Rotor disk for gas turbine engine

A gas turbine engine rotor disk has a single-piece hub with a radially-outer surface, and with an annular cavity inside the single-piece hub. The annular cavity is defined by a radially-elongated cross-sectional profile revolved at least partly about the axis of rotation. Blades extend outwardly from the radially-outer surface.

TECHNICAL FIELD

The application relates generally to gas turbine engines and, more particularly, to rotor disks for gas turbine engines.

BACKGROUND

In gas turbine engines, the compressor and turbine stages have rotating disks with blades, which are connected to a central shaft. The disks are typically designed to withstand the centrifugal and aerodynamics loads generated during operation of the gas turbine engine, and are also often designed to reduce the deflection of the rotating blades.

The design of gas turbine engines must take into consideration and mitigate the effects of failure cases such as crack initiation in rotor disks and the propagation of such crack(s). A crack propagating throughout the rotor disk could cause significant disk fragmentation, and create massive components which must be contained. To account for potential disk fragmentation, containment structures are positioned around the disk. These containment structures must be sufficiently strong to contain disk fragmentation, and may therefore incur a weight penalty.

SUMMARY

In one aspect, there is provided a gas turbine engine rotor disk, comprising: a single-piece hub having an axis of rotation, a radially-outer surface, and an annular cavity inside the single-piece hub, the annular cavity being defined by a radially-elongated cross-sectional profile revolved at least partly about the axis of rotation; and blades extending outwardly from the radially-outer surface of the single-piece hub.

There is also provided a gas turbine engine, comprising: a shaft having an axis of rotation; and a rotor disk, comprising: a single-piece hub with a shaft bore to receive the shaft, a radially-outer surface, and an annular cavity inside the single-piece hub, the annular cavity being defined by a radially-elongated cross-sectional profile revolved at least partly about the axis of rotation, the annular cavity being disposed between axially spaced apart webs of the single-piece hub; and blades extending outwardly from the radially-outer surface of the single-piece hub.

DETAILED DESCRIPTION

The compressor and turbine sections14,18have rotatable components. The compressor section14has an axial compressor15A for pressurizing the air which is then conveyed to a downstream centrifugal compressor, or impeller15B. The turbine section18has a high pressure (HP) turbine19A, and a downstream low pressure or power turbine19B which drives the fan12. One or all of the axial compressor15A, the HP turbine19A, and the power turbine19B may have multiple stages. The axial compressor15A, the impeller15B and the HP turbine19A are mechanically linked by a first shaft13A. The fan12and the power turbine19B are mechanically linked by a second shaft13B. The rotatable components of the compressor and turbine sections14,18rotate about a central axis of rotation11of the gas turbine engine10.

FIGS. 2A to 2Cshow a first example of a rotor disk20which can be adapted to the gas turbine engine10. The illustrated rotor disk20is the impeller15B. The features and functions ascribed to the rotor disk20herein may also be present in other types of rotor disks20or rotary gas turbine engine components, including the following non-limiting examples: the fan12, a component of the compressor section14, and a component of the turbine section18(e.g. the HP turbine19A, and the power turbine19B), to name but a few examples. Indeed, another type of rotor disk20, the axial compressor15A, is described in greater detail below.

The rotor disk20has a single-piece hub22which generally has a solid of revolution shape centered around the axis of rotation11. The single-piece hub22forms a corpus of the rotor disk20and provides structure thereto. The single-piece hub22(sometimes referred to herein simply as “hub22”) is a one-piece component, and is integrally formed throughout its extent. The hub22has a unitary construction. For example, in some embodiments, hub22is manufactured as a single piece instead of comprising an assembly of two or more components. The integrality or unity of the hub22can be achieved during its manufacture. For example, hub22and optionally also blades21, may be made by casting or additive manufacturing using suitable (e.g., metallic) material(s). In some embodiments, hub22and blades21can be manufactured as a single component by casting or additive manufacturing. In some embodiments, rotor disk20may undergo one or more finishing operations (e.g., grinding, machining) to achieve the desired dimensional accuracy after casting or additive manufacturing.

