www.pulse-jets.com

This notion just came to me and I was wondering if it's any good.
Basically, instead of two pipes running side by side and joined by a curve, the pipe folds back over itself.

I can see potential issues with the curve being as sharp as it is, but if that can be worked out you could save a bit of weight by only needing one augmentor.

You're going to get a lot of friction and more importantly, heat build-up. It'll overheat and buckle/ melt

Any concerns on breathing tail exhaust into the intake?
The CC might have insufficient cooling.
Real interesting concept.

So enlarge the outer tube so it's not in contact with the inner one and shift the position where the bend starts so the inlets are staggered?

Considering that this design was pulled directly from my rectum while playing around with MS paint, I think achieving "interesting" on my first iteration of it is pretty sweet.

A couple of people have thought of it before but no-one has ever actually tried it. If you can get rid of the heating and breathing problems, I'd say build it.

Played around with the design a bit more.

Added some space between the inner and outer tubes and staggered them to keep from ingesting each other's exhaust.
Also made a hollow space running straight through the middle for more suface area exposed to a cooling airflow.
This may improve breathing since it can now suck in fresh air from it's inner diameter as well as it's outer one.

Don't have the resources to build anything. I mostly play with concepts in my head. Frankly, for someone with no formal training or education in this field, just having the experienced builders say it might not be a pile of suck is a pretty big victory for me.

As much as I love the concept of concentric / annular / coaxial designs they have real major problems Heat being primary. Over heating. Warping. you name it.

I am still trying to make one work well, no luck.

I am convinced that some day some one will make a good one.

Just my .02

Ghrey wrote:As much as I love the concept of concentric / annular / coaxial designs they have real major problems Heat being primary. Over heating. Warping. you name it.

I am still trying to make one work well, no luck.

I am convinced that some day some one will make a good one.

Here's an old photo of me, holding my successful M9E concentric valveless pulsejet. This was demonstrated at Mike Everman's shop at one of our little "mini-meets" in early 2006. Not terribly powerful (7.5 lbf) but starts easily and throttles well. Also, it utilizes off-the-shelf exhaust tubing, which simplifies the construction.

Also, here's a link of her running at the meet--sorry, it's VERY short: http://www.youtube.com/watch?v=WHDTxfiZXyc

That makes me recall this relative/related design from the Symposium Book on Pulsating Combustion, Sheffield, England. Looks like you could bury it flush with the ground and it would still run.

Ghrey wrote:As much as I love the concept of concentric / annular / coaxial designs they have real major problems Heat being primary. Over heating. Warping. you name it.

I am still trying to make one work well, no luck.

I am convinced that some day some one will make a good one.

Just my .02

Add:
Too much surface drag for the volume and too critical of tolerances to achieve the intake area, and that dimension changes wildly as it heats up. It is just not worth doing. All you get is a noise maker.

..though you're going in the right direction by leaving the intake non annular!

Hmm, how about this?

If the intake is umbrella shaped, I tend to suspect that thermal distortion would make it hard to maintain the dimensions within running spec., and yes drag, pernicious drag...

If instead that represents separate feeder tubes; I would like to see that tried....


While I am trying engines that have zero length intakes, with some (limited) success, that may well be a dead end.


When in doubt build it. Either way you learn something, and your skills get better.

Just my .08

Ghrey wrote:As much as I love the concept of concentric / annular / coaxial designs they have real major problems Heat being primary. Over heating. Warping. you name it.

I am still trying to make one work well, no luck.

I am convinced that some day some one will make a good one.

Just my .02

http://www.youtube.com/watch?v=KFlGmF9S ... playnext=1

I believe I was the first one one on this forum to build a running concentric pulse jet.
I aggree with some of the other posts, that this type of pulse jet will probably not come close to a lockwood in power; but it was really fun to build and test.

Hagen

sockmonkey wrote:Hmm, how about this?

I like it. Thermal distortion won't be a problem on the intake, since the intake does not get that hot.
The pointy part where the intake comes into the CC area may need to be looked at. If you build this you may want to put a flat area there. This might help with the sound/pressure reflection back down the exhaust, which I think would be benificial, but you won't know unless you try it.

Hagen