I found it difficult in ANSYS 19.0 to subtract a surface from a solid.  Instead, I used the Thin operation to thicken the surface into a solid. I added a cylinder at the center and united that to the thickened blade. I created a large cylinder of air to enclose all the blades, then I sliced that into 120 degree slices. Finally, I was able to subtract the solid blade from the wedge of air.

Zoom into the hub at the center.  Note that on the cut faces the hub can be seen on both sides, making for a clean mesh on each slice.

If these three slices are united back into a cylinder, that is the rotating mesh domain.  An enclosure can be put outside this cylinder to represent the static domain for the air flowing toward this three blade turbine. ANSYS 19.0 archive attached.