Composite elongate member having a predetermined effective coefficient of linear expansion

Claim 2

A stator shroud ring assembly in which a turbine of a gas turbine engine is to be positioned with an annular gap of predetermined radial distance between the stator shroud ring and the periphery of the turbine rotor, the stator shroud ring assembly including a stator shroud ring constructed from at least one arcuate portion made of one material and at least one arcuate portion made of another material, the arcuate portions being assembled end-to-end and the co-efficients of linear expansion of the material employed and the total arcuate length employed of each material being such that the circumferential length of the whole shroud ring will change with temperature, within the range of working temperature for which the engine has been designed, by an amount corresponding to a predetermined effective co-efficient of linear expansion, whereby the total change in circumferential length of the stator shroud ring will substantially correspond to the alteration in diameter of the rotor, the radial dimension of said annular gap thereby being maintained at substantially the aforesaid predetermined value.

Claim 3

A stator shroud ring assembly as claimed in claim 1 in which the stator shroud ring is formed from arcuate portions of two different materials.

Claim 4

A stator shroud ring assembly as claimed in claim 1 in which one of the materials from which the arcuate portions are made is the same as that from which the rotor is formed, the material of the remaining arcuate portions having a lower co-efficient of expansion, whereby the effective expansion of the composite stator shroud ring is substantially the same as that of the rotor.

Claim 5

A stator shroud ring assembly as claimed in claim 1 in which the arcuate portions have interengageable end faces.

Claim 6

A stator shroud ring assembly as claimed in claim 1 in which a concentric enveloping ring made of a material having a co-efficient of linear expansion substantially the same as the material from which the turbine rotor is made bounds the arcuate portions of the stator shroud ring.

Claim 7

A gas turbine engine including a bladed turbine rotor and a stator shroud ring assembly, the latter defining a stator shroud ring surrounding the rotor with an annular gap of predetermined radial distance between the stator shroud ring and the periphery of the turbine rotor, the stator shroud ring being constructed from at least one arcuate portion made of one material and at least one arcuate portion made of another material, the arcuate portions being assembled end-to-end and the co-efficients of linear expansion of the materials employed and the total arcuate length employed of each material being such that the circumferential length of the whole shroud ring will change with temperature, within the range of working temperature for which the engine has been designed, by an amount corresponding to a predetermined effective co-efficient of linear expansion, whereby the total change in circumferential length of the stator shroud ring will substantially correspond to the alteration in diameter of the rotor, the radial dimension of said annular gap thereby being maintained at substantially the aforesaid predetermined value.

Claim 8

A gas turbine engine including a bladed turbine rotor and a stator shroud ring assembly, the latter defining a stator shroud ring surrounding the rotor with an annular gap of predetermined radial distance between the stator shroud ring and the periphery of the turbine rotor, the stator shroud ring being constructed from at least one arcuate portion made of one material and at least one arcuate portion made of another material, the arcuate portions being assembled end-to-end and the co-efficients of linear expansion of the materials employed and the total arcuate length employed of each material being such that the circumferential length of the whole shroud ring will change with temperature, within the range of working temperature for which the engine has been designed, by an amount corresponding to a predetermined effective co-efficient of linear expansion, whereby the total change in circumferential length of the stator shroud ring will substantially correspond to the alteration in diameter of the rotor, the radial dimension of said annular gap thereby being maintained at substantially the aforesaid predetermined value.