Just Another Valveless Front End

Post by **Mike Everman** » Wed Nov 05, 2003 5:39 am

So, Hello to all. First post so be gentle. I don't think I've found a more intriguing problem than the "air diode" (or is it "flow diode"?) and its application to pulse-jet valving, it's got me awake in the wee hours. So without further ado, I present to you Just Another Valveless Front End (JAVFE). I haven't adjusted the concept for intake or combustion chamber areas, lengths or any other critical parameters yet. It places less importance on ram intake at speed, but might get some ram in a further iteration. Perhaps when I get Bruce's book and of course, digest more of whatâ€™s important from this forum, Iâ€™ll go a bit further with it...
Basically the pulse ejecta that would come out the intake is directed across the intake area to alternating receiver channels that are larger than the intake nozzles to allow for expansion, and bent into a jacket that can also have a cooling effect on the combustion chamber, and perhaps some thrust augmentation.
The forming of sheet metal isn't too difficult but there'll be a real problem butt sealing all these parts to the flat sidewalls. Lots of welding. I see why cylindrical and conical constructions rule the home-built arena.
No grand plans as of yet, the rendering looked cool if not properly proportioned and thought you might like it.
-Mike

Mike Kirney · Post by **Mike Kirney** » Wed Nov 05, 2003 6:05 am

I don't know if your idea will work or not but that rendering (rendition?) looks fantastic!!! What did you use to do it? Most of the voices in this choir will tell you that aerodynamic valves are too leaky and inefficient to use on pulsejets and would serve only to impede airflow in both directions, but I wonder how many of these songsters have actually built a jet, especially one as large and as dodgy as the infamous Tundra-Jet. Go ahead and build it, Mike. I built my jet months ago and it still doesn't work, but thats okay, I'm still having fun with it. All my pals think its a hoot.

Post by **Mike Everman** » Wed Nov 05, 2003 6:18 am

Thanks, Mike. I use Solidworks for designing. I've had a lot of fun with this one, haven't had much need for "lofted" sections in my robot designs (that's the term for how the intake/diverter channels blend down to a straight wall. I'm thinking about the forming tools I'll have to make eventually to do something like this. At least the complicated part is identical on both sides and not a mirror! BTW, how do you get the your attached photo to come up on the post and not as "download"?

Mike Kirney · Post by **Mike Kirney** » Wed Nov 05, 2003 6:22 am

I have no idea why some pics are viewable and some aren't. Sorry.

Post by **Mike Everman** » Wed Nov 05, 2003 6:31 am

Oh, yeah, I forgot to go on about "leaky" valves. Seems to me that the Lockwood is about as leaky as it gets and works great, with the benefit of inertia and colliding air masses (pardon my ignorance of terms). Saw a four tube front end on one of Bruce Simpson's valved jets and it struck me that it was working (albeit with small thrust) mainly because it choked down the avenue for exhaust out the intake area, with the disadvantage that it also chokes the intake during intake. I just don't have the experience with this to have a meaningful opinion, but leaky valving sure looks OK if the product all goes a-rearward.
-Mike

Viv · Post by **Viv** » Wed Nov 05, 2003 1:06 pm

Well just to prove Mike wrong I realy like that! I cant at the moment find a hole and it looks original too.

Nice.

Edit?? in fact just base it on the Kentfield dimensions as that looks similar

Viv:-)

Post by **Mike Everman** » Wed Nov 05, 2003 2:59 pm

Thanks, Viv. Any links to Kentfield dimensions that work? I'll search for the any patents today. Should be an interesting looking section after converting from round to rectangular. Dreaming of a wide, flat engine suitable for embedding in an airfoil.
Mike

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Nov 05, 2003 6:02 pm

Hey, Everman, that's the neatest idea I've seen in ages! It is not really a conventional 'air diode' (they truly are all leaky). It's more of a Lockwood-style thing, inasmuch as jets on both sides serve to create some thrust. Yes, I am certain that the front exhaust channels can be turned into thrust augmentors. I love it!

If you drop me a line by e-mail, I'll mail you a document with Kentfield 4-tube dimensions, which you can adapt to your needs. You'll have to fiddle with augmentor dimensions, though. They are not provided in the paper. Talk to Bill Hinote -- he is building a 4-piper with bent rectifier tubes. Maybe he has some ideas on augmentor sizes. Or, talk to blacksmiths. They usually have extensive experience with diffusers of various sizes and shapes.

