JAVFE Redux
Moderator: Mike Everman
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JAVFE
Back to your engine. You'd better rename it; it's perilously close to blasphemy, heh-heh.
If I understand it right, the green spam-can is a kind of a dead-air pocket. Good. It will make ignition easier. Maybe some kind of an inward kink at the inner end of the inlets woould help the charge diffuse across the chamber more evenly?
Also, think about making the outer duct stretch beyond the inner one, so that the air moving through that duct is pushed along twice -- first by gas blasting out of inlets and then again by gas vlasting out of the exhaust.
I mean, a jet engine is simply a device that makes air flow faster by using heat. This would make it into a better air pump, I think.
It may be tricky adjusting the lengths of respective ducts to each other. Kentfield found out through experiment that front augmenter flow had to be timed in respect to exhaust flow for the best result, so he ended up pushing the outer flow through a spiral duct... With pulsejets, you are never home and dry, I guess. It's a never-ending quest.
Oh, yes, I forgot -- I LOVE your engine. A lot about it is anyone's guess, but on paper (that is, on screen) it looks fabulous and I like everything about it. And your threads in the forum are great fun.
Bruno
If I understand it right, the green spam-can is a kind of a dead-air pocket. Good. It will make ignition easier. Maybe some kind of an inward kink at the inner end of the inlets woould help the charge diffuse across the chamber more evenly?
Also, think about making the outer duct stretch beyond the inner one, so that the air moving through that duct is pushed along twice -- first by gas blasting out of inlets and then again by gas vlasting out of the exhaust.
I mean, a jet engine is simply a device that makes air flow faster by using heat. This would make it into a better air pump, I think.
It may be tricky adjusting the lengths of respective ducts to each other. Kentfield found out through experiment that front augmenter flow had to be timed in respect to exhaust flow for the best result, so he ended up pushing the outer flow through a spiral duct... With pulsejets, you are never home and dry, I guess. It's a never-ending quest.
Oh, yes, I forgot -- I LOVE your engine. A lot about it is anyone's guess, but on paper (that is, on screen) it looks fabulous and I like everything about it. And your threads in the forum are great fun.
Bruno
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Thanks much, whew! Let me know how you like the 3d viewer file. And I really enjoyed the story of the butter fired rail jet! Your Dad sounds like a character.
I am having one of my guys show me how to weld so I can do Javfe myself, though I'll have the side pieces water-jet pre cut. Everything else is sheared. The tool for making the inlets will be fun, too. I think I'll be re-doing the calcs so that that green tube is a readily available 3x4" section.
Now if I can just get microwave triggered pulse detonations out of my head...
Mike
I am having one of my guys show me how to weld so I can do Javfe myself, though I'll have the side pieces water-jet pre cut. Everything else is sheared. The tool for making the inlets will be fun, too. I think I'll be re-doing the calcs so that that green tube is a readily available 3x4" section.
Now if I can just get microwave triggered pulse detonations out of my head...
Mike
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What do you mean, get them out of your head? I sure don't want to lose mine. That's the only way my mind works -- it's either microwave pulse detonations or nothing at all. My wife says she doesn't know whis is worse...Mike Everman wrote:Now if I can just get microwave triggered pulse detonations out of my head...
Bruno
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Ok to move on then
Just a quick reply as i am a bit tired after welding classes, the new layout looks good but there is a but:-)
The sliding joint in the combustion chamber, sorry old mate that is not going to work, any leak no matter how small will affect things, this is from bitter experiance.
I like the through hole but can you make the hole (green) thing a bit triangular? or just taper it towards the bottome maybe, its just that the dead region were the plug would be looks a bit big.
On the augmentor it kinks in to follow the profile of the combustion chamber but by the time the air gets there it will be trying to expand and want a bit more room? or is this what you wanted to happen?
otherwise it is looking good.
Viv
The sliding joint in the combustion chamber, sorry old mate that is not going to work, any leak no matter how small will affect things, this is from bitter experiance.
I like the through hole but can you make the hole (green) thing a bit triangular? or just taper it towards the bottome maybe, its just that the dead region were the plug would be looks a bit big.
On the augmentor it kinks in to follow the profile of the combustion chamber but by the time the air gets there it will be trying to expand and want a bit more room? or is this what you wanted to happen?
otherwise it is looking good.
Viv
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Yeah the whole experiment on the bench, adjustability vs. flight configuration is a bit half-baked. suffice to say all joints seemingly sliding or fastend are in fact welded tight.viv wrote:The sliding joint in the combustion chamber, sorry old mate that is not going to work, any leak no matter how small will affect things, this is from bitter experiance.
The green centerbody is that length because when added to the median length of the intake jets it's the proper length and area for intake pipes on a 3.6" dia Kentfield. I am on the fence whether the aft face of it should be concave or convex so I left it flat like the header plate on a Kentfield. I'm not sure it is a dead region, as the inrush from the exhaust will smash the fresh air plug against it.
i am not really satisfied with my ability to change the dimensions, other than the exhaust length without great grief. Seems like a lot of work for a gamble, but I might get lucky and be within the range that would be tunable by a change in exhaust pipe.
Is there any cold tests you can imagine doing, if I seal it with caulk for instance, that might be telling? Vacuum or pressure flow from back to front, front to back, anything that would say: "yup, proper ratio of whatever to whatever..."
