System having blade segment with curved mounting geometry

A system includes a blade segment having a blade and a mounting segment coupled to the blade. Additionally, the mounting segment includes a first contact face and a second contact face, wherein the first and second contact face are concave with respect to a longitudinal axis of the blade segment. To reduce stresses within the mounting segment, the mounting segment further includes a lower face coupling the first contact face and the second contact face, wherein the lower face is convex across the longitudinal axis of the blade segment.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to turbomachine blades. More particularly, the subject matter disclosed herein relates to rotor interface geometry in turbomachine composite blades.

Turbomachines, such as compressors and turbines, include blades that rotate about a shaft or rotor to transfer energy between the rotor and a fluid. For example, turbine engines provide thrust to power airplanes, ships, and generators. The blades may be generally supported by the rotor. For example, the turbomachine blades may be attached to or mounted in the rotor. During operation of the turbomachine, the blades may experience high stresses due to rapid rotation of the blades and/or high operating temperatures. Unfortunately, the high stresses may cause the blades to degrade and, in certain situations, mechanically fail.

BRIEF DESCRIPTION OF THE INVENTION

In a first embodiment, a system includes a blade segment having a blade and a mounting segment coupled to the blade, wherein at least a portion of the mounting segment is configured to insert within a slot of a rotor to form a joint. Additionally, the mounting segment includes a first contact face and a second contact face each having a proximal end and a distal end, wherein each proximal end is configured to be inserted within the slot and each distal end is configured to remain outside of the slot when the joint is formed. The mounting segment further includes a lower face coupling the respective proximal ends of the first and second contact faces, wherein the lower face projects generally radially away from the blade.

In a second embodiment, a system includes a composite turbomachine blade segment having a blade and a mounting segment coupled to the blade. Additionally, the mounting segment includes a first contact face and a second contact face, wherein the first and second contact faces are concave with respect to a longitudinal axis of the turbomachine blade segment. The mounting segment further includes a lower face coupling the first contact face and the second contact face, wherein the lower face is curved away from the blade across the longitudinal axis of the turbomachine blade segment.

In a third embodiment, a system includes a turbomachine rotor having a plurality of slots spaced circumferentially about the turbomachine rotor and a plurality of disk posts spaced circumferentially about the rotor. Additionally, each disk post separates a first slot from a second slot of the plurality of slots, and each disk post comprises a first retaining surface configured to engage a first portion of a first turbomachine blade segment within the first slot and a second retaining surface configured to engage a second portion of a second turbomachine blade segment within the second slot, and the first and second retaining surfaces are coupled via a top surface that is curved away from a rotational axis of the turbomachine rotor.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, a turbomachine blade segment, and more specifically, a turbomachine blade mounting segment, may experience stresses during operation of the turbomachine, which may degrade the blade segment and/or the mounting segments. Specifically, as the rotor rotates, the mounting segments may experience a high compressive load, which may result in high tensile stresses within the center of the minimum neck area of the mounting segment. The tension may cause the mounting segments to crack or separate. The cracks or separations may weaken the mounting segments and may be a gateway for dirt or moisture, which may further weaken the mounting segment. Thus, it is now recognized that it may be desirable to provide a turbomachine blade segment designed to reduce or minimize the tension within the mounting segment.

With the foregoing in mind, the disclosed embodiments include a curved turbomachine blade mounting segment for coupling a turbomachine blade to a rotor of a turbomachine. Specifically, the bottom of the mounting segment may be curved outwardly with respect to the blade (e.g., arc-shaped or mushroom-shaped). The curvature of the mounting segment may serve to increase the load-bearing ability of the turbomachine blade segment and counter the loads imposed by the pull of the blade. Additionally, certain embodiments include a turbomachine rotor that includes slots and/or disk posts configured to engage with the mounting segment. One or more surfaces of the slots and/or disk posts may also be curved (e.g., arc-shaped or mushroom-shaped). As a result, stresses experienced by the mounting segment, the rotor of the turbomachine, and the turbomachine blade may be reduced, thereby increasing the useful life of the mounting segment, the rotor, and the turbomachine blade. It should be noted, that while the present embodiments are discussed within the context of turbomachines with turbomachine blade segments mounted to a rotor, they are also applicable to any system having similar attachments. For example, the present embodiments are also applicable to propellers, such as in airplanes, wind turbines, and the like.

