Duct Fan efficiency and safety & (Tilt Rotor Build).
I read over the following Wikipedia page on Duct fans and it seems to me, they would be more efficient on a Multi-rotor copter (MRC) because unlike an fast moving aircraft, the thrust required for MRC is mostly static.
- By reducing propeller blade tip losses, the ducted fan is more efficient in producing thrust than a conventional propeller, especially at low speed and high static thrust level (airships, hovercrafts).
- By sizing the ductwork appropriately, the designer can adjust the air velocity through the fan to allow it to operate more efficiently at higher air speeds than a propeller would.
- For the same static thrust, a ducted fan has a smaller diameter than a free propeller, allowing smaller gear.
- Ducted fans are quieter than propellers: they shield the blade noise, and reduce the tip speed and intensity of the tip vortices both of which contribute to noise production.
- Ducted fans can allow for a limited amount of thrust vectoring, something normal propellers are not well suited for. This allows them to be used instead of tiltrotors in some applications.
- Ducted fans offer enhanced safety on the ground.
I would like to ask your thoughts on this topic. I know the general debate has been, Duct-Fans are less efficient but I think this argument was based upon the EDF with a very small OD. I believe the largest I have seen is a 90mm.