File constant/polyMesh/boundary must be edited. First remove empty patches (w1, w2, w4-w6), rename non-empty patches and edit their properties^13.5:

3
(
    outlet
    {
        type            patch;
        nFaces          241;
        startFace       1113896;
    }
    outlet_wall
    {
        type            mappedWall;
        sampleMode      nearestPatchFace;
        sampleRegion    solid;
        samplePatch     stator_inner_wall;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          85370;
        startFace       1114137;
    }
    interface
    {
        type            mappedPatch;
        sampleMode      nearestPatchFace;
        sampleRegion    rotor;
        samplePatch     ring_0;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          23566;
        startFace       1199507;
    }
)

Patch outlet is a standard type patch, fluid can flow through. Patch outlet_wall is a wall of type mappedWall because heat transfer from fluid to solid is assumed. Patch interface is a mappedPatch to be connected to the rotor region of the model.