Big Test Lady FWE arrives in Aero/Combustion Laboratory

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milisavljevic
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Re: The double-null

Post by milisavljevic » Wed Apr 29, 2009 3:13 pm

Larry and Greg,

I am out of time. I have remodeled (once again!) with the latest and greatest details
available to me, including the 1600 mm overall length of the duct with a new tailpipe.

Here are my final changes. Anything you do differently is (as they say) your problem.

[1] intake length: 172 mm; 72 mm less than spec (245 mm, which may be incorrect)
[2] intake flare: 58 mm; Larry reports this value, so I used it (if it is more, grind it)
[3] exit flare: 96 mm; there's nothing that can be done about this (have fun with it)

There is no tailpipe length spec, as you must use the new 1600 mm overall length of
the duct with the new tailpipe Greg acquired. Forming the exit flare may reduce this
somewhat without penalty, so beat the crap out of it ( I know I want to bash it! :evil: ).

Good luck,
M.

note: Larry says Greg can "cut & paste" the flare (as a stub) to achieve the new spec.
Last edited by milisavljevic on Thu Apr 30, 2009 1:17 am, edited 1 time in total.
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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by larry cottrill » Wed Apr 29, 2009 3:22 pm

THANK YOU, THANK YOU! I have already given Greg my ideas on how to get the tail end flare accomplished on such a big tube.

"So it is written. So it shall be done." - Yul Brynner, The Ten Commandments, Paramount 1956

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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by larry cottrill » Wed Apr 29, 2009 3:44 pm

Greg -

When you cut that section out of the intake, do NOT err on the side of taking out more than specified! I say this because my "as built" dimensions for BOTH the intake length and its location aft of the chamber front edge are 2-3 mm short of the 245mm target value. So, if it can't be exact because of tool/procedural limitations or whatever, err on the side of removing a little LESS, and you will stay close to M's location.

Obviously, you can try to run her without that tailpipe flare, but your time would probably be better spent making the flare. It's only 10 or 11mm all around from the outside surface of the pipe; sounds like a lot, but shouldn't be difficult with pipe this size. It's almost identical to the actual size of the intake flare. You have a lot more of it to do, but it's just mild steel and won't be that hard, with an assistant to roll the pipe as you work it.

L Cottrill

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Re: The double-null

Post by milisavljevic » Wed Apr 29, 2009 4:08 pm

.
larry cottrill wrote:You will stay close to M's location.
That is not a location, it is a length (172 mm). That is, measure the intake from join seam to flare.
It does not matter what the present length is...it only matters that the final length with flare is 172.
larry cottrill wrote:It's only 10 or 11mm all around from the outside surface of the pipe.
Incorrect. The flare is measured as an ID, across the face of the flare. In this way it is independent
of the material thickness. Greg, always measure a flare across multiple azimuths and average them.

M.
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an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
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Re: The double-null

Post by larry cottrill » Wed Apr 29, 2009 4:44 pm

milisavljevic wrote: That is not a location, it is a length (172 mm). That is, measure the intake from join seam to flare.
It does not matter what the present length is...it only matters that the final length with flare is 172.
So the slight as-built forward "drift" of the pipe location doesn't matter?
larry cottrill wrote:It's only 10 or 11mm all around from the outside surface of the pipe.
Incorrect. The flare is measured as an ID, across the face of the flare. In this way it is independent
of the material thickness. Greg, always measure a flare across multiple azimuths and average them.
Yeah. I knew that ;-) I didn't intend to suggest a method of measuring it, just what kind of effort would be involved. But it was probably a poor way to say it, confusing to neophytes, &c. However you make a flare, you're displacing metal from where it is now, and you need to have an idea of how far to go before you start easing off to end up with it just where you want it.

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Re: The double-null

Post by milisavljevic » Wed Apr 29, 2009 5:06 pm

.
larry cottrill wrote:So the slight as-built forward "drift" of the pipe location doesn't matter?
It does matter, but I had already impounded the intake displacement in the model. So, no worries. :wink:

I spoke with Greg, but my poor brain had already liquified from lack of sleep. There's another day
I will never get back (sigh). Let's hope for good running and better data; it will be worth the crash.

M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by Dang911 » Wed Apr 29, 2009 5:12 pm

We have a running engine for instrumentation. Got to give M a round of applause, his adjustements were spot on. Still havn't flared the exhaust but since its running I think I'll just stop there, JUST KIDDING M... She is still hot from the last run but when she cools I will be out with the torch flaring the exhaust.

This puts us back on schedule for testing tomorrow!

Larry, still couldn't have done it without you so thank you to sir.

Hopefully I can get a video and some running pics today.
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YES! ... YES!

Post by larry cottrill » Wed Apr 29, 2009 5:30 pm

Great news, Greg! Yes, get that flare worked in and you'll be ready to howl with the instrumentation.

