Milo,
I believe that metal blade thing under the roasting chamber on the sono would be called a rotor-stator blade. They are used in the aeronautical engineering of planes as well as the mechanical engineering of turbo chargers. Their function is to intensify airflow, it creates a pull on upstream air, and it also makes the downstream air movement more erratic so it does not blow in a straight stream.
It is funny you mentioned that, because I was talking to a buddy, who is an aeronautical engineer, earlier today about ways to intensify airflow and make a vortex. . . . his short answer was a strator blade.
Cheers,
Mike