Turning now to the drawings,FIG. 1is a schematic block diagram of an embodiment of a combined cycle system8having various turbomachines that are equipped with improved blade mounting systems (e.g., dovetail joints). Specifically, the turbomachines include turbomachine blade segments with curved mounting segments (e.g., a first dovetail portion of a dovetail joint), which may be coupled to a slot or recess (e.g., a second dovetail portion of a dovetail joint) of a rotor. As shown, the combined cycle system8includes a gas turbine system10having a compressor12, combustors14having fuel nozzles16, and a turbine18. As discussed in further detail below, the compressor12produces compressed air and provides the compressed air to the combustors14. Similarly, the fuel nozzles16route a liquid fuel and/or gas fuel, such as natural gas or syngas, into the combustors14. The combustors14ignite and combust a fuel-air mixture produced from mixing the compressed air and the liquid and/or gas fuel, and then pass resulting hot pressurized combustion gases20into the turbine18.

In the turbine18, the hot pressurized combustion gases pass over a series of turbomachine blade segments22, which are coupled to a rotor24. As discussed in further detail below with respect toFIG. 2, each turbomachine blade segment22is coupled to the rotor24via a respective curved mounting segment (FIG. 2). Thus, as the combustion gases20pass over the turbomachine blade segments22in the turbine18, the blade segments22cause the rotor24to rotate along a rotational axis26. Eventually, the combustion gases20exit the turbine18via an exhaust outlet28(e.g., exhaust duct, exhaust stack, silencer, etc.).

In the illustrated embodiment, the compressor12includes compressor blades30. The compressor blades30within the compressor12are also coupled to the rotor24, for example using curved mounting segments in accordance with the present disclosure. The compressor blades20rotate as the rotor24is driven into rotation by the turbomachine blade segments22, as described above. Thus, at least a portion of the work performed by the hot combustion gases on the turbomachine blade segments22may be used to drive the compressor12. As the compressor blades30rotate within the compressor12, the compressor blades30compress air from an air intake into pressurized air32, which is routed to the combustors14, the fuel nozzles16, and other portions of the combined cycle system8. The fuel nozzles16then mix the pressurized air and fuel to produce a suitable fuel-air mixture, which combusts in the combustors14to generate the combustion gases20to drive the turbine18. Further, the rotor24may be coupled to a first load34, which may be powered via rotation of the rotor24. For example, the first load34may be any suitable device that may generate power via the rotational output of the combined cycle system8, such as a power generation plant or an external mechanical load. For instance, the first load34may include an electrical generator, a propeller of an airplane, and so forth.

The system8may further include a heat recovery steam generator (HRSG) system36. Heated exhaust gas38from the turbine18is transported into the HRSG system36to heat water to produce steam40used to power a steam turbine42. The HRSG system36may include various economizers, condensers, evaporators, heaters, and so forth, to generate and heat the steam40used to power the steam turbine42. The steam40produced by the HRSG system36passes over turbine blades of the steam turbine42. The turbine blades of the steam turbine42may, for example, be the turbomachine blade segments22having the curved mounting segments. As the steam40passes through the turbine blades in the steam turbine42, the steam turbine42is driven into rotation, which causes the shaft44to rotate, thereby powering a second load46.

In the following discussion, reference may be made to various directions or axes, such as an axial direction48along the rotational axis26, a radial direction50away from the axis26, and a circumferential direction52around the axis26of the turbine18or the steam turbine42. Additionally, as mentioned above, while the mounting segments (e.g., a first dovetail portion of a dovetail joint) described below may be used with any of a variety of turbomachines (e.g., compressors12, gas turbines18, or steam turbines42) or other machinery that uses blades, the following discussion describes curved mounting segments (e.g., a first dovetail portion of a dovetail joint) in the context of the turbine18(e.g., a gas turbine).