As to augmentor shape, do you think the area should be continuously increasing, or could substantially straight running next to the red hot section be also good?
Mike
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3d file and viewer
Kenneth has upped the .zip upload limit, so without further ado, I give you javfe5, This time it's personal!
Oh, a tip:
Click somewhere in space around the model, and if you have a scroll button on your mouse, rolling it will zoom in or out, and depressing it and moving rotates the view. You can control the visibility of parts on the tree to the left with a right-click.
Oh, a tip:
Click somewhere in space around the model, and if you have a scroll button on your mouse, rolling it will zoom in or out, and depressing it and moving rotates the view. You can control the visibility of parts on the tree to the left with a right-click.
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JAVFE5
That software rocks! looks very nice and it is so easy to look all over the design.
As to the last reply yes I do think the augmentor should increase in section at the end of the combustion chamber, after all the air/exhaust mix has to do something with all that heat input so it may want a bit more room to do it in.
One more thing, pulse jets resonate end to end but they can do it side to side as well! as you increase the width there is a danger that a transverse oscillation will start up and interfere with the main resonance.
I think this will design is more prone to it as it is a flat in section, its one of the reasons I keep harping on about the bottom of the c/c filler section, I can just see troublesome reflections from that big flat bottom.
Could you curve it?
More later
Viv
As to the last reply yes I do think the augmentor should increase in section at the end of the combustion chamber, after all the air/exhaust mix has to do something with all that heat input so it may want a bit more room to do it in.
One more thing, pulse jets resonate end to end but they can do it side to side as well! as you increase the width there is a danger that a transverse oscillation will start up and interfere with the main resonance.
I think this will design is more prone to it as it is a flat in section, its one of the reasons I keep harping on about the bottom of the c/c filler section, I can just see troublesome reflections from that big flat bottom.
Could you curve it?
More later
Viv
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I am obviously getting old. It is only on the animated 3D rendering that I understood what the green thing in the middle was. LoL! I thought it was the upper part of the chamber, whereas it's just a hole in the engine...
The engine now makes much more sense to me than it did before and I liked it even then.
I think you can disregard Viv's ramblings about internal wave reflections -- they reflect off concave mirrors far worse. (Waves, not Viv's ramblings.) I think you may perhaps have trouble in the intake tract with wave reflections from 8 tubes and 8 augmentor passages, but you can burn that bridge when it's behind you.
I loved playing with that animation.
Bruno
The engine now makes much more sense to me than it did before and I liked it even then.
I think you can disregard Viv's ramblings about internal wave reflections -- they reflect off concave mirrors far worse. (Waves, not Viv's ramblings.) I think you may perhaps have trouble in the intake tract with wave reflections from 8 tubes and 8 augmentor passages, but you can burn that bridge when it's behind you.
I loved playing with that animation.
Bruno
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Never let it be said that I can't eventually make myself understood, right or wrong. My mom is fond of saying that like my father, I am often wrong, but never uncertain.bruno wrote:The engine now makes much more sense to me than it did before and I liked it even then.
I loved playing with that animation.
Thanks for the compliments, guys! I am very excited to build it, and will be making full plans, my software makes that pretty easy, it'll even put the weld beads in.
Don't think I'm having a lack of focus when I start the Micro-wave triggered PDE thread... oh I don't care, think what you want! Where should I put it, though? Valveless? Should we ask Kenneth for a new master category, conspicuously absent? Perhaps it will collect too much bs about Aurora and crop circles if we do...
While you think about that, off topic, but check me out, 18 yrs ago in my 12' dia rotary joints for the space station. Fine set of pettycoats, don't you think?
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No Bruno I must disagree! my ramblings would be much worse reflected from a concave mirror.brunoogorelec wrote:I think you can disregard Viv's ramblings about internal wave reflections -- they reflect off concave mirrors far worse. (Waves, not Viv's ramblings.)
Bruno
You need to focus more my friend:-)
Viv
PS I am still waiting for this trip to Hungary to sort its self out so I may still pop down for a beer yet.
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but I may be wrong:-) I havent finished reading this new papaerViv wrote:I think I said you need a current in the ionised flow? did I not?Mike Everman wrote: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.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.
Mike
Viv
http://trs.nis.nasa.gov/archive/00000625/
23Mb so dont hit download to quickly.
Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke
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[quote="Viv"]
I think I said you need a current in the ionised flow? did I not?
Viv[/quote]
True -- but has anyone stopped to think that, thanks to the fact we have *pulsating* combustion and therefore the velocity of the ionized gas is constantly changing, the mere act of placing a magnet near the flow will cause a current to be automatically induced into it -- ie: we have a self-exciting MHD generator.
I think I said you need a current in the ionised flow? did I not?
Viv[/quote]
True -- but has anyone stopped to think that, thanks to the fact we have *pulsating* combustion and therefore the velocity of the ionized gas is constantly changing, the mere act of placing a magnet near the flow will cause a current to be automatically induced into it -- ie: we have a self-exciting MHD generator.
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My point exactly, but I think the thermocouple idea of Viv's is easier to implement, and more energetic, as he suggests.mike everman wrote: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...
Perhaps the explosive welding was off-putting, so I'd suggest dip brazing the metal sheets together. I'd be happy to go on about the process, but it essentially gets you a perfect bond between dissimilar metals. Copper and steel is a snap.viv wrote: 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:-)
Mike Often wrong, never unsure.
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