Variable diffuser and compressor

Abstract

There is provided a variable diffuser for a compressor in which the efficiency can be further improved. In a variable diffuser 30 in which a diffuser passage 33 , which restores a static pressure from a dynamic pressure by decelerating an air flow that is discharged from an outer peripheral end of an impeller that rotates within a housing, is formed between a hub side wall 32 a and a shroud side wall 31 a , and diffuser vanes are provided in the diffuser passage 33 , fixed vanes 35 and movable vanes 34 that are the diffuser vanes, are alternately fixed in the circumferential direction to a fixed circular plate 32 and a movable circular plate 31 that form the hub side wall 32 a and the shroud side wall 31 a , and there is provided a driving device 40 that turns the movable circular plate 31 about the same axis as the rotation of the impeller.

1 . A variable diffuser in which a diffuser passage, which restores a static pressure from a dynamic pressure by decelerating an air flow that is discharged from an outer peripheral end of an impeller that rotates within a housing, is formed between a hub side wall and a shroud side wall, and diffuser vanes are provided in the diffuser passage,
 said diffuser vanes being alternately fixed in the circumferential direction to a wall member that forms said hub side wall and said shroud side wall, and there being provided a driving device that turns either one of said wall members about the same axis as the rotation of said impeller.   
   
   
       2 . A variable diffuser according to  claim 1 , wherein a movable range of said wall member which turns as a result of said driving device, is set such that it encompasses the entire width of an interval between adjacent diffuser vanes that are fixed on the wall member of the fixed side. 
   
   
       3 . A variable diffuser according to  claim 1 , wherein a leading edge radius (R1) of a diffuser vane provided on a turning side of said wall member is set larger than a leading edge radius (R2) of a diffuser vane provided on a fixed side of said wall member (R1>R2). 
   
   
       4 . A variable diffuser according to  claim 3 , wherein a vane leading edge angle (αk1) of a diffuser vane provided on a turning side of said wall member is set smaller than a leading edge angle (αk2) of a diffuser vane provided on a fixed side of said wall member at the same radial position (αk1<αk2). 
   
   
       5 . A variable diffuser according to  claim 3 , wherein a vane leading edge angle (αk1) of a diffuser vane provided on a turning side of said wall member is set larger than a leading edge angle (αk2) of a diffuser vane provided on a fixed side of said wall member at the same radial position (αk1>αk2). 
   
   
       6 . A variable diffuser according to  claim 3 , wherein a diffuser vane provided on a fixed side of said wall member is a low chord-pitch ratio vane. 
   
   
       7 . A variable diffuser according to  claim 6 , wherein a trailing edge radius (R3) of a diffuser vane provided on a turning side of said wall member is set larger than a trailing edge radius (R4) of a diffuser vane provided on a fixed side of said wall member (R3>R4). 
   
   
       8 . A variable diffuser according to  claim 3 , wherein the setting of the fixed side and the turning side is reversed. 
   
   
       9 . A variable diffuser according to  claim 1 , wherein said driving device is furnished with a sliding mechanism section that moves a turning side of said wall member back and forth between a space formation position and a space reduction position with respect to a fixed side of said wall member. 
   
   
       10 . A compressor comprising a variable diffuser according to  claim 1  on the peripheral end of the impeller that rotates within the housing.