Why don't you keep the thing square? It will be easier to build than round. Just make a round exhaust pipe.

Again, a refreshing, nifty idea that made my day. Thank you!

Bruno

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Nov 05, 2003 6:14 pm

Mike,

One more detail -- don't worry about utilization of ram pressure. Your engine will be able to take advantage of it to the same extent as any other pulsejet -- that is, only partial.

What we call 'ram pressure' is really better called 'velocity head'. It is the kinetic energy of traveling air molecules.

The problem is that a pulsejet can only suck in fresh air that is motionless. Remember, it stops all intake air when the exhaust phase commences. When it starts sucking again, the air at the intake is motionless. No velocity. No velocity head.

A part of the velocity head is utilized -- the part that gets converted to static pressure in the intake tract. It does help the engine ingest more air than when it is stationary, but this is nowhere near the amount of ram pressure utilized by other jet engines.

So, don't worry. In that respect, your engine is no worse than any other pulsejet.

Bruno

Post by **Mike Everman** » Wed Nov 05, 2003 6:20 pm

Boy, the response has been beyond expectations, and thanks. Private messaging appears not to work, so you can contact me at everspare@yahoo.com (at least that's my broadcastable address). I'll check it today. No luck on the patent search for Kentfield, so I appreciate the help. Is Hinote the fella that had the bent four tube that he had to plug one after the other to get it to sustain? Don't remember where I saw that. I'm wondering if conventional augmenter dimensions will be of any value since one wall of it will be red hot. I was expecting (hoping) for a good deal of raw thermal expansion of entrained air in this region.
-Mike

Post by **Mike Everman** » Wed Nov 05, 2003 6:24 pm

Bruno,
As to velocity head, any thoughts on the fact that even during combustion phase air is being sucked into the intake? Seems as if incoming air is never stopped??
Mike

Bruno Ogorelec · Post by **Bruno Ogorelec** » Wed Nov 05, 2003 6:43 pm

You mean, it doesn't stop in your engine? No, it doesn't. That's good. Your engine will not stop the main flow into the engine, just the flow in the small bent intake passages. Most of the air will flow continuously, with the engine just taking a small gulp 200 times a second (or so).

You should shape your outer mantle so that it heats the passing air and accelerates it, like a low-temperature ramjet.

Bruno

Post by **Mike Everman** » Thu Nov 06, 2003 6:34 am

Thanks to Bruno for the Kentfield paper.
OK, so now I have some dimensions and I've made an excel converter to get it to rectangular sections. Do I keep the area relationships for all transitions and vary the lengths given to preserve the volume to surface area ratios? I think that's what I caught somewhere along the thread...
Bruno- I wonder why you suggested I mimic the four pipe inlet design, is this one proven? The SNECMA/Lockwood while a lot longer seems to be working for all who try it.
Mike

Bruno Ogorelec · Post by **Bruno Ogorelec** » Thu Nov 06, 2003 6:59 am

Yes, the four-pipe design is proven. Ask Bill Hinote. It is so much shorter than the incredibly long regular single-piper you wouldn't believe.

The regular Lockwood I am calculating dimensions for at the moment is 11 feet long, stretched out, yet its combustion chamber is only 9 inches in diameter! What do you do with 11 feet of engine?

I'm thinking of coiling it around an imaginary central drum. maybe the propane tank could be inside. It should keep it warm, if nothing else.

Bruno

Viv · Post by **Viv** » Thu Nov 06, 2003 10:31 am

Mike Everman wrote:Thanks to Bruno for the Kentfield paper.
OK, so now I have some dimensions and I've made an excel converter to get it to rectangular sections. Do I keep the area relationships for all transitions and vary the lengths given to preserve the volume to surface area ratios? I think that's what I caught somewhere along the thread...
Bruno- I wonder why you suggested I mimic the four pipe inlet design, is this one proven? The SNECMA/Lockwood while a lot longer seems to be working for all who try it.
Mike

Mike, make it an 8 tube inlet, the tubes then corrospond to the inlets in your design, just alter the depth of the green filler section on your engine to get the length of inlet required (add ridges down the sides too).

It was why I suggested the Kentfield engine as your design tidys it up realy nicely.

Viv

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