M, I pray that the God you don't believe in will bless you mightily in every endeavour! "Thank you!" doesn't even BEGIN to say it ...

Incredible as it by now must seem, we are Go For Launch. Greg, keep us posted here, even with comments on construction and test setup, if you somehow have time. What did you end up with for an injector? What does your Chief Engineer friend think of it, now that it's running?

L Cottrill

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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by Kool » Wed Apr 29, 2009 5:45 pm

Maybe you can compare him with this pulsejet (Antares 18p) :wink:
I think a beginner will say that they are the same :lol:

Image
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Re: The double-null

Post by milisavljevic » Wed Apr 29, 2009 6:12 pm

Larry,
larry cottrill wrote: Great news, Greg! Yes, get that flare worked in and you'll be ready to howl with the instrumentation.
I just spoke with Greg ( he's soooo sorry that he gave me his cell no. :lol: ) and told him that the flare
may be unnecessary for this FWE; too late, as the work is now in progress. The flare allows the open
and closed pipe modes to synchronise with one other and the upper Helmholtz mode at 1:1; however,
as an FWE, this duct is probably quite content to run as a closed pipe resonator. I was a tad too slow...

No worries: it will (should?) run better in full-sync; if not, Greg can hack the flare off, then tack on a
bit of the remaining pipe. If there were more time, it would be instructive to collect data both ways.

Sorry, Greg! :roll:

M.

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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by Dang911 » Wed Apr 29, 2009 7:21 pm

OK, things have settled down for me today, looking back I don't know how I managed to make all the progress I did with the somewhat limited resources I had. M, I said I would get you a run clip of some kind today, as it turns out that won't happen, but I can assure you in the next 2 days all data I can possibly get will be collected for that is my only time I have left. Tomorrow is going to be test day, and I should be able to get a clip then. While on the phone with you (I don't know if you could hear the torch in the backgroud) I hammered out a partial flare. It comes to about 3.25", so its somewhere in between, hopefully that won't screw anything up, I doubt it will but I never ran it after the flare. With such a long pipe my nichrome is barely holding on and once I do a test to make sure its still working, I am going to have the tail pipe welded in.

Due to my modification I lost 2 of the intake pressure taps, no worries 6 are left...

So technical information I have learned. Well this engine was build with chrome-molly with hopes that it wouldn't flake and would last better than a plain carbon steel engine. I can say it flakes off just the same.

I will have more info about my injector tomorrow with flow data. I hope to try up to 3 nozzles, taking test data over a range of fuel pressures/flow - that is the plan at least.
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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by Dang911 » Wed Apr 29, 2009 8:18 pm

The new engine is a monster in length, just thought I would post a pic of what should be the final engine.
poech prut wrote:I think a beginner will say that they are the same :lol:
I think a beginner can tell the difference in our tests, can you?
Attachments
IMG_0343.JPG
Where I will be taking data from.
IMG_0363.JPG
Ready for testing at last....
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Re: The double-null

Post by milisavljevic » Thu Apr 30, 2009 1:15 am

Greg,
Dang911 wrote: I hammered out a partial flare. It comes to about 3.25" [ID 82.55 mm],
so its somewhere in between, hopefully that won't screw anything up.
I will remodel tonight (just for grins...argh!). At this point I think you would be better served
by cutting the flare off, then replacing the missing length with straight pipe. As a closed pipe
resonator, this FWE will be fine. With my rush to help get you two back on track, I did not do
as thorough a job as I would have liked (eg., not thinking more on open and closed pipes). In
an effort to save time I ran with my default model (full acoustic synchronisation), which does
much better with open pipe dominant designs (eg., Thunderchine)...that flare is unnecessary.

The clues were there (eg., very large flare), but I was going to fast to grok their significance.

M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Big Test Lady FWE arrives in Aero/Combustion Laboratory

Post by Dang911 » Thu Apr 30, 2009 1:43 am

Do we even have to call it a flare? Why not decorative trim. As you called me in the middle of my flaring ceremony, I decided to just leave it were it was at, plus I was getting bored hamming a nitrogen tanks valve-stem cap into the pipe (got to get creative)... With all due respect, I would rather leave the pipe alone if it isn't going to cause a catastrophic flaw in the design/performance, but when you get around to it, you will know the answer to that question better than me.
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Re: The double-null

Post by milisavljevic » Thu Apr 30, 2009 2:26 am

.
Dang911 wrote: Do we even have to call it a flare? Why not decorative trim.
"Decorative trim", it is.

By all means, leave the flare intact. From a selfish perspective, the results may be more instructive
than the alternatives. I have remodeled the duct with the present flare and a loss of 5 mm from the
pounding you gave the tailpipe during the, ahem...flaring ceremony. Model say: everything is good.

I will post the predicted acoustic and thrust performance data later tonight, well before you can test.

M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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