Turbomachine comprising a seal assembly

Abstract

A turbomachine comprising a first component and a second component; wherein; the first component and the second component separate a low-pressure domain and a high-pressure domain from one another; the first component has a first surface facing a second surface of the second component; the first surface comprises a first circular cavity extending around a rotation axis of the turbomachine; the second surface comprises a second circular cavity extending around the rotation axis; the first circular cavity and the second circular cavity face each other and form a circular seat housing a seal assembly (50), the circular seat having a radially inner seat wall and a radially outer seat wall; the seal assembly (50) comprises multiple annular sealing members (51) concentrically stacked and in contact with each other, arranged around the rotation axis of the turbomachine; each annular sealing member (51) having an inner surface and an outer surface, at least the sealing member (51) facing the low-pressure domain is provided with circumferential ridges or corrugations which define contact surfaces with the one of said radially outer seat wall and radially inner seat wall positioned at the side of the low-pressure domain.

Description

A TURBOMACHINE COMPRISING A SEAL ASSEMBLYDESCRIPTIONTECHNICAL FIELD

[0001] The present disclosure generally relates to turbomachines, such as gas turbine engines and expanders. More particularly the disclosure relates to seal assemblies for turbomachines.BACKGROUND ART

[0002] Turbomachines often include adjacent components, i.e. components which are in contact with one another and between which a seal is provided, to prevent gas leakage between mutually contacting surfaces of the components. The components can form part of a turbomachine stator or of a turbomachine rotor. In current art arrangements, the seal is usually in the form of a circular sealing member having a W-shaped cross section, which is positioned within a suitably shaped cavity of one of the adjacent components of the turbomachine. In other known arrangements, the seal arrangement includes a so-called dog bone seal. The seal includes contact surfaces, in sealing contact with both adjacent components, to provide a sealing effect therebetween.

[0003] In some turbomachines, particularly in gas turbine engines or expanders, the seals must withstand high pressure differences across the seal, and high temperature gradients. They must, furthermore, allow relative displacements between the adjacent components, e.g. due to temperature expansions.

[0004] When used in turbomachines operating at high temperature and high pressure differences, W-shaped seals and dog bone seals are subject to stress and creep deformation, adversely impacting seal efficiency.

[0005] One object of the seal assembly disclosed herein is to overcome or alleviate the drawbacks of the seal assemblies of the current art using W-shaped seals, dog bone seals, or the like.SUMMARY

[0006] According one aspect, embodiments disclosed herein relate a turbomachine comprising a first component and a second component. The first component and the second component separate a first-pressure domain, i.e. a first-pressure region, and a second-pressure domain, i.e. a second-pressure region from one another. One of said pressure domains or region is a low-pressure domain and the other is a high-pressure domain. The pressure in the two pressure domains is different, one being higher than the other, such that a seal therebetween must be provided to efficiently prevent or reduce fluid leakages from the high-pressure domain towards the low-pressure domain.

[0007] In the present context the terms “low-pressure domain” or “low-pressure region” and “high-pressure domain” or “high-pressure region” are relative terms, in the sense that the pressure in the “low pressure domain” is lower than the pressure in the “high-pressure domain.

[0008] In embodiments disclosed herein, the first component has a first surface facing a second surface of the second component and the first surface comprises a first circular cavity extending around a rotation axis of the turbomachine. The second surface comprises a second circular cavity extending around the rotation axis. The first circular cavity and the second circular cavity face each other and form a circular seat housing a seal assembly. The circular seat has a radially inner seat wall and a radially outer seat wall. The seal assembly comprises multiple annular sealing members concentrically stacked and in contact with each other, arranged around the rotation axis of the turbomachine; each annular sealing member having an inner surface and an outer surface. At least the sealing member facing the low-pressure domain is provided with circumferential ridges or corrugations which define contact surfaces with the one of said radially outer seat wall and radially inner seat wall positioned at the side of the low-pressure domain.

[0009] In embodiments disclosed herein, each annular sealing member exerts a radi- allv inward or radially outward force by virtue of its geometry. I.e. the annular sealing members are configured such that when the seal assembly is in a mounted condition inside the relevant seat, each sealing member is elastically deformed to generate on the adjacent ring a compression force in a radially outward or radially inward direction,depending on whether the seal action is performed on the radially inner or radially outer seat wall of the seal in which the seal assembly is mounted. The forces of the sealing members sum up and generate a pressure against the respective radially inner or radially outer annular seat wall, against which the seal assembly is pressed to provide its sealing action.

