FWE Development 2004 - Today

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larry cottrill
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FWE Development 2004 - Today

Post by larry cottrill » Thu Jan 18, 2007 5:37 pm

All right - here's my drawing summarizing FWE development. My intent was to show significant mods to the standard size design, not scaling attempts such as Eric's giant and the one or two tiny ones that have been built and run successfully. The most recent "failed attempts" are included, as well as a preliminary look at the Rev06 that I want to build when the weather warms up again. Only "critical" dimensions are shown, and all are inside dimensions - all main tube cross sections are circular. Please provide any omissions / corrections that you happen to notice.

L Cottrill

EDIT: Later versions of this drawing have been posted! Scroll through the following pages of the thread for the latest revision.
Attachments
FWE_evolution_(preliminary).GIF
Standard size FWE pulsejet development from 2004 to the present. Dates shown are approximate "first run" dates. Drawing Copyright 2007 Larry Cottrill
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Last edited by larry cottrill on Tue Mar 06, 2007 5:42 pm, edited 1 time in total.

Zippiot
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Post by Zippiot » Fri Jan 19, 2007 12:57 am

So you tell me to go looking for the data only to post it a day later!!!!!!!!!!

Can you post the thrust:weight of the previous engines?
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francisco
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EXPERIMENTAL FWE'S

Post by francisco » Fri Jan 19, 2007 5:11 am

ghhg

here accent a picture with all the cameras of fwe combustion

3 of stainless steel and 3 of common metal


my idea was to make the entrance with a pipe bend in place in a cut pipe.


good. . . I will already fix some drawings

francisco cooreman
Attachments
Imagen009.jpg
inox
Imagen009.jpg (35.04 KiB) Viewed 5627 times
Imagen013.jpg
SAE 1010
Imagen013.jpg (30.86 KiB) Viewed 5626 times
Imagen015.jpg
Imagen015.jpg (27.37 KiB) Viewed 5627 times
"I DONT`T SUFFER OF MADNESS, I ENJOY IT CONTINUALLY"

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Zippiot
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Post by Zippiot » Fri Jan 19, 2007 5:19 am

How is everyone pumping out beautiful cones!!!!!!!!!!
Sailing Student- How do I know if my life jacket is tight enough?
Me- Can you breathe?
Sailing Student- Yes
Me- Then its too loose!

Irvine.J
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Experimental FWE

Post by Irvine.J » Fri Jan 19, 2007 7:07 am

CONE DESIGNER .ZIP in the FILE MENU!!! Lol

EDIT!
Larry, I was thinking....
The 32mm 1st point worked quite well. Even more thrust then the 2.25 FWE...
I was thinking maybe if the 29mm point was slightly rounded instead of angle to angle, you know what I mean, a smoother transition between the points.
What do you think? By the way I took the sparkplug out of your now completely distorted engine, and inside its completely bent and has areas that look imploded. (Though only small ones)... I think there is major potential right there.
Last edited by Irvine.J on Fri Jan 19, 2007 7:57 am, edited 1 time in total.

Zippiot
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Post by Zippiot » Fri Jan 19, 2007 7:13 am

I got that, I mean how do you make them all smoothe and shiny?
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larry cottrill
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FWE Thrust and T/W Ratio

Post by larry cottrill » Fri Jan 19, 2007 3:09 pm

Zippiot wrote:So you tell me to go looking for the data only to post it a day later!!!!!!!!!!
Well ... I told you I was working on it. I thought you were in a hurry for information ;-)
Can you post the thrust:weight of the previous engines?
Most of them have never had a thrust measurement! In general, the straight pipe FWEs are pretty weak - on the order of a pound of thrust or so, which is about what they weigh!. The best one of those is undoubtedly Eric's "Advanced FWE" which he measured at 2.25 lb. Since I could build that engine at a weight of right at 1.0 lb, the T/W would be 2.25.

The first Lady Anne that James D built tested out at 2.6 lb. I can't build one of those that would come in at less than about 1.25 lb, so the T/W ratio would be slightly better than 2. Of course, Eric can probably build them much lighter from thinner SS; if so, he could make them much better.

In the real world of aeronautical design, an engine T/W ratio of less than 4.0 must be considered fairly pathetic. Of course, with ultra-lightweight construction, you could build a model plane that would actually fly these engines with a usable overall T/W, even taking into account some reasonable fuel weight. They would not be world-beaters - probably way underpowered for stunt flight, and boasting loooooong takeoff runs. For some perspective, consider the very long, rocket assisted launch rail of the V-1 buzz bomb, which also had a pretty low T/W figure, I think.

I have always thought that the ideal test vehicle for these motors would be a hydroplane speed boat. Of course, even on a boat you don't want the weight to be excessive, if you expect any kind of real performance.

L Cottrill

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Re: EXPERIMENTAL FWE'S

Post by larry cottrill » Fri Jan 19, 2007 3:11 pm

francisco wrote:here accent a picture with all the cameras of fwe combustion

3 of stainless steel and 3 of common metal
Francisco -

Beautiful work!

