One hell of a noisy engine

[Eric]

This weekend I was able to fire up quite possibly the loudest engine pound for pound that I have ever made. It also puts out considerable thrust. Unfortunately I ran out of propane from a mostly empty tank I found. Maybe next weekend I can get some good video footage of it. Im debating wether I want to try to bend it.

Eric

[Mark]

Well it looks like a horn and it's pleasing to the eye. I did some barking tube experiments by misting methanol into various shaped pipes while blocking one end with my hand and lighting the open "tail pipe" end. One of the loudest was a straight duct with a flare very similar to the one on your jet. It made a very sharp loud, almost bang sound. It really hurt my ears. I wish someone else would try some barking tubes, they are kind of interesting even though it's simple to do. With my copper pipes, I get a bark and a beautiful green flash each time I light the tail end with a flame. Just mist the insides with methanol and you can do some interesting tests.
Again, good work there Eric!
Mark

[Eric]

Thanks, I am thinking of plating it with brass and polishing it up like a trumpet ;) I tried it out by connecting the magneto to the spark plug and spraying some starting fluid into the intake. It was quite peppy even with that. I then sloshed about 1/2" of methanol into the bottom of the combustion chamber, fed it some forced air, and it reved up and blew out liquid methanol for about 4 seconds.

It is insanely loud, even by pulsejet standards. It almost hurt through my shooting earmuffs. A friend of mine who has heard many of my other engines including dynajets, who was standing 20 feet away just lipsynched "WOW" and covered his ears and ran away when it was running on propane!

Eric

[Mike Everman]

Faaaaascinating!

[Mark]

Here's a few doodads that I have dwelled on making something with. The copper pipe with black rifle scope is the one that barks/raps quite fiercely, and the exhaust end of the scope is only 1.5 inches in diameter. I seal off the opposite end and mist with methanol and it goes bang, near instantaneously, right after a millisecond of reving. It is remarkably loud for so small too.
You might be able to get away with using some copper on the tail end of a pulsejet where the backflow of air would keep it cool enough for long runs. I'm sure copper would melt if you didn't stop your pulsejet after a few seconds. But copper tubing, like a glass jam jar, is plenty good for short experiments. And it makes a pretty green color.
Mark

[Mark]

Here's one of those resonance stopping devices to prevent your pipes from hammering. It's the long tube with a spun closed end and neck at the opposite end. They come in shorter lengths too.
Just some meager copper tidbits perhaps of some use to someone.
Mark

[Eric]

If I made the tail sections from coper I think it would need a water cooling jacket around it. The tailpipe gets really hot right up to the middle of the cone section. Plus im not one for running engines only a few seconds at a time ;)

eric

[Mark]

Well maybe if you switched to methanol and a lighter fuel tank. ; ) Methanol burns cooler, but it puts out, so to speak. And copper will catalytically react with methanol. It will produce some extreme green and blue colors. There's a way around everything. Perhaps you could preheat/drive a fuel pump with the heat and cool a section of your jet with fuel at the same time. Don't besmirch copper, it is an interesting metal and it has some interesting qualities.
Mark

[Eric]

Wow! I ran the engine again today with a brand new full tank of propane and it was so incredibly loud that you can feel the vibrations in your body from about 20 feet (more so than normal), within 5 feet its like your sitting on top a harley, im not sure what the resonant frequency of levi jeans are but they were actually "buzzing" against my leg.

When its first starting up it fires like a 308 minigun absolutely deafening, and then transitions to more stable and slightly less loud regular operation which is still deafening.

Here are some pics, ill get the video edited up tonight. I didnt have the spark plug tightened down super tight and it actually started spinning free and I quick put the camera on it and it went flying up into the air and kept running for about a second.

Eric

[Eric]

Pictures.....

Is there any way to make the upload thing have like 5 blanks that would make things much much easier?

[Mike Everman]

Beautiful. I assume it's a 2.5" CC? Bill Hinote's engine of the same dia was the same kind of earthshaking deafening thing, too. Is that 1/4" brake line fuel feed? How deep into the intake was the sweet spot?

[Rossco]

very nice!

I like that hot spot and the start of your bell end. Pressure diff?
I would really like to see some sort of thrust figures for this engine.
Youve inspired me t knock up a big bell end for my test rig i think. (it needed a bit of work at the end anyway)
I think i will do a radicaly big one like yours, but im thinking that some flowed holes or augmentor set up at the start of it could be interesting.
Flow some cold air right into that hot spot.

The other thing that i might look into is a small ventury tip, just as it enters the bell. Give it an even greater press. diff.

Rossco

[Mike Everman]

BTW, good to see you back in force Rossco. I'm going to Sydney and the Barrier Reef this August. I'll wave as I go over.

[Eric]

The fuel injector is 1/8" id about 3/16" od and extends about 2.5" into the intake.

Yea I based the tailpipe fare off the data I calculated off the FWE that showed the various hot spots. The flare begins where the hotspot starts and the big end of the flare helps accelerate the flow, assuming it is supersonic at any point in time.

Rossco, as for thrust figures "a hell of a lot" will have to do for now. It puts out probably 3-5 from the front intake alone. For the size its a pretty potent little beast.

I made a thrust recouperator from 2 6" stovepipe elbows, but i need to make a flare for the recouperator so it works properly. As you can see it does a nice job on the water even from a few feet away. I also have a stainless augmenter that was only partially visible in the picture on the first post. I will post the video soon, its quite exciting and the end is funny.

Eric

[Rossco]

Eric, Pressure, not flow. That is a difuser not a venturi?

What im sugesting is a venturi to increase speed right at the exhast tip, and a diffuser augmenter to induce cold air, to utilise the heat in that section. The difuser then increases pressure. The resulting product of pressure and gas velocity, the factors of thrust, would be higher?

Since you seem to have an engine with such a hot spot there, could you see it viable to make an add on, removeable attatchment to accomplish this?

Rossco