[0010] In some embodiments, each annular sealing member is mechanically separate from the adjacent sealing member(s) and comprises a circular component with at least one radial split extending from the inner surface to the outer surface of the annular sealing member. The radial splits of adjacent annular sealing members are angularly offset from each other around the axis of the seal assembly. In preferred embodiments, the annular sealing members are interconnected to prevent angular displacements between the annular sealing members.

[0011] In other embodiments, the seal assembly comprises a continuous spirally wound strip. Each annular sealing member is formed by a respective turn of the spirally wound strip.

[0012] Further features and embodiments of the turbomachine and of the seal assembly are described below with reference to the attached drawings and are set out in the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Reference is now made briefly to the accompanying drawings, in which:Fig. l illustrates a partial sectional view of an expander including seal assemblies according to the present disclosure, applied to stator components of the expander;Fig.2 illustrates an enlargement of a detail of Fig.2;Fig.3 illustrates an enlargement of three seal assemblies positioned between two stator rings and an inner casing of the expander of Fig.l;Fig.4 illustrates a detailed enlargement of a seal assembly in one embodiment;Figs. 5 and 6 illustrate axonometric sectional views of opposite ends of the annular sealing members of a seal assembly according to Fig.4;Figs. 7, 8, 9 and 10 illustrate schematic side views, along the direction of the rotation axis of the seal assembly of Fig.4 in different embodiments;Figs 11, 12, 13, 14, 15, 16, 17 and 18 illustrate a detailed enlargement similar to Fig.4 of seal assemblies of the present disclosure in alternative embodiments;Fig.19 illustrates a further embodiment of a seal assembly according to the present disclosure;Fig.20 illustrates the use of the seal assembly of Fig.19 in a rotor of a turbomachine; andFig.21 illustrates an enlargement of the detail XXI in Fig.20.

[0014] The figures are not to scale. The dimensions and dimensional relationships of the components shown have been exaggerated for ease of illustration. Specifically, the thickness of the seal-forming strip has been exaggerated with respect to the diagonal dimension thereof, for the sake of clarity of representation.DETAILED DESCRIPTION

[0015] In some embodiments, the seal assembly is positioned between two stator components of a turbomachine. Embodiment of seal assemblies positioned between stator components of a turboexpander is shown in Figs.1-18. In other embodiments, the seal assembly of the present disclosure can be used between rotor components of a turbomachine. An embodiment of the seal assembly applied to rotor components will be described later, referring to Figs. 19-21.

[0016] Fig.1 illustrates a sectional view of one embodiment of an expander 1, including a plurality of seal assemblies according to the present disclosure. The section is taken along a plane containing a rotation axis A-A of the expander. The sectional view shows only half expander, which is substantially axial-symmetrical. The expander of Fig.1 is by way of example only. It shall be understood that the seal assembly disclosed herein can be used in different expanders, i.e. gas turbines, and more in general in turbomachines including stator components, between which a seal assembly is required. As mentioned, in some embodiments, the seal assembly can also be used to provide a sealing action between rotor components, see below.

[0017] In the embodiment of Fig. 1, the expander 1 includes an outer casing 3 and an inner casing 5. The outer casing 3 can include a main body 3 A and a closure 3B on the aft side of the expander. In the exemplary embodiment of Fig.1, the main body 3 Aand the closure 3B are coupled, through respective flanges, along a plane orthogonal to the rotation axis of the expander. In this embodiment, therefore, the outer casing 3 is a so-called vertically split casing. Conversely, in the embodiment disclosed herein, the inner casing 5 is a horizontally split casing.

[0018] This combination of inner horizontally split casing 5 and outer vertically split casing 3 is particularly beneficial in case of a supercritical carbon dioxide expander, or other expanders which process a gas under similar thermodynamic conditions involving high temperature gradients and elevated pressure drops across some at least of the expansion stages.

[0019] Nevertheless, in other embodiments, the novel features disclosed herein can be used in a different expander or turbine structure, for instance including a single casing, or a vertically split inner casing and a horizontally split outer casing, for instance.

[0020] An annular chamber 6 is positioned between the outer casing 3 and the inner casing 5.

[0021] In this embodiment, the expander comprises a combustor. In some embodiments, the combustor can be a can combustor including a plurality of combustion chambers 7. The combustor 7 is positioned at the forward side of the expander.

