Centrifugal compressor diffuser and centrifugal compressor provided with the same

Abstract

A centrifugal compressor diffuser includes a shroud-side wall ( 58 ) provided downstream of a centrifugal impeller; a hub-side wall provided so as to face the shroud-side wall ( 58 ); a plurality of shroud-side blades ( 3 ) fixed at base ends thereof to the shroud-side wall ( 58 ) and hub-side blades ( 4 ) fixed at base ends thereof to the hub-side wall. The shroud-side blades ( 3 ) and the hub-side blades ( 4 ) are combined in such a state that inlet angles thereof differ from one another and that at least portions of top ends thereof in a blade height direction are abutted onto one another. In gaps where the top ends of the combined shroud-side blades ( 3 ) and hub-side blades ( 4 ) are not abutted onto one another, a connecting member ( 5 ) that connects the top ends is provided so as to fill at least portions of the gaps.

1 . A centrifugal compressor diffuser comprising:
 a shroud-side wall provided downstream of a centrifugal impeller;   a hub-side wall provided so as to face the shroud-side wall;   a plurality of shroud-side blades fixed at base ends thereof to the shroud-side wall; and   a plurality of hub-side blades fixed at base ends thereof to the hub-side wall, wherein   the shroud-side blades and the hub-side blades are combined in such a state that inlet angles thereof differ from one another and that at least portions of top ends thereof in a blade height direction are abutted onto one another,   in gaps where the top ends of the combined shroud-side blades and hub-side blades are not abutted onto one another, a connecting member that connects the top ends so as to fill at least portions of the gaps is provided,   the connecting member has a ring-like shape that continuously connects the top ends of the plurality of shroud-side blades and hub-side blades in a circumferential direction, and   the inside diameter of the ring-like connecting member is smaller than a radius defined by leading edges of the shroud-side blades and hub-side blades.   
     
     
         2 - 3 . (canceled) 
     
     
         4 . The centrifugal compressor diffuser according to  claim 1 , wherein the connecting member is provided so as to fill an area from leading edges of the top ends of at least one of the combined shroud-side blades and hub-side blades to 60% positions in the length of the blades on the downstream side. 
     
     
         5 . The centrifugal compressor diffuser according to  claim 1 , wherein
 the combined shroud-side blades and hub-side blades are arranged such that their leading edges are shifted from one another in the circumferential direction.   
     
     
         6 . The centrifugal compressor diffuser according to  claim 1 , wherein
 the combined shroud-side blades and hub-side blades are arranged so as to be shifted from one another in the circumferential direction such that they do not overlap one another from the leading edges to 60% positions in the length of the blades.   
     
     
         7 . A centrifugal compressor diffuser comprising:
 a shroud-side wall provided downstream of a centrifugal impeller;   a hub-side wall provided so as to face the shroud-side wall;   a plurality of shroud-side blades fixed at base ends thereof to the shroud-side wall; and   a plurality of hub-side blades fixed at base ends thereof to the hub-side wall, wherein   the shroud-side blades are thick blades having a wedge shape or a channel shape gradually widening from leading edges toward trailing edges of the shroud-side blades in cross-section in a direction perpendicular to a blade height direction,   the hub-side blades are thin blades, and   the hub-side blades and the shroud-side blades to be combined with the hub-side blades are combined in such a state that inlet angles thereof differ from one another and that top ends, in a blade height direction, of the shroud-side blades to be combined with the hub-side blades overlap one another over the entire blade lengths of the hub-side blades.   
     
     
         8 - 9 . (canceled) 
     
     
         10 . A centrifugal compressor comprising the centrifugal compressor diffuser according to  claim 1 . 
     
     
         11 . The centrifugal compressor diffuser according to  claim 7 , wherein the hub-side blades and the shroud-side blades to be combined with the hub-side blades are combined in such a state that leading edges of the top ends, in the blade height direction, of the hub-side blades and the leading edges of the top ends, in the blade height direction, of the shroud-side blades overlap one another. 
     
     
         12 . The centrifugal compressor diffuser according to  claim 7 , wherein the hub-side blades and the shroud-side blades to be combined with the hub-side blades are combined in such a state that trailing edges of the top ends, in the blade height direction, of the hub-side blades and trailing edges of the top ends, in the blade height direction, of the shroud-side blades overlap one another. 
     
     
         13 . The centrifugal compressor diffuser according to  claim 7 , wherein the hub-side blades and the shroud-side blades to be combined with the hub-side blades are combined in such a state that the entire top ends, in the blade height direction, of the hub-side blades overlap the top ends, in the blade height direction, of the shroud-side blades. 
     
     
         14 . The centrifugal compressor diffuser according to  claim 7 , wherein the width of the shroud-side blades in cross-section in the direction perpendicular to the blade height direction is two or more times greater than the width of the hub-side blades in cross-section in the direction perpendicular to the blade height direction. 
     
     
         15 . A centrifugal compressor diffuser comprising:
 a shroud-side wall provided downstream of a centrifugal impeller;   a hub-side wall provided so as to face the shroud-side wall;   a plurality of shroud-side blades fixed at base ends thereof to the shroud-side wall; and   a plurality of hub-side blades fixed at base ends thereof to the hub-side wall, wherein   the hub-side blades and the shroud-side blades to be combined with the hub-side blades are combined such that their inlet angles differ from one another,   side portions, on the side of the shroud-side blades, of the top ends, in the blade height direction, of the hub-side blades and side portions, on the side of the hub-side blades, of the top ends, in the blade height direction, of the shroud-side blades form overlapping portions extending over the blade length of the hub-side blades, and   side portions, opposite to the side of the shroud-side blades, of the top ends, in the blade height direction, of the hub-side blades are separated from the overlapping portions.   
     
     
         16 . The centrifugal compressor diffuser according to  claim 15 , wherein the shroud-side blades have a wedge shape or a channel shape gradually widening from the leading edges toward trailing edges of the shroud-side blades in cross-section in a direction perpendicular to a blade height direction. 
     
     
         17 . The centrifugal compressor diffuser according to  claim 15 , wherein the hub-side blades have a wedge shape or a channel shape gradually widening from the leading edges toward trailing edges of the hub-side blades in cross-section in a direction perpendicular to a blade height direction.