Fan Stall Inhibitor

Abstract

An impeller blade hub profile which inhibits stall is described. In an embodiment, the hub profile includes a frontal rising contour followed by a rear constant contour. In another embodiment, the hub profile includes a frontal rapidly rising contour followed by a substantially rear constant contour. It was discovered that this combination is much more effective than conventionally known profiles. Also, the present invention provides a unique way of turning the flow within the passages of the rotating impeller blades. In an embodiment, the blade does not turn much over either the front portion of the hub or the rear portion of the hub, but instead turns near the boundary between the front portion and the rear portion.

1 . An impeller comprising:
 a hub;   a plurality of fan blades connected to the hub;   a first part of the hub having a rising hub contour along an axial length thereof; and   a second part of the hub having a substantially constant hub contour along an axial length thereof,   wherein one or more of the fan blades, each, is connected to both the first part of the hub and to the second part of the hub.   
     
     
         2 . The impeller of  claim 1  wherein a length of the first part of the hub is at least one-quarter of a total length of the hub. 
     
     
         3 . The impeller of  claim 1  wherein a length of the first part of the hub is about 30% to 60% of a total length of the hub. 
     
     
         4 . The impeller of  claim 1  wherein a leading edge portion of each of said one or more of the fan blades is connected to the first part of the hub and a trailing edge portion of said each of said one or more of the fan blades is connected to the second part of the hub. 
     
     
         5 . The impeller of  claim 1  wherein for each fan blade, a first portion of said each fan blade is attached to the first part of the hub and a second portion of said each fan blade is attached to the second part of the hub, wherein about 10% of a length of said each fan blade measured from a leading edge thereof has a first blade angle, wherein about 10% of a length of said each fan blade measured from a trailing edge thereof has a second blade angle. 
     
     
         6 . An impeller comprising a hub and a plurality of fan blades attached to the hub, wherein a radius of the hub increases in the axial direction from a first location on the hub proximate a hub leading edge to a second location on the hub that is distal a hub trailing edge, wherein the radius does not substantially vary in the axial direction from the second location on the hub to a third location on the hub proximate the hub trailing edge. 
     
     
         7 . The impeller of  claim 6  wherein a distance between the first location and the second location is about 30% to 60% of a distance between the first location and the third location. 
     
     
         8 . The impeller of  claim 6  wherein each fan blade is attached to the hub between the first location and the third location. 
     
     
         9 . The impeller of  claim 6  wherein a leading edge portion of each fan blade is attached between the first location and the second location and has a first blade angle, wherein a trailing edge portion of each fan blade is attached between the second location and the third location and has a second blade angle different from the first blade angle. 
     
     
         10 . The impeller of  claim 9  wherein blade turning in said each fan blade occurs proximate the second location on the hub. 
     
     
         11 . The impeller of  claim 6  wherein the radius of the hub increases between the first location and the second location in linear fashion. 
     
     
         12 . An impeller comprising a hub having a first segment and a second segment, the impeller further comprising a plurality of fan blades attached symmetrically about the hub, each fan blade being attached to a part of the first segment of the hub and a part of the second segment of the hub, the first segment of the hub having a rising hub profile, the second segment of the hub having a substantially constant hub profile. 
     
     
         13 . The impeller of  claim 12  wherein a radius of the first segment of the hub varies along the axial direction thereof, wherein a radius of the second segment of the hub remains substantially the same along the axial direction thereof. 
     
     
         14 . The impeller of  claim 13  wherein the radius of the first segment of the hub varies in linear fashion. 
     
     
         15 . The impeller of  claim 12  wherein a length of the first segment is about 30% to 60% of the sum of the length of the first segment and a length of the second segment. 
     
     
         16 . The impeller of  claim 12  wherein for each fan blade, a blade inlet angle is β 1  for a portion of said each fan blade equal in length to about 10% of a length of said each blade measured from its leading edge, and a blade exit angle is β 2  for a portion of said each fan blade equal in length to about 10% of the length of said each blade measured from its trailing edge. 
     
     
         17 . The impeller of  claim 16  wherein a length of a camber line of said each blade constitutes the length of said each blade. 
     
     
         18 . The impeller of  claim 16  wherein for said each fan blade, blade turning occurs in a middle portion of said hub between a first portion of said hub and a second portion of said hub. 
     
     
         19 . A fan comprising an impeller of  claim 12  disposed in a fan housing and connected to a fan motor.