[0022] As used herein “forward” and “aft” are referred to the direction of flow of the process gas through the expander 1. Therefore, “forward” indicates a position on the side of the combustor chambers 7 and “aft” indicates a position on the side opposite the combustor chambers 7, i.e., the discharge side of the expander 1.

[0023] The expander 1 further comprises a rotor 11 housed in the inner casing 5 and adapted to rotate around the rotation axis A-A. The rotor 11 comprises a rotor shaft 13 and a plurality of annular rows, arrays, or sets of rotor blades. The blades of each array of rotor blades are arranged circumferentially around the rotation axis A-A of the rotor 11.

[0024] An annular row, array, or set of stationary blades, aka stationary vanes, 17 is positioned upstream of each annular array of rotor blades 15. The blades of the annulararrays of stationary blades 17 are circumferentially arranged around the rotation axis A-A.

[0025] Pairs of adjacent stationary blades define respective nozzles which orient the expanding gas in the correct orientation with respect to the downstream annular row or rotor blades 15.

[0026] Each annular array of stationary blades 17 and respective annular array of rotor blades 15 form together a stage of the expander 1.

[0027] In the embodiment shown in Fig. l, all stationary blades 17 of each annular array or set of stationary blades, except those of the last stage, are supported by a respective ring assembly 18. The ring assemblies 18 will be referred to herein after also simply as “rings”. The most downstream annular array of stationary blades 17 is mounted on an aft portion 5B of the inner casing 5. The aft portion 5B of the inner casing is coupled to a main body 5 A of the inner casing 5. The main body 5 A can in turn be formed by a plurality of casing portions. Each casing portion can be split along a plane containing the rotation axis A-A of the rotor 11, i.e., the inner casing 5 is a so- called horizontally split casing.

[0028] The ring assemblies 18 can be centered and locked against rotation in the casing by means of pins, keys or other locking features, to prevent rotation of the ring assemblies 18 during operation of the expander.

[0029] Each annular array of rotor blades 15 is surrounded by a respective shroud 19. In the embodiment of Fig.1, each shroud 19 is supported by a respective one of the above-mentioned ring assemblies, or rings, 18. The unit including the shroud 19 and the ring assembly, or ring, 18 whereto the shroud 19 is coupled and by which the shroud is supported, is referred to herein as a “shroud assembly”. The most upstream ring 18 supports the forward-most annular row of stationary vanes, or stationary blades 17 and does not support the shroud 19 which surrounds the respective most upstream annular row of rotor blades. A separate ring supports the shroud 19 of the first expander stage.

[0030] In the embodiment of Fig.1 the shroud assemblies of all stages, except the first and the last, include respective rings 18, i.e. ring assemblies, which also supportthe respective stationary vanes or stationary blades 17.

[0031] In the exemplary embodiment of Fig.1, some of the ring assemblies 18, i.e. rings 18, can comprise a first ring component and a second ring component. The first ring component and second ring component of the ring assembly 18 are coaxial and are coupled to one another, e.g. by shrink-fitting or interference fitting. In general terms, in embodiments disclosed herein the interface between ring components is formed by matching surfaces, which can be adapted to couple the first ring component and the second ring component to one another by interference-fitting, and more specifically by shrink-fitting. In the enlargement of Fig.2, two rings 18 are shown as formed by two ring components, labeled 18A and 18B, respectively, coupled to one another by shrink-fitting. In other embodiments each ring 18 can be formed monolith- ically, i.e. as a single mechanical piece.

[0032] The rings 18 form a structure which supports the stationary blades 17 and the shrouds 19 and which separates the expansion flow path of the hot expanding gas from the inner casing 5. The expansion flow path extends through the stationary vanes or stationary blades 17 and the rotor blades 15 and is surrounded by the shrouds 19.

[0033] The rings 18 decouple the expansion flow path from the inner casing 5 and form with the latter a gap 61 for a pressurized cooling or purging fluid, between the rings 18 and the inner casing 5. Calibrated flow passages (not shown) can be foreseen in the structure formed by the rings, such that a controlled amount of cooling or purging gas can flow from the pressurized fluid gap towards the expansion flow path.

