Stainless FWE with small intake runs at -3 F !!!!!!!!!!!!!!!

Moderator: Mike Everman

Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Mark » Wed Jan 26, 2005 2:28 am

Eric wrote:Well I made a little removeable test stand for the first all stainless FWE prototype and started it up today when it was 5 degrees out. I waited until dark and started it up again at -3 degrees F !!!!!!!!!!

Eric


I found this today on flash points, methanol 54, gasoline -45, and propane -156. I got it from this site about midway down the page.
Mark
http://www.eere.energy.gov/de/pdfs/road ... thanol.pdf
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Eric » Wed Jan 26, 2005 3:34 am

Hmm. Thats interesting that it is that low. Overall I dont think it has anything to do with the flash point (to a point) since the other engines and designs wouldnt work at these temperatures. The design changes like the lockwood style intake flare (kind of ironical since we just all saw the lockwood pictures with the 60's lockwood engine that has the exact poportions as a FWE). I think the lockwood style flare lets the air flow in a lot more smooth and the design just seems less picky. I also smushed the intake down unlike the others.

It turns out the pressure tap 1 way valve I got from the hobby shop was for attaching to the crank case, and required a slightly higher pressure to start it. I got this little "hyper" valve that is supposed to be used from the over pressure in the exhaust pipe of a 2 stroke, which is much better suited for pulsejetting. The new valve also resonates at like a 1000 htz or so with very little pressure at all. I tried that out with a traxxis needle valve and everything worked, still probably needs a clien valve to help cut down on excess fuel loss. Without something to keep the excess fuel from being sprayed into the intake at all times (durring the exhaust phase you can see the excess spraying backwards like a mist bottle). the engine drains a 12 ounce tank in maybe 30 - 45 seconds!!! it definately needs a clien valve. Other than that it is too freaking cold out to be screwing around trying to perfect liquid fuel systems.

Well I put the stainless engine up on ebay $45 with no reserve.
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 38424&rd=1
Eric
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Ogge » Wed Jan 26, 2005 5:10 am

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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Eric » Wed Jan 26, 2005 5:24 am

Sorry, I meant intake flare, as in the edge curling back on itself to form an aerofoil type shape, not like th exhaust flare. On this engine there is only a gradual flare from about 2" back on the exhaust with not much expansion.

eric
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Ogge » Wed Jan 26, 2005 5:48 am

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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Bruno Ogorelec » Wed Jan 26, 2005 8:25 am

Adam,

You seem to be convinced that the standing wave is difficult to establish under the conditions obtaining in the pulsejet. As you seem to be basing your thinking about pulsejets on this notion, let me tell you that you are wrong.

Despite your conviction, the standing wave is exactly what keeps the pulsejet operating. Look at a few pulsejet research papers and you will find experimentally established sine curves for pressures and speeds at point locations (in time) as well as for duct lengths.

Temperature variations along the duct and in time make them look skewed, but there is no doubt that they are sine curves and that standing waves do get established. There's simply too much evidence for that for you to dismiss it.
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Mark » Wed Jan 26, 2005 12:16 pm

Mark wrote:
Eric wrote:Well I made a little removeable test stand for the first all stainless FWE prototype and started it up today when it was 5 degrees out. I waited until dark and started it up again at -3 degrees F !!!!!!!!!!

Eric


I found this today on flash points, methanol 54, gasoline -45, and propane -156. I got it from this site about midway down the page.
Mark
http://www.eere.energy.gov/de/pdfs/road ... thanol.pdf


Here's some definitions of the flash point.
http://www.google.com/search?hl=en&lr=& ... lash+Point
But yes, there are a lot of criteria as to whether a pulsejet runs at a certain temperature or when it is easy enough to start. Take the Dynajet, it often likes to start after a few warm up pops to make the gasoline more amicable.
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Ogge » Wed Jan 26, 2005 5:11 pm

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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Eric » Wed Jan 26, 2005 6:03 pm

You are not going to find any simple way to describe what is going on in a pulsejet, by anymeans. Wether using CFD, pressure sensors, or anything else.

You have an engine at one second full of 2500 degree ++ gases expanding, flowing out of the engine and continuing to burn and expand along the way, have various restrictions from pipe design, imparting heat to the tailpipe depending on local tailpipe heat pressure velocity etc, and at this point your speed of sound will be very high, so naturally any frequency will differ at any point in the engine at any time.

Then during the intake stage you have (in my case) below 0 air temp flowing over a thin boundry layer clinging to the metal. This cold air is ever changing in volume, as is differential between the two layers, and their wildly varying temperatures, and pockets of mixing gas, will throw off the speed of sound average drastically, and if you look at the individual sections not as an average things are even more different.

When the speed of sound changes, the frequency will change, and since there will be no single speed of sound in the engine at any point in time you will get grotesque looking wave patterns, all in rapidly changing proportions and frequencies.


Heck half the people here cant even agree on how the fuel is reignited each cycle! Once you come to terms with all this and realize that no one REALLY knows what the hell is going on in these engines, you will become a much happier person, and less prone to speculative arugments about tremendously oversimplified veiwpoints and theories of how these engines work.

Just go with the flow and eventually after enough testing and prototyping someone might figure it out.
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Eric » Wed Jan 26, 2005 6:35 pm

Ok, here is what I think is going on inside the FWE with chinese style intake. I obsevered the same flame pattern with the Jumbo FWE while actually looking down the tailpipe.

Especially in the pictures of the stainless FWE thats now on ebay, you can see where there are hot spots, that just happen to correspond with exactly where I had observed the flame path. The rest of the spots remain a realitively cool red glow.

