Axial-flow pump

Abstract

An axial-flow pump employs an increased boss ratio Dh/Dt, wherein Dh is the hub diameter of a rotary shaft of a rotor, and Dt is the tip diameter of impeller vanes of the rotor. Specifically, the boss ratio is 0.65 to 0.85, preferably 0.7 to 0.8.

1 . An axial-flow pump for propelling fluid under pressure by means of impeller vanes, the axial-flow pump having such a boss ratio as to suppress biased flow of the fluid caused by reverse flows arising in an outer circumferential portion of an inlet region of the impeller vanes and reverse flows arising in an inner circumferential portion of an outlet region of the impeller vanes.  
   
   
       2 . An axial-flow pump according to  claim 1 , wherein the boss ratio is 0.65 to 0.85.  
   
   
       3 . An axial-flow pump comprising a housing, an impeller provided rotatably in the housing, and a drive mechanism for rotating the impeller, and adapted to axially propel fluid under pressure by means of the drive mechanism rotating the impeller, 
 wherein the drive mechanism is fixedly attached to a downstream stationary member which, in turn, is fixedly attached to a diffuser located downstream of the impeller and projecting from an inner wall surface of the housing;    the impeller comprises a rotary shaft coupled with the drive mechanism and impeller blades projecting from an outer circumferential surface of the rotary shaft; and    a boss ratio, which is the ratio between an outside diameter of the rotary shaft and an outside diameter of the impeller vanes, is 0.65 to 0.85.