[0034] A seal assembly can be positioned between mutually contacting stator components of the expander 1. Stator components of the expander 1 include the inner casing 5, the rings 18, the shrouds 19, and the platforms 17A of the stationary blades 17. Seals are omitted in Fig.1. Some seal assemblies 50 positioned between adjacent rings 18, between one ring 18 and the inner casing 5, and between a shroud 19 and the platforms 17 of the adjacent stationary blades 17 are shown by way of example in Fig.2 and are labeled 50. One or more seals 50 can be positioned between each pair of adjacent stator components of the expander 1.

[0035] With continuing reference to Figs. 1 and 2, an exemplary embodiment of threeseal assemblies including respective seals positioned between adjacent stator components is shown in Fig.3.

[0036] Specifically, Fig.3 illustrates a first seal assembly 50A between the inner casing 5 and a first ring 18 supporting a shroud 19, and a second seal assembly 50B between the inner casing 5 and a second ring 18 supporting an array of stationary blades 19. The two rings 18 are in mutual contact and a third seal assembly 50C is positioned therebetween, at the area of contact. A generic seal assembly will be referred herein as seal assembly 50. The various seal assemblies can be identical to one another. Different embodiments of the seal assemblies 50 are described in more detail below. The same expander 1 may comprise seal assemblies which are identical to one another, or which are designed according to two or more of the various embodiments disclosed herein, e.g. based on the operating conditions of the seal assemblies in the various positions inside the expander 1.

[0037] An enlargement of a generic one of said seal assemblies 50 in one embodiment is shown in Fig.4. The components between which the seal assembly 50 is positioned are labeled 18. It shall be understood, however, that the seal assembly 50 can be positioned between different components of the expander 1, as mentioned above.

[0038] In this embodiment, the seal assembly 50 comprises a plurality of annular sealing members 51. The annular sealing members 51 are overlaid concentrically to one another around an axis of the seal assembly, which (when the seal assembly is mounted) coincides with the rotation axis A-A of the expander 1. The annular sealing members 51 are in mutual contact with one another. Each annular sealing member 51 is formed by a circular component, again referred to with reference number 51, having at least one radial split 53 extending from an inner surface to an outer surface of the circular component 51, as best shown in Figs. 7 and 8, wherein the seal assembly 50 is shown in a front view, i.e. in a view according to the direction of the axis A-A.

[0039] Each sealing member 51 is thus formed by at least one strip of suitable material, e.g. a metal strip, which is shaped as a radially split ring body, having the two opposite ends of the strip which face each other and which are abutting one against the other and form the radial split 53.

[0040] The opposite ends of the strips, which form the annular sealing members 51, are best shown in an axonometric view in Figs. 5 and 6.

[0041] To prevent gas leakages through the seal assembly 50, the radial splits 53 of adjacent, i.e. consecutive annular sealing members 51 are angularly staggered from one another around the axis A-A. In Fig. 7 the radial splits 53 of two adjacent sealing members 51 are angularly offset from one another by an angle a.

[0042] The annular sealing members 51 are interconnected to prevent angular relative displacements of one sealing member 51 with respect to the others. In one embodiment (Fig.7) each pair of adjacent, i.e. radially consecutive, sealing members 51 are interconnected by a respective coupling feature 54. Each coupling feature 54 can include a rivet, a pin, a peg, or similar mechanical coupling device.

[0043] In other embodiments (Fig.8) a single coupling feature 54 connects all annular sealing members 51 together.

[0044] While in Figs. 7 and 8 each annular sealing member 51 is monolithic, i.e. is formed by a single strip configured in a circular shape with abutting ends 51 A, 5 IB (see Figs. 5 and 6) forming the radial split 53, in other embodiments each sealing member 51 can include more than one strip, each strip forming a portion of the annular sealing member 51 and the ends of two successive portions of the annular sealing member 51 forming a respective radial split 53.

[0045] For example, in the exemplary embodiment of Fig.9, each annular sealing member 51 is comprised of two portions, each portion covering an angle of 180°, and each annular sealing member 51 comprising two radial splits 53. In the exemplary embodiment of Fig. 10, each annular sealing member 51 is comprised of four portions, each portion covering an angle of 90°, and each annular sealing member 51 comprising four radial splits 53.

[0046] Figs. 4, 5 and 6 illustrate how the seal assembly 50 is mounted in the turbomachine 1.

