Ducted fans are by nature less efficient than propellers. This is one reason that the next big leap in engine efficiency may come from what are essentially unducted fans.
I thought adding a shroud to propellers increased efficiency? That's why we use turbofan engines instead of turboprops.
One of the latest designs appears to do away with the duct/shroud, for the thrust creation part of the engine. It also hopes to achieve a 20$ decrease int fuel usage.
Doesn't this vary for different cruising speed targets? I thought jets & ducted fans were more efficient above 400 kts or so, while (non ducted) propellers were more efficient below maybe 300 kts. But I'm mostly thinking in terms of turboprop vs. turbofan designs - not 100% sure if it applies the same way for electric types, although I assume it probably would.