You can use Combine to join the blade and the bottom and yes you get a small D-shaped face at the outer edge. (width ~0,01mm). It shows up in Geometry Analysis as a Sliver face. This face can be removed by the Delete Face tool (Delete and Patch).
Maha,.. good to see you're paying attention... (this will be fun to explain)
Anyway, I honestly did not have time to "Combine" before I sent last night and now see what you see...
Ok... this is a great example of "almost perfect"... the curves and surfaces do not resolved exactly.. that is.. line/line or surface/surface,.. or as we expect. (ztg or zero thickness error candidate for sure!)
unfortunately/sadly/ (and other not so nice things to say),.. the cresent edge is the result of how SolidWorks or the Parasolid modeler handles or solves these types of sketches (arc/line versus splines)...that is, "ALMOST"... (0.000000101)
as a fix... you can remove that top surface curve in the "3dsketch - end fan" and add the edge of the cylinder.. it should resolve well,..maybe? that is,..I'm guessing your loft will probably fail (so, you'd need to redo it).. because,.. well.. SW Corp has ALWAYS had problems (it gets confused so how?) with replacing sketches in features... and we have become use to paying for half baked software. (well.. that is the real truth)..
I have found a tutorial. Demonstrator is saying that
I haven't found any good tutorials there......
How to draw a turbo compressor wheel in solidworks - YouTube
Time 00.09-00.20
yeah,.. what he does show is a good way to handle some of this, forcus on the compressor blade shape (very important),.. then merge/cut later. so, cuting back or removing the rounding/surface/edge/split or rounding errors.
And, in general.. the blades placed on hubs would be independent and over extended the hub.. and then merged/cut back to the hub.
btw.. in the next video.. (which I think you followed?)... How to Make an Axial Centrifugal Compressor in SolidWorks |JOKO ENGINEERING| - YouTube
..between times 8:40 and 8:55, he makes a ZTG statement.. interesting.. because I I'm really surprised this loft resolved or did not give him and you more errors?
try cut with surface for solid bodies