Quote: the fin pitch, stator design and construction can essentially make a smaller diameter converter flash AND become efficient at speeds...
picture a pinwheel behind a fan - one will push the other and it will eventually get close to the same speed.
That is a positive pitch on the fins, the old school way to get stall was to put a negative pitch, and it would work against itself never getting efficient. Not anymore.
I put this together a few years ago - might be worth the read.
