Expander comprising an inner ring supporting stationary vanes

Abstract

The expander (1) comprises an outer casing (3) and an inner casing (5) housed in the outer casing. A plurality of annular arrays of stationary vanes (17) are housed in the inner casing. A rotor (11) is housed in the inner casing for rotation therein. The rotor comprises a rotation axis and a plurality of annular arrays of rotor vanes (15) surrounding the rotation axis. Each annular array of rotor vanes is arranged downstream of a respective one of the annular arrays of stationary vanes and forms a respective expander stage therewith. The stationary vanes (17) in each annular array of stationary vanes are mounted on one respective ring (18) housed in the inner casing. Each ring is in pressure contact axially oriented with two adjacent rings or with one adjacent ring (18) and the inner casing (5). A cooling fluid gap (61) is formed between the rings and the inner casing.

Description

Technical Field

[0001] This disclosure relates to power generation turbines. The embodiments disclosed herein relate to supercritical carbon dioxide expanders, or more generally to expanders operating at high pressure ratios. Background Technology

[0002] Fossil fuels are the primary source of chemical energy used to generate mechanical power. Fossil fuels are mixed with air and burned to produce high-pressure, high-temperature combustion gases, which expand in a turbine or expander. The expander or turbine converts the enthalpy of the combustion gases into mechanical power that can be obtained at the output shaft of the expander or turbine and used to drive loads, such as compressors or compressor units, or to rotate generators and convert mechanical power into electrical power.

[0003] 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.

[0004] To reduce the environmental impact of power generation through the combustion of fossil fuels, post-combustion carbon dioxide (CO2) capture options have been investigated. CO2 capture facilities have been developed to treat flue gas (i.e., combustion gases) from gas turbines and remove CO2 from it before it is released into the environment. The cost of CO2 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 CO2 capture facilities, making the capture process particularly inefficient.

[0005] 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.

[0006] The combustion gases expand in an expander to generate mechanical power, which is ultimately converted into electrical power by a generator driven by the expander. The exhaust gases from the expander's discharge side are cooled in a regenerative heat exchanger and further refrigerated into condensate, which is thus removed from the cooled combustion gases. The majority of the cryogenic combustion gases, consisting mainly or solely of carbon dioxide, is pressurized and recirculated through the regenerative heat exchanger toward the expander's burner. The remaining portion of the combustion gases is removed, and the carbon dioxide contained within is captured.

[0007] 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.

[0008] Oxygen-fuel cycles, such as those mentioned above, are of particular interest in terms of efficiency, reduction of harmful emissions, and more effective carbon capture. However, they operate under supercritical CO2 conditions at the expander inlet and are characterized by high pressure drops in each stage of the expander, for example, including pressure drops between 20 bar and 60 bar. These high pressure drops at both ends of the expander stages result in high reaction forces on the components supporting the stationary blades and other stationary components in the hot gas flow path within the expander. These high reaction forces can cause deformation of the support structures connected to the stationary blades.

[0009] Oxygen-fueled expanders are characterized by the high temperature of the expanding combustion gases. Recirculated, compressed, and cooled combustion gases, primarily or solely composed of carbon dioxide, are recommended as the cooling and / or purging medium for the expander's fixed blades and shrouds. The temperature difference between the cooling fluid and the combustion gases in the expander's flow path, combined with the high density of the compressed and recirculated combustion gases, is crucial for the integrity of expander components in thermal contact with the expanding combustion gases.

[0010] According to one aspect, this disclosure aims to provide a novel structure that overcomes or mitigates the aforementioned disadvantages. Summary of the Invention

[0011] This paper discloses a novel structure for an expander that overcomes or mitigates the aforementioned drawbacks. Specifically, this paper proposes a novel structure that avoids or reduces elastic deformation of the structure supporting hot gas path components, such as, specifically, fixed blades and shrouds. This is achieved through mechanical decoupling between the fixed blades on one side and the housing surrounding the rotor on the other side. In the embodiments disclosed herein, the structure also provides thermal decoupling between a gap containing pressurized fluid, which can be used as a cooling or purging fluid.

