Centrifugal Fluid Pump

Abstract

A centrifugal fluid pump has an impeller having a hub with vanes that may be airfoil shaped and may be twisted along their lengths. A shroud having an inlet is connected to the vanes to define with the impeller flow chambers between the vanes, at least a portion of each flow chamber having a substantially constant flow area to increase pump efficiency. An entrance feature may also be provided to improve entrance flow into the impeller, further enhancing pump efficiency.

1 . A centrifugal fluid pump comprising:
 an impeller having a hub with airfoil shaped vanes; and   a shroud having an inlet; wherein the shroud is connected to the vanes such that the impeller, shroud, and vanes cooperate to define flow chambers between the vanes, at least a portion of each flow chamber having a substantially constant flow area.   
     
     
         2 . The centrifugal fluid pump of  claim 1 , wherein each vane is twisted lengthwise. 
     
     
         3 . The centrifugal fluid pump of  claim 1 , wherein each vane has a tip surface at which the vane is connected to the shroud; and wherein each vane decreases in thickness from the hub to the tip surface. 
     
     
         4 . The centrifugal pump of  claim 1 , wherein the vanes are configured such that each flow chamber is bounded by facing sides of adjacent vanes, one of the facing sides being shorter than the other of the facing sides and defining the length of the portion of the flow chamber of constant flow area, so that fluid is expelled past the shorter side by the longer side after flowing through the portion of the flow chamber of constant flow area. 
     
     
         5 . The centrifugal fluid pump of  claim 1 , further comprising:
 an entrance feature extending away from the shroud at the inlet and configured to provide generally laminar flow into the chambers.   
     
     
         6 . The centrifugal fluid pump of  claim 5 , wherein the entrance feature includes a cylindrical extension extending from the shroud and a conical extension extending from the shroud within the cylindrical extension. 
     
     
         7 . The centrifugal fluid pump of  claim 1 , wherein the shroud has an inner surface tapering toward the impeller from the inlet in a radially outward direction. 
     
     
         8 . A centrifugal fluid pump comprising:
 an impeller having a hub configured to be rotatably driven about an axis;   a shroud defining an inlet aligned with the axis and sloping radially outward toward the hub;   wherein the impeller has vanes extending axially from the hub toward the shroud and curving radially outward along the hub from the axial inlet; wherein the hub, the shroud and the vanes define flow chambers between adjacent vanes;   wherein each of the vanes is airfoil shaped, gradually decreasing in thickness from the hub to a tip surface adjacent the shroud and from an inner end at the axial inlet to an outer end; wherein adjacent ones of the vanes are nearer one another at the inner ends than at the outer ends; and wherein surfaces of the shroud, the hub, and the vanes hub defining the flow chambers are configured to maintain a substantially constant flow area in at least a portion of the flow chambers.   
     
     
         9 . The centrifugal fluid pump of  claim 8 , wherein each of the vanes is twisted along its length. 
     
     
         10 . The centrifugal fluid pump of  claim 8 , further comprising:
 an entrance feature at the axial inlet configured to direct flow into the flow chambers.   
     
     
         11 . The centrifugal fluid pump of  claim 10 , wherein the entrance feature is a cylindrical extension connected coaxially with the shroud. 
     
     
         12 . The centrifugal fluid pump of  claim 10 , wherein the entrance feature is a generally conical extension mounted to the hub and extending coaxially through the axial inlet. 
     
     
         13 . The centrifugal fluid pump of  claim 8 , wherein the hub and vanes are a unitary, injection molded component; and wherein the shroud is ultrasonically friction-welded to the unitary hub and vanes. 
     
     
         14 . A centrifugal fluid pump comprising:
 an impeller having a hub with vanes twisted along their lengths;   a shroud connected to the vanes and tapering outward toward the hub from an inlet; wherein the hub, vanes and shroud define flow chambers each having a portion with a substantially constant cross-sectional flow area.   
     
     
         15 . The centrifugal fluid pump of  claim 14 , wherein each vane tapers from the hub to a tip, and tapers from an inner end to an outer end. 
     
     
         16 . The centrifugal fluid pump of  claim 14 , further comprising:
 an entrance feature extending away from the shroud at the inlet and configured to provide generally laminar flow into the chambers through the inlet.   
     
     
         17 . The centrifugal fluid pump of  claim 16 , wherein the entrance feature includes a cylindrical extension extending from the shroud and a conical extension extending from the shroud within the cylindrical extension.