Austenitic steam turbine ring segment for a steam turbine guide device and steam turbine guide device

Abstract

Austenitic steam turbine ring segment (52), comprising: a body section (54) dimensioned to substantially fill a pocket (68) in an outer steam turbine intermediate floor ring (56), wherein the body section (54) has a circumferential length greater than an axial depth or a radial width; and a hook-shaped section (58) extending radially inwards from the body section (54), wherein the hook-shaped section (58) is dimensioned to engage with a hook-shaped slot (60) in the outer steam turbine intermediate floor ring (56), wherein the body section (54) and the hook-shaped section (58) form a single structure which is a structure which does not have a hole passing through it; wherein the pocket (68) and the hook-shaped slot (60) are open in an axial direction along an axis (A) of the austenitic steam turbine ring segment (52) and the body section (54) and the hook-shaped section (58) are arranged to fit the pocket (68) and the hook-shaped slot (60) in such a way as to allow the austenitic steam turbine ring segment (52) to be coupled to and detached from the steam turbine intermediate floor ring (56) in the axial direction.

Description

BACKGROUND TO THE INVENTION

[0001] The subject matter disclosed herein relates to a steam turbine nozzle or intermediate stage. Specifically, the subject matter disclosed herein relates to an austenitic segment structure for a steam turbine nozzle.

[0002] Steam turbines contain stationary nozzle assemblies that direct a flow of working fluid onto turbine blades connected to a rotating rotor. The nozzle assembly (containing a plurality of guide vanes or "airfoils") is sometimes referred to as a "trim" or "guide stage." Steam turbine trims comprise two halves that are assembled around the rotor, forming horizontal joints between the two halves. Each turbine trim stage is vertically supported on either side of the trim at the corresponding horizontal joints by support bars, support bosses, or support bolts. The trim horizontal joints also correspond to horizontal joints of the turbine casing surrounding the steam turbine trim.

[0003] US 1 352 278 A discloses a turbine element for use between a casing and a diaphragm ring of a steam turbine, the turbine element comprising: a body portion sized to substantially fill a pocket in the diaphragm ring, the body portion having a circumferential length greater than an axial depth or a radial width; and a hook-shaped portion extending radially inwardly from the body portion, the hook-shaped portion being sized to engage a hook-shaped slot in the diaphragm ring.The pocket and the hook-shaped slot are open in a horizontal or radially outward direction relative to an axis of the intermediate bottom ring, and the body portion and the hook-shaped portion are configured to mate with the pocket and the hook-shaped slot such that the turbine element can be coupled to and detached from the intermediate bottom ring in a radial direction. The turbine element has bolt holes therethrough and is secured to both the housing and the intermediate bottom ring by means of screw bolts.

[0004] US 3 021 110 A discloses a steam turbine guide device with a steam turbine intermediate base ring and a plurality of austenitic steam turbine ring segments which are received in a circumferential groove in a housing of the steam turbine and secured thereto by means of bolts.

[0005] Proceeding from this, it is an object of the invention to provide a steam turbine ring segment and a steam turbine guide device with a steam turbine intermediate base ring and a steam turbine ring segment, which enable an effective, simple mechanism for locking the steam turbine ring segment to the steam turbine intermediate base ring. SUMMARY OF THE INVENTION

[0006] To achieve this object, the invention provides a steam turbine ring segment having the features of independent claim 1 and a steam turbine guide device having the features of independent claim 6. Particularly preferred embodiments of the invention are specified in the dependent claims.

[0007] A first aspect of the disclosure includes: an austenitic steam turbine ring segment comprising: a body portion sized to substantially fill a pocket in an outer steam turbine intermediate ring, the body portion having a circumferential length greater than an axial depth or a radial width; and a hook-shaped portion extending radially inward from the body portion, the hook-shaped portion sized to engage a hook-shaped slot in the outer steam turbine intermediate ring, the body portion and the hook-shaped portion forming a unitary structure that is a structure that does not have a hole therethrough.The pocket and the hook-shaped slot are open in an axial direction along an axis of the austenitic steam turbine ring segment, and the body portion and the hook-shaped portion are configured to fit the pocket and the hook-shaped slot so as to enable the austenitic steam turbine ring segment to be coupled to and detached from the steam turbine intermediate bottom ring in the axial direction.