FIG. 2is a partial cross-sectional axial view of the turbine18taken within line2-2ofFIG. 1. In particular,FIG. 2illustrates an embodiment of a single stage53of the turbine18having turbomachine blade segments22coupled to the rotor24via joints54(e.g., dovetail joints). As noted above, each blade segment22includes a turbine blade56and a mounting segment58. Additionally, each blade segment22has a longitudinal axis76. Each mounting joint54includes a first joint portion60(e.g., a first dovetail portion) disposed on each blade segment22, and a second joint portion62(e.g., a second dovetail portion) disposed on the rotor24. For example, the first joint portion60may be a male joint portion and the second joint portion62may be a female joint portion, or vice versa. In the illustrated embodiment, the first joint portion60comprises the mounting segment58that is male, and the second joint portion62comprises a recess or slot64that is female.

Specifically, each of the mounting segments58is partially disposed within one of the slots64(e.g., an axial slot) formed in an outer surface66of, and circumferentially52spaced about, the rotor24. For example, a plurality of the slots64may encircle the rotor24. As illustrated, a first portion68of each mounting segment58is disposed within the slot64of the rotor24, while a second portion70of each mounting segment58extends in the radial direction50outward from the outer surface66of the rotor24and is coupled to the respective turbine blade56. Thus, the second portion70of each mounting segment58may be disposed completely outside of the slot64, or partially inside of the slot64. To install each turbomachine blade segment22, each mounting segment58may be inserted along the axial direction48into a respective slot64.

FIG. 3is an exploded perspective view taken within line3-3ofFIG. 2, illustrating an embodiment of the turbomachine blade segment22in which the turbine blade56and the mounting segment58are a single piece (e.g., are integrally formed).FIG. 3also depicts the relative arrangement of the geometries of the mounting segment58and the slot64of the rotor24. For instance, as noted above, the mounting segment58is configured to be at least partially inserted into the slot64of the rotor24. It should be noted that while it the mounting segment58is illustrated and described in the context of being axially48inserted into the slot64, it is also contemplated that the mounting segment58may be radially50inserted into a circumferential slot64of the rotor24. As depicted, the mounting segment58and the slot64may have complimentary geometries that enable the turbomachine blade segment22and the rotor24to couple to one another.

In the illustrated embodiment, the slot64is formed between two disk posts78. The disk posts78are spaced in the circumferential direction52about the rotor24and extend in the radial direction50outward from the rotor24. The rotor24may include a plurality of disk posts78defining a plurality of slots64, which may be configured to couple with a plurality of mounting segments58. Accordingly, while specific slots64or disk posts78may be discussed for clarity, that the embodiments discussed below may be applicable to any one of the plurality of slots64or disk posts78.

With the foregoing in mind, in the illustrated embodiment, the slot64is formed as a spacing between a first disk post80and a second disk post82. The first disk post80includes a first retaining surface84, and the second disk post includes a second retaining surface86, which are connected by a bottom surface88. The retaining surfaces84and86are configured to abut portions of the mounting segment58such that the mounting segment58is retained within the slot64. The particular configuration of the first and second retaining surfaces84and86is discussed in further detail below. The bottom surface88may be disposed about the inner bottom of the slot64, and the retaining surfaces84and86may be disposed about the inner sides of the slot64. Additionally, the first retaining surface84may be connected with a top surface90of the first disk post80, and the second retaining surface86may be connected with a top surface92of the second disk post82. While bottom surface88is depicted as a surface that is continuous with the first and second retaining surfaces84and86(e.g., not separated by ends or corners), it should be noted that the disk posts80and82may be connected by more than one surface, in which each surface is separated from another by a corner.

The disk posts78may be configured to engage at least a portion of the mounting segment58when the joint54is formed. That is, the disk posts78may be designed to retain at least a portion of the mounting segment58within the slot64when the turbomachine blade segment22is installed in the turbine18. For example, the first and second retaining surfaces84and86, as well as the top surfaces90and92, may be configured to abut portions of the mounting segment58. In particular, in the illustrated embodiment, the first and second retaining surfaces84and86are configured to abut a first contact face94and a second contact face96of the mounting segment58. As defined herein, a face is defined as a surface that is delineated by ends (e.g., corners). Furthermore, as defined herein, a contact face is a surface in which at least a portion of the surface abuts a disk post when the turbine is spinning Additionally, each contact face94and96includes a distal end98configured to remain outside of the slot64and a proximal end100configured to be inserted into the slot64. In accordance with present embodiments, when the joint54is formed (FIG. 2) and the turbine18is spinning, the first retaining surface84may abut at least the proximal end100of the first contact face94. Similarly, the second retaining surface86may abut at least the proximal end100of the second contact face96. Additionally, the top surface90may abut at least the distal end98of the first contact face94, while the top surface92may abut at least the distal end98of the second contact face96.

The mounting segment58may further include a lower face102generally connecting the first and second contact faces94,96. The lower face102may be separated from the first contact face94and the second contact face96by corners104. Specifically, each corner104may be an angled portion where two faces converge and, more specifically, each corner104may be a transition point from an inwardly curved face (e.g., the first or second contact face96) to an outwardly curved face (e.g., the lower face102). In the illustrated embodiment, the lower face102is curved to create a lobe, or U-shaped protrusion, on the bottom of the mounting segment58. Similarly, the bottom surface88and the top surfaces90,92may be curved. The curved surfaces may enhance the load-bearing capability of the mounting segment58, when compared to non-curved mounting segments (e.g., angled and/or flat) to stiffen the structure of the turbomachine blade segment22, and additionally the disk posts78, to reduce blade strain (e.g., due to interlaminar tension (ILT)). Indeed, as discussed in further detail below, any of the above listed surfaces may be modified with various degrees of curvature to reduce blade strain.

As discussed above, the turbomachine blade segment22may experience stresses. These stresses may increase the likelihood or the magnitude of cracks in the mounting segment58during operation of the turbine18(FIG. 1). Generally, metal turbomachine blade segments22experience stresses in the radial direction50(e.g., radially upward). In contrast, composite turbomachine blades22are more susceptible to different types of stresses, such as ILT. Indeed, ILT may be particularly detrimental for composite blades, which will be described in more detail below. However, composite turbomachine blade segments22having composite mounting segments58, such as ceramic matrix composite (CMC) turbomachine blade segments22, may be advantageous for use within components that are placed within a hot gas path, such as in an engine, as they may be capable of operating without receiving cooling air inside the hot gas path of a gas turbine. Thus, the mounting segment58may be a composite assembly of one or more laminated plies.

FIG. 4is a partial cross-sectional view of the mounting segment58taken along line4-4ofFIG. 3, illustrating an embodiment of a composite assembly106of laminated plies108forming a bulk of the mounting segment58. In some embodiments, as illustrated, the laminated plies108may extend in the radial direction50from the proximal end100to the distal end98(FIG. 3) of the mounting segment58. Further, the laminated plies108may be oriented substantially parallel with respect to one another, and may include a plurality of fibers114disposed within a matrix, as discussed below.

The laminated plies108may have characteristics (e.g., geometry and/or material composition) which may be uniform or non-uniform within or among the mounting segment58. For example, the stress or compression loading of the mounting segment58may not be uniform in the radial48, axial50, or circumferential52directions, and thus, the characteristics of the laminated plies108may be designed to vary within the mounting segment58.

In certain embodiments, the material composition of the laminated plies108may be designed for the mounting segment58to withstand high mechanical or thermal stresses. For example, the laminated plies108may be constructed of a ceramic, a metal, a polymer, a fiberglass, an epoxy, another suitable material, or any combination thereof. In certain embodiments, the laminated plies108may be a ceramic matrix composite. For example, the material composition may alternate from ceramic to metal between adjacent laminated plies108. In other embodiments, as noted above, the laminated plies108may be a CMC material in which a plurality of fibers114(e.g., silicon carbide fibers) are disposed within a matrix material, which may be the same as the material used to construct the fibers114, contain one or more components of the materials used to construct the fibers114(e.g., silicon/silicon-carbide), or may be different than the fibers114. Additionally, in embodiments where the laminated plies108include such fibers114, the fibers114may have any relative orientation. For example, as illustrated, a first set of fibers116may have a first orientation while a second set of fibers118have a second orientation. Indeed, the first and second orientations may take on any geometric form and have any geometric relationship with respect to one another. Thus, the first and second sets of fibers116,118may be oriented substantially parallel with respect to one another, crosswise with respect to one another (e.g., in a converging, diverging, orthogonal, or similar relationship), or may be oriented in an arcuate, circular, or semi-circular fashion. In certain embodiments, it may be desirable for the fibers114to be substantially aligned in the radial direction50within the mounting segment58so as to increase the ability of the mounting segment58to withstand shear, strain, and tension during operation.

While composite mounting segment58may be advantageous for at least the reasons set forth above, they may experience interlaminar stresses exceeding the tensile strength of the composite material. Specifically, as the composite turbine blade segment22spins, the composite mounting segment58may experience high ILT in a minimum neck area110of the mounting segment58. More specifically, the strain may occur in a direction as indicated by arrow112. The ILT may cause the laminated plies108to transversely separate or delaminate (e.g., in the circumferential direction52). The separation of the laminated plies108may create or exacerbate preexisting cracks in the mounting segment58. Furthermore, the mounting segment58may experience a high radial load along a portion117of the contact surfaces94and96, which may rupture the laminated plies114. To address these issues, the disclosed embodiments provide the curved mounting segments58and the disk posts78with varying degrees of curvature, which may function to stiffen the structure and reduce strain of the mounting segment58, and thus reduce the stresses of the turbomachine blade segment22.

FIG. 5is a partial cross-sectional axial view, taken within line3-3ofFIG. 2, of the turbomachine blade segment22and the slot64, illustrating an embodiment of the mounting segment58and the disk posts78. In the illustrated embodiment, the first pressure second contact face94and96of the mounting segment58are curved inwardly with respect to the longitudinal axis76of the turbomachine blade segment22. Thus, in the illustrated embodiment, the first and second contact faces94and96are concave with respect to the longitudinal axis76. Indeed, as defined herein, with respect to the mounting segment58, concave is defined as curved toward the turbomachine blade segment22, and convex is defined as curved away from the turbomachine blade segment22. Accordingly, the first and second retaining surface84and86, which may be configured to abut the first and second contact faces94and96when the joint54is formed, may also be concave with respect to the turbomachine blade segment22. Furthermore, the first retaining surface84may be curved away from, or convex with respect to a longitudinal axis120of the first disk post80. Similarly, the second retaining surface86may be curved away from a longitudinal axis122of the second disk post82.

In the illustrated embodiment, each contact face94and96is curved from its distal end98to its proximal end100, respectively. As such, each top surface90and92may also be curved to engage with the first and second contact faces94and96, respectively. Specifically, each top surface90and92may be curved away from the rotational axis26of the rotor24. In other words, each top surface90and92may be curved across the longitudinal axes120and122, respectively. The longitudinal axes120and122may be substantially parallel to the longitudinal axis76of the turbomachine blade segment58when the joint54is formed. That is, the longitudinal axes120and122may be offset from the longitudinal axis76to the extent that there is some uncertainty in measurements. In other embodiments, the longitudinal axes120and122may not be parallel. In the illustrated embodiment, the top surfaces90and92are curved as arc surfaces124. In one embodiment, the arc surfaces124are curved such that the peaks of the first and second disk post80and82(e.g., the farthest point from the rotation axis26) substantially align with their longitudinal axes120and122, respectively. Furthermore, the degree of curvature may vary for certain embodiments. For example, each arc surface124may be one-quarter, one-third, one-half, two-thirds, or three-quarters of a circle. Each arc surface124may have an arc angle greater than approximately 0° and less than approximately 270°. By way of non-limiting example, each arc surface124may have an arc angle between approximately 30° and 240°, 60° and 210°, 90° and 180°, or 120° and 150°.

