Axial compressor with radially outer annulus

An axial compressor comprising:

• a plurality of compressor stages;
• a casing configured to encase said plurality of compressor stages positioned axially adjacent within said casing, wherein each of said plurality of compressor stages comprises:
• a rotor segment comprising a bladed disc configured to be coupled to a rotatable shaft;
• a banded stator segment positioned axially adjacent said rotor segment, said stator segment comprising an outer flowpath ring, an inner flowpath ring, and a plurality of vanes extending between said rings and being spaced around the circumferences thereof, said stator segment further comprising one or more tangs extending radially outward from said outer flowpath ring to engage said casing and thereby space said outer flowpath ring radially inward from said casing forming an annulus between said casing and said outer flowpath ring;
• and
• a pathway providing an air flowpath between an entry aperture and an exit aperture, said entry aperture disposed in a first of said compressor stages and providing an air flowpath between the bulk flowpath of said compressor stage and the annulus of said stage and said exit aperture disposed in a second of said stages positioned axially downstream of said first stage, said exit aperture providing an air flowpath between the annulus of said stage and the exterior of said casing, wherein said entry aperture and said exit aperture are in fluid communication.

A method of cooling an axial compressor comprising:

• providing a plurality of compressor stages encased in a casing, said plurality of compressor stages positioned axially adjacent within said casing and each of said plurality of compressor stages comprising:
• a rotor segment comprising a bladed disc configured to be coupled to a rotatable shaft;
• a banded stator segment positioned axially adjacent said rotor segment, said stator segment comprising an outer flowpath ring, an inner flowpath ring, and a plurality of vanes extending between said rings and being spaced around the circumferences thereof, said stator segment further comprising one or more tangs extending radially outward from said outer flowpath ring to engage said casing and thereby space said outer flowpath ring radially inward from said casing forming an annulus between said casing and said outer flowpath ring;
• providing a pathway between an entry pathway and an exit pathway, said entry pathway disposed in a first of said compressor stages and providing an air flowpath between the bulk flowpath of said compressor stage and the annulus of said stage and said exit pathway disposed in a second of said stages positioned axially downstream of said first stage, said exit pathway providing an air flowpath between the annulus of said stage and the exterior of said casing, wherein said entry pathway and said exit pathway are in fluid communication;
• and
• introducing air flow through said pathway.