[0047] Specifically, in the exemplary embodiments of Figs. 4, 5 and 6, each seal assembly 50 is housed in a seat 55 formed between mutually contacting stationarycomponents 18. The seat 55 comprises two mutually facing seat portions 55X, 55 Y. Each seat portion is in the shape of an annular groove or circular cavity, i.e. in the shape of an annular recess. Each seat portion is formed in a respective one of the two abutting stator components, between which the seal assembly 50 is positioned.

[0048] As best shown in Fig.4, the two stationary components 18, between which the seal assembly 50 is positioned, are in contact with one another at respective first contact surface 18X, belonging to one of the two stationary components 18, and second contact surface 18Y, belonging to the other of the two stationary components 18. The first seat portion 55X is machined along the first contact surface 18X and the second seat portion 55 Y is machined along the second contact surface 18Y. In the assembled condition, the opposing seat portions 55X and 55Y form in combination the seat 55, which develops circumferentially around the rotation axis A-A of the expander 1. The seal assembly 50 is housed in the seat 55, and specifically partly in the seat portion 55X and partly in the seat portion 55Y.

[0049] In some embodiments, not shown, the first seat portion 55X and the second seat portion 55 Y can be formed respectively along a first surface of the first turbomachine component and along a second surface of the second turbomachine components, which face each other but which are not in mutual contact, or only partially in mutual contact.

[0050] With this arrangement, the seal assembly 50 spans across a plane P-P, which represents the interface between the stator components 18, between which the seal assembly 50 is housed. The plane P-P can be orthogonal to the rotation axis A-A. The seal assembly 50 provides a sealing action between the two stator components 18 along the plane P-P, preventing or reducing leakages from a first pressure domain to a second pressure domain, which are separated by the two stator components 18 in mutual contact with one another along the plane P-P.

[0051] In Figs. 4, 5 and 6, the two stator components are by way of example abutting rings 18. As noted above, however, the same seal assembly 50 can be used between different stator components of the expander 1, e.g. a ring 18 and the inner casing 5, or a ring 18 and a shroud 19, or else a shroud 19 and the platforms 17A of an annular array of stator blades 17. In all cases, the two stator components, between which theseal assembly 50 is positioned, separate a first pressure domain from a second pressure domain. The first pressure domain and the second pressure domain are characterized by the presence of a fluid medium, in particular a gaseous medium, at different pressures. The seal assembly 50 forms a barrier against fluid leakages from the domain at higher pressure towards the domain at lower pressure.

[0052] While in the illustrated embodiment the seal assembly 50 is positioned between two stator components, in other embodiments, the seal assembly 50 can be positioned between two rotor components of the turbomachine.

[0053] The seat 55 formed by the two facing portions 55X, 55 Y has a radially inner seat wall 57, i.e. a radially inner seat surface facing away from the rotation axis A-A of the turbomachine. Moreover, seat 55 formed by the two facing portions 55X, 55 Y has a radially outer seat wall 59, i.e. a radially outer surface facing towards the rotation axis A-A of the turbomachine. The radially inner seat wall 57 and the radially outer seat wall 59 are cylindrical and are coaxial to the axis A-A of the expander or turbomachine.

[0054] The radially innermost sealing member 51 of the seal assembly 50 is in surface contact with the radially inner seat wall 57. Specifically, the radially innermost sealing member 51 comprises a radially inner surface in surface contact with the radially inner seat wall 57, and a radially outer surface in contact with the adjacent sealing member 51. The radially outermost sealing member 51 of the seal assembly 50 comprises a radially outer surface in surface contact with the radially outer seat wall 59, and a radially inner surface in contact with the outer surface of the adjacent annular sealing member 51.

[0055] In some embodiments, at least one of the inner surface and outer surface of said annular sealing members comprises circumferential ridges extending around the axis A-A of the seal assembly 50. The ridges of the outermost or innermost sealing member 51 define contact surfaces with the radially outer seat wall 59 or with the radially inner seat wall 57. In some embodiments, at least the sealing member facing the low-pressure domain is provided with circumferential ridges or corrugations.

[0056] Specifically, in the embodiment of Figs. 4, 5 and 6, each annular sealingmember 51 has a corrugated cross-sectional shape, including crests and valleys. The crests on the radially inner surface of each annular sealing member 51 nests into valleys on the radially outer surface of the adjacent sealing member 51. The crests on the inner surface of the radially innermost annular sealing member 51 are in surface contact with the radially inner seat wall 57, while the crests on the outer surface of the radially outermost annular sealing member 51 are in surface contact with the radially outer seat wall 59.