In the depicted embodiment, the hub22has an optional bore26being coaxial with the axis of rotation11to receive the first shaft13A therein. In an alternate embodiment, the single-piece hub22is filled or solid along its central axial portion, and is free of a central aperture or bore. The hub22has a contoured radially-outer surface24A and a radially-inner surface24B defining bore26. The radially-outer surface24A is further from the axis of rotation11than the radially-inner surface24B along a radial direction that is transverse to the axis of rotation11. In the depicted embodiment, the radially-outer surface24A is the surface of the hub22that is exposed to air flow. In the depicted embodiment, the radially-outer surface24A is the radially-outermost surface of the hub22, it being the surface of the hub22that is farthest from the axis of rotation11. The radially-inner surface24B defines the bore26, and is the radially-innermost surface of the hub22, it being the surface of the hub22that is closest to the axis of rotation11.

A plurality of blades21extend outwardly from the radially-outer surface24A of the single-piece hub22. The blades21have a radial dimension, an axial dimension, and may also have a tangential or circumferential dimension. The blades21may be integral with the hub22to form a single bladed disk (or “blisk”), or the blades21may be attached to the hub22. The rotor disk20in the depicted embodiment is in the form of the centrifugal impeller15B, and thus the blades21are impeller blades. In various embodiments, the blades21may be other types of blades21(e.g. blades21for the fan12, blades21for the axial compressor15A, blades for the HP turbine18A or for the power turbine18B, etc.).

Referring toFIGS. 2B and 2C, the hub22has one or more annular cavities30. The cavities30may be hollow and contribute to reducing the weight of the hub22, and thus of the rotor disk20. The cavities30also help mitigate the damage that could be caused by the propagation of one or more cracks through the hub22, as explained in greater detail below.

The cavities30are annular in shape. The cavities30are defined by a radially-elongated cross-sectional profile revolved at least partly about the axis of rotation11. By “radially-elongated”, it is understood that the radial dimension of the cavities30is greater than the axial dimension of the cavities30. In the depicted embodiment, the cavities30are defined by their radially-elongated cross-sectional profiles revolved completely about the axis of rotation11. The cavities30are thus circumferentially uninterrupted, and thus form circumferentially uninterrupted annuli being co-axial with the axis of rotation11. Each of the cavities30lies entirely within a single plane being normal to the axis of rotation11. In an alternate embodiment, one or more of the cavities30is defined by its radially-elongated cross-sectional profile revolved only partly about the axis of rotation11, i.e. less than 360° about the axis of rotation11.

The cavities30are radially delimited by radially-outer and radially-inner portions of the hub22, and are axially delimited by axially-spaced apart portions of the hub22. In the depicted embodiment, each cavity30is delimited at a radially-outer portion thereof by a relatively thin skin segment28A of the hub22which defines part of the radially-outer surface24A, and is delimited at radially-inner portion thereof by a radially-inner portion28B of the hub22which defines part of the radially-inner surface24A. The radially-inner portion28B of the hub22has a greater radial dimension than the skin segment28A of the hub22. The thickness of the skin segment28A is greater than or equal to a thickness of the back plate29of the hub22. The thickness of the back plate29is thus related to the radial extent or dimension of the cavities30.

The cavities30can be empty internal voids or holes in the hub22which are disposed entirely within the hub22. In the depicted embodiment, each cavity30is delimited by internal walls of the hub22. In the depicted embodiment, each cavity30is spaced radially inwardly from the radially-outer surface24A, and spaced radially outwardly from the radially-inner surface24B. The cavities30are thus closed cavities. The cavities30form circumferential pockets within the hub22. The annular cavities30are spaced radially outwardly from the bore26, and extend radially outwardly in a direction away from the bore26. In the depicted embodiment, the cavities30are delimited and enclosed entirely on all sides by portions of the single-piece hub22. No portion of the cavities30is delimited by a component which is separate from the single-piece hub22and which may be attached thereto. The cavities30may be formed as part of the single-piece hub22of the rotor disk20using any suitable technique such as casting and additive manufacturing.

Referring toFIG. 2B, the annular cavities30are disposed between axially spaced apart webs23of the single-piece hub22. The webs23are radially-elongated portions of the hub22that extend in the depicted embodiment radially-inwardly from the radially-outer surface24A of the hub22. Each web23includes a portion of the radially-outer surface24A. The webs23have a radial dimension which is larger than their axial dimension. The webs23are annular in shape, and are axially spaced apart. The webs23are circumferentially continuous solid bodies. Axially-adjacent webs23are separated from each other by one of the cavities30. In the depicted embodiment, the webs23are continuous with the radially-inner portion28B of the hub22, and extend radially-outwardly therefrom. In the depicted embodiment, the webs23are spaced radially outwardly from the bore26, and extend radially outwardly in a direction away from the bore26. The webs23thus form toroidal-shaped structures of the single-piece hub22of the rotor disk20. The webs23define corners27delimiting part of the cavities30. The corners27are rounded to reduce stress concentration.

Referring toFIGS. 2A to 2C, the depicted rotor disk20may help better distribute throughout the rotor disk20the centrifugal and aerodynamic loads generated during operation of the gas turbine engine10. The presence of the cavities30may also reduce the weight of the rotor disk20.

The cavities30and associated webs23may also change the failure mode of the rotor disk20. The axial spacing apart of some of the structures of the single-piece hub22may result in a single crack propagation leading to reduced fouling of components of the blades21on the surrounding containment structure, instead of a more significant rupture of the rotor disk20that could otherwise occur with other rotor disk designs. The reduced risk of massive rupture or “burst” of the rotor disk20may allow for reducing the containment requirement in the event of disk failure, and thus may allow for reducing the complexity and/or weight of the containment structures around the rotor disk20.

The single-piece hub22may therefore be designed to mitigate the propagation of a crack which may form therein. Referring toFIGS. 2B and 2C, the hub22has a central region. The central region25is a portion of the hub22along which a crack may initiate and propagate through the hub22. It is understood that cracks typically propagate in a radially-outward direction due to loading generated during operation of the rotor disk20. Crack propagation may occur very quickly and in some cases almost instantaneously, in contrast to other material failure modes like creep.

In the depicted embodiment, the central region25is defined between the radially-inner surface24B of the hub22and radially-inner ends31A of the cavities30. In the depicted embodiment, the central region25includes the radially-inner portion28B of the hub22. The central region25has a radial dimension or extent less than a radial distance between the radially-inner surface24B and the radially-outer surface24A of the single-piece hub22. The central region25is thus an annular portion or volume of the hub22. It will be appreciated that the central region25may take other shapes or forms than that shown, depending on the number and shape of the cavities30, for example.

The number and shape of the cavities30and the webs23may be selected to reduce the potential for crack formation and mitigate the effects of crack propagation through the hub22. Consider the following description of the possible formation and propagation of a crack through the hub22, which is given for illustrative purposes only, it being understood that cracks may form and propagate differently than as described. Referring toFIG. 2B, an exemplary crack C forms at an initiation point IP along the radially-inner surface24B of the hub22due to loads acting on the rotor disk20. The crack C may propagate radially outwardly from the initiation point IP through the central region25. The crack C may encounter one of the cavities30at the radially-inner end31A thereof. The crack C may then be prevented from propagating further after encountering the cavity30, and may thus lead to the fragmentation of only a relatively small portion of the hub22compared to a disk design having no cavities.

The cavities30therefore help reduce the likelihood of the crack C propagating through the entire hub22. Additional energy would be needed for the crack C to further propagate once it reaches one of the cavities30, which contributes to improving the containment requirement, and thus may allow for reducing the weight of the containment structures. The webs23contribute to dividing the hub22into axially-spaced apart internal hub segments. If the crack C develops in one of the webs23, it is unlikely to propagate through all of the webs23before failure occurs, thus contributing to the containment requirement.

The presence of the cavities30and webs23provide some control over crack propagation so that any fragmentation of the rotor disk20would result in smaller potential fragment size compared to a solid hub without the cavities. It is understood that the problem of crack propagation can be more important in a single-piece hub than in a multi-piece hub, because in multi-piece hubs disk fragmentation may more predictably occur along the partition lines of the pieces of the hub.

The cavities30and associated webs23may have any suitable shape, or be of any suitable number, to facilitate the mitigation of crack propagation described above, and examples of possible shapes are described with reference toFIGS. 2B and 2C.

For example, each of the webs23has first surface23A and an axially-spaced apart second surface23B. The first and second surfaces23A,23B partially delimit the axial extent of the cavities30. At least part of the first and second surfaces23A,23B have curved segments23C with a curvature. The curved segments23C are concave. One or more of the webs23have a radially-elongated cross-sectional profile. The cross-sectional profile of some of the webs23tapers in a direction toward the radially-outer surface24A of the hub22. The cross-sectional profile of some of the webs23thus decreases in axial dimension in a radially-outward direction, such that the axial dimension at a radially outer end of the webs23is less than that at the radially inner end. It may be possible to design the path of propagation of the crack C along one of the webs23. This confinement of the crack C may also help to reduce the size of a disk fragment and improve containment because the crack C may cause the fragmentation of only that portion of the hub22where the web23is located, and thus not a larger or more massive part of the rotor disk20.

For example, the annular cavities30may have a radial dimension, measured along a radial line from the axis of rotation11at a given axial position that is between 5% and 95% of a radial dimension of the hub22measured between the radially-inner surface24B and the radially-outer surface24A at the same axial position. The radial extent of the cavity30may be selected as a function of the lifing or stress requirements of the rotor disk20(i.e. how long the rotor disk20is expected to function for). Each of the annular cavities30has a radially-inner portion32A and a radially-outer portion32B. The radially-outer portion32B has a first axial dimension measured in a direction parallel to the axis of rotation11that is greater than a second axial dimension of the radially-inner portion32A. Each of the cavities30in the depicted embodiment therefore has a greater axial extent closer to the radially-outer surface24A than the axial extent closer to the radially-inner surface24B of the hub22. This shape of the cavities30may help to optimize stress distribution through the hub22.

The hub22in the depicted embodiment has a first annular cavity30A and a second annular cavity30B inside the single-piece hub22. The first and second annular cavities are axially-spaced apart, and axially separated by one of the webs23.FIG. 2Bshows three webs23. The first annular cavity30A has a first volume and the second annular cavity30B has a second volume different from the first volume. The first volume is greater than the second volume. The first and second cavities30A,30B have different sizes in the depicted embodiment. The first cavity30A is larger than the second cavity30B. The radial dimension or extent of the first cavity30A is greater than the radial dimension or extent of the second cavity30B. A structure for the hub22with two to three webs23may help to better distribute centrifugal stress and decrease the strain on the blades21. The number of cavities30may be related to the ability of the hub22to resist or arrest crack propagation. For example, it may be possible to further control crack propagation by increasing the number of cavities30.

Another rotor disk20of the gas turbine engine10is the axial compressor15A, shown more clearly in cross-section inFIG. 3. The hub22inFIG. 3includes only one annular cavity30. The radially-outer portion32B of the cavity30has a first axial dimension measured in a direction parallel to the axis of rotation11that is greater than a second axial dimension of the radially-inner portion32A. The hub22has two annular webs23. A first web23A thickens, or increases in axial dimension, in a radially-outward direction from the axis of rotation11. The second web23B tapers, or decreases in axial dimension, in a radially-outward direction from the axis of rotation11. The description above of the features and functions of the rotor disk20in the form of the impeller15B applies mutatis mutandis to the rotor disk20shown inFIG. 3in the form of the axial compressor15A.

There is also disclosed a method of forming the rotor disk20. The method includes providing the single-piece hub22and blades21. The method also includes forming one or more annular cavities30extending radially through the single-piece hub22to define the webs23. Providing the single-piece hub22may include making the single-piece hub22by casting or additive manufacturing using powder bed fusion technology. The cavities30may be formed simultaneously with the single-piece hub22. Forming the one or more cavities30may include selecting a number of the cavities30as a function of structural requirements of hub22and desired effect over propagation of the crack C through the single-piece hub22. As explained above, the number and/or configuration of cavities30may be related to the ability of the hub22to resist or arrest crack propagation.