Patent ID: 8602730

Claim:
A multistage radial compressor ( 1 ) with at least two compressor stages for compressing a fluid, comprising a compressor housing ( 16 ); a flow channel ( 2 ) formed within said housing for compressing the fluid; a deflecting channel having a radius of curvature and a length; an impeller ( 4 ) having a plurality of impeller vanes ( 5 ) arranged in said flow channel ( 2 ) and rotatable with said impeller ( 4 ) around a driveshaft (A); a 3D return blading ( 8 ) having a plurality of return vanes ( 9 ; 9 ′) each comprising a vane base and a vane head axially downstream thereof, said return vanes being fixed with respect to rotation relative to said compressor housing ( 16 ); said flow channel ( 2 ) having a curved deflecting channel ( 7 ; 7 ′) arranged in front of said return vanes ( 9 ; 9 ′) in the direction of flow; wherein at least one of said vane base ( 11 ) and said vane head ( 12 ) of said return vanes ( 9 ) of said 3D return blading ( 8 ) has a curvature; and wherein at least one of said radius of curvature (R(ρ)) of said deflecting channel ( 7 ′) varies over said length of said deflecting channel and said return vanes ( 9 ; 9 ′) of said 3D return blading ( 8 ) have a first vane angle distribution ( 17 ) at said vane base ( 11 ) and a second relatively different vane angle distribution ( 18 ) at said vane head ( 12 ), wherein at least one of an axial height (H) of said vane base ( 11 ) and an axial height (h) of said vane head ( 12 ) varies over said length of said return vanes ( 9 ), said vane base ( 11 ) being curved so that its axial height (H) initially increases over the length of said return vanes ( 9 ), starting from a minimum at a vane inlet ( 13 ) until a maximum approximately in the center of said return vanes and then decreases again to another minimum.