[0057] The corrugated cross-sectional shape of the annular sealing members 51 define reduced areas of contact with the radially inner wall 57 and / or with the radially outer wall 59 of the seat 55, where a concentrated contact pressure is generated by a pressure difference between the radially inner seat wall 57 and radially outer seat wall 59. The concentrated contact pressure increases the efficiency of the seal assembly 50.

[0058] For instance, in the embodiment of Fig.4, if the pressure on the radially outer side of the seal assembly 50 is higher than the pressure on the radially inner side of the seal assembly 50, the ridges or crests on the inner surface of the radially innermost annular sealing member 51 are pressed along lines P against the radially inner wall 57 of the seat 55. The pressure difference generates a concentrated force of contact at lines P, which provides enhanced sealing action.

[0059] Alternative embodiments of annular sealing members 51 having a corrugated cross-sectional shape are shown in Figs. 11, 12, 13, 15, 16 and 17. In these figures, where the same reference numbers of Fig.4 are used to designate the same or equivalent elements, references Pl and P2 indicate the pressure at the opposite (radially inner and radially outer) sides of the seal assembly 50, wherein P1>P2.

[0060] The shape of the corrugated annular sealing members 53 depends on the orientation of the pressure difference, i.e. on which side is the high-pressure side and which side is the low-pressure side. In some embodiments, the shape of the corrugated sealing members 53 is such that crests extending circumferentially around axis A-A of the annular sealing members 51 are positioned at a distance from the plane P-P, along which the respective components 18 are in mutual contact. Specifically, at least one annular ridge or crest is positioned on a left side of the plane P-P and at least one ridge or crest is positioned on the right side of the plane P-P.

[0061] This arrangement ensures that at least one crest or ridge on each side of the plane P-P is pressed by the pressure difference across the seal assembly 50 against the respective surface of the seat 55 in which the seal assembly is mounted, thus providing efficient sealing between the two components 18.

[0062] In alternative embodiments, each annular sealing members 51 can have a cross section with a flat side and a corrugated or wavy side, as shown in Figs. 14 and 18. In Fig. 14, the corrugated side of the cross section of each annular sealing member 51 is the radially inner side, i.e. the side facing the low-pressure domain (P2) . In Fig.18, the corrugated side of the cross section of each annular sealing member 51 is the radially outer side and the low-pressure domain (P2) is located radially outside the seal assembly.

[0063] In all embodiments of Figs. 4, 11, 12, 13, 14, 15, 16 17 and 18 circular ridges or crests are located on the left and on the right side of the plane P-P along which the components 18 match each other and are positioned on the radially inner or radially outer side of the seal assembly, depending on which side of assembly 50 is the high- pressure side. Specifically, the ridges are on the low-pressure side (pressure P2) of the seal assembly 50, to provide enhanced pressure contact sealing, the contact pressure being generated by the pressure difference across the seal assembly 50.

[0064] The number of the annular sealing members 51, the thickness thereof and their shape can be selected based on the operating conditions of the seal assembly 50, in particular based on the temperature and pressure across and around the seal assembly 50.

[0065] In all embodiments, the annular sealing members 51 are subject to reduced stress and deformation, compared to W-shaped seal assemblies of the prior art, for instance, such that their life time is much longer than that of W-shaped seals of the current art.

[0066] Figs.19, 20 and 21 illustrate a further embodiment of a seal assembly according to the present disclosure. In this embodiment, the seal assembly is labeled 100. The seal assembly 100 comprises a single strip 102 wound in a spiral, forming a plurality of overlapping turns 104, in mutual contact with one another. A first end 106 of thespirally wound strip 102 is positioned on the radially innermost surface of the seal assembly 100. A second end 108 of the spirally wound strip 102 is positioned on the radially outermost surface of the spirally seal assembly 100.

[0067] Each turn 104 of the spirally wound strip forms an annular sealing member. Thus, in this case the seal assembly 100 is formed by a single mechanical member (strip 102), which forms a plurality of annular sealing member 104, each represented by a respective turn 104 of the spiral. Each sealing member comprises an outer surface 104Y and an inner surface 104X. The outer surface of each sealing member 104 (turn), except the most external one, is in contact with the inner surface of the next sealing member 104 (turn) surrounding it. The inner surface of each sealing member 104, except the most internal one, is in contact with the outer surface of the adjacent sealing member 104 surrounded thereby.

