Compressor sound suppression

Abstract

A compressor includes a housing and one or more working elements. A muffler is located downstream of the discharge plenum and a helmholtz resonator is located in the discharge plenum upstream of the muffler.

1 . A compressor comprising: 
 a housing;    a first rotor having a first rotational axis;    a second rotor having a second rotational axis and enmeshed with the first rotor;    a third rotor having a third rotational axis and enmeshed with the first rotor;    an outlet plenum;    a muffler downstream of the outlet plenum;    a centerbody within the outlet plenum and having: 
 an outer surface;  
 at least one internal volume; and  
 at least one port in the outer surface providing communication between the internal volume and an interior of the outlet plenum.  
   
   
   
       2 . The compressor of  claim 1  wherein: 
 the centerbody is coaxial with the first rotor.    
   
   
       3 . The compressor of  claim 1  wherein: 
 the centerbody outer surface is essentially frustoconical.    
   
   
       4 . The compressor of  claim 1  wherein: 
 a downstream portion of the centerbody has a diameter at least 10% greater than an upstream portion of the centerbody.    
   
   
       5 . The compressor of  claim 1  wherein: 
 the centerbody outer surface is essentially divergent in a direction toward the muffler.    
   
   
       6 . The compressor of  claim 1  wherein the centerbody consists essentially of at least one of molded plastic, polymeric foam, and expanded bead material.  
   
   
       7 . The compressor of  claim 1  having: 
 first and second such internal volumes; and    a first such port communicating with the first internal volume and a second such port communicating with the second internal volume.    
   
   
       8 . The compressor of  claim 7  wherein: 
 measured about the first axis, the first port is within 20° of the second axis; and    measured about the first axis, the second port is within 20° of the third axis.    
   
   
       9 . The compressor of  claim 7  wherein: 
 measured about the first axis, the first port is essentially aligned with the second axis; and    measured about the first axis, the second port is essentially aligned with the third axis.    
   
   
       10 . The compressor of  claim 7  wherein: 
 the first and second internal volumes and the first and second ports are effective to provide first and second helmholtz resonators.    
   
   
       11 . A method for engineering the compressor of  claim 1  comprising: 
 measuring sound intensity at a target frequency for pulsation; and    selecting at least one parameter of the at least one internal volume or the at least one port to achieve a desired level of said intensity.    
   
   
       12 . A compressor comprising: 
 a housing;    a one or more working elements;    a discharge plenum;    a muffler downstream of the discharge plenum; and    a helmholtz resonator in the discharge plenum upstream of the muffler.    
   
   
       13 . The compressor of  claim 12  wherein: 
 the helmholtz resonator is in a centerbody, coaxial with the muffler.    
   
   
       14 . A compressor comprising: 
 a housing;    a one or more working elements;    a discharge plenum;    a muffler downstream of the discharge plenum; and    means in the discharge plenum upstream of the muffler for limiting external sound radiated by the housing due to resonating of discharge pulsation from the one or more working elements.    
   
   
       15 . A method for remanufacturing a compressor or reengineering a configuration of the compressor comprising: 
 providing an initial such compressor or configuration having: 
 a housing;  
 a first rotor having a first rotational axis;  
 a second rotor having a second rotational axis and enmeshed with the first rotor;  
 a third rotor having a third rotational axis and enmeshed with the first rotor; and  
 a discharge plenum; and  
   placing a helmholtz resonator in the discharge plenum.    
   
   
       16 . The method of  claim 15  wherein: 
 the placing, locates the helmholtz resonator in a centerbody upstream of a muffler.    
   
   
       17 . The method of  claim 15  wherein: 
 the placing, locates the helmholtz resonator in a centerbody upstream of a muffler and downstream of a bearing case element and coupling the bearing case element to the muffler.    
   
   
       18 . The method of  claim 15  wherein: 
 the placing, locates first and second such helmholtz resonators in a centerbody upstream of a muffler.    
   
   
       19 . The method of  claim 15  wherein: 
 the placing leaves the housing and the first, second, and third rotors essentially unchanged.