Inlet Plenum with Shock Wave Suppression

Abstract

An inlet plenum for a compressor that suppresses acoustic shock waves generated by the compressor, which inlet plenum has an inlet duct with a wall that surrounds an air flow path between a mouth of the inlet plenum and the compressor, comprises: at least one cavity that penetrates an inner surface of the wall, circumscribes the inner surface generally transversely to the air flow path and has a position along the air flow path that is generally coincident with at least one constructive interference peak of the acoustic shock waves along the inner surface; a width of the cavity along the direction of the air flow that is less than or equal to the wavelength of at least one of the acoustic shock waves; and a depth of the cavity generally perpendicular to the direction of the air flow that approximates a multiple of a quarter wavelength of at least one of the acoustic shock waves.

1 . An inlet plenum for a compressor that suppresses acoustic shock waves generated by the compressor, which inlet plenum has an inlet duct with a wall that surrounds an air flow path between a mouth of the inlet plenum and the compressor, comprising:
 at least one cavity that penetrates an inner surface of the wall, circumscribes the inner surface generally transversely to the air flow path and has a position along the air flow path that is generally coincident with at least one constructive interference peak of the acoustic shock waves along the inner surface;   a width of the cavity along the direction of the air flow path that is less than or equal to the wavelength of at least one of the acoustic shock waves; and   a depth of the cavity generally perpendicular to the direction of the air flow path that approximates a multiple of a quarter wavelength of at least one of the acoustic shock waves.   
     
     
         2 . The inlet plenum of  claim 1 , wherein corrugation of the wall forms the cavity. 
     
     
         3 . The inlet plenum of  claim 1 , wherein indentation of the inner surface forms the cavity. 
     
     
         4 . The inlet plenum of  claim 1 , wherein multiple cavities along the inner surface have positions generally coincident with respective multiple constructive interference peaks of the acoustic shock waves along the inner surface. 
     
     
         5 . The inlet plenum of  claim 4 , wherein some of the multiple constructive interference peaks correspond to acoustic shock waves of different wavelengths and each one of the multiple cavities has its depth corresponding to a multiple of a quarter of the wavelength of its corresponding constructive interference peak. 
     
     
         6 . The inlet plenum of  claim 1 , further comprising acoustic damping material that at least partially fills the cavity. 
     
     
         7 . The inlet plenum of  claim 1 , wherein the width of the cavity is equal to one wavelength of at least one of the acoustic shock waves. 
     
     
         8 . The inlet plenum of  claim 1 , wherein side surfaces of the cavity are generally parallel to each other. 
     
     
         9 . The inlet plenum of  claim 1 , wherein side surfaces of the cavity are generally non-parallel to each other. 
     
     
         10 . The inlet plenum of  claim 1 , wherein the depth of the cavity is equal to one quarter wavelength of at least one of the acoustic shock waves. 
     
     
         11 . The inlet plenum of  claim 10 , wherein an acoustic dampening material fills the cavity. 
     
     
         12 . The inlet plenum of  claim 1 , further comprising an air flow deflector that extends along a portion of the width of the cavity from an upstream side of the cavity along the inner surface of the wall. 
     
     
         13 . An inlet plenum for a compressor that suppresses acoustic shock waves generated by the compressor, which inlet plenum has an inlet duct with a wall that surrounds an air flow path between a mouth of the inlet plenum and the compressor, comprising:
 multiple cavities that penetrate an inner surface of the wall, circumscribe the inner surface generally transversely to the air flow path and each have a position along the air flow path that is generally coincident with a corresponding constructive interference peak of the acoustic shock waves along the inner surface;   a width of each cavity along the direction of the air flow that is less than or equal to the wavelength of at least one of the acoustic shock waves at its corresponding constructive interference peak; and   a depth of each cavity generally perpendicular to the direction of the air flow that approximates a multiple of a quarter wavelength of at least one of the acoustic shock waves at its corresponding constructive interference peak.   
     
     
         14 . The inlet plenum of  claim 13 , wherein corrugation of the wall forms each cavity. 
     
     
         15 . The inlet plenum of  claim 13 , wherein indentation of the inner surface forms each cavity. 
     
     
         16 . The inlet plenum of  claim 13 , further comprising acoustic damping material that at least partially fills the cavity. 
     
     
         17 . The inlet plenum of  claim 13 , wherein the width of the cavity is equal to one wavelength of at least one of the acoustic shock waves. 
     
     
         18 . The inlet plenum of  claim 13 , wherein the depth of the cavity is equal to one quarter wavelength of at least one of the acoustic shock waves. 
     
     
         19 . The inlet plenum of  claim 13 , further comprising an air flow deflector that extends along a portion of the width of each cavity from an upstream side of the cavity along the inner surface of the wall. 
     
     
         20 . An inlet plenum for a compressor that suppresses acoustic shock waves generated by the compressor, which inlet plenum has an inlet duct with a wall that surrounds an air flow path between a mouth of the inlet plenum and the compressor, comprising:
 multiple cavities that penetrate an inner surface of the wall, circumscribe the inner surface generally transversely to the air flow path and each have a position along the air flow path that is generally coincident with a corresponding constructive interference peak of the acoustic shock waves along the inner surface;   a width of each cavity along the direction of the air flow path that is less than or equal to the wavelength of at least one of the acoustic shock waves at its corresponding constructive interference peak; and   a depth of each cavity generally perpendicular to the direction of the air flow path that approximates a quarter wavelength of at least one of the acoustic shock waves at its corresponding constructive interference peak.   
     
     
         21 . The inlet plenum of  claim 20 , further comprising an air flow deflector that extends along a portion of the width of each cavity from an upstream side of the cavity along the inner surface of the wall.