That look very much like a rotor from Woelfe Engineering's Aixro rotary kart engine.
http://www.woelfle-engineering.com/
It's a 294cc single rotor engine that gets about 40hp. The housing is water cooled and the rotor and bearing are cooled by the air/fuel/oil mixture, like NoDOHC said.
Here's an illustration from K. Yamamoto's Rotary Engine book:
