Rotor disc

Abstract

A rotor disc having an enlarged radially outer rim defining a circumferentially-extending dovetail groove for housing the root portion of a rotor blade. The groove has a groove axis and the groove is unsymmetrical about the groove axis. For example, the dovetail groove may have a restricted radially outer opening extending to an enlarged radially inner bulb profile having a pair of axially opposed curved surfaces and the opposing curved surfaces may unsymmetrical about the groove axis.

Claims

1. A rotor disc having an enlarged radially outer rim defining a circumferentially-extending dovetail groove for housing the root portion of a rotor blade, the groove having a groove axis wherein the groove is unsymmetrical about a radially-extending plane through the groove axis, wherein the dovetail groove has a pair of axially opposed curved surfaces on opposite sides of the radially-extending plane, a first one of the pair of opposing curved surfaces is a multi-radii surface while a second one of the pair of opposing curved surfaces has a single radius, and the multiple radii of the multi-radii surface vary with respect to a same direction from the multi-radii surface.

2. The rotor disc according to claim 1 wherein the dovetail groove has a restricted radially outer opening extending to an enlarged radially inner bulb profile having the pair of axially opposed curved surfaces.

3. The rotor disc according to claim 2 wherein the radius of the first one of the opposing curved surfaces is greater than the radius (radii) of the second one of the curved surfaces.

4. The rotor disc according to claim 2 wherein each curved surface has a respective radially outer section and radially inner section.

5. The rotor disc according to claim 4 wherein the radially outer sections and the radially inner sections of the curved surface are unsymmetrical about the radially-extending plane through the groove axis.

6. The rotor disc according to claim 4 wherein the radially outer sections or the radially inner sections of the curved surface are unsymmetrical about the radially-extending plane through the groove axis.

7. The rotor disc according to claim 1 wherein the opposing curved surfaces are unsymmetrical about the radially-extending plane through the groove axis.

8. The rotor disc according to claim 1 further comprising a bridging section for connection to an adjacent rotor disc.

9. The rotor disc according to claim 8 wherein the bridging section extends from the radially outer rim such that its radially outer surface is radially outwards of the opening of the groove.

10. The rotor disc according to claim 8 wherein the dovetail groove has a restricted radially outer opening extending to an enlarged radially inner bulb profile having the pair of axially opposed curved surfaces and wherein the curved surface proximal the bridging section has a greater radius of curvature than the curved surface distal the bridging section.

11. The rotor disc according to claim 8 wherein the dovetail groove has a restricted radially outer opening extending to an enlarged radially inner bulb profile having the pair of axially opposed curved surfaces and wherein the curved surface distal the bridging section has a multi-radii profile.

12. The rotor disc according to claim 8 wherein: the dovetail groove has a restricted radially outer opening extending to an enlarged radially inner bulb profile having the pair of axially opposed curved surfaces; each curved surface has a respective radially outer section and radially inner section; and the radially inner sections of the curved surfaces each have a respective radius with the radially inner section of the curved surface proximal the bridging section having a greater radius than the curved surface distal the bridging section.

13. The rotor disc according to claim 8 wherein: the dovetail groove has a restricted radially outer opening extending to an enlarged radially inner bulb profile having the pair of axially opposed curved surfaces; each curved surface has a respective radially outer section and radially inner section; and the radially outer section of the curved surface distal the bridging section has a multi-radii surface.

14. The rotor disc according to claim 8 wherein a distance from the groove to an exterior surface of the rim proximal the bridging section is less than the distance from the groove to an exterior surface of the rim distal the bridging section.

15. A compressor drum comprising at least one rotor disc according to claim 1.

16. A compressor drum comprising two rotor discs according to claim 1, each of the two rotor discs including a bridging section for connection to an adjacent rotor disc, the two rotor discs being arranged adjacent one another with the bridging sections joined.

17. A gas turbine engine comprising a rotor disc according to claim 1.

18. A gas turbine engine comprising a compressor drum, the compressor drum including at least one rotor disc according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a ducted fan gas turbine engine;

(3) FIG. 2 shows a radially outer portion of a rotor disc according to a first embodiment of the present invention with dotted lines showing a radially outer portion of a prior art rotor disc; and

(4) FIG. 3 shows three adjacent rotor discs with two of the rotor discs being according to the first embodiment of the present invention.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES OF THE INVENTION

(5) FIG. 2 shows the radially outer portion of a rotor disc 32 having an enlarged radially outer rim 31 defining a circumferentially-extending dovetail groove 30 for housing the root portion of a rotor blade (not shown). The groove has a groove axis and the groove 30 is unsymmetrical about a radially extending plane 35 through the groove axis as discussed below.

(6) The dovetail groove 30 has a restricted radially outer opening 36 extending to an enlarged radially inner bulb profile 33.

(7) The radially inner dovetail bulb profile 33 has two inclined shoulder surfaces 37, 37 extending from the restricted opening 36 to a respective curved surface. The two curved surfaces are axially opposed (across the axis of the rotor disc) and are joined by a planar surface 39 forming the base of the groove 30 (radially opposite the restricted opening).

(8) Each curved surface has a respective radially outer section 38A, 38A and radially inner section 38B, 38B.

(9) As shown in FIGS. 2 and 3, the rotor disc 32 further comprises a bridging section 34 for connection (e.g. by inertia welding) to an adjacent rotor disc 32. The bridging section 34 extends axially from the radially outer rim 31 such that its radially outer surface 40 is radially aligned with or radially outwards of the opening 36 of the groove 30 i.e. above the gauge plane of the rotor disc. The bridging section 34 abuts a bridging section 34 on the adjacent rotor disc 32 and the bridging sections 34, 34 act to provide bracing between the circumferential grooves on adjacent rotor discs 32, 32 above the gauge plane 43 of the rotor disc 32 and to limit distortion under the blade loads in operation. A spacer portion 42 is provided between the rotor disc 32 and another rotor disc 32 on the opposing side of the circumferential groove 30 to the bridging section 34.

(10) The radially outer section 38A of the curved surface proximal the bridging section 34 has a single radius (R2) whilst the radially outer section 38A of the curved surface distal the bridging section 34 has a multiple radii (R2 and R4) i.e. the outer sections 38A, 38A of the curved surfaces are unsymmetrical about radially extending plane 35 through the groove axis.

(11) The radially inner sections 38B, 38B of the curved surfaces both have a single radius with the radially inner section 38B of the curved surface proximal the bridging section 34 having a greater radius of curvature (R5.3) than the radius of curvature (R4) of the radially inner section 38B of the curved surface distal the bridging section 34 i.e. the inner sections 38B, 38B of the curved surfaces are unsymmetrical about the radially extending plane 35 through the groove axis.

(12) The enlarged outer rim 31 of the rotor disc 32 has an exterior surface 41 distal the bridging portion 34 and an exterior surface 41 proximal the bridging section 34. The distance from the groove 30 to the exterior surface 41 of the rim 31 proximal the bridging section 34 is less than the distance from the groove 30 to the exterior surface 41 of the rim 31 distal the bridging section 34.

(13) The dotted lines in FIG. 2 show a radially outer portion of a prior art rotor disc with a symmetrical circumferential groove. It can be seen that the change in shape of the circumferential groove allows material to be removed from the exterior surface 41 which, in turn reduces component weight and stresses at the weld join. The amount of material that can be removed is greater than the amount of material that is added as a result of having a greater radius of curvature in the radially inner section 38B of the curved surface proximal the bridging section 34 thus resulting in a reduction in component weight.

(14) While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.