Propless ducted fan ?

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Bart

Well-Known Member
Joined
Apr 13, 2007
Messages
308
Here's a better video of the craft I'm discussing, which has no axial fans, VTOL tilt, etc., but with some much needed explanation shown in its comments section:


They put the compressor engine in the cockpit and cut out the forward section of the canopy to serve as the inlet.

See the comments section via YouTube link, which includes comments on low noise, efficiency, placement within the wing, as well as prospect of a 500 lb. plane, about same performance envelope ballpark as that of a homebuilt airplane.

This proves the basic concept of fluidic propulsion in an aircraft.

How might such concept benefit homebuilt airplanes?

How might it be improved or modified for such use?

Here's a link to Jetoptera website: http://www.jetoptera.com/technology/
 
Last edited:

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,680
Location
Rochester, NY, USA
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?
Yes.

a conventional prop driven by the engine ( a turbo jet "gas generator" in the full scale version or an electric motor in the scale model ) would be far more efficient .

The smart thing on The website is the comparison between the turbo jet & batteries. When batteries are an order of magnitude better, Then electric will work.

would it be more efficient to just use one sided jet slots? Um. Depends on your goal. For a conventional horizontal take off & land aircraft, probably. For a diverted air with rotating nozzle VTOL, probably not.

This is an application where you have to balance pure efficiency of power to thrust vs. Variable thrust direction.

And! Other considerations. Like fitting in the garage for the hypothetical "flying car" footprint. A V-22 Osprey is far more efficient at converting jet fuel to thrust for lifting straight up. But you need to fold wings and rotors to fit in the hanger of your yacht. Or heavy cruiser in full scale version used by the Marines.

In a previous post I mentioned you need modern jet engines to get the power density for these things. That's exactly what the so far imaginary full size Jetoptera uses.

My question is, will the Jetoptera work better than the Rockwell where they found far more internal duct losses than expected?
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,680
Location
Rochester, NY, USA
Re: using compressed air...

it would be reasonably easy to build a hand launched free flight model using the cartridge and valve mechanism from a BB pistol & CO2 cartridges for a very brief thrust period. That mental image should give you a perspective on the practicality of compressed gas cylinder power.

Or if you want a Human scale flight example... I don't have video, but I've seen twin CO2 fire extinguisher power used for a small altitude gain after hill foot launch mounted on the control bar of a hang glider. Better nozzle design probably would double the thrust meaning 27 vs. 20 foot altitude gain! Fun to watch, but not practical.

Better, also witnessed, was a big rubber band driving a 9 foot folding propeller mounted on the keel of a glider & triggered after takeoff. A year later iirc, twin chain saw engines worked much better in a Gemini power pack then commercially available. Marginal for level ground take off, but worked well after a hill launch.

Yeah, I've seen things.... Terrible things.... ;)
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,104
Location
Flint, Mi, USA
The question is not "does it work?" the question is does it work well enough or give enough advantages to choose it over something conventional.
The quiet and bystander safety are nice, but not enough to justify it on it's own without improving the efficiency.
On the plus side, the fact that it's meant to use compressed air means that the system meshes well with a combustion engine because you can use some of that compressed air to supercharge a four-stroke or scavenge a two-stroke.
Making the engine a little more efficient and powerful for it's size gets back a little of what the duct drive costs you.
Opposed-free-piston engines do a good job of compressing air because the power piston can drive the compression piston directly without additional parts, so it would be a good match for this type of thruster.
It lowers the parts count, reduces vibration, and runs on a wider variety of fuels.
Combining those advantages with the quiet and safety features, then you have something that could be viable.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,737
Location
Port Townsend WA
Peter Sripol flew a battery leaf blower fan (barely). Shows how inefficient the centrifugal fan is.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,680
Location
Rochester, NY, USA
Ah, but the full scale plane doesn't run on compressed air. Any more than a Lycoming. It uses a turbo jet as a "gas generator ", so it's In some ways like the Rockwell project. Which feeds back to the earlier question, "why not just blow through slots on the wing?" & the answer is the rectangular exterior gizmos are more efficient at moving air than the open/ one sided wing slots would be. It was duct losses that killed the Rockwell XFV-12, plus the thrust augmentation wasn't as good as planned for.

My bet is the same here, but I could be wrong, that's not based on math, just gut & guess.

I do admit, the Dyson Fan tech like thrusters are elegant. The only moving parts are the ones that rotate or retract thrusters. No need for power shafts, slip rings for electric motors, or controls just a hollow tube to tube joint. Oh, and air. Tons of air.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,034
Location
US
I do admit, the Dyson Fan tech like thrusters are elegant. The only moving parts are the ones that rotate or retract thrusters. No need for power shafts, slip rings for electric motors, or controls just a hollow tube to tube joint. Oh, and air. Tons of air.
And it is air under relatively elevated pressure, which is relatively "lossy" to produce. It may be unwise to pay that price if the desired end goal is to move a lot more air under very low pressure anyway, provided there is a more efficient way to do that.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,104
Location
Flint, Mi, USA
Ah, but the full scale plane doesn't run on compressed air. Any more than a Lycoming. It uses a turbo jet as a "gas generator ", so it's In some ways like the Rockwell project. Which feeds back to the earlier question, "why not just blow through slots on the wing?" & the answer is the rectangular exterior gizmos are more efficient at moving air than the open/ one sided wing slots would be. It was duct losses that killed the Rockwell XFV-12, plus the thrust augmentation wasn't as good as planned for.
The Rockwell was trying to be a supersonic VTOL. A regular plane trying to be a regular plane that used wing slots for propulsion and improved lift would likely do fine.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,680
Location
Rochester, NY, USA
A conventional takes off & lands horizontally craft can be relatively inefficient & still fly. A VTOL that weighs a ton but only produces 1700 pound of thrust is a parked noise machine.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,104
Location
Flint, Mi, USA
Having given it more thought, you only really need to blow the wing during takeoff and landing, so your STOL plane can shut the slots and use the full power of the engine for straight thrust during cruise.

As compressing air tends to heat it, the ducts could possibly double as a de-icing system as well as being a substitute for slats and flaps.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,680
Location
Rochester, NY, USA
I'm imagining the consternation on the ramp as you start up your "ducted thrust/slot/thing" craft, either the OP fantasy plane or Sockmonkey's, after a month parked on the grass, and the hornets start ejecting from the system at just subsonic speed. Angry, tumbling, hornets.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,104
Location
Flint, Mi, USA
I'm imagining the consternation on the ramp as you start up your "ducted thrust/slot/thing" craft, either the OP fantasy plane or Sockmonkey's, after a month parked on the grass, and the hornets start ejecting from the system at just subsonic speed. Angry, tumbling, hornets.
The slots would be closable during level flight so you would also keep them shut when parked.
 
Top