Eric
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby mk » Wed Jan 26, 2005 6:59 pm

Ogge wrote:All I was pointing out is that geometry will change pulse shapes of the reflections. Yes, standing waves exist, but they are not perfect standing waves. If they were, you would get basicly a single tone out of a pulsejet. That is obviously not the case. Yes there are dominant frequencies and they are the ones you are using to establish your standing waves with.

As a matter of fact you will be getting at least 3 standing waves if not more. You will get a standing wave in the exhaust tube as well as in the intake tube and the interaction of their sum. These standing waves are generated by the interaction of waves propogating down the tube vs the reflections from the other end. To get a standing wave you MUST have waves traveling in opposite directions that sum to generate the standing wave.


Surely you're also getting other harmonics of the basic standing waves. Therefore, shouldn't it be an aim shifting the harmonics for forming a kind of "minimal multiple" as sum?
By trying to apply or rather applying a special temperature distribution and/or (depends on each other and the above) a special wavelength distribution?

Or even forming a special frequency distribution, depending on the energy/heat release amount and thereof the temperatures that are then (re-)affecting the cycle?
If I understood it right, forming a "lock-up" that Milisavljevic mentioned some day?

But he never really clarified what he ment by "lock-up". Bill Hinote, could you eventually help here?


Eric wrote:You are not going to find any simple way to describe what is going on in a pulsejet, by anymeans. Wether using CFD, pressure sensors, or anything else.

You have an engine at one second full of 2500 degree ++ gases expanding, flowing out of the engine and continuing to burn and expand along the way, have various restrictions from pipe design, imparting heat to the tailpipe depending on local tailpipe heat pressure velocity etc, and at this point your speed of sound will be very high, so naturally any frequency will differ at any point in the engine at any time.

Then during the intake stage you have (in my case) below 0 air temp flowing over a thin boundry layer clinging to the metal. This cold air is ever changing in volume, as is differential between the two layers, and their wildly varying temperatures, and pockets of mixing gas, will throw off the speed of sound average drastically, and if you look at the individual sections not as an average things are even more different.

When the speed of sound changes, the frequency will change, and since there will be no single speed of sound in the engine at any point in time you will get grotesque looking wave patterns, all in rapidly changing proportions and frequencies.


We all should internalize these facts.
But surely most of the "insiders" (I mean people being more or less deeper in the pulsejet theoretics) here should already know it.
We rather should want to work with these facts, not against them.
Sooooo complicated. But simplified models are necessary.
Last edited by mk on Wed Jan 26, 2005 7:15 pm, edited 1 time in total.
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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Ogge » Wed Jan 26, 2005 7:05 pm

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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Eric » Wed Jan 26, 2005 7:37 pm

Sorry Eric, you are wrong here. The frequency is not changing!

http://www.glenbrook.k12.il.us/gbssci/p ... 10l4b.html

The tempature of the medium is changing this will affect the speed in the following formula:

Speed = Wavelenght * frequency

A change in speed will change the Wavelenght not the frequency. The frequency is FIXED by the chemical composition of the fuel.




HAVE YOU EVER EVEN TAKEN A PHYSICS CLASS? You claim to be a PDE engineer but you seem more like an Ivar type to me.

Speed = wavelenght * frequency

Frequency = speed / wavelength

wavelenght = speed / frequency


FREQUENCY AT WHICH A CLOSED END PIPE WILL RESONATE ( FIRST HARMONIC) :
f=v/4L

f (frequency of sound (Hz)) = v (
velocity of sound in air (m/s)) / 4 L (lenght of tube in meters)

WHEN THE SPEED OF SOUND IS 330 M/S A PIPE 1 meter long (keeping the math simple for PDE engineers) will have a 1st harmonic resonance of 82.5 htz.

82.5 htz = 330m/s / 4* 1 meter

WHEN THE SPEED OF SOUND IS 660 M/S A PIPE 1 METER LONG WILL HAVE A 1st harmonic at 165 htz

165 htz = 660 m/s / 4* 1 meter.

THE SPEED OF SOUND IS AFFECTED BY TEMPERATURE!!! YOU CANT CHANGE THE TEMPERATURE WITHOUT CHANGING HOW A PIPE WILL RESONATE! DID YOU GET YOUR ENGINEERING DEGREE BY MAIL? WHERE EVER YOU GOT IT I THINK YOU SHOULD GET A REFUND, BECAUSE AS FAR AS I AM CONCERNED YOU HAVE NO CREDIBILITY. YOU THINK BY CITING SOME PHYSICS CLASS WEBSITE YOU CAN CONVINCE SOMEONE WHO HAS HAD 4 YEARS OF PHYSICS CLASSES THAT TEMPERATURE HAS NOTHING TO DO WITH FREQUENCY?

Eric


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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby hinote » Wed Jan 26, 2005 7:39 pm

mk wrote:
Or even forming a special frequency distribution, depending on the energy/heat release amount and thereof the temperatures that are then (re-)affecting the cycle?
If I understood it right, forming a "lock-up" that Milisavljevic mentioned some day?

But he never really clarified what he ment by "lock-up". Bill Hinote, could you eventually help here?


Sorry--I'd only be conjecturing; I can't offer any hard evidence.

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Re: Stainless FWE with small intake runs at -3 F !!!!!!!!!!!

Postby Tom » Wed Jan 26, 2005 7:43 pm

Eric wrote: YOU THINK BY CITING SOME PHYSICS CLASS WEBSITE YOU CAN CONVINCE SOMEONE WHO HAS HAD 4 YEARS OF PHYSICS CLASSES THAT TEMPERATURE HAS NOTHING TO DO WITH FREQUENCY?

Eric


Hear Hear, I'm with Eric. *Coming out of two years triple science physics class, moving on to A level this year at college.*

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