Air cooled shroud for a gas turbine engine

Claim 2

In a gas turbine engine having a rotor and a shroud positioned about said rotor, said rotor being rotatable about a given axis, said shroud having a generally annular portion encircling said rotor, a radially inwardly directed first surface of said annular portion having a predetermined clearance from the outer circumference of said rotor, a second surface of said annular portion being the side opposite said first surface, means together with said second surface defining a plurality of slots. said slots forming a portion of passage means connecting a higher pressure area to a lower pressure area whereby air moves through said slots during engine operation, said slots having a depth in a range of 0.005 to 0.020 inches and being sufficiently small so that the air passing therethrough disturbs the normal boundary layer of heated air against said second surface.

Claim 3

In a gas turbine engine according to claim 1, said first mentioned means comprising a band positioned about said second surface, said slots being formed within the radially inner surface of said band and extending from the forward axial edge to the rearward axial edge.

Claim 4

In a gas turbing engine having a rotor constructed to rotate about a given axis, a shroud assembly positioned about said rotor, said shroud assembly constructed to define an annular chamber about said rotor, inlet means communicating said chamber with a source of compressed air, one wall of said chamber being spaced at a predetermined clearance from the outer circumference of said rotor, said wall having radially outwardly directed surface comprising an interior wall of said chamber, a band overlying and secured to said surface, a plurality of grooves formed in the inner surface of said band extending from one axial side of the band to the other, a plurality of axial recesses formed in one edge of the band providing inlets from the remainder of said chamber to said grooves, said axial recesses and said grooves in cooperation with the contiguous interior surfaces of said chamber defining a plurality of passages, outlet means formed in said chamber adjacent said first mentioned chamber wall surface, interposing said inlet means and said outlet means, a positive pressure differential existing between said inlet means and said outlet means inducing an air flow through said passages, said grooves being sufficiently shallow so that the air flow through said passages disturbs the boundary layer of heated air against said first mentioned chamber wall surface.

Claim 5

In a gas turbing engine having a rotor constructed to rotate about a given axis, a shroud assembly positioned about said rotor, said shroud assembly constructed to define an annular chamber about said rotor, inlet means communicating said chamber with a source of compressed air, one wall of said chamber being spaced at a predetermined clearance from the outer circumference of said rotor, said wall having radially outwardly directed surface comprising an interior wall of said chamber, a band overlying and secured to said surface, a plurality of grooves formed in the inner surface of said band extending from one axial side of the band to the other, a plurality of axial recesses formed in one edge of the band providing inlets from the remainder of said chamber to said grooves, said axial recesses and said grooves in cooperation with the contiguous interior surfaces of said chamber defining a plurality of passages, outlet means formed in said chamber adjacent said first mentioned chamber wall surface, interposing said inlet means and said outlet means, a positive pressure differential existing between said inlet means and said outlet means inducing an air flow through said passages, said grooves being sufficiently shallow so that the air flow through said passages disturbs the boundary layer of heated air against said first mentioned chamber wall surface.

Claim 6

In a gas turbine engine according to claim 3, said grooves having depths in a range of 0.500 to 0.020 inches.

Claim 7

In a gas turbine engine according to claim 3, said inlet means to said chamber being in communication with a source of centrifugal compressor discharge pressure.

Claim 8

In a gas turbine engine according to claim 3, said outlet means formed in said chamber being in communication with a source of exhaust pressure downstream of said rotor.

Claim 9

In a gas turbine engine according to claim 3, said rotor comprising the gasifier rotor of said engine.