[0008] The hook-shaped portion of the austenitic steam turbine ring segment may complement the hook-shaped slot in the outer steam turbine intermediate ring.

[0009] The body portion of each above-mentioned austenitic steam turbine ring segment may further include a recess extending partially within a radially outer side of the body portion along the length of the circumference of the body portion.

[0010] The hook-shaped portion of each above-mentioned austenitic steam turbine ring segment may include: a first flange extending substantially perpendicularly from the body portion; and a second flange extending substantially perpendicularly from the first flange.

[0011] Both the first flange and the second flange of each above-mentioned austenitic steam turbine ring segment may be formed of an austenitic material common to the body portion.

[0012] A second aspect of the disclosure includes a steam turbine nozzle comprising: a turbine casing; a semi-annular diaphragm segment including an outer steam turbine diaphragm ring, the semi-annular diaphragm segment being at least partially received by the turbine casing, the semi-annular diaphragm segment having a horizontal connecting surface and a pocket below the horizontal connecting surface, the pocket having a main pocket and at least one hook-shaped slot extending from the main pocket, the main pocket and the hook-shaped slot being open in an axial direction along an axis of the semi-annular diaphragm segment;and an austenitic steam turbine ring segment connected to the semi-annular intermediate base segment, the austenitic steam turbine ring segment comprising: a body portion sized to substantially fill the main pocket in the outer ring, the body portion having a circumferential length greater than an axial depth or a radial width;and a hook-shaped portion extending radially inward from the body portion, the hook-shaped portion being sized to engage the hook-shaped slot in the outer steam turbine intermediate ring, the body portion and the hook-shaped portion forming a unitary structure that is a structure that does not have a hole therethrough. The body portion and the hook-shaped portion are configured to mate with the main pocket and the hook-shaped slot to allow the austenitic steam turbine ring segment to be coupled to and released from the steam turbine intermediate ring in the axial direction.

[0013] The steam turbine guide device may further comprise a holding member contacting the austenitic ring segment, wherein the holding member holds the austenitic steam turbine ring segment at least partially in contact with the semi-annular intermediate bottom segment.

[0014] The semi-annular intermediate base segment of each steam turbine guide device mentioned above may have an opening on a radially outwardly facing surface, wherein the holding member is at least partially held in the opening.

[0015] The hook-shaped portion of each steam turbine guide device mentioned above may complement the hook-shaped slot in the outer steam turbine intermediate ring.

[0016] The body portion of each steam turbine nozzle mentioned above may further include a recess extending partially within a radially outer side of the body portion along the length of the circumference of the body portion.

[0017] The hook-shaped portion of each steam turbine nozzle mentioned above may include: a first flange extending substantially perpendicularly from the body portion; and a second flange extending substantially perpendicularly from the first flange.

[0018] Both the first flange and the second flange of each steam turbine nozzle mentioned above may be formed of an austenitic material common to the body portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other features of this invention will become more apparent from the following detailed description of the various embodiments of the invention taken in conjunction with the accompanying drawings, which illustrate different embodiments of the disclosure, in which: Fig. 1 shows a longitudinally sectioned schematic partial view of a steam turbine according to various embodiments. Fig. Figure 2 shows a general schematic end view of a pair of annular intermediate floor ring segments joined at a horizontal split surface, according to the prior art. Fig. 3 an end view and a more detailed perspective view of a section of the outer intermediate floor ring in Fig. 2 according to the state of the art. Fig. 4 illustrates, in a three-dimensional perspective view, a portion of a steam turbine nozzle according to various embodiments of the disclosure. Fig. 5 is a plan view of a portion of the arrangement of Fig. 4 according to various embodiments of the disclosure. Fig. 6 a separate three-dimensional perspective view of the arrangement of Fig. 4-5 according to various embodiments of the disclosure.

[0020] Please note that the drawings of the invention are not necessarily to scale. The drawings are intended to illustrate only typical aspects of the invention and should therefore not be considered limiting the scope of the invention. Throughout the drawings, like reference numerals designate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0021] Aspects of the description provide an austenitic segment for use in a steam turbine nozzle. In special cases, the austenitic segment can be inserted into the assembly from the rear (in the axial direction).

