Diffuser for centrifugal compressor and method of producing the same

Abstract

At least the throat of the suction surface of a conventionally-used diffuser blade having a two-dimensional shape is cut into a concave shape with a ball end mill. In the throat, the nearer to the bottom of the concave shape, the higher the gas pressure becomes, and therefore the gas flows from the concave bottom toward the hub end and the shroud end thereby to reduce the thickness of the boundary layer formed on the hub end and the shroud end.

1 . A diffuser for a centrifugal compressor comprising a diffuser blade including a suction surface which is concave toward a pressure surface in a cross section, perpendicular to the flow direction.  
   
   
       2 . A diffuser for a centrifugal compressor comprising a diffuser blade including a concave suction surface which defines an acute angle, in a cross section perpendicular to the flow direction, in relation to at least one of a shroud surface and a hub surface.  
   
   
       3 . A diffuser for a centrifugal compressor comprising a diffuser blade including a suction surface which is concave toward a pressure surface in a cross section, perpendicular to the flow direction at least in a throat portion or a portion upstream thereof.  
   
   
       4 . A diffuser for a centrifugal compressor comprising a concave suction surface which defines an acute angle, in a cross section perpendicular to the flow direction at least in a throat portion or a portion upstream thereof, in relation to at least one of a shroud surface and a hub surface.  
   
   
       5 . A method of fabricating a diffuser for a centrifugal compressor comprising the steps of fabricating a two-dimensional blade, and cutting one of the side surfaces of the blade, fabricated in the preceding step, into a concave shape with a ball-end mill.