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Overall view of the fuel impeller.

The fuel turbopump's design makes it seem to be mounted upside-down, with the inducer at the bottom and the impeller mounted above it.

I believe the scallops on the left edge are where material was removed from the impeller to balance it.

The fuel impeller is a shrouded impeller (the vanes of the impeller are covered, rather than being open). The fuel enters via the inlet at the top of the impeller and is accelerated to a high speed via the impeller's slinger vanes.

It seems counter-intuitive to me (I'm not really a rocket scientist; I just play one on TV): The fluid is not "cupped" by the concave side of the vanes, but rather "flung off" the convex side of the vanes.