Shrouded Dual-Swept Fan Impeller

Abstract

A fan impeller includes rotating ring attached to the tip of dual-swept fan blades. Besides shrouding the impeller; the blades are dual-swept forward, and sweep increases in magnitude towards the tip. The shrouded dual-swept impeller resides inside classical fan housing. The integrated effects of shrouding the impeller, forward sweep into the direction of incoming flow, and forward sweep into the direction of rotation (circumferential forward sweep) render the fan quiet; the magnitude of noise reduction is between 7 and 12 dB.

1 . A fan comprising an impeller and a motor connected to the impeller to spin the impeller thereby creating an airflow, wherein the impeller comprises:
 a hub;   a plurality of blades attached to and disposed about the hub; and   a tip ring attached to one or more tips of the plurality of blades,   wherein for each blade, respective centers of mass of successive blade sections from the hub toward the tip thereof are (1) located upstream of the airflow along an axial direction with respect to centers of mass of previous blade sections and (2) located forward in the direction of rotation of the impeller with respect to the centers of mass of the previous blade sections.   
   
   
       2 . The fan of  claim 1  wherein the blades are further characterized in having a forward axial sweep. 
   
   
       3 . The fan of  claim 1  wherein the blades are further characterized in having a forward circumferential sweep. 
   
   
       4 . The fan of  claim 1  wherein the blades are further characterized in having both a forward axial sweep and a forward circumferential sweep. 
   
   
       5 . The fan of  claim 4  wherein the forward axial sweep occurs along substantially the full length of each blade, where the forward circumferential sweep occurs along substantially the full length of each blade. 
   
   
       6 . The fan of  claim 1  wherein the distribution of the centers of mass of the blade sections define a straight line in a plane containing the axis of rotation of the impeller. 
   
   
       7 . A method of operating a fan comprising:
 providing a plurality of dual-swept fan blades disposed about a hub;   attaching a tip ring at tips of the dual-swept fan blades;   providing a motor having a rotor connected to the hub; and   providing a base to which the motor can be anchored,   wherein at least some of the dual-swept fan blade each is characterized in having a first sweep in an upstream direction along an axis of rotation,   wherein said at least some of the dual-swept fan blade each is further characterized in having a second sweep in a direction of rotation of the hub.   
   
   
       8 . The method of  claim 7  wherein the first sweep occurs along the length of the fan blade. 
   
   
       9 . The method of  claim 7  wherein the second sweep occurs along the length of the fan blade. 
   
   
       10 . A fan comprising:
 a hub; and   a plurality of fan blades attached to the hub at respective roots thereof, the fan blades creating an incoming flow of air when the fan blades are rotated,   each of the fan blades having a first sweep in the direction of rotation of the fan blades,   each of the fan blades further having a second sweep along an axis of rotation in a direction opposite the direction of the incoming flow of air.   
   
   
       11 . The fan of  claim 10  further comprising a tip ring disposed about an outer circumference circling the fan blades. 
   
   
       12 . The fan of  claim 10  wherein the locus of centers of mass of representative airfoils of each fan blade defines a first line projected onto a first plane and a second line projected onto a second plane, wherein the first line and the second line each is either a substantially straight line or an arcuate line. 
   
   
       13 . The fan of  claim 10  wherein the first sweep and the second sweep each occurs along the length of at least one of the fan blades. 
   
   
       14 . The fan of  claim 10  wherein for each of the fan blades, its axial blade length increases in the direction from the blade root to the blade tip. 
   
   
       15 . A fan comprising:
 a hub; and   a plurality of fan blades attached to and disposed about the hub,   for at least some of the fan blades, centers of mass of successive blade sections between the blade root and the blade tip thereof being displaced forward of the center of mass of a previous blade section in the upstream direction,   wherein the centers of mass are further displaced in the direction of rotation relative to the center of mass of a previous blade section.   
   
   
       16 . The fan of  claim 15  further comprising a tip ring disposed about an outer circumference circling the fan blades. 
   
   
       17 . The fan of  claim 15  wherein the center of mass of successive blade sections are displaced forward of the center of mass of a previous blade section in the upstream direction and along the length of said at least some of the fan blades. 
   
   
       18 . The fan of  claim 15  wherein the center of mass of the successive blade sections are displaced in the direction of rotation relative to the center of mass of a previous blade section and along the length of said at least some of the fan blades. 
   
   
       19 . An impeller for a fan comprising:
 a hub; and   a plurality of blades disposed about the hub,   wherein at least some of the blades each has a center of mass position that advances in the direction of rotation of the blades and in the upstream direction with successive airfoil sections between a root of said each blade to a tip of said each blade.   
   
   
       20 . The impeller of  claim 19  further comprising a tip ring disposed about an outer circumference of the impeller. 
   
   
       21 . The impeller of  claim 19  wherein the blades have a axial sweep in the upstream direction and a circumferential sweep in the direction of rotation of the blades. 
   
   
       22 . The impeller of  claim 19  wherein the center of mass position advances in the direction of rotation along either a substantially straight line or along an arcuate line as projected on a radial plane. 
   
   
       23 . The impeller of  claim 19  wherein the center of mass position advances in the upstream direction along either a substantially straight line or along an arcuate line as projected on an axial plane.