Just Another Valveless Front End

[Mike Everman]

Yes, exactly, it is essentially an 8 tube design. I'm clear with preserving the areas and lengths as shown in the 4-tube diagram, about the calculating level I'm up to without an in-depth design guide. Must I preserve the volume/internal surface area ratios by varying the section lengths? there is a disparity.
when preserving this ratio, all lengths become a bit shorter when moving to a rectangular section. The exhaust section for the lockwood is a lot shorter, but as you say still long; though a 4" dia combustion chamber in a rectangular section goes from 67" over-all to 49.5.
I wonder, does the bend the intakes go through demand a reduction in thier length, owing to the resistance in flow
I'll re-tool the spreadsheet for the four-pipe design.
Thanks.

[Pieter van Boven]

Could somebody send me a copy of the Kentfield paper?
p_van_boven@hotmail.com

Thanks,
Pieter.

[Bruno Ogorelec]

>Must I preserve the volume/internal surface area ratios by varying the section lengths? there is a disparity.

Mike, preserve the lengths as much as you can. At this size of the engine, the survace/volume ratio is less critical.

I wonder, does the bend the intakes go through demand a reduction in thier length, owing to the resistance in flow

Ditto. Preserve the lengths and sections (cross-sectional areas). Fudge the rest.

See if you can make some things variable. Kentfield made both the intakes and the exhaust adjustable. That's a very useful trick, though I don't think Bill Hinote needed the adjustments all that much. He built it and fired it and it worked. He has converted it to gasoline injection and again it just works. A great engine. Kentfield has built a lot of them; he knows what he's doing.

Bruno

[Mike Everman]

Yeah, I think some adjustability is in order, especially since I am morphing this thing around so much from known geometry. Sure would be nice if I could adjust it while it's running...
I sent Pieter the paper.
Mike
Oh, and Viv, I did some work for Motorola once, I like your tag line for them; they certainly were resistant to my "attachment of the electrodes of knowledge to the teats of ignorance" !

[Bruno Ogorelec]

they certainly were resistant to my "attachment of the electrodes of knowledge to the teats of ignorance" !

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The approach reminds me of my late grandmother on the mother's side. She was convinced that children had a special nerve running between the brain and the backside. "You have to stimulate them at the backside," she would say, "and suddenly their brains work better!"

Bruno

[Mark]

Yeah, I think some adjustability is in order, especially since I am morphing this thing around so much from known geometry. Sure would be nice if I could adjust it while it's running...
I sent Pieter the paper.
Mike
Oh, and Viv, I did some work for Motorola once, I like your tag line for them; they certainly were resistant to my "attachment of the electrodes of knowledge to the teats of ignorance" !

Wasn't their slogan, "From the mind of Motorola..." ?
Mark

[Graham C. Williams]

Dear Mike.
Very nice idea.
Viv's idea of 8 induction channels sounds about correct. These channels may need to be about the same length as the combustion chamber or a little longer.
I'm trying to imagine the reverse gas flow, the hot gas flow under positive combustion chamber pressure. Do you think it'll get flushed down the augmenter channels?

Graham.

[Bruno Ogorelec]

I'm trying to imagine the reverse gas flow, the hot gas flow under positive combustion chamber pressure. Do you think it'll get flushed down the augmenter channels?Graham.

Why not? It shoots straight into the augmenter channels and will vbe helped additionally by the increased static pressure in the intake area (a result of ram pressure), which will be relieved through those same channels.

Bruno

[Graham C. Williams]

I'm trying to imagine the reverse gas flow, the hot gas flow under positive combustion chamber pressure. Do you think it'll get flushed down the augmenter channels?Graham.

Why not? It shoots straight into the augmenter channels and will vbe helped additionally by the increased static pressure in the intake area (a result of ram pressure), which will be relieved through those same channels.

Bruno

And under static running conditions?
Graham.

[Viv]

yes but we also have opposed high velocity gas streams, the vortexs set up should be interesting

Viv

[Mike Everman]

Thanks Graham, I'm hooked. It's a good thing I have a full machine shop...
Hmmm. Vortices... Can we harness that? Never mind. I'll be making some changes tonight to get the proper proportions based on the Kentfield dimensions. As to augmentation, I think I need to push forward the inlet diffuser (pre-diffuser?) so there is more of an augmenter inlet area. Currently I think there was only enough augmenter inlet area to account for expansion of the (let's call them:) cross-jets.
There's some interesting relationships between the Lockwood/Snecma and the Kentfield, and hell, the rectangular section equivalents. I've attached a first cut spreadsheet (in progress) that allows you to look at this and draw your own conclusions of course if the mistakes aren't too many... Like the inlet area to chamber area ratio is the same, the chamber surface to volume ratios are the same, as are the tailpipes. Cool stuff. Seems everyone says "let's just use 45 deg" for the CC to tail taper, etc.
Anyone know what the thrust of a Kentfield with a 4" dia CC would be? It's lookin like it's only 36" long; nice manageable size.
Mike

[Mike Everman]

One more thing Viv's got me thinking about. What if there is a similar interlacing of intake streams in the CC, if we inject fuel in any or all of the high shear regions we'd get some good mixing, I think...

[Bruno Ogorelec]

yes but we also have opposed high velocity gas streams, the vortexs set up should be interesting

I don't think so. You need time to get vortices. The streams themselves should be slipping by each other unhindered, I think. Remember, their speed relative to each other should be well above Mach 1, possibly above Mach 2. For all practical purposes, they will be laminar.

But, things are never simple in pulsejets.

We also have wavefronts to consider. How those will behave is anyone's guess. Having four sets propagate within a square-section duct in two opposed pairs boggles imagination. It may well boggle the air, too, expelling it out of the intake tract with a highly amplified 'bang'. I hesitate to pronounce on this but get a headache trying to imagine what happens.

Hey you acoustical experts out there, care to comment on this?

Bruno

[Mike Everman]

Here's something along the same lines that might be machinable in mirrored halves, maybe a chance at a mini since the NC contours will be so smooth.
got sidetracked.

[Bruno Ogorelec]

Yes indeed. When I was rather younger, I toyed with a similar layout that aped an airfoil in section, thinking it could be used as an engine integral with wing. Your layout can also fit withinn an airfoil. It never occurred to me that it would shake itself loose from the aircraft quickly -- or shake the aircraft to pieces -- given the hammering pulsejets normally produce.

However, the layout just might be squeezed inside a somewhat fattened end of a helicopter rotor...

Bruno