[0012] As will become clear from the following detailed description of the implementation, the novel structure is advantageous in controlling the cooling of expander components, particularly those facing the expansion flow path. Furthermore, the amount of recirculated gas used for cooling or purging purposes can be minimized, resulting in a beneficial effect on the overall efficiency of the thermal cycle. The structure can also be used to control the clearance between the stationary and rotating components of the expander.

[0013] In the embodiments disclosed herein, the expander includes an outer housing and an inner housing housed within the outer housing. A plurality of fixed blades in annular arrays or rows are housed within the inner housing. The expander also includes a rotor housed within the inner housing for rotation about an axis of rotation therein. The rotor includes a plurality of rotor blades in annular arrays or rows surrounding the axis of rotation, each annular array of rotor blades being arranged downstream of a corresponding fixed blade in the fixed blades of the annular array and forming a corresponding expansion stage therewith. Fixed blades in each annular array are mounted on at least one ring housed within the inner housing. Each ring is in pressure contact with two adjacent rings or with one adjacent ring and the inner housing. A gap containing a pressurized fluid (such as a cooling or purging fluid) may be formed between the ring and the inner housing. As will become clear from the following description, and as understood herein, "pressure contact" is contact between the surfaces of two machine components (e.g., two adjacent rings, or a ring and the inner housing) that generates a reaction force at the contact surfaces.

[0014] The expander may include additional fixed blades, which are supported by different structures or rings, for example, rings mounted in different ways in the internal housing.

[0015] The blades in the fixed blades of each annular array mounted on the rings can be mounted on a single ring or on two or more rings. Conversely, a ring can support the fixed blades of a single annular array, or more than one such array.

[0016] Additional rings that do not support the fixed blades may be provided within the internal housing. For example, a ring supporting a shroud surrounding the rotor blades of the annular array may be positioned between two subsequent rings supporting the fixed blades of two adjacent expansion stages. Alternatively or in combination, one or more rings may (fully or partially) support the fixed blades of the annular array and the shrouds of the rotor blades of adjacent annular arrays.

[0017] In some embodiments, at least some of the rings each support a shroud that surrounds the rotor blades of the annular array, the rotor blades of the annular array being arranged downstream of the fixed blades of the annular array mounted on the ring.

[0018] In some implementations, the ring is configured to transmit only the axial reaction forces (if friction is neglected) generated by the fluid flowing through the respective stationary blades of one or more stages to the inner housing. As used herein, the term "axial" refers to the axis of rotation parallel to the rotor.

[0019] Further embodiments and features of the expander according to this disclosure are described below and set forth in the appended claims. Attached Figure Description

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

[0021] Figure 1 This is a cross-sectional view of the expander of the first embodiment of this disclosure, taken along a plane containing the axis of rotation;

[0022] Figure 2A and Figure 2B yes Figure 1 Enlarged image;

[0023] Figure 3 This is an enlarged cross-sectional view of a portion of an expander according to another embodiment of the present disclosure, taken along a plane containing the axis of rotation;

[0024] Figure 4 It is an enlarged cross-sectional view of the modified implementation scheme; and

[0025] Figure 5 This is a cross-sectional view of another modified implementation scheme. Detailed Implementation

[0026] Figure 1 The figure shows a cross-sectional view of the expander 1 according to the present disclosure. The cross-section is taken along a plane containing the axis of rotation AA of the expander. This cross-sectional view only shows the axially symmetrical semi-expander.

[0027] Expander 1 includes an outer housing 3 and an inner housing 5. The outer housing 3 may include a body 3A and a closure 3B on the rearward side of the expander. The body 3A and the closure 3B are coupled 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 split housing.

[0028] The burner (such as a canister burner comprising multiple combustion chambers 7) is positioned on the forward side of the expander, upstream of the fixed blades or impeller of the first annular array. The annular chamber 6 is positioned between the outer casing 3 and the inner casing 5.

[0029] As used herein, "forward" and "backward" refer to the direction of flow of the process gas (i.e., the combustion gas) through the expander 1. Thus, "forward" indicates the position on the burner chamber 7 side, and "backward" indicates the position on the side opposite to the burner chamber 7 (i.e., the discharge side of the expander 1).

[0030] 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 arrays, i.e., annular rows or groups of rotor blades. Figure 1In an exemplary embodiment, rotor 11 includes eight annular arrays of rotor blades. The rotor blades of each array extend about the rotation axis AA of rotor 11. The rotor blades are designated 15.j, where j indicates the position of the array in the forward-reverse 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.

[0031] The fixed blades of the annular array (i.e., annular rows or groups) are positioned upstream of the rotor blades 15.j of each annular array. Blades in the fixed blades of the annular array are designated 17.j. More specifically, blades in the fixed blades of the most upstream annular array are designated 17.1, and blades in the fixed blades of the most downstream array are designated 17.8. Typically, blades in the fixed blades of the j-th annular array are designated 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 direction of combustion gas flow through the expander 1.

[0032] 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.

[0033] 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 on the inner housing 5, but is mounted on at least one corresponding ring, or on a pair of adjacent rings. Figure 1 In this embodiment, all the fixed blades 17 in each annular array or group of fixed blades are supported by a corresponding single ring. The ring is designated 18. More specifically, each ring is designated 18.j (where j = 1-7). As used herein, reference numeral 18 refers to a general ring. The fixed blades 17.j (where j = 1-7) of each annular array 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 rearward portion 5B of the inner housing 5. The rearward portion 5B of the inner housing is coupled to the body 5A of the inner housing 5. The body 5A may in turn be formed by multiple housing portions. Each housing portion may be divided along a plane containing the axis of rotation AA of the rotor 11; that is, the inner housing 5 is a so-called horizontally divided housing.

[0034] The ring is centered and locked relative to the inner housing by means of centering and anti-rotation features, which are known to those skilled in the art and are not shown.

[0035] Each annular array of rotor blades 15.j is surrounded by a corresponding shroud. The shrouds are designated 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 positioned directly upstream of the shield is mounted. Therefore, shield 19.j is mounted on ring 18.j of the fixed blade 17.j supporting the annular array, where j = 2 to 7.

[0036] 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.

[0037] The rings 18 form a structure that supports and fixes the blades 15 and the shroud 17, and separates the flow path of the thermally expanding gas from the inner shell 5. As will be explained in more detail below, the rings 18 are configured such that, if friction is neglected, 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 forces between the rings and the shell, allows for different thermal expansions of the rings on one side and the shell on the other side, determined by a thermal gradient.

[0038] Furthermore, ring 18 decouples the hot gas flow path from the inner housing 5 and forms a fluid gap 61 with the inner housing for pressurizing fluid, specifically, for cooling or purging fluid between ring 18 and the inner housing 5. The pressurizing fluid gap 61 will be described in more detail below. A calibrated flow path can be provided in the structure formed by the rings, allowing a controlled amount of cooling or purging gas to flow from the cooling or purging fluid gap to the hot gas flow path. The purging or cooling gas may further leak along the contact surfaces between adjacent rings or between the rings and the housing.

[0039] The shape of ring 18.j and the combined effect between adjacent rings 18 and between the ring and the inner housing 5 Figure 2A and Figure 2B The enlarged view is best shown and described below.

[0040] As will be apparent from the following description, in the embodiments disclosed herein, rings to which fixed blades or impellers are constrained are arranged in the housing such that, in use, each ring abuts against at least one downstream ring, or against both an upstream and downstream ring, or against an upstream ring and the inner housing. The uppermost fixed blades or impellers are constrained to a peripheral ring that abuts against the inner housing and / or against a downstream ring, and are further constrained to a fixed internal structure.

[0041] In the following description, reference will be made to the reaction forces generated on the contact surfaces between adjacent rings 18 and between ring 18 and the inner housing 5. The reaction forces referred to herein are primarily generated by the process gas flowing in the hot flow path of the expander and the pressure acting on the rings supporting the shroud and fixing the blades or impellers. Frictional forces between contacting components are not considered. These forces are generated by the expansion of the combustion gases and by the pressure difference across the respective stages. Frictional forces can be generated, for example, by the different thermal expansions of the components in contact with each other during the operational transients of the expander 1.

[0042] like Figure 2A As shown, the first ring 18.1 supports the fixed blades 17.1 in the fixed blades of the first annular array, that is, the fixed blades of the uppermost group, which are arranged at the outlet of the combustor chamber 7. The fixed blades 17.1 are constrained to the first ring 18.1 and the internal fixing structure 16.

[0043] The first ring 18.1 includes a forward surface 31 that is in pressure contact with the inner housing 5. In other embodiments, the forward surface 31 may not contact the inner housing 5. In some embodiments, the forward contact surface 31 is a flat surface orthogonal to the axis of rotation AA of the expander 1. Through the forward contact surface, the first ring 18.1 can transmit only the axial reaction force (i.e., the force oriented parallel to the axis of rotation AA) to the housing 5. As mentioned, frictional forces arising from the mutual displacement between the ring 18.1 and the inner housing 5 due to, for example, different thermal expansion are not considered.

[0044] The first ring 18.1 also includes a rearward contact surface 33 that is in pressure contact with the downstream auxiliary ring 18.0. The rearward contact surface 33 may be a flat surface orthogonal to the axis of rotation AA of the expander, and is therefore suitable for transmitting only axial reaction forces.

[0045] In other embodiments, the first ring 18.1 may only be in pressure contact with the auxiliary ring 18.0 and not in contact with the housing 5 at 31. Alternatively, the first ring 18.1 may be in pressure contact with the inner housing 5 at 31 and not in contact with the auxiliary ring 18.0.

[0046] In any case, the resultant force generated at the pressure contact area is axially oriented, and apart from the force generated by friction, no radial force is transmitted from the first ring 18.1 to the inner housing 5.

[0047] The rearward contact surface 33 of the first ring 18.1 corresponds to the forward contact surface of the auxiliary ring 18.0. The forward contact surface of the auxiliary ring 18.0 is marked with the same reference numeral 33. The auxiliary ring 18.0 also includes a rearward contact surface 35 through which the auxiliary ring 18.0 makes pressure contact with the second ring 18.2. The reaction forces applied to the auxiliary ring 18.0 at surfaces 33 and 35 balance the thrust generated on the shroud 19.1 by the pressure difference across the expansion stage.

[0048] exist Figure 1 and Figure 2A , Figure 2B In one embodiment, the second ring 18.2 supports the fixing components of the second expansion stage, namely the fixing blades 17.2 in the fixing blades of the second annular array, and the shroud 19.2 surrounding the rotor blades 15.2 in the rotor blades of the second annular array. The second ring 18.2 includes a forward contact surface corresponding to the rearward contact surface 35 of the auxiliary ring 18.0, and is designated by the same reference numeral 35. The second ring 18.2 also includes a rearward contact surface 37 at which the second ring 18.2 makes pressure contact with the third ring 18.3.

[0049] In some embodiments, one or both of the forward contact surface 35 and the backward contact surface 37 of the second ring 18.2 are flat with the upstream adjacent ring 18.0 and the downstream adjacent ring 18.3 and orthogonal to the rotation axis AA of the expander 1, such that the reaction force generated at said surface is axially oriented, i.e. parallel to the rotation axis AA.

[0050] In some implementation schemes, such as Figure 2A As shown, the second ring 18.2 is designed such that the distance from its forward contact surface 35 to the rotation axis AA is greater than the distance from its rear contact surface 37 to the rotation axis AA. This results in the reaction forces applied to the contact surfaces 35 and 37 of the second ring 18.2 generating a clockwise (in the figure) torque, which is balanced by the counterclockwise torque applied to the second ring 18.2 by the fixed blades 17.2 of the second expansion stage. This counterclockwise torque is generated by the pressure difference across the fixed blades 17.2 and the force exerted by the expanding combustion gases flowing through the fixed blades 17.2. This leads to a better balance of reaction forces on the second ring 18.2. Additionally, this design limits the elastic deformation of the second ring, aiming to avoid or reduce changes in the clearance between the stator and rotor components during machine operation.

[0051] Next, the third ring 18.3 supports the fixed components of the third expansion stage, namely blades 17.3 in the fixed blades of the third annular array, and a shroud 19.3 surrounding rotor blades 15.3 in the rotor blades of the third annular array. The third ring 18.3 includes a forward contact surface corresponding to the rearward contact surface 37 of the second ring 18.2, and is designated by the same reference numerals. The rearward contact surface of the third ring 18.3 is shown as 39, at which the third ring 18.3 makes pressure contact with the fourth ring 18.4. In the embodiments disclosed herein, the rearward contact surface 39 of the third ring 18.3 is flat and orthogonal to the axis of rotation AA, so that only axial forces are transmitted to the adjacent downstream ring 18.4.

[0052] The reaction force applied to the third ring 18.3 is reduced by positioning the rearward contact surface 39 at a distance from the rotation axis AA, which is as close as possible to the distance from the forward contact surface 37 to the axis. In the illustrated embodiment, the rearward contact surface 39 and the forward contact surface 37 of the third ring 18.3 are at substantially the same radial distance from the rotation axis AA.

[0053] The fourth ring 18.4 supports the fixed components of the fourth expansion stage of the expander 1, namely the fixed blade 17.4 in the fixed blades of the fourth annular array and the shroud 19.4 surrounding the rotor blade 15.4 in the rotor blades of the fourth annular array.

[0054] The fourth ring 18.4 has a forward contact surface that makes pressure contact with the inner housing 5. More specifically, the fourth ring 18.4 is characterized by a radial protrusion 18.41 that forms a contact surface 41 between the fourth ring 18.4 and the inner housing 5. The contact surface 41 is flat and orthogonal to the axis of rotation AA, such that the reaction force between the fourth ring 18.4 and the inner housing 5 is axially oriented, i.e., parallel to the axis of rotation AA, and no radial reaction force is transmitted from the fourth ring 18.4 to the inner housing 5.

[0055] The fourth ring 18.4 also includes another forward contact surface that is in pressure contact with the upstream third ring 18.3. This other forward contact surface coincides with the rearward contact surface 39 of the third ring 18.3 and is labeled with the same reference numerals.

[0056] The fourth ring 18.4 also includes a rearward contact surface 43, at which the fourth ring 18.4 makes pressure contact with the fifth ring 18.5. The rearward contact surface 43 has a convex cylindrical shape coaxial with the rotation axis AA of the expander 1. A radial reaction force, i.e., a force orthogonal to the rotation axis AA, is generated at the cylindrical surfaces forming the rearward contact surface 43 of the fourth ring 18.4 and the forward contact surface of the fifth ring 18.5. The radial reaction force applied to the fourth ring 18.4 by the fifth ring 18.5 is oriented towards the rotation axis AA. The radial reaction force applied to the ring at the rearward surface 43 of the ring 18.4 (which is located at...) Figure 2A The torque generated by the clockwise orientation is balanced by the counterclockwise orientation torque applied to the ring 18.4 by the expanding combustion gas through the fixed blade 17.4 and the counterclockwise torque generated by the axial reaction force acting on the forward contact surfaces 41 and 39.

[0057] The fifth ring 18.5, which supports the fixed blades 17.5 and the shroud 19.5 of the fifth expansion stage, is characterized by an annular groove or notch at its forward end, where the rearward end of the fourth ring 18.4 engages. The annular groove or notch has a concave shape, i.e., an inner cylindrical surface. The inner cylindrical surface of the annular groove corresponds to the rearward contact surface 43 of the fourth ring and is marked with the same reference numerals. Thus, the inner cylindrical contact surface 43 represents the forward contact surface of the fifth ring 18.5 that is in pressure contact with the upstream ring 18.4.

[0058] The inner cylindrical contact surface 43 may be continuous, or it may include one or more discontinuous portions, such as slots, holes, or recesses. The same applies to the rearward end of the fourth ring 18.4, which engages in the groove forming the inner cylindrical contact surface 43. The rearward end of the fourth ring may be a continuous cylindrical surface, or it may include one or more discontinuous portions, such as recesses, slots, or holes.

[0059] The fifth ring 18.5 also includes a rearward contact surface 45 that pressure-contacts the contact surface of the inner housing 5. The contact surface 45 is positioned closer to the axis of rotation AA than the contact surface 43, allowing for better balancing of the torque applied to the ring 18.5 by the expanding combustion gases. In some embodiments, the rearward contact surface 45 is flat and orthogonal to the axis of rotation AA, so that only axial reaction forces are transmitted to the inner housing 5.