[0022] With reference to Fig. 1 shows a partial sectional schematic view of a steam turbine 2 (e.g., a high-pressure / intermediate-pressure steam turbine). The steam turbine 2 may, for example, have an intermediate-pressure (IP) section 4 and a high-pressure (HP) section 6. The intermediate-pressure section 4 and the high-pressure section 6 are at least partially encapsulated in the casing 7. Steam may enter the high-pressure section 6 and the intermediate-pressure section 4 via one or more inlets 8 in the casing 7 and flow axially downstream from the one or more inlets 8. In some embodiments, the high-pressure section 6 and the intermediate-pressure section 4 are connected by a common shaft 10, which may contact bearings 12, allowing the shaft 10 to rotate while the working fluid (steam) in both the intermediate-pressure section 4 and the high-pressure section 6 rotates the rotor blades. After the working fluid (e.g.,Once steam has performed mechanical work on the rotor blades in the intermediate-pressure section 4 and the high-pressure section 6, it can escape through the outlet 14 in the casing 7. The centerline (CL) 16 of the high-pressure section 6 and the intermediate-pressure section 4 is shown as a reference point. Both the intermediate-pressure section 4 and the high-pressure section 6 may include intermediate floor devices housed in segments of the casing 7. Fig. Figure 2 illustrates, in a schematic end view of a section (e.g., the intermediate pressure section 4 or high pressure section 6) of the steam turbine 2, an intermediate bottom device 16 comprising a pair of semi-annular intermediate bottom ring segments 20, 22 connected at a horizontal connecting surface 24. The intermediate bottom ring segments 20, 22 are each housed in casing segments 30, 32 (a part of the casing 7), which are also connected at the horizontal connecting surface 24. Each semi-annular intermediate bottom ring segment 20, 22 carries a semi-annular row of turbine guide vanes 26 and an inner web 28, as known from the prior art. The intermediate bottom ring segments 20, 22 together surround a rotor 29 (shown in dashed lines) which is connected to the shaft 10 ( Fig. 1) can be connected, as is known from the prior art.

[0023] Fig. Figure 3 illustrates in an end view and a more detailed perspective view of a portion of the conventional outer intermediate floor ring segment 22 according to Fig. 2 further includes conventional austenitic ring segments 40, which are used to forcefully hold the outer intermediate base ring against the casing segments 30, 32 during operation of the steam turbine 2. In this conventional arrangement, the conventional austenitic ring segments 40 are bolted / screwed to the outer intermediate base ring 22 by axial bolts or radial bolts (a radial bolt configuration being shown). In order to securely hold the conventional austenitic ring segments 40, as in the case of adjusting the position of the support strips 32 ( Fig. 2), below the horizontal connecting surface 24, the upper halves of the housing 30 and the intermediate base 20 are removed in order to access the austenitic ring segments 40 below the horizontal connecting surface 24 ( Fig. 2) to access. Fig. 3-6 show different views of steam turbine support devices according to both the state of the art ( Fig. 3) as well as according to different embodiments of the disclosure ( Fig. 4-6). As indicated in these figures, the "z" axis represents a vertical orientation, "x" represents a horizontal (or radial) orientation, and the "A" axis represents an axial orientation (along the axis of the turbine rotor, omitted for clarity). As used herein, the terms "axial" and / or "axially" refer to the relative position / direction of objects along the A axis, which is substantially parallel to the rotational axis of the turbomachine (in particular, the rotor section). Further, the terms "radially" and / or "radially" refer to the relative position / direction of objects along the x axis, which is substantially perpendicular to the A axis and intersects the A axis only at one location.Furthermore, the terms “at the circumference” and / or “circumferentially” refer to the relative position / direction of objects along a circumference that surrounds the A axis but does not intersect the A axis at any point.