In the illustrated embodiment, lower face102of the mounting segment58is also curved. Specifically, the lower face102is curved radially away from the turbomachine blade segment22. More specifically, the lower face102is curved between the corners104to create a convex arc surface126. The convex arc surface126is also concave with respect to the rotational axis26of the rotor24. As noted above, the arc surface126is curved such that the nadir of the mounting segment58(e.g., the farthest point from the blade56) substantially aligns with the longitudinal axis76. The arc surface126may have a same or different degree of curvature as the arc surfaces124. That is, the arc surface126may have an arc angle greater than approximately 0° and less than approximately 270° . By way of non-limiting example, the arc surface126may have an arc angle between approximately 30° and 240°, 60° and 210°, 90° and 180°, or 120° and 150°.

As discussed above, the curvature of the top surfaces90and92and the lower face102may be desirable to stiffen the structure of the turbomachine blade segment22when the joint54is formed. In particular, the curvature may act to increase the load bearing capability of the blade segment22and may counteract or reduce the ILT during operation. Furthermore, the degree of curvature may be related to load bearing capability. For example, an arc angle between 90° and 270° or 100° and 200°, may be optimal for load bearing capabilities.

In certain embodiments, the bottom surface88may also be curved, such that the bottom surface88curves inward toward the rotational axis26of the rotor24. Indeed, it may be desirable for the geometry of the bottom surface88to substantially match the geometry of the lower face102to enable some movement between them while also providing a substantially uniform fit. Accordingly, in the illustrated embodiment, the bottom surface88has a geometry128substantially matching that of the convex arc surface126. Furthermore, in the illustrated embodiment, the slot64is deeper than the inserted portion of the mounting segment58, such that a cavity130may be disposed between the bottom surface88and the lower face102when the joint54is formed. In one embodiment, the cavity130may be configured to receive cooling air (e.g., compressed air) to enable cooling of the turbomachine blade segment22. However, in certain embodiments, the slot64and the mounting segment58may be configured such that the cavity130is minimized, or such that the lower face102abuts the bottom surface88.

FIG. 6is a partial cross-sectional axial view, taken within line3-3ofFIG. 2, of the turbomachine blade segment22and the slot64, illustrating an embodiment of the mounting segment58and the disk posts78. In the illustrated embodiment, the lower face102and the bottom surface88may be designed as the convex arc surfaces126and128, respectively, as described with respect toFIG. 4. However, the top surfaces90and92may be substantially flat across the longitudinal axes120and122, respectively. Accordingly, the distal ends98of the first and second contact faces94and96may also be flat to engage with the flat top surfaces90and92, respectively.

FIG. 7is a partial cross-sectional axial view, taken along line3-3ofFIG. 2, of the turbomachine blade segment22and the slot64, illustrating an embodiment of the mounting segment58and the disk posts78. In the illustrated embodiment, the lower face102may project generally radially away from the turbomachine blade segment22. That is, at least a portion of the lower face102may be curved outwardly with respect to the turbomachine blade segment22, and portions of the lower face may be flat or slanted away with respect to the turbomachine blade segment22. In certain embodiments, the lower face102may be curved, or convex, across the longitudinal axis76. For example, the lower face102may be curved over 0 to 100, 10 to 90, 20 to 80, 30 to 70, or 40 to 60 percent of the lower face102. Additionally, in the illustrated embodiment, the top surfaces90and92are also generally curved, such that at least a portion of each top surface90and92projects radially outward with respect to the rotation axis26. Specifically, the top surfaces90and92are curved across the longitudinal axes120and122, respectively. Furthermore, the top surfaces90and92may be curved over 0 to 100, 10 to 90, 20 to 80, 30 to 70, or 40 to 60 percent of their respective surface.

The bottom surface88may also be designed to project generally radially outward from the turbomachine blade segment22. Similar to the lower face102, at least a portion of the bottom surface88may be curved toward the rotational axis26, and portions of the lower face may be flat or slanted inward with respect to the rotational axis26. In certain embodiments, the bottom surface88may be curved, or convex, across the longitudinal axis76, when the joint54is formed. Additionally, the longitudinal axis may substantially align with a central region120of the bottom surface88when the joint54is formed. In certain embodiments, the bottom surface88may be curved across the central region120. Furthermore, the bottom surface88may be curved over 0 to 100, 10 to 90, 20 to 80, 30 to 70, or 40 to 60 percent of the bottom surface88.