Centrifugal fan with resonant silencer

Abstract

A centrifugal fan with a resonant silencer has a centrifugal impeller and an outer housing. The outer housing has an inlet, an outlet and a resonant silencer. An inlet is positioned along an axial direction of the centrifugal impeller. An outlet is positioned along a radial direction of the centrifugal impeller. The resonant silencer, extended from a cut-off, can reduce noise caused by a vortex. The resonant silencer can be I- or L-shaped. The cut-off can be covered by a net filter, which isolates the resonant silencer from the flow motivated by the centrifugal impeller.

1 . A centrifugal fan with a noise reduction functionality, said centrifugal fan comprising: 
 a centrifugal impeller; and    an outer housing, said centrifugal impeller being housed inside said outer housing, said outer housing comprising:    an inlet, positioned along an axial direction of said centrifugal impeller;    an outlet, positioned along a radial direction of said centrifugal impeller; and    a resonant silencer, extending for a predetermined distance from a cut-off of said outer housing, wherein said predetermined distance is proportional to a wavelength of a blade passing frequency of said centrifugal impeller.    
   
   
       2 . The centrifugal fan of  claim 1 , wherein said predetermined distance is one-fourth the wavelength of said blade passing frequency of said centrifugal impeller.  
   
   
       3 . The centrifugal fan of  claim 1 , wherein said resonant silencer is made of an elastic material.  
   
   
       4 . The centrifugal fan of  claim 1 , wherein said resonant silencer is made of a plastic tube.  
   
   
       5 . The centrifugal fan of  claim 1 , wherein said resonant silencer is made of an I-shaped structure.  
   
   
       6 . The centrifugal fan of  claim 1 , wherein said resonant silencer is made of an L-shaped structure.  
   
   
       7 . The centrifugal fan of  claim 1 , further comprising a spiral-shaped flow channel between said centrifugal impeller and said outer housing.  
   
   
       8 . The centrifugal fan of  claim 1 , wherein said cut-off is covered by a net filter.  
   
   
       9 . The centrifugal fan of  claim 1 , wherein said blade passing frequency is proportional to a product of a number of blades and a blade rotation rate.  
   
   
       10 . A centrifugal fan with a noise reduction functionality, said centrifugal fan comprising: 
 a centrifugal impeller; and    an outer housing, said centrifugal impeller being housed inside said outer housing, said outer housing comprising:    an inlet, positioned along an axial direction of said centrifugal impeller;    an outlet, positioned along a radial direction of said centrifugal impeller;    a cut-off, positioned near said an outlet; and    a resonant silencer, extending from said cut-off around said outer housing, said resonant silencer having a resonant frequency, wherein said cut-off is covered by a net filter.    
   
   
       11 . The centrifugal fan of  claim 10  further comprising a spiral-shaped flow channel between said centrifugal impeller and said outer housing.  
   
   
       12 . The centrifugal fan of  claim 10 , wherein said resonant silencer is made of a plastic tube.  
   
   
       13 . The centrifugal fan of  claim 10 , wherein said resonant silencer is made of an I-shaped structure.  
   
   
       14 . The centrifugal fan of  claim 10 , wherein said resonant silencer is made of an L-shaped structure.  
   
   
       15 . The centrifugal fan of  claim 10 , wherein said resonant frequency and a performance of said resonant silencer vary as a function of said resonant silencer volume, via hole cross sectional area of said net filter, and via hole number of said net filter and a thickness of said net filter.  
   
   
       16 . A centrifugal fan with a noise reduction functionality, said centrifugal fan comprising: 
 a centrifugal impeller; and    an outer housing, said centrifugal impeller being housed inside said outer housing, wherein said outer housing includes a resonant silencer, extending for a predetermined distance from a cut-off of said outer housing, said resonant silencer having a resonant frequency for reducing noise.    
   
   
       17 . The centrifugal fan of  claim 16 , wherein said predetermined distance is proportional to a wavelength of a blade passing frequency of said centrifugal impeller.  
   
   
       18 . The centrifugal fan of  claim 16 , wherein said resonant silencer is made of an I-shaped structure.  
   
   
       19 . The centrifugal fan of  claim 16 , wherein said resonant silencer is made of an L-shaped structure.  
   
   
       20 . The centrifugal fan of  claim 16 , wherein said cut-off is covered by a net filter.