[0068] The strip 102 which forms the seal assembly 100 can be corrugated, i.e. can provide a fluted or wavy shape.

[0069] The cross-sectional shape of the seal assembly 100 in one embodiment is best shown in Fig. 21. The cross section of Fig.21 is taken along a radial plane containing the axis A-A around which the strip forming the seal assembly 100 is wound. When the seal assembly 100 is mounted in a turbomachine, the axis A-A of the seal assembly 100 coincides with the rotation axis of the turbomachine. As shown in Fig. 21, the spirally wound strip 102 has a corrugated shape. In other embodiments the cross-sectional shape of the strip 102 can be configured as shown in Figs. 4, 11-18.

[0070] Fig.20 illustrates the seal assembly 100 applied to a section of a turbomachine rotor, e.g. an expander rotor. Thus, in this exemplary embodiment the seal assembly 100 provides a seal between two rotor components in mutual contact with one another. In other embodiments, the seal assembly 100 can be positioned between mutually contacting stator components, as described above with respect to seal assembly 100.

[0071] In Fig.20 a rotor disk 107 and a sealing disk 109 of the turbomachine rotor are schematically shown. Specifically, Fig.20 illustrates only half sectional view of the disks taken along a sectional plane containing the rotation axis A-A of the rotor. The seal assembly 100 is positioned between the rotor disk 107 and the seal disk 109 in aposition where seal against leakages of expanding process gas towards an inner cavity 111 of the rotor is required.

[0072] Specifically, in some embodiments, the seal assembly 100 is housed in a seat 115 formed between mutually contacting stationary components 107, 109. The seat 115 is formed by two mutually facing seat portions 115X, 115Y, each seat portion being shaped as an annular groove or circular cavity, i.e. in the shape of an annular recess. Each seat portion is formed in a respective one of the two abutting rotor components 107, 109, between which the seal assembly 100 is positioned.

[0073] As best shown in Fig.21, the two rotor components 107, 109 are in contact with one another at respective first contact surface 107X belonging to the rotor disk 107, and second contact surface 109X, belonging to the sealing disk 109. The seat portion 115X is machined along the first contact surface 107X and the second seat portion 115Y is machined along the second contact surface 109X. In the assembled condition, the opposing seat portions 115X and 115Y form in combination the seat 115, which develops circumferentially around the rotation axis A-A of the rotor. The seal assembly 100 is housed in the seat 115, and specifically partly in the seat portion 115X and partly in the seat portion 115Y.

[0074] In some embodiments, not shown, the first seat portion 115X and the second seat portion 115Y can be formed respectively along a first surface of the first turbomachine component and along a second surface of the second turbomachine components, which face each other but which are not in mutual contact, or only partially in mutual contact.

[0075] With this arrangement, the seal assembly 100 spans across a plane P-P, which represents the interface between the rotor disk 107 and the sealing disk 109, between which the seal assembly 100 is housed. The plane P-P can be orthogonal to the rotation axis A-A. The seal assembly 100 provides a sealing action between the two rotor components 107, 109 along the plane P-P, preventing or reducing leakages from a first pressure domain positioned radially outwardly of the seal assembly 100 to a second pressure domain, positioned radially inwardly of the seal assembly 100. Ridges, flutes or corrugations, as described with respect to the embodiments of Figs.3-19 can be positioned at both sides of the plane P-P, on the side of the seal assembly 100 facing thelow-pressure domain, to provide enhanced sealing action, as described above.

[0076] Regardless of whether the annular sealing members are formed by successive turns of a spirally wound strip or are configured as discrete annular strip segments, each annular sealing member is formed from an elastic material and, in its free (i.e., unmounted) state, exhibits a diameter that differs from the diameter it assumes in a mounted or installed condition.

[0077] Specifically, when the low-pressure domain, i.e. the region at lower pressure is disposed radially inward of the high-pressure domain, i.e. the region at higher pressure, the sealing members in their free state have a diameter that is smaller than their mounted diameter.

[0078] Conversely, when the low-pressure domain, i.e. the region at lower pressure is disposed radially outward of the high-pressure domain, i.e. the region at higher pressure, the sealing members in their free state have a diameter that is greater than their mounted diameter. In this way the elastic deformation caused by the installation generates a contact pressure between the seal arrangement and the respective wall of the seat on the low-pressure domain.

