Turbine casings

A turbine casing for a gas turbine comprises a casing defining the boundary of part of the turbine flow duct and formed from a plurality of segments, each segment being mounted from fixed structure by a plurality of radially extending struts. At least some of the struts are arranged to deform to allow relative thermal expansion between the hot segments and the supporting casing with at least one of the struts interposed between the deformable struts being relatively rigid.

1. A turbine casing assembly for a gas turbine engine comprising:

an annular support casing: a plurality of separate arcuate segments spaced radially inwardly of the annular support casing to define an annular boundary casing around at least one stage of a turbine rotor; and means to support each of said arcuate segments from said annular support casing whereby there can be circumferential thermal expansion of said segments and said boundary casing defined thereby relative to said annular support casing, said last-mentioned means including a plurality of circumferentially spaced apart radially extending struts greater than two for each arcuate segment to support the same from said annular support casing, at least one of said plurality of struts is relatively rigid and is interposed between the remaining of said plurality of struts with the same number of the remaining struts being on either side of the at least one relatively rigid strut, the remaining of said plurality of struts being resilient and deformable out of their radial alignment to allow for the thermal expansion

2. A turbine casing assembly as claimed in claim 1 in which each of said plurality of struts extends longitudinally and substantially parallel to the axis of the turbine.

3. A turbine casing assembly as claimed in claim 1 in which each of said plurality of struts for each arcuate segment is an odd number of struts with the central strut being relatively rigid and the remaining struts being resilient and deformable.

4. A turbine casing assembly as claimed in claim 1 and comprising a turbine shaft supported from said support casing, and two bearing panels between which the casing extends and which support the shaft or shafts.

5. A turbine casing assembly as claimed in claim 4 and in which there are two sets of said segments carried from said support casing extending between two said bearing panels.

6. A turbine casing assembly as claimed in claim I in which each of said plurality of struts for each arcuate segment includes three struts with the central strut being rigid.

7. A turbine casing assembly as claimed in claim 1 including a further annular support casing spaced radially outwardly from said first-mentioned annular support casing for supporting the same.

8. A turbine casing assembly as claimed in claim 1 in which each strut of said plurality of struts for each of said arcuate segments is structurally integral with the respective arcuate segment and said support casing. respective arcuate segment and said support casing.