JAVFE Redux

[Bruno Ogorelec]

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

[Mike Everman]

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

[Bruno Ogorelec]

Now if I can just get microwave triggered pulse detonations out of my head...

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...

Bruno

[Viv]

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

[Mike Everman]

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.

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.
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

[Bruno Ogorelec]

[quote="Mike EvermanIs there any cold tests you can imagine doing?[/quote]

Oh, yes; test some cold beer before you fire the thing up. Good to steady your nerves before the onslaught of terrible noise.

Bruno

[Mike Everman]

Oh, yes; test some cold beer before you fire the thing up. Good to steady your nerves before the onslaught of terrible noise.

that is an absolute given. I also liked your idea of pre-lining the CC with whacky and testing in a small room.

[Mike Everman]

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.

[Viv]

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

[Bruno Ogorelec]

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

[Mike Everman]

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.

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.

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?

[Viv]

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

No Bruno I must disagree! my ramblings would be much worse reflected from a concave mirror.

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.

[Viv]

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.


Mike

I think I said you need a current in the ionised flow? did I not?

Viv

but I may be wrong:-) I havent finished reading this new papaer

http://trs.nis.nasa.gov/archive/00000625/

23Mb so dont hit download to quickly.

Viv

[Bruce]

[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.

[Mike Everman]

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...

My point exactly, but I think the thermocouple idea of Viv's is easier to implement, and more energetic, as he suggests.

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:-)

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.