[0079] Referring to the previously described figures, for example, in the embodiment of Fig.4, where the radially inner wall or surface 57 of the seat 55 is adjacent the low- pressure domain, the seal assembly is produced with an inner diameter which is smaller than the diameter of the radially inner wall or surface 57. When mounted in the seat 55, the annular seal arrangement is elastically expanded and the annular sealing members thereof generate a pressure contact force along ridges (at P). A similar condition is provided in Figs. 11, 12, 13 and 14. An opposite condition is provided in Figs. 15, 16, 17 and 18, where the seal assembly expands elastically against the outer wall or outer surface 59 of the seat 55, which in this case is oriented towards the low-pressure domain.

[0080] In general, when installed the seal assembly is pre-loaded such as to generate a contact pressure against one of the radially inner wall or radially outer wall of the seat and specifically against that one of said walls which is on the side of the low- pressure domain.

[0081] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS1. A turbomachine comprising a first component and a second component; wherein; the first component and the second component separate a low-pressure domain and a high-pressure domain from one another; the first component has a first surface facing a second surface of the second component; the first surface comprises a first circular cavity extending around a rotation axis of the turbomachine; the second surface comprises a second circular cavity extending around the rotation axis; the first circular cavity and the second circular cavity face each other and form a circular seat housing a seal assembly, the circular seat having a radially inner seat wall and a radially outer seat wall; the seal assembly comprises multiple annular sealing members concentrically stacked and in contact with each other, arranged around the rotation axis of the turbomachine; each annular sealing member having an inner surface and an outer surface, at least the sealing member facing the low-pressure domain is provided with circumferential ridges or corrugations which define contact surfaces with the one of said radially outer seat wall and radially inner seat wall positioned at the side of the low-pressure domain.

2. The turbomachine claim 1, wherein the radially inner seat wall and the radially outer seat wall are cylindrical and coaxial to the axis A-A of the expander or turbomachine.

3. The turbomachine of claim 1 or 2, wherein at least one of said ridges or corrugations positioned in the first circular cavity and at least one of said ridges or corrugations is positioned in the second circular cavity.

4. The turbomachine of any one of claims 1 to 3, wherein each one of said annular sealing members comprises circumferential ridges or corrugations at leaston the respective side facing the low-pressure domain.

5. The turbomachine of any one of claims 1 to 4, wherein each annular sealing members have a cross section with a corrugated shape forming circumferentially developing crests and valleys on the outer surface and inner surface thereof; and wherein the annular sealing members are overlaid with one another such that the crests of the outer surface of each annular sealing member are nested into valleys of the inner surface of the adjacent annular sealing member.

6. The turbomachine of any one of claims 1 to 5, wherein each annular sealing member comprises a circular component with at least one radial split extending from the inner surface to the outer surface of the annular sealing member; wherein radial splits of adjacent annular sealing members are angularly offset from each other around the axis of the seal assembly.

7. The turbomachine of claim 6, wherein the annular sealing members are interconnected to prevent angular displacements between the annular sealing members.

8. The turbomachine of any one of claims 1 to 7, wherein at least one of said annular sealing members comprises a single ring body with a single radial split.

9. The turbomachine of any one of claims 1 to 5, wherein the seal assembly comprises a continuous spirally wound strip, and wherein each annular sealing member is formed by a respective turn of the spirally wound strip.

10. The turbomachine of any one of the preceding claims, wherein the first surface of the first component and the second surface of the second component are in contact with one another.

11. The turbomachine of any one of the preceding claims, wherein the first component and the second component are stator components of the turbomachine.

12. The turbomachine of any one of the preceding claims, wherein thefirst component is a casing of the turbomachine.

13. The turbomachine of any one of the preceding claims, wherein the first component is a ring which supports at least one of: an annular array of stationary blades, and a shroud surrounding an annular array of rotary blades of a rotor of the turbomachine.

14. The turbomachine of any one of the preceding claims, wherein the second component is a ring which supports at least one of: an annular array of stationary blades, and a shroud surrounding an annular array of rotary blades of a rotor of the turbomachine.

15. The turbomachine of any one of the preceding claims, wherein the first component is a shroud surrounding an array of rotor blades and the second component is an array of platforms of stationary blades.

16. The turbomachine of any one of claims 1 to 9, wherein the first component and the second component are rotor components of the turbomachine.

17. The turbomachine of any one of the preceding claims, wherein the seal assembly is pre-loaded such as to generate a contact pressure against the one of said radially inner wall and radially outer wall of the seat.

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