Propless ducted fan ?

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poormansairforce

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henryk

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=how it works...
 

Orange4sky

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Correct me if I'm wrong but "air amplification" ≠ thrust amplification. It simply spreads the energy of the high velocity stream over a wider area. You get a larger volume of moving air but at a lower velocity. I would think a turbofan does this far more efficiently.
 

Victor Bravo

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Correct me if I'm wrong but "air amplification" ≠ thrust amplification. It simply spreads the energy of the high velocity stream over a wider area. You get a larger volume of moving air but at a lower velocity. I would think a turbofan does this far more efficiently.
^^^^^^ THIS guy needs to be de-platformed and sent off somewhere where he can think about all the harm he's doing to the Silicon Valley economy by callously putting common sense in the way of commerce !
 

Vigilant1

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Correct me if I'm wrong but "air amplification" ≠ thrust amplification. It simply spreads the energy of the high velocity stream over a wider area. You get a larger volume of moving air but at a lower velocity. I would think a turbofan does this far more efficiently.
It apparently is possible use gas/fluid under pressure to entrain additional gas/fluid in a "thrust augmenting ejector"and thereby produce more thrust compared to just jetting the high pressure gas by itself ( more here: Anybody want to build one of these?).
This might have some utility if you already have some sort of high pressure gas (maybe a pulse jet exhaust, or a by-product of some other process). Normally, though, it wouldn't be efficient to pay the high losses of compressing a gas just to use it in this way.

But, there's no free lunch. The uninitiated (or charlatans) will see that these thrust augmenting ejectors can double the thrust available from the high pressure source gas and believe (or say) that it is a new and fantastic means of efficient propulsion. To believe that, you generally have to ignore the initial high inefficiency of producing the high pressure gas in the first place.
 
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poormansairforce

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=how it works...
I looked at this years ago. It's a silly idea!

The 8" model I posted uses 21 hp to create 120 cfm at 80 psi to produce about 17+/- lbs of thrust while creating an exit velocity of just 97 mph. Horrible idea! Does anyone happen to have a 1470 hp power source laying around to get 1200 lbs of thrust for VTOL and are willing to pay the fuel bill....

P.S. If someone else does the math and proves me wrong I'm be thrilled.
 

Bart

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OTOH, the inventors appear to have a flying model propelled by the Coanda phenomenon. The sailplane test aircraft is of unknown size, perhaps a half-scale RC model, which operates in more or less the same flight envelope as a small homebuilt plane. If so, this proves the concept works for a plane of comparable size to a homebuilt, regardless of the source of the compressed air, which may as well come from a pressure bottle.

So, assuming Coanda propels this small plane (if not, what else propels it?), we're down to asking what source of compressed air and ducting geometry is most efficient, and how all this compares to a conventional engine/prop.

And, are Coanda nozzle/slots limited to oval cross-section boxwing applications, or can such nozzle/slots be fitted to, say, a hollow conventional wing or aileron? In other words, why not dispense with the twin oval thrusters, and simply install the nozzle/ducts on the upper surface of the wing?
 

poormansairforce

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OTOH, the inventors appear to have a flying model propelled by the Coanda phenomenon. The sailplane test aircraft is of unknown size, perhaps a half-scale RC model, which operates in more or less the same flight envelope as a small homebuilt plane. If so, this proves the concept works for a plane of comparable size to a homebuilt, regardless of the source of the compressed air, which may as well come from a pressure bottle.

So, assuming Coanda propels this small plane (if not, what else propels it?), we're down to asking what source of compressed air and ducting geometry is most efficient, and how all this compares to a conventional engine/prop.

And, are Coanda nozzle/slots limited to oval cross-section boxwing applications, or can such nozzle/slots be fitted to, say, a hollow conventional wing or aileron? In other words, why not dispense with the twin oval thrusters, and simply install the nozzle/ducts on the upper surface of the wing?
Taking my post above, if we use 12' wing panels with a slot the same width as the 8" amplifier I used above then when we fit (8" x π = 25.12") into (144" x 2) is 11.46 times that we need to multiply the cfm and hp requirements for the wing slot.
So approximately 240 hp just to operate the slots. I had looked at this a long time ago and the question is...do the slots give enough lift/thrust to negate the need for a prop? Otherwise you'll need another power source....
 

Aesquire

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This is one of many variations on ducts, and changing the direction of air, in general, that all fall under the category of "yes, you can. but you can't afford it".

The cost is usually a large and heavy power plant you then can't actually lift. Many of these ideas only work when you get to the power to weight ratios of turbojets.

And nearly every time, it would just be better in almost every way to just hang the turbojet on the outside and use the thrust.

There are exceptions. The X-14 and the Harrier, for example. The loss in efficiency is less a problem than the difficulty of flying an otherwise conventional airplane backwards, hanging on the prop or balanced on the jet.
 

BBerson

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It isn't a typical axial flow propeller but it is a centrifugal propulsor or fan or turbine.
Centrifugal fans/rotors are normally high pressure, not the high mass flow as needed like an axial prop.
 

Bart

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Let me rephrase my question from above, considering the following testbed for the Coanda propulsion. Consider the modified sailplane model shown in the opening picture and @ 23 seconds into this video:


Suppose you transplanted those ~2mm ducts now contained in the oval rings, so the duct slots are straight and imbedded in the wings, perhaps in conjunction with the upper flap surfaces. (i.e., same air source, same pressure and flow, same size and length now-straight Coanda ducts, but no oval rings hanging out in the breeze.)

So, there's less weight and drag from the ovals, because now they're gone.

Why wouldn't this be simpler, cheaper, and more efficient than the shown oval ring testbed?

And, how might such an aircraft compare with an otherwise identical aircraft of identical energy input driving a conventional propeller? In otherwords, for a given amount of energy input, which gets better miles per gallon?
 
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BBerson

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There is no such thing called Coanda propulsion. There is Coanda effect.
The model used ordinary axial fans. They have proved nothing about using centrifugal fans for propulsion.
 

Bart

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Huh? Exactly where are the "ordinary axial fans" on the flying model shown briefly at 23-24 seconds and again from above at 1:26-29 into the video? (Video is poorly presented, jumps back and forth between different testbed models, but here I'm referring solely to the 23-24 second and 1:26-29 depictions of a sailplane planform.) So, what's propelling that model, if not the oval Coanda ducts?

And, as to Coanda propulsion, someplace in Europe there is reportedly an ancient biplane with Coanda propulsion. I don't claim it works, but here it is, per Google images.:

1614911544703.png
 
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