Can axial flow fan manufacturers eliminate the gap between impeller and casing?
This gap caused pressure leakage and thus creates a drag on the fan's performance.
Why not adopt the same procedure as air turbine engine manufacturers? Why not make the impeller's outer diameter slightly larger than the casing's inner diameter. The impeller would then grind its own groove into the casing.
Another option would be to mount some kind of brushes or flexible material on the impeller's tips so as to seal the gap between it and the casing.
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