[0024] Conventional austenitic segment designs are, as in Fig. 3, by means of a radial or axial bolt to each segment of the outer ring. As shown, the conventional bolted / screwed austenitic ring segments 40 are formed with bolt holes 42 (or simply openings) that extend entirely through the body of these conventional bolted / screwed austenitic ring segments 40. These bolt holes 42 (openings) must extend entirely through the ring segments 40 so that the bolt, screw, or the like passing through the bolt hole can further engage an opening in the (radially) outer ring of the intermediate base segment 22. In the conventional bolted / screwed austenitic ring segments 40, the design conditions require some type of sliding fit on the bolt or threaded bolt head so that the segments 40 can expand axially without damaging the bolt.These design constraints result in significant complexity during assembly / disassembly. The primary function of the austenitic segments is to ensure that the outer ring of the vane plate (outer ring of the intermediate plate segment 22) is firmly held in a groove in the casing 30 during operation of the turbine 10. The use of the austenitic ring segment 40 also contributes to sealing the axial face of the outer ring (of the intermediate plate segment 22) against the casing 30. This sealing is achieved due to the higher thermal expansion coefficient of the austenitic segment 40 compared to the material from which the intermediate plate segment 22 and the casing 30 are made.

[0025] Conventional methods for servicing the intermediate vane ring or plate may require several shifts or days to complete due to the fact that each vane plate half must be removed to remove the radial or axial bolt on each austenitic ring segment 40. Furthermore, attaching the austenitic ring segments 40 to the outer ring (the intermediate vane 22) and maintaining the required torque on the bolts prior to welding (e.g., tungsten inert gas (TIG) spot welding) the bolt or threaded bolt heads (to prevent back-rotation) can be time-consuming. Furthermore, as stated herein, the austenitic ring segment 40 cannot be removed from the intermediate vane 22 without removing the intermediate vane 22 from the turbine casing 30.

[0026] In contrast to the conventional nozzle arrangement and plate configuration, various embodiments include an austenitic ring segment for a steam turbine nozzle having a unitary structure connected to an outer steam turbine intermediate ring without the use of bolts. Fig. 4 illustrates a three-dimensional perspective view of a portion of a steam turbine nozzle 50 according to various embodiments. Fig. Figure 5 illustrates a plan view of a portion of the steam turbine guide device 50 of Fig. 4 and Fig. 6 a separate three-dimensional perspective view of the steam turbine guide device 50 of Fig. 4-5.

[0027] With reference to Fig. 4-6, an austenitic steam turbine ring segment (or austenitic ring segment) 52 is shown according to various embodiments. The austenitic ring segment 52 may include a body portion 54 sized to substantially fill a pocket 68 in an outer steam turbine intermediate ring 56 (wherein the outer intermediate ring is connected to the Fig. 1-3). As shown, the body portion 54 has a circumferential length (L) that is greater than an axial depth (along axis A) or a radial width (along axis x). Additionally, the austenitic ring segment 52 may include a hooked portion 58 extending radially inwardly (along the x-axis) from the body portion 54. The hooked portion 58 is sized to engage a hooked slot 60 in the outer intermediate base ring 56, as described in more detail herein. As described herein, the hooked portion 58 is sized to complement the hooked slot 60 in the outer intermediate base ring 56, i.e., the hooked portion 58 substantially (fully or nearly fully) fills the hooked slot 60.Furthermore, the body portion 54 and the hook-shaped portion 58 form a unitary structure, in other words, a structure that does not have any openings therethrough. In other words, the body portion 54 and the hook-shaped portion 58 do not have any openings therethrough, which is in contrast to conventional ring segments (such as those shown in, for example, FIG. Fig. 3) which are provided with openings for receiving fastening screws.

[0028] For example, in Fig. 4-6, the body portion 54 may further include a recess 62 extending partially within a radially outer side 64 of the body portion 54 along a circumferential length (L) of the body portion 54. This recess 62 may only extend partially axially along the radially outer side 64, but may extend the entire circumferential length (L). This recess 62 may be sized to engage a lip 66 in a pocket 68 in the outer intermediate base ring 56, the lip 66 extending at least partially axially from the outer intermediate base ring 56 toward the pocket 68. The pocket 68 may include a main pocket 70 and at least one hook-shaped slot 60 extending from the main pocket 70.

[0029] The hooked portion 58 of the austenitic ring segment 52 may further include a first flange 72 extending substantially perpendicularly from the body portion 54 and a second flange 74 extending substantially perpendicularly from the first flange 72. The first flange 72 and the second flange 74 may each be formed from an austenitic material common to the body portion 54. As shown, the hooked slot 60 is formed by a flange 76 extending from the body of the outer intermediate base ring 56 in the main pocket 70.

