Turbomachine for a gas turbine engine

1. A turbomachine for a gas turbine engine, comprising:

a rotor disc arranged to rotate about a fixed central axis;

a plurality of rotor blades connected to the rotor disc, the rotor blades extending within a gas flow path; and

a rotating annulus arranged to rotate in a fixed rotational alignment relative to the rotor disc;

wherein an outer surface of the rotating annulus is arranged to define part of the boundary of the gas flow path, and

wherein the rotating annulus is mounted directly to the rotor disc to provide the rotational alignment between them.

2. The turbomachine according to claim 1 , wherein each of the rotor blades is connected to the rotor disc by a respective interlocking connection, each interlocking connection comprising an interlocking profile on the rotor disc and a corresponding interlocking profile on the respective rotor blade, and wherein the rotating annulus comprises one or more interlocking profiles each adapted to form an interlocking connection with one or more of the interlocking profiles provided on the rotor disc.

3. The turbomachine according to claim 2 , wherein the one or more interlocking profiles provided on the rotating annulus has a different size and/or shape compared to the interlocking profile provided on each of the rotor blades.

4. The turbomachine according to claim 2 , wherein one or more of the interlocking connections further comprises an adapter member, the adapter member having a first interlocking profile shaped to interlock with the interlocking profile on the respective rotor disc and a different second interlocking profile shaped to interlock with the interlocking profile on the rotating annulus.

5. The turbomachine according to claim 3 , wherein the interlocking profile provided on each rotor blade comprises at least three lobes or recesses and the, or each, interlocking profile formed on the rotating annulus comprises two lobes or recesses.

6. The turbomachine according to claim 2 , wherein the rotor disc comprises a peripheral cantilevered portion extending axially from the body of the rotor disc, wherein each of the interlocking profiles adapted to form an interlocking connection with the rotating annulus is formed in the cantilevered portion.

7. The turbomachine according to claim 2 , wherein the rotor disc comprises a protrusion extending axially from a face of the rotor disc, wherein the rotating annulus is mounted to the rotor disc via the protrusion, and optionally, wherein a fastening mechanism is provided to axially retain the rotating annulus to the rotor disc.

8. The turbomachine according to claim 1 , wherein the rotating annulus is mounted to an intermediate rotor disc, wherein the intermediate rotor disc is arranged to rotate around the central axis in a stationary rotational alignment with the rotor disc.

9. The turbomachine according to claim 8 , wherein the rotating annulus is mounted to the intermediate rotor disc by an interlocking connection, and optionally wherein the interlocking connection is a dovetail connection.

10. The turbomachine according to claim 1 , wherein the rotating annulus is mounted to one or more of the plurality of rotor blades to provide rotational alignment between the rotor disc and the rotating annulus.

11. The turbomachine according to claim 10 , wherein the rotating annulus is mounted to a blade platform of one or more of the plurality of rotor blades.

12. The turbomachine according to claim 11 , wherein the blade platform further comprises an axially extending hook member, wherein the rotating annulus is mounted to the hook member, and optionally wherein:

an outer surface of each blade platform forms part of the boundary of the gas flow path, and wherein the hook member extends from a point at or near the outer surface of the blade platform.

13. The turbomachine according to claim 12 , wherein the rotating annulus comprises a plurality of blade apertures, and wherein the rotating annulus is mounted to the rotor disc such that one or more of the plurality of rotor blades is received in a respective one of the plurality of blade apertures and such that each rotor blade extends through the body of the rotating annulus.

14. The turbomachine according to claim 1 , wherein the rotating annulus is formed from a high temperature capable material, and optionally wherein the high temperature capable material is a ceramic matrix composite (CMC) material.

15. The turbomachine according to claim 1 , wherein the rotating annulus comprises a sealing feature adapted to seal to a static guide vane disposed within the gas flow path, and optionally wherein:

the sealing feature comprises a trench region formed in the outer surface of the rotating annulus, the trench region arranged to receive a platform of the static guide vane, and further optionally wherein:

the sealing feature comprises one or more seal fins disposed on a surface of the trench region, and wherein the one or more seal fins are adapted to form a seal between the rotating annulus and the static guide vane.

16. The turbomachine according to claim 1 , wherein the rotating annulus is formed from a plurality of segments, and optionally wherein each segment is individually mounted in a fixed rotational alignment with the rotor disc.

17. The turbomachine according to claim 1 , wherein the rotor disc is a first rotor disc and the turbomachine further comprises a second rotor disc, the first and second rotor discs defining the interdisc cavity between them, and wherein the rotating annulus is arranged to define a boundary between the gas flow path and the interdisc cavity.

18. A gas turbine engine for an aircraft, the gas turbine engine comprising the turbomachine according to claim 1 .

19. A method of defining the boundary of a gas flow path within a turbomachine, the method comprising:

mounting the rotating annulus defined in claim 1 such that the rotating annulus is arranged to rotate in a fixed alignment relative to a rotor disc of the turbomachine.