JAVFE Redux

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Mike Everman
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JAVFE Redux

Post by Mike Everman » Mon Nov 10, 2003 6:28 am

Getting down to something I think I can build, so I thought it warrants a fresh sheet.
It's comparable to a Kentfield with a 4" dia combustion chamber, about 32" over-all. CC and exhaust are .094" sheet, tubes are OD.75x.040" wall welded to flanges. 4 M3 socket head cap screws per flange.

Mark has ruined me tonight with "flow capacitors", too funny (see previous thread).

Bruno, oh lexicon of the art, do you have a picture of a Logan I can see?

Best Regards,
Mike
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Bruce
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Post by Bruce » Mon Nov 10, 2003 10:28 am

I would be tempted to offset the alignment of the two sets of intake tubes where they enter the combustion chamber.

By placing one row slightly ahead of the other (referenced to the front of the chamber) you might encourage some of the intake charge to be pulled into the front of the chamber by the vortext that could be generated there.

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Post by Mike Everman » Mon Nov 10, 2003 2:13 pm

I'd have to, of course, change it's name to "Tornado".
I am hoping that impingement on the far wall will fill top and bottom well, but now: where to inject fuel? And you're just the guy to ask: How would a glow plug work for this?
Mike

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Re: JAVFE Redux

Post by Viv » Mon Nov 10, 2003 2:54 pm

Mike Everman wrote:Getting down to something I think I can build, so I thought it warrants a fresh sheet.
It's comparable to a Kentfield with a 4" dia combustion chamber, about 32" over-all. CC and exhaust are .094" sheet, tubes are OD.75x.040" wall welded to flanges. 4 M3 socket head cap screws per flange.
Mike just remind me, why are you concentrating so much on an opposed inlet arrangement.

Yes turbulance is good to a certain degree but the arrangment you have will be detrimental I think.

The most succesfull engine todate has to be the Argus V1 engine (by Deitrich) (by number built and flown:-), look at the airofoil section flow correctors placed directly after the valve grid.

They are there to get rid of turbulance so that the engine could fill properly, that engine is designed to work with a 360mph gale coming down its inlet tract.

If your engine runs at 50hz you dont have a lot of time for the air to get in, going round and round in circles in the front of the engine is not as good as filling it up all the way down to the end of the tailpipe.

Forget about having a combustion chamber what you have is a combustion zone that is defined by how much A/F mixture is in the engine when it starts burning.

Your first design had a nice flow through for the mixture that would have been perfect, the little dead spot below the green filler section could have been removed by changing to a triangle section instead of the square section.

The current design I think has too many bends in the inlet tract and excessive turbulance in the combustion zone resulting from the side entry.

Viv
PS by no means an expert at this I have just been doing it wrong for longer:-)
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Post by Bruno Ogorelec » Mon Nov 10, 2003 3:47 pm

Mike,

You have provided more entertainment here in two threads than we have seen in two months. I have enjoyed this greatly. Thank you.

I hate the new layout, though. First it is uneconomical in design. Your first had a nice feel of something that could be assembled from pre-cuts in a flatpack.

I'd really go for square (or oblong) section passages formed by flat sheet partitions, rather than mandrel-bent tubes. Broad passages (augmentors) alternating with narrower passages (intakes). I particularly like the one in which their ends coincided or even overlapped a bit.

We are talking about an el cheapo machine that an Indonesian sweatshop would be able to churn out at $ 3.95 apiece and we (you) could sell to the unsuspecting American enthusiasts at 993.95 plus p&h. Don't go for a Porsche. The market is already full of those.

But, that's my view. You may have different ideas.

Bruno

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2x4 upside the head

Post by Mike Everman » Mon Nov 10, 2003 4:28 pm

Bruno and Viv,
You know, considering the pressures of both my customers and the economy here in the U.S., this is by far what I'd rather be doing all day. I am enjoying it immensely, too.
I'd like very much to see both the Argus V1 and the Logan, if you have time to dredge them up and post them here?

As to Redux, I get it... the original design is still the background on my desktop for some reason. There's something about it. I do this a lot in my professional life, throwing out the baby with the bath water, spinning off into permutations ad nauseum.

All points well taken; let me attempt again to get the original in to proportion. I tend to agree, the new one is starting to look mundane. If you just make the intakes have a 45deg bend, and put them on the angled butt-end of the CC, it looks distinctly Chinese.

