Ducted fan UAVs maintain a higher payload to stored volume ratio. The vehicle can carry 4x the payload of a similar footprint fixed- or open-rotor UAV.
I have heard different things online about ducted fans vs open wing proppellers. Some say they are less efficient some say they are much more efficient!?
Ive heard of some people saying they are twice or even 4x more efficient. I'm thinking of designing a heavy lift drone and wondering if I shouls go with ducted fans..
Any input appreciated thanks!
Ducted fans are less efficient, because a smaller mass of air is used for propulsion and additional friction drag and added weight from the shroud and support structure.
The highest propulsion efficiency is a large, slow-spinning prop, not a small high revving fan.
However, large ducted propellers could overcome the disadvantages. They are very seldom used though, even with the high budgets of some major companies.
But there are so many online sources saying that its efficient.. I actually dont care about drag or wind resistance. Just lift. And payload compacity..
If these articles are accurate I can achieve the same amount of thrust/lift with motors that are half the size? Am i wrong??
First and second article are really convincing
Rafi, I'm not sure about the 2x or 4x efficiency claims, but you could expect a 30% or 40% increase in static thrust for a well designed ducted fan compared to an open propellor of an equivalent diameter.
I'll keep meaning to work through the calculations again to compare the two, but never quite find the time.
I suspect part of the difficulty with a ducted fan quad, is that the airflow gets complex as it moves from hover into forward flight. I don't think there is a lot of thought put into the aerodynamic design of a lot of quads and shrouding the rotors with the aim of increasing efficiency would require that extra effort.
Have a look at the following two papers for some fact-based discussion: