Turbomachine comprising stationary vanes with single hooks

Abstract

A fixed blade (17) component for an expander (1) of a turbine is disclosed, the fixed blade component comprising an outer platform (71), which in turn includes a radially outer surface (71.1), a radially inner surface (71.2), a leading edge (71.3), a trailing edge (71.4), and a mechanical coupling feature adapted to mechanically attach the outer platform to a support structure (18) of the turbine. The fixed blade component also includes at least one airfoil (75) extending from the radially inner surface of the outer platform and including a leading edge (75.1) and a trailing edge (75.2). The mechanical coupling feature includes a single front hook (77) projecting from the radially outer surface of the outer platform and oriented toward the trailing edge (71.4) of the outer platform.

Description

Technical Field

[0001] Exemplary embodiments of this disclosure relate to turbines. Specifically, the embodiments disclosed herein relate to power generation turbines, i.e., expanders or turbines. The embodiments disclosed herein are particularly applicable to supercritical CO2 expanders. As understood herein, a supercritical CO2 expander is an expander in which the working fluid mainly or almost entirely contains carbon dioxide and in which the carbon dioxide is under supercritical conditions in at least a portion of the flow path. Background Technology

[0002] A turbine or expander includes a combustor that ignites a pressurized gas mixture containing fuel and oxidizer. The resulting pressurized flow of the hot combustion gas expands in an expansion flow path comprising one or more expansion stages. Each expansion stage includes at least one annular row or array of fixed guide vanes (also called fixed blades) and an annular row or array of rotor blades that form part of the turbine rotor and are arranged to rotate within the turbine housing.

[0003] In some expanders or turbines, at least one fixed guide vane or fixed blade of the expansion stage is cantilevered and supported by a support member, such as a ring mounted in the turbine housing. One or more fixed guide vanes or guide vane components typically include an arcuate outer platform from which one or more airfoils forming the actual fixed blade or guide vane project radially inward (i.e., toward the rotor's axis of rotation). Typically, the innermost end of the airfoil is coupled to an arcuate inner platform, which forms part of the fixed guide vane component. The fixed guide vane component, including the outer platform, airfoils, and the inner platform attached thereto, experiences high thermal and mechanical stresses as it faces the expansion flow path and is therefore in contact with the expanding flow of hot and pressurized combustion gases.

[0004] A major concern regarding the combustion of fossil fuels involves the production of carbon dioxide, a greenhouse gas considered one of the main causes of global warming and climate change.

[0005] In recent years, thermal cycles have been developed to reduce the environmental impact of power generation cycles using fossil fuels. To this end, post-combustion capture (PCC) options have been investigated. PCC capture facilities have been developed to treat flue gas from gas turbines and remove CO2 from it before it is released into the environment. The cost of PCC capture facilities is high in terms of both CAPEX and the energy required to operate them, which reduces the overall thermodynamic efficiency of the system. The percentage of CO2 in the flue gas is low. This necessitates processing large volumes of flue gas through PCC capture facilities, making the capture process particularly inefficient.

[0006] In recent years, the oxy-fuel cycle (also known as the oxy-fuel cycle) has been developed, in which fuel (such as natural gas) is blended under high pressure into a mixture of oxidant consisting mainly of oxygen (O2) and carbon dioxide (CO2). The blend of fuel, oxygen, and carbon dioxide is burned in the burner of an expander, producing pressurized combustion gases consisting only or almost only of carbon dioxide and water.

[0007] Combustion gases expand in an expander or turbine to generate mechanical power, which can ultimately be converted into electrical power by a generator driven by the expander or used for mechanical driving purposes. The exhaust gases (i.e., flue gas) exiting the expander are cooled in a regenerative heat exchanger and further refrigerated into condensate, which is removed from the cooled flue gas. The majority of the low-temperature flue gas, mainly or solely composed of carbon dioxide, is pressurized and recirculated through the regenerative heat exchanger toward the expander's burner. The remaining portion of the flue gas is removed, and any carbon dioxide it contains is captured.

[0008] The oxygen supplied to the expander's combustor can be obtained by separating nitrogen from ambient air, resulting in a working fluid primarily composed of oxygen and carbon dioxide, excluding nitrogen. The resulting combustion gas is nitrogen-free and has a significantly higher percentage of carbon dioxide than combustion gas from a standard gas turbine cycle. This higher percentage of carbon dioxide in the combustion gas makes carbon capture more efficient and cheaper.

[0009] Oxygen-fuel cycles (such as those described above) are particularly promising in terms of efficiency, reduction of harmful emissions, and efficient carbon capture. However, oxygen-fuel cycles operate under supercritical CO2 conditions at the inlet of the expander and are characterized by elevated pressure and temperature values, as well as high pressure drops in each stage of the expander and strong temperature gradients across machine components facing the expansion flow path.

[0010] These key aspects affect the fixed guide vanes or blades of the expander and the structures supporting them. Specifically, the fixed guide vanes or blades experience high thermal gradients and require a degree of flexibility to accommodate the relative displacements of the expander's stationary components caused by thermal expansion and mechanical loads during operation. Conversely, mechanically connected features (such as ribs or hooks) on the outer surface of the arcuate platform require enhanced stiffness, thereby reducing the platform's flexibility, as the fixed blades protrude radially from this outer surface toward the expander's axis of rotation. This increases thermally induced stress, particularly in expanders that include burners. These aspects become particularly challenging in supercritical CO2 expanders, where pressure drops are especially high, and more specifically in supercritical CO2 expanders that include burners, where thermal gradients are high.

[0011] The purpose of the embodiments disclosed herein is to provide an improved design for fixed guide vanes or blades and their associated support structures for expanders, which are particularly suitable for expanders or turbines characterized by critical pressure and temperature conditions. Summary of the Invention

[0012] According to one aspect, this document discloses a fixed blade assembly for a turbine, the fixed blade assembly comprising an outer platform, the outer platform further comprising: a radially outer surface, a radially inner surface, a leading edge, a trailing edge, and a mechanically connected feature adapted to mechanically attach the outer platform to a support structure of the turbine. The fixed blade assembly also includes at least one airfoil extending from the radially inner surface of the outer platform and including a leading edge and a trailing edge. The mechanically connected feature includes a front hook projecting from the radially outer surface of the outer platform and oriented toward the trailing edge of the outer platform, i.e., toward the trailing edge of the airfoil forming the corresponding fixed blade of the fixed blade assembly.

[0013] In practical implementations, each fixed blade component has a single hook, instead of the two hooks typically provided in the prior art. The single hook is positioned midway between the leading and trailing edges of the outer platform, preferably closer to the leading edge, and oriented in a rearward direction. In some implementations, the single hook may be discontinuous in the tangential direction. This is particularly likely if the fixed blade component comprises more than one fixed blade or guide vane and therefore has a significant extension in the tangential direction (i.e., in the circumferential direction around the turbine axis).

[0014] Therefore, compared with the design of the prior art, the radial dimension of the rear part of the fixed blade component is reduced, which reduces the thermal stress in the fixed blade component and improves its service life.

[0015] Furthermore, the installation of the fixed blade components on the support structure is faster and simpler.

[0016] The front hook can be positioned midway between the front and rear edges of the outer platform. In some embodiments, the outer platform includes a rib that projects radially outward from its radially outer surface and forms a resting surface adapted to rest against a turbine support structure. The rib can be positioned at the rear edge of the outer platform, or between the rear edge of the outer platform and the front hook.

[0017] According to another aspect, an expander is disclosed herein, comprising: at least one annular array of fixed blade components housed within a housing; and a rotor housed within the housing for rotation therein. The fixed blade components of the annular array are mounted on at least one corresponding support structure housed within the housing. Each fixed blade component includes an outer platform, which in turn includes: a radially outer surface, a radially inner surface, a leading edge, and a trailing edge. Each fixed blade component further includes: at least one airfoil extending radially from the radially inner surface of the outer platform toward the axis of rotation of the rotor; and a front hook projecting from the radially outer surface of the outer platform and oriented toward the trailing edge of the outer platform; wherein each front hook engages in a circular groove formed in an annular surface of the corresponding support structure, the circular groove having a forward opening for insertion of the front hook.

[0018] Unlike prior art fixed blade components, each fixed blade component according to this disclosure includes a single hook oriented in a rearward direction, adapted to engage an annular slot formed in the turbine's support structure. The single hook is positioned midway between the front and rear extensions of the platform, near its leading edge, for example, in the middle between the leading and rear edges. No rear hook is provided. Therefore, assembling the fixed guide vane component or fixed blade component is much easier and faster than with prior art turbines. Furthermore, the fixed blade component can have an optimal shape in terms of thermal stress.

[0019] Specifically, the design disclosed in this paper reduces the radial extension of the rear rib radial height, thereby improving the nozzle sector life; 2) the nozzle sector is assembled along the longitudinal engine axis. Attached Figure Description

[0020] Now, please briefly refer to the attached diagram, in which:

[0021] Figure 1 A cross-sectional view of an expander in one embodiment is shown;

[0022] Figure 2 Examples Figure 1 Magnified details;

[0023] Figure 3 A cross-sectional view of an expander according to another embodiment is illustrated; and

[0024] Figure 4 Examples Figure 3 The magnified portion. Detailed Implementation

[0025] Figure 1A cross-sectional view of one embodiment of the expander 1 according to this disclosure is shown. The section is taken along a plane containing the axis of rotation AA of the expander. The cross-sectional view shows only half of the expander that is axially symmetrical.

[0026] Expander 1 includes an outer housing 3 and an inner housing 5. The outer housing 3 may include a main body 3A and a closure 3B on the rear side of the expander. The main body 3A and the closure 3B are connected by corresponding flanges along a plane orthogonal to the axis of rotation of the expander. Therefore, in this embodiment, the outer housing 3 is a so-called vertically separated housing.

[0027] The burner (such as a canister burner comprising multiple combustion chambers 7) is positioned in front of the expander 1, upstream of the fixed guide vanes or blades of the first annular row. The annular chamber 6 is positioned between the outer casing 3 and the inner casing 5.

[0028] As used herein, “front” and “back” refer to the flow direction of the process gas through expander 1. Therefore, “front” indicates the position on the burner chamber 7 side, and “back” indicates the position on the side opposite to burner chamber 7 (i.e., the discharge side of expander 1).

[0029] The expander 1 also includes a rotor 11, which is housed within an inner casing 5 and adapted to rotate about a rotation axis AA. The rotor 11 includes a rotor shaft 13 and multiple annular rows, arrays, or groups of rotor blades. Figure 1 In an exemplary embodiment, rotor 11 includes eight annular arrays of rotor blades. Each array of rotor blades comprises rotor blades arranged circumferentially about a rotation axis AA of rotor 11. The rotor blades are designated 15.j, where j indicates the position of the array in the front-to-back direction. Specifically, the rotor blades of the first annular array are designated 15.1, the rotor blades of the last annular array are designated 15.8, and the blades of the j-th array are designated 15.j. As used herein, reference numeral 15 refers to a rotor blade in a general annular array of rotor blades.

[0030] Fixed blades in annular arrays or groups are positioned upstream of rotor blades 15.j in each annular array. The blades in the fixed blades of the annular array are designated 17.j and are arranged circumferentially around the axis of rotation AA. As will be explained in more detail below, each blade in the fixed blades of the annular array forms part of a fixed blade component. Thus, the fixed blades of each annular array comprise a set (i.e., an array) of fixed blade components arranged annularly (i.e., circumferentially).

[0031] The fixed blades are also referred to as guide vanes. Each pair of adjacent fixed blades or guide vanes defines a corresponding nozzle, which orients the expanding gas in the correct orientation relative to the downstream annular stack or rotor blades 15.

[0032] More specifically, the blades in the fixed blades of the upstream annular array are labeled 17.1, and the blades in the fixed blades of the downstream array are labeled 17.8. Generally, the blades in the fixed blades of the j-th annular array are labeled 17.j. As used herein, reference numeral 17 refers to a fixed blade in a general array. As used herein, "upstream" and "downstream" refer to the flow direction of the flue gas through the expander 1.

[0033] In the implementation scheme, the fixed blades or guide vanes are formed by or include airfoils that are coupled to the respective internal and external platforms, as will be described in more detail below.

[0034] Generally, an outer platform, an inner platform (if present), and one or more airfoils extending radially inward from the outer platform form a fixed blade assembly. Therefore, the fixed blades of each annular array comprise a fixed blade assembly arranged in an annular (i.e. circular) array around the rotation axis of the expander 1.

[0035] As will be explained in more detail below, a fixed blade assembly may include one or more airfoils, i.e., one or more blades, that are rigidly connected to an external platform. Fixed blade assemblies that include one, two, or three airfoils integrally formed with an external platform (and an internal platform (if present)) are generally referred to as “single,” “double,” or “triple,” respectively.

[0036] The fixed blades 17.j of each annular array and the rotor blades 15.j of the corresponding annular array together form the stage of the expander 1.

[0037] The fixed blade 17 is housed within the inner housing 5. As will be described in more detail below, the fixed blade 17 in one, some, or each annular array is not directly mounted to the inner housing 5, but is mounted on at least one corresponding ring, or on a pair of adjacent rings. In some embodiments, at least one fixed blade of an expansion stage may be directly connected to the housing 5, for example, as... Figure 1 The last expansion stage is shown in the diagram.

[0038] exist Figure 1 In this embodiment, the annulus becomes a component mechanically separable from the housing and can be held non-rotating by a suitable locking pin (not shown) and non-axially displaced by a suitable axially adjacent portion, such as... Figure 1 As shown. The novel features relating to the way the fixed blades or guide vanes, more specifically the fixed blade components, are mechanically connected to the support structure inside the housing can also be used in combination with other support structures, such as a support ring integral with the housing or a part thereof.

[0039] In the embodiments disclosed herein, the expander includes an inner shell 5 and an outer shell 3. Specifically, the inner shell 5 is a horizontally separated shell, and the outer shell 3 is a vertically separated shell. This is particularly advantageous in the case of supercritical carbon dioxide expanders or other expanders that process gases under similar thermodynamic conditions involving high pressure drops across at least some of the expansion stages and processing gases with high heat transfer coefficients that determine high temperature gradients. However, in other embodiments, novel features related to the manner in which the fixed guide vane components or fixed blade components are coupled to the support structure may be used in different expander structures, such as including a single shell, or, for example, a vertically separated inner shell and a horizontally separated outer shell.

[0040] Now go to Figure 1 In the embodiment shown in the figure, all the fixed blades 17 in each annular array or group of fixed blades, except for those in the first and last stages, are supported by a corresponding single ring. The ring is labeled 18.

[0041] exist Figure 1 In the implementation scheme, each ring can be a single ring, that is, it can be a whole and unfolded around 360°.

[0042] In some embodiments, each ring 18 may be divided into two ring components, each extending approximately 360°, and the ring components are coaxial with each other. The ring components may be connected and constrained to each other, for example, by interference fit or shrink fit.

[0043] The first-stage fixed blades are supported by radial outer and radial inner rings. More specifically, each ring is designated 18.j (where j = 1-7). As used herein, reference numeral 18 refers to a general ring. Fixed blades 17.j (where j = 1-7), and more precisely, each fixed blade component, which is a part of the fixed blade, are mounted on the corresponding ring 18.j. The fixed blades 17.8 of the most downstream annular array are mounted on ring 18.8, which forms part of the rear portion 5B of the inner housing 5, i.e., directly mounted on a part of the housing itself. Thus, the housing itself has a support structure (e.g., in the form of a groove) for fixing the blade components. This arrangement of support structures excluding the rings inside the housing simplifies the overall structure of the expander and is particularly useful in the most downstream expander stages, where thermodynamic conditions (pressure and temperature) are less critical. The rear portion 5B of the inner housing is connected to the body 5A of the inner housing 5. The body 5A can then be formed from multiple housing portions. Each housing section can be separated along the plane containing the rotation axis AA of the rotor 11, that is, the inner housing 5 is a so-called horizontally separated housing.

[0044] In the contact area between adjacent rings or between a ring and the housing, a fixed seal (not shown) may be positioned to prevent, limit, or control the amount of cooling or purging gas leaking through the contact surfaces.

[0045] Each annular array of rotor blades 15.j is surrounded by a corresponding shroud. The shrouds are labeled 19.1, ..., 19.j, 19.8. Figure 1 In one embodiment, shields 19.2 to 19.7 are each supported by a corresponding ring 18, on which a fixed blade directly positioned upstream of the shield is mounted. Thus, shield 19.j is mounted on ring 18.j, which supports the annular array of fixed blades 17.j and more precisely supports the corresponding fixed blade components, where the fixed blades form part of these fixed blade components, and j = 2 to 7.

[0046] exist Figure 1 In one embodiment, the first shroud 19.1 surrounding the rotor blades 15.1 of the first (i.e., the most upstream) annular array is supported by an auxiliary ring 18.0, which does not support any fixed blades and is positioned between the first ring 18.1 and the second ring 18.2.

[0047] Ring 18 forms a structure that surrounds and supports the fixed blades 15 and the shroud 19, and this structure separates the flow path of the thermally expanding gas from the inner shell 5. As mentioned, the first-stage fixed blades are also supported by the inner ring. As will be explained in more detail below, rings 18 are configured such that they transmit only the axial reaction force generated by the hot gas expanding along the flow path to the inner shell 5. This design of the support structure (which prevents the transmission of radial reaction force between the ring and the shell) allows for different thermal expansion on one side of the ring and on the other side of the shell, which is determined by a thermal gradient.

[0048] Furthermore, ring 18 disconnects the hot gas flow path from the inner housing 5 and, together with the inner housing, forms a cooling fluid gap 61 between ring 18 and the inner housing 5, as will be described in more detail below. A calibrated flow channel (e.g., see channel 62 in ring 18.5) is provided in the structure formed by the ring, allowing a controlled amount of cooling gas to flow from the cooling fluid gap to the hot gas flow path.

[0049] The first ring 18.1 supports the fixed blades 17.1 in the first annular array of fixed blades, i.e., the fixed blades of the uppermost group, which are arranged at the outlet of the combustor chamber 7. The fixed blades 17.1 of the first row of fixed blades or guide vanes are constrained to the ring 18.1 and the inner annular support 20, i.e., the fixed blades 17.1 have airfoils that are connected and supported at both the radially outer and radially inner ends.

[0050] The remaining fixed blades or guide vanes 17.j are cantilevered and mounted on the corresponding rings 18.j, such as... Figure 2 The enlarged view is best shown. The latter illustrates an enlarged view of the fixed blades or guide vanes 17.2 of the second expansion stage of expander 1. However, as... Figure 1 As can be seen, in this embodiment, the fixed blades of the subsequent expansion stage (i.e., blades 17.3 to 17.8) are also cantilevered from the corresponding rings 18.3 to 18.7 and (relative to blade 17.8) from the housing portion 5B. The following description of the mechanical structure connecting the fixed blades or guide vanes to the rings or inner housing (see reference) Figure 2 The second expansion state shown also applies to the remaining expansion stages.

[0051] Now for reference Figure 2 However, generally referring to any expansion stage starting from the second expansion stage and the associated fixed blade 17, each fixed blade component or fixed guide vane component includes at least one fixed guide vane or fixed blade 17. Figure 2 The fixed guide vane 17.2 and the corresponding external platform 71. Each fixed guide vane component or fixed blade component may also include an internal platform 73. The external platform 71 has a way to connect the fixed blade 17 to the corresponding support ring 18. Figure 2 (18.2) or a connecting member directly connected to the housing.

[0052] The outer platform 71 includes a radially outer surface 71.1 facing the ring 18. The outer platform 71 also includes a radially inner surface 71.2 facing the inner platform 73 and the rotation axis AA of the rotor 11.

[0053] The internal platform includes a radially outer surface 73.1 facing the external platform 71 and a radially inner surface 73.2 facing the axis of rotation AA. Surfaces 73.1 and 73.2 represent the boundaries of the expansion flow path.

[0054] The external platform 71 also includes a front edge 71.3 and a rear edge 71.4, as well as mechanical connection features adapted to mechanically attach the external platform 71 to a support structure in which... Figure 2 The middle is characterized by support ring 18.2. As noted, the remaining annular rows of fixed blades or guide vanes 17.3 to 17.7 and fixed guide vane components (which form part of it) are attached to the support structure characterized by the corresponding rings 18.3 to 18.7, while in this embodiment, the fixed blades 17.8 of the lowest row are directly attached to the inner housing 5 via the corresponding external platform.

[0055] It should be noted that each external platform 71 may be integrally formed with a single fixed blade 17, i.e., each fixed blade 17 may have its own platform. In this case, each fixed blade component will include a single airfoil. However, this is not mandatory. In some embodiments, or for one or more expansion stages of an expander, the fixed blade component may have an arcuate extension and include two or more fixed blades 17 integrally formed with a single external platform 71, i.e., two or more airfoils. Fixed blades integrally formed with a common external platform 71 may also be coupled to a common internal platform 73.

[0056] Generally speaking, the inner platform 73 and the outer platform 71 are shaped such that when the fixed blades 17 of the annular row are assembled and connected to the corresponding rings 18, the multiple platforms 71 and 73 are arranged circumferentially around the axis of rotation AA and form corresponding circular bands, thereby framing multiple airfoil elements between them, as described below.

[0057] Each fixed blade 17 includes or is composed of at least one airfoil 75 extending from the radially inner surface 71.2 of the outer platform 71 to the radially outer surface 73.1 of the inner platform 73. Each airfoil 75 includes a forward-oriented leading edge 75.1 and a rearward-oriented trailing edge 75.2.

[0058] The mechanical connection feature includes a front hook 77 that protrudes from the radially outer surface 71.1 of the outer platform 71 and is oriented toward the rear edge 71.4 of the outer platform 71. The front hook 77 includes a foot 77.1 at the radially outer surface 71.1 of the outer platform 71 and a protrusion 77.2 at the distal end of the front hook 77, the protrusion 77.2 being oriented in a rearward direction (i.e. toward the rear edge 71.2 of the outer platform 71).

[0059] The front hook 77 is positioned midway between the front edge 71.3 and the rear edge 71.4 of the outer platform 71. Ideally, the platform 71 is divided into a front portion 71F and a rear portion 71A, where the plane PP is orthogonal to the axis of rotation AA and equidistant from the front edge 71.3 and the rear edge 71.4. The foot 77.1 of the front hook 77 is preferably positioned in the front portion 71F of the outer platform 71. This means that the front hook 77 is arranged on the side of the outer platform 71 closer to its front edge 71.1. In some embodiments, the distal protrusion 77.2 may protrude beyond the central plane PP toward the rear edge 71.4 of the outer platform 71.

[0060] In some embodiments, the outer platform 71 includes a rib 71.5 that projects radially outward from the radially outer surface 71.1 of the outer platform 71 and forms an abutment portion adapted to abut against a corresponding ring 18. The rib 71.5 extends adjacent to the rear edge 71.4 of the outer platform 71, and... Figure 2 In one embodiment, the rib 71.5 engages with a circumferential groove 18G formed in the radially inward-facing surface of the ring 18. The bottom of the groove 18G forms a cylindrical resting surface, on which the rib 71.5 abuts, and the radially outward-oriented reaction force is transmitted from the fixed blade 17 to the ring 18 or directly to the housing 5 and then to the cylindrical resting surface, or to any other intermediate support structure that connects the row of fixed blades 17 to the housing 5 and then to the cylindrical resting surface.

[0061] In some embodiments, the rear platform portion 71A extending from the center plane PP (and from the foot of the front hook 77) to the rear edge 71.4 is in the radial direction ( Figure 2 The thickness at arrow R) is less than the thickness of the front platform portion 71F in the radial direction. Furthermore, in some embodiments, the outer platform may include a recess 71.6 on its radially outer surface, the recess 71.6 being positioned between the front hook 77 and the rear edge 71.4 of the outer platform 71, and extending substantially parallel to the front edge 71.3 and the rear edge 71.4 of the outer platform 71.

[0062] Each front hook 77 engages with a circular groove 18A formed in the annular surface 18B of the corresponding ring 18. The annular surface 18B may be a plane orthogonal to the axis of rotation AA, i.e., a flat surface. The circular groove 18A has a forward opening for inserting the front hook 77 and, more specifically, its distal protrusion 77.2, which is oriented in a rearward direction.

[0063] Figure 3 and Figure 4 Another embodiment of the expander according to this disclosure is illustrated. Figure 3 The sectional view is taken along a plane containing the axis of rotation AA of the expander, and only the first four expansion stages of the expander are shown.

[0064] Expander 1 includes an outer housing 3 and an inner housing 5. The outer housing 3 may include a main body and a closure (not shown) on the rear side of expander 1, in a manner similar to... Figure 1 The main body 3A and the closure 3B are completely identical. Similar to... Figure 1 Similarly in Figure 3 In one implementation, the outer casing 3 can be a vertically separated casing.

[0065] The burner (such as a canister burner comprising multiple combustion chambers 7) is positioned in front of the expander 1, upstream of the fixed guide vanes or blades of the first annular row. The annular chamber 6 is formed between the outer housing 3 and the inner housing 5.

[0066] The expander 1 also includes a rotor 11, which is housed within an inner casing 5 and adapted to rotate about a rotation axis AA. The rotor 11 includes a rotor shaft 13 and a plurality of annular rows, arrays, or groups of rotor blades arranged circumferentially around the rotation axis AA. As mentioned, in Figure 3 The diagram shows only the first four expansion stages of the expander, each of which includes a corresponding annular row or array of rotor blades 15 and a corresponding annular row or array of fixed guide vanes or fixed blades 17. Specifically, the fixed blades 17 of each annular row and the corresponding annular row of rotor blades 15 form the expansion stage of the expander 1.

[0067] Fixed blades 17 are housed within the inner housing 5. As will be described in more detail below, the fixed blades 17 in one, some, or each annular array are not directly mounted on the inner housing 5, but are mounted on at least one corresponding ring, designated 18. Figure 3 In the implementation scheme, all the fixed blades 17 of the first four expansion stages are supported by corresponding single rings 18.

[0068] Each annular array of rotor blades 15 is surrounded by a corresponding shroud. The shroud is designated 19. Figure 3 In one implementation, each of the shields 19 from the second expansion stage is supported by a corresponding ring 18, on which a fixed blade is mounted directly upstream.

[0069] The shroud of the first expansion stage is supported by a ring 18, which is separate from the ring supporting the fixed blades of the annular row of the first expansion stage. That is, the fixed guide vanes or blades of the row are positioned directly downstream of the burner.

[0070] As relative to Figure 1 and Figure 2 As described, also in Figure 3 In one embodiment, the ring 18 forms a structure that surrounds and supports the fixed blade 15 and the shroud 19, and this structure separates the flow path of the thermally expanding gas from the inner housing 5. As will be explained in more detail below, the rings 18 are configured such that they transmit only the axial reaction force generated by the hot gas expanding along the flow path to the inner housing 5. This design of the support structure (which prevents the transmission of radial reaction forces between the ring and the housing) allows for different thermal expansions on one side of the ring and on the other side of the housing, which are determined by a thermal gradient.

[0071] Furthermore, ring 18 disconnects the hot gas flow path from the inner housing 5 and, together with the inner housing, forms a cooling fluid gap 61 between ring 18 and the inner housing 5, as described in more detail below. A calibrated flow channel is provided within the structure formed by ring 18 (see, for example, [link to relevant documentation]). Figure 1 Channel 62 in the middle, Figure 3 (not shown in the figure), allowing a controlled amount of cooling gas to flow from the cooling fluid gap to the hot gas flow path.

[0072] Now for reference Figure 4 An enlarged view, but generally refer to any fixed blade 17 starting from the second expansion stage, each fixed blade or fixed guide vane 17 including an outer platform 71 and may also include an inner platform 73. Figure 3 The external platform 71 has a connecting member that connects the fixed blade 17 to the corresponding support ring 18 or directly to the housing.

[0073] The outer platform 71 includes a radially outer surface 71.1 facing the ring 18 (or housing). The outer platform 71 also includes a radially inner surface 71.2 facing the inner platform 73 and the rotation axis AA of the rotor 11.

[0074] The external platform 71 also includes a front edge 71.3 and a rear edge 71.4, as well as mechanical connection features adapted to mechanically attach the external platform 71 to a support structure in which... Figure 3 and Figure 4 The middle is characterized by support ring 18.

[0075] Such as combination Figure 1 and Figure 2 As mentioned, each external platform 71 may be integrally formed with a single fixed blade 17, that is, each fixed blade 17 may have its own external platform 71. However, this is not mandatory. In some embodiments, or for one or more expansion stages of an expander, the fixed blade 17 may be configured as an arcuate segment, wherein each segment includes two or more fixed blades 17 integrally formed with a single external platform 71. Fixed blades integrally formed with a common external platform 71 may also be coupled to a common internal platform 73.

[0076] Generally speaking, the inner platform 71 and the outer platform are shaped such that when the fixed blades 17 of the annular row are assembled with corresponding rings 18, the multiple platforms 71 and 73 are arranged circumferentially around the axis of rotation AA and form corresponding circular bands, thereby framing multiple airfoil elements between them, as described below.

[0077] Each fixed blade 17 includes or is composed of an airfoil 75 extending from the radially inner surface 71.2 of the outer platform 71 to the radially outer surface 73.1 of the inner platform 73 and includes a leading edge and a trailing edge. Each airfoil 75 includes a forward-oriented leading edge 75.1 and a rearward-oriented trailing edge 75.2.

[0078] Similar to Figure 1 and Figure 2 The mechanical coupling feature (each fixed blade 17 is coupled to a ring 18 or other support structure housed in the housing via this mechanical coupling feature) includes a front hook 77 that protrudes from the radially outer surface 71.1 of the outer platform 71 and is oriented toward the rear edge 71.4 of the outer platform 71. More specifically, in Figure 3 and Figure 4 In the implementation plan, similar to Figure 1 and Figure 2 The front hook 77 includes a foot 77.1 at the radial outer surface 71.1 of the outer platform 71 and a protrusion or tooth 77.2 at the distal end of the front hook 77, the protrusion 77.2 being oriented in a rearward direction (i.e. toward the rear edge 71.2 of the outer platform 71).

[0079] The front hook 77 is positioned midway between the front edge 71.3 and the rear edge 71.4 of the outer platform 71. Considering the geometric plane PP (which divides the outer platform 71 into a front platform portion 71F and a rear platform portion 71A) orthogonal to the axis of rotation AA and equidistant from the front edge 71.3 and the rear edge 71.4, the front hook 77 is preferably constrained to the outer platform 71 in its front portion 71F. Therefore, similar to... Figure 1 and Figure 2 In one embodiment, the front hook 77 is positioned on the side of the outer platform 71 closer to its front edge 71.1. In some embodiments, the distal protrusion 77.2 may protrude beyond the center plane PP toward the rear edge 71.4 of the outer platform 71.

[0080] In some embodiments, the outer platform 71 includes a rib 71.5 that projects radially outward from the radially outer surface 71.1 of the outer platform 71 and forms a resting surface, i.e., an abutment surface, suitable for resting against the corresponding ring 18. The rib 71.5 extends adjacent to the rear edge 71.4 of the outer platform 71, and... Figure 4 In one embodiment, the rib 71.5 contacts the cylindrical inner surface 18C of the ring 18. The diameter of the inner cylindrical surface 18C allows each fixed blade 17 to be mounted on the ring 18 via a back-and-forth insertion movement.

[0081] Cylindrical surface 18C forms a cylindrical resting surface, rib 71.5 is adjacent to this cylindrical resting surface, and the radially outward oriented reaction force is transmitted from the fixed blade 17 to the ring 18 and then to the cylindrical resting surface, or directly to the housing 5 and then to the cylindrical resting surface. If the ring 18 is not provided, the cylindrical surface 18C can be formed on the inner surface of the housing 5.

[0082] In some embodiments, the rear platform portion 71A extending from the front hook 77 to the rear edge 71.4 has a radially smaller thickness than the front platform portion 71F. Furthermore, in some embodiments, the outer platform may include a recess 71.6 on its radially outer surface. The recess 71.6 may be positioned between the front hook 77 and the rear edge 71.4 of the outer platform 71, and more precisely between the foot and rib 71.5 of the front hook 77, and may extend substantially parallel to the front edge 71.3 and the rear edge 71.4 of the outer platform 71. (As in...) Figure 1 and Figure 2 In one embodiment, the recess 71.6 provides a reduction in the thickness of the rear portion 71A of the outer platform 71.

[0083] Each front hook 77 engages with a circular front groove 18A formed in the annular surface 18B of the corresponding ring 18. The annular surface 18B may be a plane orthogonal to the axis of rotation AA, i.e., a flat surface. The circular groove 18A has a front hook 77 for insertion into the outer platform 71 and, more specifically, a forward opening of its distal protrusion 77.2.

[0084] and Figure 1 and Figure 2 The implementation plans are different, in Figure 3 and Figure 4 In one embodiment, the rib 71.5 does not engage the radial groove of the ring 18, but rests on its inner cylindrical surface 18C, which extends in the forward direction to the front flat annular surface 18B forming the circular groove 18A. With this arrangement, each fixed blade 17 and its corresponding outer platform 71 can be easily moved in the forward / backward direction (…). Figure 4 Arrow f71) is mounted on its support ring 18. Therefore, the fixed blade 17 can be mounted on an integral ring, i.e., on a ring that extends continuously for 360° around its axis of symmetry, i.e., with an integral deployment of approximately 360°. An integral ring without discontinuities in the tangential or circumferential directions is particularly advantageous in terms of its ability to resist mechanical stress, especially in the case of high pressure drops across the corresponding expansion stage.

[0085] In supercritical carbon dioxide expanders, pressure drops of, for example, 20 barA or higher, such as 30 barA or higher, or even 40 barA or higher, are feasible. Integral annular structures are particularly useful in such turbines.

[0086] In both embodiments, each fixed blade or fixed guide vane 17 is constrained to the housing by a front hook 77 (directly or via another support structure, such as a ring 18), which is positioned toward the front edge 71.3 of the outer platform 71 but oriented in the rearward direction, i.e., having a distal protrusion 77.2 oriented toward the rear edge 71.4 of the outer platform 71. The reaction force between the support structure (ring 18 or housing 5) and the fixed blade 17 is transmitted through the single hook 77 located near the front edge of the platform 71 and oriented in the rearward direction, and through a resting surface formed by a rib 71.5, which abuts against a cylindrical surface (bottom of groove 18G or cylindrical surface 18C) formed by the support structure.

[0087] This results in a reduction in the radial extension of platform 71 (i.e., the radial height of the fixed blades 17 of the annular row). The rear portion of the platform (i.e., the portion 71A positioned downstream of the central plane PP) does not have hooks, as this is typically the case in prior art fixed blades. Instead, at the rear of platform 71, radial loads are transferred to the support structure (ring 18 or directly to housing 5) through pressure contact between rib 71.5 and the inward-facing surface of the support structure. Figure 1 and Figure 2 In this context, the inward-facing surface is the bottom of the groove 18G, while... Figure 3 and Figure 4 In the implementation scheme, the inward-facing surface is a cylindrical surface 18C of the ring 18.

[0088] In addition to the reduction in radial dimension of the fixed blades 17 in each annular row, the reduction in thickness in the radial direction achieved by the novel structure described above allows for a reduction in thermal stress in the outer platform 71, since the thinner rear portion 71A of the platform may thermally deform when subjected to a thermal gradient, thereby reducing the thermal stress in the annular row of the fixed platform.

[0089] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. Those skilled in the art will understand that various changes, omissions, and additions may be made to the specific disclosure herein without departing from the scope of the invention as defined in the following claims.

Claims

1. A fixed blade assembly for a turbine, the fixed blade assembly comprising: • An external platform, comprising: a radially outer surface, a radially inner surface, a front edge, a rear edge, and a mechanical connection feature adapted to mechanically attach the external platform to a support structure of the turbine; • At least one airfoil extending from the radially inner surface of the outer platform and including a leading edge and a trailing edge; The mechanical connection feature includes a front hook that protrudes from the radially outer surface of the outer platform and is oriented toward the rear edge of the outer platform.

2. The component according to claim 1, wherein the front hook is a single hook of the mechanical connection feature.

3. The component according to claim 1 or 2, wherein the hook is discontinuous in the tangential direction.

4. The component according to any one of the preceding claims, wherein the front hook is positioned at an intermediate position between the front edge and the rear edge of the outer platform.

5. The component according to any one of the preceding claims, wherein the outer platform includes a rib that projects radially outward from the radially outer surface of the outer platform and forms a resting surface adapted to rest against the support structure of the turbine.

6. The component of claim 5, wherein the rib is positioned at the rear edge of the outer platform, or between the rear edge of the outer platform and the front hook.

7. The component according to any one of the preceding claims, wherein the external platform comprises: The front platform portion extends from the front edge to the front hook; and The rear platform portion extends from the front hook to the rear edge; wherein the thickness of the front platform portion in the radial direction is greater than the thickness of the rear platform portion in the radial direction.

8. The component according to any one of the preceding claims, wherein the outer platform includes a recess located on the radially outer surface, the recess being positioned between the front hook and the rear edge of the outer platform and extending substantially parallel to the front and rear edges of the outer platform.

9. The component according to any one of the preceding claims, the component comprising an inner platform having a radially outer surface and a radially inner surface; wherein the airfoil extends from the radially inner surface of the outer platform to the radially outer surface of the inner platform.

10. An expander comprising at least one annular array of fixed blade components, the at least one annular array of fixed blade components being housed within a housing; A rotor, which is housed in the housing for rotation therein; the rotor includes a rotation axis and rotor blades in at least one annular array around the rotation axis; The fixed blade component of the at least one annular array is mounted on at least one corresponding support structure housed in the housing; and Each of the fixed blade components in the at least one annular array comprises: • External platform, the external platform comprising: a radial outer surface, a radial inner surface, a front edge, and a rear edge; • At least one airfoil extending radially from the radially inner surface of the outer platform toward the axis of rotation of the rotor; and • Front hooks, which protrude from the radially outer surface of the outer platform and are oriented toward the rear edge of the outer platform; wherein each front hook engages in a circular groove formed in the annular surface of the respective support structure, the circular groove having a forward opening for inserting the front hook.

11. The expander of claim 10, wherein each of the fixed blade components in the at least one annular array comprises a single hook.

12. The expander according to claim 10 or 11, wherein the front hook is discontinuous in the tangential direction about the axis of rotation.

13. The expander according to any one of claims 10 to 12, wherein the front hook of each fixed blade component is positioned at the middle of the outer platform, between the front edge and the rear edge of the outer platform.

14. The expander according to claim 10 or 13, wherein the outer platform of each fixed blade component includes a rib that projects radially outward from the radially outer surface of the outer platform and forms a cylindrical resting surface adapted to rest against a radially inner cylindrical surface of the corresponding support structure.

15. The expander of claim 14, wherein the cylindrical resting surface extends in the forward direction to the annular surface of the support structure; wherein the diameter of the inner cylindrical surface is such that each fixed blade component can be mounted on the support structure by means of a fore-and-aft insertion movement, whereby the front hook engages the circular groove.

16. The expander according to any one of claims 10 to 15, wherein the support structure comprises a ring mounted in the housing.

17. The expander of claim 16, wherein the support structure comprises an integrally unfolded ring having approximately 360°.

18. The expander according to any one of claims 10 to 17, wherein the rib of each fixed blade component extends adjacent to the rear edge of its outer platform.

19. The expander according to any one of claims 10 to 18, wherein the external platform of each fixed blade component comprises: The front platform portion extends from the front edge to the front hook; and The rear platform portion extends from the front hook to the rear edge; wherein the thickness of the front platform portion in the radial direction is greater than the thickness of the rear platform portion in the radial direction.

20. The expander according to any one of claims 10 to 19, wherein the outer platform of each fixed blade component includes a recess located on the radially outer surface, the recess being positioned between the front hook and the rear edge of the outer platform and extending substantially parallel to the front and rear edges of the outer platform.

21. The expander according to any one of claims 10 to 20, wherein each fixed blade component includes an inner platform having a radially outer surface and a radially inner surface; wherein the airfoil extends from the radially inner surface of the outer platform to the radially outer surface of the inner platform.

22. The expander according to any one of claims 10 to 21, wherein the housing comprises an outer housing and an inner housing; wherein the inner housing is housed within the outer housing, and the rotor is supported to rotate within the inner housing.

23. The expander according to any one of claims 10 to 22, the expander further comprising a burner arranged upstream of the expansion flow path extending through the fixed blade component and the rotor blades of the at least one array.

24. The expander according to any one of claims 10 to 23, wherein the support structure includes a groove in the inner surface of the housing.

Images