[0030] As shown in various embodiments, the hook-shaped portion 58, in particular the second flange 74, may have a slot 78 extending radially through the second flange 74. In various embodiments, a plurality of slots 78 are present in the second flange 74.

[0031] According to different embodiments, the guide device arrangement 50 may further comprise at least one holding member 80 ( Fig. 5) that contacts the austenitic ring segment 52. The one or more retaining members 80 can at least partially hold the austenitic ring segment 52 in contact with the semi-annular intermediate base segment 56 by engaging a slot 78 in the second flange 74. Fig. 5 shows this configuration in more detail, illustrating how the retention member(s) 80 each engage a slot 78 in the second flange 74. The retention member 80 may include a radial dowel or a spring pin and may further serve to align the austenitic ring segment 52 with the pocket 68. In various embodiments, the semi-annular intermediate base segment 56 may have an opening 82 on a radially outwardly facing surface 84 (in the pocket 68) in which the retention member 80 is at least partially retained. That is, the retention member 80 (e.g., the radial dowel or spring pin) may sit within the opening 82, which may be internally threaded in some scenarios, and may serve to align / retain the austenitic ring segment 52 with the pocket 68.

[0032] As in Fig. 4-6, the austenitic ring segment 52 is configured to couple with and / or detach from the semi-annular intermediate base segment 56 in the axial direction (A). This means that the austenitic ring segment 52 can be inserted into and removed from the pocket 68 from behind, which allows for a reduction in the duration of repair, maintenance, and / or replacement of the ring segment 52. It is understood that in an arrangement, several ring segments (e.g., austenitic ring segments 52), e.g., several segments for each section of the lower intermediate base half 22 (e.g., the intermediate base segment 56) and several segments for each section of the upper intermediate base half 20 ( Fig. 2) can be arranged.

[0033] As described herein, the assembly 50, according to various embodiments, can provide an effective mechanism for locking austenitic ring segments (e.g., ring segments 52) to a false floor (e.g., false floor segment 56) without the use of bolts or other fasteners. In other words, the austenitic ring segments 52 can engage the false floor segment 56 without being attached to the false floor segment 56 (e.g., bolted, screwed, clamped, and the like). This eliminates the need for access below the horizontal connecting surface 24 for handling fasteners (e.g., inserting / removing bolts, driving / undriving screws, and the like).

[0034] In a variety of embodiments, these austenitic ring segments 52 can be used in a first stage of the turbine 10, for example, at locations where the highest pressure differential exists in the machine. As described herein, the use of an austenitic material for the ring segments 52 allows the ring segments 52 to expand more rapidly when heated than the material of the intermediate plate segment 56 (e.g., steel), so that an axial force is exerted on the intermediate plate segment 56. The austenitic material, as known in the art, includes gamma-phase iron (γ-Fe), which is a metallic, non-magnetic allotrope of iron or a solid solution iron with an alloying element.

[0035] The terminology used herein is for convenience in explaining specific embodiments and is not intended to be limiting of this description. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that the terms “comprising” and / or “having” as used in this description specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0036] Various embodiments include an austenitic steam turbine ring segment 52 comprising: a body portion 54 sized to substantially fill a pocket 68 in an outer steam turbine intermediate ring 56, the body portion 54 having a circumferential length greater than an axial depth or a radial width; and a hooked portion 58 extending radially inward from the body portion 54, the hooked portion 58 sized to engage a hooked slot 60 in the outer steam turbine intermediate ring 56, the body portion 58 and the hooked portion 54 forming a unitary structure. LIST OF REFERENCE SYMBOLS: 2 steam turbines 4 Medium pressure (IP) section 6 High pressure (HP) section 7 housings 8 inlets 10 common waves 12 camps 14 Outlet 16 Center line (CL) 20, 22 semi-annular intermediate floor ring segments 24 horizontal connecting surface 30, 32 housing segments 26 turbine guide vanes 28 inner bridge 29 Rotor 40 conventional austenitic ring segments 42 bolt holes 50 steam turbine control system 52 austenitic steam turbine ring segment 54 body section 68 bag 56 outer steam turbine intermediate floor ring 58 hook-shaped section 60 hook-shaped slot 62 recess 64 outer side 66 Lippe 68 bag 70 main pocket 72 first flange 74 second flange 76 flange 78 slot 80 Holding link 82 Opening

