ultra-high specific speed impellers

[HomeMadeSin]

Has anyone used or designed impellers above the classic limit of 18,000 ns? We've got an application that would require well above this limit (if at b.e.p. and 2 pumps). I realize I could fall into the norm and stick to the books, but I can't help wondering, what's a 40k impeller/propeller look like? Or is there a limit to ns?

 

[d23]

HomeMadeSin:

I assume that you require a very high Q at a comparatively low head. In most cases I believe that at a Ns that high your efficiency will tend to fall off enough that even three or four pumps in parallel would be deemed "economically practical" compared to your propeller.

This is just my personal guess, but I think that power savings will prevent you from making the high Ns pump.

Good Luck!!!

 

[PVRV]

I would think that nss limitation is to ensure mechanical stability of the rotor. Which is not a problem with roller bearings but with hydrodynamic bearing I believe the protective film starts cracking.