switch to liquid fuel. He could of just gotten a chinese valveless with no documentation and then just figured the one was an air attachment.

Larry,
The intake tapers down to 3/8" at the CC. It is the same lenght of my last steel prototype, 1 inch shorter than original dimensions. I also ran the engine at 40 degrees F back a few days ago. The temperature of the engine has absolutely nothing to do with its running characteristics, within reason. The other prototypes wouldnt even run at below 5 degrees with spark plug going and the torch heating the side wall, so it dosnt have anything to do with the torch preheating. The other engines would glow red hot, and if the engine can start up in cold weather at cold temperature the 40 degree difference of air temperature cooling the outside compared to 1000 degree engine heat is negligible. Even though the steel engines were hot you could hear that the fuel wasnt being mixed properly, that it would run really ruff, and after a minute or so quit entirlely. The stainless prototype runs perfectly smooth at these tempereatures, and shows no sign of wanting to quit.

It by no means is the nicest looking FWE yet either! :) I just didnt take pictures of the Stainless Mark II and III and IV yet, each being an advancement in welding technology/quality. Mark V will be entirely tig welded, fusing the metal together and polishing the seam. The Mark III - IV are very carefully mig welded with the seams polished down to be level with the rest of the piece, giving the appearance that the engine is made from seamless tubing, I then take the CC / tailpipe as one piece and put it on the lathe and use 600 grain sand paper to regrain it all to one direction.

Let me get this straight, you want me to make parts thinner than 24 gauge stainless, and then you are going to oxy weld it.... without a henrob 2000.... At the moment I dont have anything thinner than 24 gauge, depending on how the tig welding goes I may buy some 26-27 gauge. Email me at my yahoo address ERJABE007@yahoo.com with exact dimensions of what you want. For some reason on my website my email on every page changed to ERJABE @ yahoo . net instead of .com

Eric

Eric,

To photograph the flow at the ports (of any engine, Lockwood, FWE etc), you migh want to set up a Schlieren system. You can build one easily enough using a cosmetic mirror, or you can set up a strip system.

If you use a microphone, you should be able to set up a comparator to trigger a strobe, so that you can get the exhaust "field" at a particular point in the cycle. I have dissected a few Kodak MAX strobes and Fui disposable camera strobes and devised triggers for them (basically a triggerable strobe for under $5.00). I can post details if you are interested.

As far as Schlieren photography is concerned, I can publish some diagrams that show how to set up various systems if you are interested, but there are far better resources on the web. One of the best is Andrew Davidhazy's site at RIT: (btw here's one of the coolest and simplest setups -- http://www.rit.edu/~andpph/text-schlieren-color.html)

Eric wrote:It by no means is the nicest looking FWE yet either! :) I just didnt take pictures of the Stainless Mark II and III and IV yet, each being an advancement in welding technology/quality. Mark V will be entirely tig welded, fusing the metal together and polishing the seam. The Mark III - IV are very carefully mig welded with the seams polished down to be level with the rest of the piece, giving the appearance that the engine is made from seamless tubing, I then take the CC / tailpipe as one piece and put it on the lathe and use 600 grain sand paper to regrain it all to one direction.

Yeah ... we've got to see those!

Let me get this straight, you want me to make parts thinner than 24 gauge stainless, and then you are going to oxy weld it.... without a henrob 2000.... At the moment I dont have anything thinner than 24 gauge, depending on how the tig welding goes I may buy some 26-27 gauge. Email me at my yahoo address ERJABE007@yahoo.com with exact dimensions of what you want. For some reason on my website my email on every page changed to ERJABE @ yahoo . net instead of .com

Yes, I think if I can weld steel to a shaving cream can [see below] I should be able to weld thin stainless. The Henrob is a beautiful thing - but it's just a highly developed oxyacetylene torch. I can set up a flame so small on my old Victor outfit that you can't even hear it run, and can hardly see the inner cone down past the tip. That ought to do it. The one flaw might be in trying to use the 1/16-inch filler rod [though that size worked OK for me on the mild steel pressure cans I've done] - but, I can always get some spooled 312 filler wire to use instead. I couldn't commit to exact part dimensions until you publish your last overall dimensions, of course.

Well, you've definitely earned an official Certificate, even without more running of the big one. I'll send you a free poster, too!

Another question, though: With the apparently excellent fuel setup and intake dimensions you now have, has the use of starting air changed any?

L Cottrill

HAHAHAHAHA I finally get why the engine is named the Fo Mi Chin. I didnt see any pictures of it or anything and I just figured it was some chinese pulsejet design.

The sandy lockwood was just a halfassed attempt at doing something a lot more simple than a Schlieren. In the summer I might try something that complex, but when you cant stand to be outside using your bare hands for more than a minute it kinda is hard to tinker around setting something like that up. Thanks for the link though.

Larry,

The end cap dome is 3/8 deep, the cc cone is 7.25 and the tailpipe is 17. The intake is about 5.25, situated 3" from the front end of the CC cone. Free posters are always good! As for the air, I have seen the light and went back to using my air compressor. That way i can run it 40 feet out and not have to worry about stupid electrical plugs in snow/puddes of water. Everything starts up about the same with the compressor. In the same position and orientation as the vac nozzle.

Eric

Eric wrote:The intake is about 5.25, situated 3" from the front end of the CC cone.

Is that 3 inches from the front cone edge to the intake CenterLine at the point where it enters the chamber?

L Cottrill

3.5" from middle of the intake to the front of the CC. The 3" was from the front of the intake cc intersection. I also might note now that I just took another look at your drawings that your dimension of 3.26" from the front of the engine to the midline of the intake opening. If you go from the front of mine to the middle of the intake its 3.875".

Eric