www.pulse-jets.com

tufty wrote:

astroadrian99 wrote:So wait, are they more fuel efficient than the Chinese design?

Well, the models made, tuned, tested and run by SNECMA got a TSFC of ~1.8. That's pretty damn good, and it's for an engine designed to put out the sort of thrust you want. The "Chinese" design will get you TSFC around 2, and you'll have to scale it up to get 100lb, IMO you'd be lucky to get tsfc < 5 for a "rule of thumb" scaling.

Remember - 100lb at tsfc 2 == 200 lbs of fuel per hour. Or, if you prefer, somewhere between 3 and 6 minutes runtime on a 20lb tank of propane, depending on when it starts icing up. Probably closer to 3 than 6.

It occurs to me that Eric had one of his TP-180 series with tuned augmentor where he was claiming TSFC <1 for 100lb thrust. Not only is that way better than anything out there, but I'm pretty sure you can trust Eric.

Do u happen to know where I can check Eric's TP-180? I was trying to check his website but everything is in Japanese. I was also wondering, do u happen to know where I can find some detailed plans on this engine. It sounds like the exact kind of engine I need but its little though to build by just trying to look at pictures and no actual dimensions.

I'm fairly certain Eric has moved to pulsejetengines.com (that's where his youtube channel is pointing these days, at least), so that's probably a decent way of getting in touch with him. He's not been online here for a good while.

tufty wrote:I'm fairly certain Eric has moved to pulsejetengines.com (that's where his youtube channel is pointing these days, at least), so that's probably a decent way of getting in touch with him. He's not been online here for a good while.

Ok I'll try to contact him there. In the mean time, I have one question. I've heard in some place that I could use an augementor to increase my thrust without increasing fuel consumption. Is this something thats worth putting on my engine or does it only work on stationary ones? Also, by about how much thrust does it add to the engine?

tufty wrote:http://www.interestingprojects.com/pjbo ... 211711.pdf

Thanks man, for everything.

Hey, tufty I've been reading what you sent me over and over but I still don't understand what it's trying to say. It's just so complex. Could you explain it to me in simpler words please.

Of course it's complex. We're talking about pulsejets, which are remarkably simple in mechanical terms, but enormously complex in fluid-mechanical terms. Adding an augmentor means (at least partially) coupling one poorly-understood fluid-dynamic system to another one; any guess as to the results in a given situation would be just that - a guess.

Effectively, there are 4 parameters at play, and only one of these is "easy" according to the NASA document :
- Augmentor diameter, which for the dynajet they were using, was 2.4 x the diameter of the pulsejet.
- Placing of the augmentor relative to the exhaust - as close as possible but not too close.
- Augmentor length - tuned to some other factor of the jet, probably to some harmonic of the pulsejet's fundamental frequency
- "lip curl".

Now, the paper I linked is only one, and they didn't play with any other elements - divergent / convergent-divergent / divergent-convergent augmentors, nor did thy play with the variations you're going to see with a valveless, especially one where the inlet and exhaust are liable to be in proximity to the augmentors (and each other), and so on.

TL;DR version - it's not as simple as "for this size pulsejet, use this size augmentor" - most , if not all, of the variables are dependent on the design of the individual jet. About the best you're gonna be able to do is guesstimate the best diameter(s) based on the 2.4 ratio rule of thumb, curl the lips, and then burn a load of gas experimenting with lengths.

astroadrian99 wrote:

sid_raptor wrote:Check the looking for plans section. Im sure you will find what you need there.

Alternatively search for thunderchine or lockwood or m40...

Which 12 lb engine are you going to build? I am starting with Larry's original short lady just because it looked easy to build. I have a thread running documenting the trials and tribulations of my build! (I am a noob too).

I'm going to try to build this one download/file.php?id=14565 cause it seems simple enough to do.

Wow that looks nice! i might give it a try at some point!

I have almost finished my FWE build and i will post updates in my thread tmmrw. Like i said i am pretty new here so if someone says the chinese is not as efficient they are probably right.
I was only going by what i had read in earlier posts.

Good luck with the build!

On thing, if I wanted to scale up an engines size, would the thrust scale up too. For example, if I were to get plans for an engine that has 10 lb of thrust and I decide to make it 10x the size the plans state, would the thrust increase to 100 lb?

No. scaling engines doesn't work like that. You can't just increase all dims x 2 and expect twice the thrust (or even a running engine)
A nice ballpark to double thrust is to take a running engine and scale the diameter of the combustion chamber x1.4 (and then design the rest of the engine accordingly, so no simple scaling) Try Pyrojoe's recipe for beginners if you want to design something yourself.

metiz wrote:No. scaling engines doesn't work like that. You can't just increase all dims x 2 and expect twice the thrust (or even a running engine)
A nice ballpark to double thrust is to take a running engine and scale the diameter of the combustion chamber x1.4 (and then design the rest of the engine accordingly, so no simple scaling) Try Pyrojoe's recipe for beginners if you want to design something yourself.

Ok thanks so much.