Asymmetric compressor air extraction method

Abstract

A method to mistune rotating stall aerodynamics by preventing the formation of coherent unsteady loads. Compressor air is extracted in an asymmetric circumferential pattern. The asymmetric bleed pattern disrupts the rotating stall cell rotational pattern, preventing the formation of a coherent aerodynamic excitation.

1 . A method of controlling air flow in a compressor comprising:
 extracting high pressure air from a vicinity of or downstream of the chosen axial portion through a casing of the compressor, in a circumferentially asymmetric pattern to act against flow disturbances such as rotating stall.   
   
   
       2 . A method as in  claim 1 , wherein said extraction of high pressure air is through a plurality of holes or slots disposed asymmetrically about the circumference of the casing of the compressor. 
   
   
       3 . A method as in  claim 1 , wherein said casing is a split casing, and wherein said extraction of high pressure air is through a plurality of holes or slots disposed in a top casing part of said split casing. 
   
   
       4 . A method as in  claim 1 , comprising extracting high pressure air through a plurality of holes or slots disposed in an arc defined by the required flow volume and nature of the rotating stall formation. 
   
   
       5 . A method as in  claim 4 , wherein said holes or slots are asymmetrically disposed in said arc. 
   
   
       6 . A method as in  claim 1 , wherein said extraction is terminated after a predetermined period. 
   
   
       7 . A method as in  claim 1 , wherein said extraction may be gradually reduced after it is initiated. 
   
   
       8 . A method of controlling air flow in a compressor comprising: actuating extraction of compressor air, asymmetrically about a circumference of said compressor casing to act against a disturbance such as rotating stall. 
   
   
       9 . A method as in  claim 8 , wherein said extraction of high pressure air is through a plurality of holes or slots disposed asymmetrically about the circumference of the casing of the compressor. 
   
   
       10 . A method as in  claim 8 , wherein said casing is a split casing, and wherein said extraction of high pressure air is through a plurality of holes or slots disposed in a top casing part of said split casing. 
   
   
       11 . A method as in  claim 8 , comprising extracting high pressure air through a plurality of holes or slots disposed in an arc defined by the required flow volume and nature of the rotating stall formation. 
   
   
       12 . A method as in  claim 11 , wherein said holes or slots are asymmetrically disposed in said arc. 
   
   
       13 . A method as in  claim 8 , wherein said extraction is terminated after a predetermined period. 
   
   
       14 . A method as in  claim 8 , wherein said extraction may be gradually reduced after it is initiated.