Yes, it improves the flow to the propeller and hence, its efficiency. There are different types 'on the market', partly creating the 'pre-swirl' mentioned.

Hello gents.
As long as I know it is a device to improve energy efficiency management.
If I am not mistaken, it is called "pre-swirl"
Rgds¡

Looks like some form of shroud to reduce cavitation. She also appears to be 'ice class' as she has an 'ice knife above the rudder - lets you go astern in ice without icy bits ( technical term) getting jammed between rudder and hull.
Hard to tell but also seems to have a Becker rudder or some such - looks like a 'trim tab' on the trailing edge

What is that arch like structure behind the propeller?