Claims

[1] Austenitic steam turbine ring segment (52), comprising: a body portion (54) dimensioned to substantially fill a pocket (68) in an outer steam turbine intermediate ring (56), the body portion (54) having a circumferential length greater than an axial depth or a radial width; and a hook-shaped portion (58) extending radially inwardly from the body portion (54), the hook-shaped portion (58) being dimensioned to engage a hook-shaped slot (60) in the outer steam turbine intermediate base ring (56), wherein the body portion (54) and the hook-shaped portion (58) form a unitary structure which is a structure having no hole therethrough; wherein the pocket (68) and the hook-shaped slot (60) are open in an axial direction along an axis (A) of the austenitic steam turbine ring segment (52), and the body portion (54) and the hook-shaped portion (58) are adapted to mate with the pocket (68) and the hook-shaped slot (60) to enable the austenitic steam turbine ring segment (52) to be coupled to and detached from the steam turbine intermediate base ring (56) in the axial direction. [2] Austenitic steam turbine ring segment (52) according to claim 1, wherein the hook-shaped portion (58) complements the hook-shaped slot (60) in the outer steam turbine intermediate base ring (56). [3] The austenitic steam turbine ring segment (52) of claim 1, wherein the body portion (54) further includes a recess (62) extending partially within a radially outer side (64) of the body portion (54) along the length of the circumference of the body portion (54). [4] Austenitic steam turbine ring segment (52) according to claim 1, wherein the hook-shaped portion (58) comprises: a first flange (72) extending substantially perpendicularly from the body portion (54); and a second flange (74) extending substantially perpendicularly from the first flange (72). [5] The austenitic steam turbine ring segment (52) of claim 4, wherein both the first flange (72) and the second flange (74) are formed from an austenitic material common to the body portion (54). [6] Steam turbine guide device (50), comprising: a turbine housing (7); a semi-annular intermediate base segment (20, 22) having an outer steam turbine intermediate base ring (56), wherein the semi-annular intermediate base segment (20, 22) is at least partially received by the turbine casing (7), wherein the semi-annular intermediate base segment (20, 22) has a horizontal connecting surface (24) and a pocket (68) below the horizontal connecting surface (24), wherein the pocket (68) has a main pocket (70) and at least one hook-shaped slot (60) extending from the main pocket (70), wherein the main pocket (70) and the hook-shaped slot (60) are open in an axial direction along an axis (A) of the semi-annular intermediate base segment (20, 22); and an austenitic steam turbine ring segment (52) connected to the semi-annular intermediate base segment (20, 22), the austenitic steam turbine ring segment (52) comprising: a body portion (54) dimensioned to substantially fill the main pocket (70) in the outer steam turbine intermediate ring (56), the body portion (54) having a circumferential length greater than an axial depth or a radial width; and a hook-shaped portion (58) extending radially inwardly from the body portion (54), the hook-shaped portion (58) being dimensioned to engage the hook-shaped slot (60) in the outer steam turbine intermediate base ring (56), wherein the body portion (54) and the hook-shaped portion (58) form a unitary structure which is a structure having no hole therethrough; wherein the body portion (54) and the hook-shaped portion (58) are adapted to mate with the main pocket (70) and the hook-shaped slot (60) to enable the austenitic steam turbine ring segment (52) to be coupled to and detached from the steam turbine intermediate base ring (56) in the axial direction. [7] Steam turbine nozzle assembly (50) according to claim 6, further comprising a retaining member (80) contacting the austenitic steam turbine ring segment (52), the retaining member (80) at least partially retaining the austenitic steam turbine ring segment (52) in contact with the semi-annular intermediate base segment (20, 22). [8] Steam turbine guide device (50) according to claim 7, wherein the semi-annular intermediate base segment (20, 22) has an opening (82) on a radially outwardly facing surface, and wherein the holding member (80) is at least partially held in the opening (82). [9] Steam turbine guide device (50) according to claim 6, wherein the hook-shaped portion (58) complements the hook-shaped slot (60) in the outer steam turbine intermediate base ring (56).

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