Mike

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Argos As014

Post by Viv » Mon Nov 10, 2003 4:48 pm

Lets see if this works

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Post by Mike Everman » Mon Nov 10, 2003 7:06 pm

Cool Viv, thanks.
I just realized why I had a problem with the proportions of the original JAVFE! Damned flawed initial assumptions. Prepare to be Astounded! (or not...)
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Post by Mike Everman » Mon Nov 10, 2003 7:30 pm

Oh yeah, any views on pulsing vs. continous fuel injection?
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Post by Viv » Mon Nov 10, 2003 7:41 pm

Mike Everman wrote:Cool Viv, thanks.
I just realized why I had a problem with the proportions of the original JAVFE! Damned flawed initial assumptions. Prepare to be Astounded! (or not...)
Mike
Ok waiting:-)

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Post by Viv » Mon Nov 10, 2003 7:43 pm

Mike Everman wrote:Oh yeah, any views on pulsing vs. continous fuel injection?
Mike
Pulsing! oh yea baby pulsing with timed ignition too:-)

Viv
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Post by Mike Everman » Mon Nov 10, 2003 8:01 pm

Waitaminnit, timed ignition will be too heavy a system for flight uses, won't it? Unless we can coax some electricity out of the motor somehow. Anybody ever try putting a coil of wire around an exhaust pipe to see if it generates AC?
Mike

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Re: JAVFE Redux

Post by Bruce » Mon Nov 10, 2003 8:12 pm

[quote="Viv"][quote="Mike
If your engine runs at 50hz you dont have a lot of time for the air to get in, going round and round in circles in the front of the engine is not as good as filling it up all the way down to the end of the tailpipe.
[/quote]

No, you don't want the engine filled with air/fuel because it will have an absolutely lousy TSFC if you do that.

Remember -- any combustion that takes place *outside* the engine will not contribute significantly to thrust.

If the engine is filled with air/fuel then a significant proportion of that air/fuel will be blown out of the tailpipe before it is ignited -- that's wasted fuel.

The idea is to have an optimal amount of air/fuel (about 20-30% of the engine's total volume) right up the front and as much cold, dense air in the tailpipe as possible.

This will produce the maximum displacement of mass, the maximum early-combustion containment, and therefore the maximum thrust.

The issue of turbulence is an important one too. It is indisputable that a turbulent mixture burns more rapidly and more efficiently than a calm mixture. Since the only containment we have for our combustion process is the mass of the gases in the tailpipe, then it stands to reason that we want the most rapid combustion we can get (the PDE is an example of this when taken to extremes). Rapid combustion promotes higher combustion pressures which equals better efficiency and more thrust.

I'm not so sure that the aerodynamic vane in the Argus intake was put there to try and reduce turbulence so much as to provide additionalrigidity to a structure that is subjected to significant thermal and physical stress when the engine is running.

To be effectively straighten and stabilize the flow of air that's just passed through the valve grid would require a lot of very closely spaced flow-straighteners -- not just one or two big plates.

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Post by Viv » Mon Nov 10, 2003 8:17 pm

Mike Everman wrote:Waitaminnit, timed ignition will be too heavy a system for flight uses, won't it? Unless we can coax some electricity out of the motor somehow. Anybody ever try putting a coil of wire around an exhaust pipe to see if it generates AC?
Mike
I suggested it in a magnetohydrodynamic thread in the old forum a long time ago, but you do need to provide a current into the ionised gas stream to generate a magnetic field for the coil to work against.

I also suggested explosively welding a copper and steel sheet together to make a Big thermocouple and then rolling it to form the engine casing.

It would only nock out 1.2 volts but a thermocouple five foot long and two foot wide should have enough umph to spot weld with:-)

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Post by Mike Everman » Mon Nov 10, 2003 9:04 pm

viv wrote:I suggested it in a magnetohydrodynamic thread in the old forum a long time ago, but you do need to provide a current into the ionised gas stream to generate a magnetic field for the coil to work against.
Faaascinating, but I believe you need to add current to the flow in order to move the fluid through (thrusting against) with current supplied to the primary coil, at least with fluids. I was thinking that for the brief moment of combustion, the gas is ionized and therefore charged, and happens to be moving back and forth while ionized, depending on where you are on the engine, perhaps generating AC in the coil. There was some old stuff about one-shot explosive generators the Russians were using to pump lasers, but I digress. This all deserves a lofty new topic.
bruce wrote:then it stands to reason that we want the most rapid combustion we can get (the PDE is an example of this when taken to extremes).
OK, off topic again, but couldn't we get a mass of fuel/air to very, very close to the proper mix and temp for combustion, and touch the whole volume off at once with a microwave burst, or 30kv lightning bolt or something? Poor man's PDE. The way I understand it, if you get it close enough to combustion, you could set it all off with a stern look. Current supersonic shock wave type efforts are impossibly finicky, I'm thinking.
OK, back to JAVFE...
Mike

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