Annular-ducted lift fan aircraft more efficient than helicopters

[Flyingeagle]

Study show an annular-ducted lift fan aircraft can have higher hover efficiency and fly faster than helicopters and tiltrotors:

http://www.mdpi.com/2226-4310/2/4/555

 

[Flyingeagle]

Is this a possible future VTOL aircraft?

 

[hesham]

Hi Flyinggeagle,

maybe that's a future,but hard to expect how it will be.

 

[shedofdread]

In the real world, these advantages aren't quite so easy to realise.... I've seen work done in this area and and if you need more lifting efficiency, it's much easier to make the rotors a 'smidge' bigger.

 

[Flyingeagle]

But bigger rotor causes other problems, such as more dangerous, fly slower.

 

[shedofdread]

The danger of rotors is all too real (Schiebel CamCopter ) but as for the speed thing, the story becomes a little less simple. Factors such as duct drag, gust response etc etc. Not saying it can't be done but it certainly is FAR from easy....

 

[AeroFranz]

Ducted rotors have been around for almost a century. The physics behind them are well known. The fact they find niche applications says plenty about their advantages over open rotors.

 

[Flyingeagle]

Boeing's Phantom Swift X-plane uses two internal ducted fans and two wingtip ducted fans. It's expected to fly faster than the V-22 tiltrotor.

 

[sublight_]

Study show an annular-ducted lift fan aircraft can have higher hover efficiency and fly faster than helicopters and tiltrotors:

Which is completely meaningless when your "hover saucer" weighs five times as much as a Bell jet ranger.

 

[AeroFranz]

Boeing's Phantom Swift X-plane uses two internal ducted fans and two wingtip ducted fans. It's expected to fly faster than the V-22 tiltrotor.

If you take some time to dig into ducted fans design, you will find that their claimed superiority for static thrust requires a flared inlet lip that creates a lot of drag at high speeds. Conversely, if you design for high speed, you get poor static thrust. If it was so clear cut, it would have been done fourty fifty yearss ago in the golden age of VTOL.

 

[Flyingeagle]

If you take some time to dig into ducted fans design, you will find that their claimed superiority for static thrust requires a flared inlet lip that creates a lot of drag at high speeds. Conversely, if you design for high speed, you get poor static thrust. If it was so clear cut, it would have been done fourty fifty yearss ago in the golden age of VTOL.

Yes, it's true for the wingtip ducted fans. For the internal ducted fans, they will be shut during forward flight, so they can be made efficient for static thrust. The only problem is they take so much space of the fuselage.

 

[ynm]

IMO for extreme large duct fan then the structure weight may out weight efficiency. If someone can find the right balance between the fan size and the overall weight, then may be