Houseless fan with rotating tip ring as silencer

Abstract

The stationary housing of a conventional fan assembly is replaced with a rotating tip ring. The rotating tip ring has a shaped cross-sectional profile to enhance performance and eliminate tonal noise associated with the fundamental (or blade passing) frequency and its harmonics.

1 . A fan impeller for an axial fan comprising:
 a hub;   a plurality of fan blades disposed about the hub; and   a band disposed circumferentially about the fan blades and attached to the fan blades at respective tips of the fan blades, the ring having a thickness dimension measured between an inlet side of the ring and an outlet side of the ring, the thickness dimension exceeding the axial chord dimension of the fan blades,   the inside diameter of the ring varying from the inlet side thereof to the outlet side thereof and having a minimum inside diameter measurement at a location downstream of the inlet side of thereof and upstream of the outlet side thereof,   wherein the inside diameter measurement of the ring at the inlet side thereof exceeds the minimum inside diameter measurement,   wherein the inside diameter measurement of the ring at the outlet side thereof exceeds the minimum inside diameter measurement.   
   
   
       2 . The impeller of  claim 1  wherein the inside diameter measurement of the ring at the inlet side thereof is substantially equal to the inside diameter measurement of the ring at the outlet side thereof. 
   
   
       3 . The impeller of  claim 1  wherein the inlet side of the ring extends beyond leading edges of the fan blades in the upstream direction and the outlet side of the ring extends beyond trailing edges of the fan blades in the downstream direction. 
   
   
       4 . The impeller of  claim 1  wherein air enters the inlet side of the ring and the air exits the outlet side of the ring when the impeller is made to spin. 
   
   
       5 . A fan impeller for an axial fan comprising:
 a hub;   a plurality of fan blades radially disposed about the hub and connected to the hub; and   an annulus attached to tips of the fan blades, wherein an inside diameter of the annulus from a location between an inlet face of the annulus and an outlet face of the annulus increases in the direction toward the inlet face and also increases in the direction toward the outlet face.   
   
   
       6 . The impeller of  claim 5  wherein the inside diameter of the annulus at the inlet face is substantially equal to the inside diameter of the annulus at the outlet face. 
   
   
       7 . The impeller of  claim 5  wherein the measurement between the outlet face and the inlet face exceeds the axial chord dimension of the fan blades. 
   
   
       8 . The impeller of  claim 5  wherein the inlet face of the annulus extends beyond leading edges of the fan blades in the upstream direction and the outlet face of the annulus extends beyond trailing edges of the fan blades in the downstream direction. 
   
   
       9 . An axial fan comprising an impeller, the impeller comprising a plurality of blades disposed about a hub and an impeller ring attached at tips of the blades, the impeller ring having a compression zone at the inlet side thereof wherein a flow of air entering the inlet side is subject to compression, the impeller ring having an expansion zone at the outlet side thereof wherein the flow of air exiting the outlet side expands. 
   
   
       10 . The fan of  claim 9  wherein the impeller ring has a thickness measurement that exceeds the axial chord measurement of the blades. 
   
   
       11 . The fan of  claim 9  wherein the impeller ring has a minimum inside diameter at a location downstream of leading edges of the blades and upstream of trailing edges of the blades. 
   
   
       12 . The fan of  claim 9  wherein an inlet face of the impeller ring extends beyond leading edges of the blades, wherein an outlet face of the impeller ring extends beyond trailing edges of the blades. 
   
   
       13 . The fan of  claim 9  wherein the inner surface of the impeller ring has an arcuate profile. 
   
   
       14 . An axial fan comprising a hub and a plurality of fan blades disposed about the hub, the impeller further comprising a tip ring encircling the fan blades and attached to respective tips of the fan blades, the tip ring having an inlet zone on an inlet side thereof and an outlet zone on an outlet side thereof, wherein air that enters the inlet zone when the impeller is made to spin is subject to compression, wherein air that exits the outlet zone when the impeller is made to spin expands. 
   
   
       15 . The fan of  claim 14  wherein the tip ring has a thickness measurement that exceeds the axial chord measurement of the fan blades. 
   
   
       16 . The fan of  claim 14  wherein the fan ring has a minimum inside diameter at a location downstream of leading edges of the fan blades and upstream of trailing edges of the blades. 
   
   
       17 . The fan of  claim 14  wherein an inlet face of the tip ring extends beyond leading edges of the fan blades, wherein an outlet face of the tip ring extends beyond trailing edges of the fan blades. 
   
   
       18 . The fan of  claim 14  wherein the inner surface of the tip ring has an arcuate profile, or an angulated profile, or a segmented profile. 
   
   
       19 . A method for a fan comprising:
 rotating an impeller of the fan;   during rotation of the impeller, confining an incoming flow of air to within a region about equal to a diameter of the impeller;   further during rotation of the impeller, compressing the incoming flow of air in an inlet region of the impeller; and   further during rotation of the impeller, expanding an outflow of air at an outlet region of the impeller.   
   
   
       20 . The method of  claim 19  wherein the step of confining includes providing a ring about tips of blades of the impeller. 
   
   
       21 . The method of  claim 20  wherein the ring has a minimum inside diameter at an inner distance between an inlet face of the ring and an outlet face of the ring. 
   
   
       22 . The method of  claim 20  wherein an inlet face of the ring extends beyond leading edges of the blades, wherein an outlet face of the ring extends beyond trailing edges of the blades.