L Cottrill

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Re: Experimental FWE

Post by larry cottrill » Fri Jan 19, 2007 3:21 pm

Irvine.J wrote:Larry, I was thinking....
The 32mm 1st point worked quite well. Even more thrust then the 2.25 FWE...
I was thinking maybe if the 29mm point was slightly rounded instead of angle to angle, you know what I mean, a smoother transition between the points.
What do you think?
I think the improvement would be so small as to be immeasurable. It IS true that the smoothness of a tight point is important, of course! But, IF there is no roughness to the joint, the slight 'angle' is almost meaningless. The whole issue might really be eliminating any welding roughness or misalignment roughness at the joint. If a rounded throat accomplished that, it would indeed be an improvement. It's a joint that's hard to "clean up" after welding - though possible, if you leave the front dome till last, as you apparently did.
By the way I took the sparkplug out of your now completely distorted engine, and inside its completely bent and has areas that look imploded. (Though only small ones)... I think there is major potential right there.
Man, you were running that baby pretty hard! Probably a lot longer at a stretch than I'm used to, as well (though I once had to run my original Short Lady for about 45 minutes with no letup, for a magazine photo shoot). I'm not too surprised at this, considering there was no significant cooling other than natural convection. Had the engine been used in flight, with plenty of air hitting her, she would have held up very well, I think. Plain steel just isn't the right stuff for prolonged wringing out, just for initial test prototyping of the kind I do (occasionally). BUT - I DO agree with you that a poorly performing engine probably wouldn't "cave in" like that!

L Cottrill

James D
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FWE Development 2004 - Today

Post by James D » Sat Jan 20, 2007 7:29 pm

Larry, its nice to see them all together, I noticed one very minor typo though, the first Lady Anne should have had a 23mm intake not 20mm (although the one i built was actually 22.5mm)

James D

Eric
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Post by Eric » Sat Jan 20, 2007 8:44 pm

Was it caved in on the outside too? lol I know sometimes mild steel can make ridiculously large bubbles that look like it has a major dent on the inside.

Eric
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Re: FWE Development 2004 - Today

Post by larry cottrill » Sat Jan 20, 2007 10:38 pm

James D wrote:Larry, its nice to see them all together, I noticed one very minor typo though, the first Lady Anne should have had a 23mm intake not 20mm (although the one i built was actually 22.5mm)
Thanks, James - I'll note that for the updated version.

L Cottrill

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FWE Development 2004 - Today

Post by Irvine.J » Mon Jan 22, 2007 5:54 am

Eric forgot to mention that yes it was, I'll grab a pic when I'm finished testing out my valved engine, which I really don't think is going to work :(

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Fwe Development 2004-Today

Post by Irvine.J » Mon Jan 29, 2007 3:17 am

ok Larry, today I'll start building this beast. However I just wanted to run something by you. From the pictures above, I notice that the tailpipe Exit diameter, the straight section immediately after the CC, and the CC lengths are all different from the engine that James D got running. Let alone the inlet pipe.

So I'm thinking, maybe I should keep the cc/inlet pipe the same length (and D) as the one James D got working, and change the rest from there. (29mm cc exit etc.) Simply, the inlet location, diameter, and CC seemed to work very well. If you want to go directly off your drawing thats fine, though perhaps you can explain the lower volume CC for me, my thirst for knowledge is increasing each day.

Also, from the Uflow models the temporal sin waves looks as if they are in perfect sync, and from bruno's PDF file I was to understand it should follow or trail the sin curve by 1/4, slightly out of time. See :D I'm trying to get my head around the wonderful world of unsteady flow dynamics :D

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Re: Fwe Development 2004-Today

Post by larry cottrill » Mon Jan 29, 2007 1:25 pm

Irvine.J wrote:From the pictures above, I notice that the tailpipe Exit diameter, the straight section immediately after the CC, and the CC lengths are all different from the engine that James D got running. Let alone the inlet pipe.
That's right.
So I'm thinking, maybe I should keep the cc/inlet pipe the same length (and D) as the one James D got working, and change the rest from there. (29mm cc exit etc.) Simply, the inlet location, diameter, and CC seemed to work very well. If you want to go directly off your drawing thats fine, though perhaps you can explain the lower volume CC for me, my thirst for knowledge is increasing each day.
No no no ... we already know that the original dimensions will run. What we're trying to prove out is Graham's re-proportioning of the main tube. There are reasons for the smaller chamber, mostly having to do with pulling the choke cone forward significantly. The proportions of the front end AND the decreased nozzle ID (the 29mm) are important elements in milking the last drop of thrust out of this beast! Proving this is what we're after. Note that James D has given a correction for the intake pipe ID of 23mm - you can use that, but don't let it get any bigger! 20 or 21mm would be adequate, though, and would be better for intake pipe Q.
Also, from the Uflow models the temporal sin waves looks as if they are in perfect sync, and from bruno's PDF file I was to understand it should follow or trail the sin curve by 1/4, slightly out of time. See :D I'm trying to get my head around the wonderful world of unsteady flow dynamics :D
Be sure you're thinking of the right curves. What I showed above are the velocity and mass flow curves, which will generally be tightly sync'd up. What you're thinking of are the pressure and mass flow curves, which will have the 90-degree phase relationship you're getting at. All I was doing was showing that there is, indeed, a place in the engine where everything grinds to a halt. It is that point where the pressure swing is fully developed, which I could have shown but didn't.

L Cottrill

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