[0060] The next sixth ring 18.6, supporting the fixed blades 17.6 and shroud 19.6 of the sixth expansion stage, has a rearward contact surface 49 that pressure-contacts the downstream seventh ring 18.7. In some embodiments, the rearward contact surface 49 has an outer cylindrical surface portion 49A coaxial with the axis of rotation AA of the expander, and a flat surface portion 49B orthogonal to the axis of rotation AA. The inner cylindrical contact surface portion 49A surrounds the rearward portion of the upstream ring 18.6, i.e., the rearward portion of the upstream ring 18.6 (which forms the rearward contact surface of ring 18.6) engages in an annular groove at the forward end of ring 18.7.

[0061] An axial reaction force is applied at the flat surface portion 49B, and a radial reaction force is applied at the outer cylindrical surface portion 49A.

[0062] The rearward end of the sixth ring 18.6 (characterized by its rearward contact surface 49) engages in an annular groove or slot formed in the forward end of the next seventh ring 18.7, which supports the fixed blade 17.7 and the shroud 19.7 of the seventh expansion stage. The annular groove of the seventh ring 18.7 is characterized by a forward contact surface that pressure contacts the rearward end of the sixth ring 18.6. The forward contact surface of ring 18.7 has a shape complementary to the shape of the rearward contact surface of ring 18.6, namely, including an inner cylindrical surface portion again designated 49A and a flat surface portion again designated 49B.

[0063] Therefore, at surfaces 49A and 49B, axial and radial reaction forces are transmitted between the sixth ring 18.6 and the seventh ring 18.7. The seventh ring supports the fixed blades 17.7 and the shroud 19.7 of the seventh expansion stage.

[0064] In addition to the forward contact surfaces 49A and 49B, the seventh ring 18.7 is also characterized by a backward contact surface 51, which is in pressure contact with ring 18.8 and forms the backward portion 5B of the inner housing 5. In some embodiments, the backward contact surface 51 is flat and orthogonal to the axis of rotation AA, so as to transmit the axial reaction force to the eighth ring 18.8, which forms part of the backward portion 5B of the inner housing 5.

[0065] Therefore, the only part of the inner housing 5 loaded with radial force is the rearward portion 5B, to which a reaction force is applied to balance the torque generated by the expansion of the combustion gas in the final stage (i.e., on the fixed blades 17.8 and the shroud 19.8), while the remaining sections of the inner housing 5 are only loaded with axial reaction forces transmitted by the structure formed by the rings 18.1 to 18.7.

[0066] like Figure 2A and Figure 2BAs shown, the structure formed by the stacked rings 18 defines a cooling or purging fluid gap 61 between the radially outward surface of the rings 18 and the inner surface of the inner housing 5. The cooling or purging fluid gap 61 is adapted to receive pressurized cooling or purging fluid, such as cooling recirculated gas. For example, the cooling or purging fluid can be used to cool the stationary blades 17 or purge the empty volume surrounding the stationary blades. The pressurized cooling or purging fluid can leak from the cooling or purging fluid gap 61 in a controlled manner toward the stationary blades 17 and / or toward the shroud 19. Controlled leakage of the cooling or purging fluid can be obtained along a contact surface where the rings are in pressure contact with each other and / or through conduits formed in the rings. As a non-limiting example, in Figure 2B The image shows one such pipe, number 62.

[0067] Therefore, the ring set 18 provides mechanical decoupling between the inner housing 5 and the stationary components (stationary blades 17 and shroud 19). This mechanical decoupling allows for thermal expansion of the inner ring during expander operation. Simultaneously, the ring set 18 provides thermal and fluid decoupling between the cooling or purging gap 61 and the stationary components 17, 19. These stationary components are located at a high temperature determined by the temperature of the expanding combustion gases flowing in the expander's flow path. Controlled leakage of cooling or purging fluid from gap 61 towards the stationary blades 17 and shroud 19 prevents thermal damage to the stationary blades 17 and shroud 19, which would be caused by uncontrolled or excessive flow of the cooling or purging fluid. The controlled leakage cools the stationary components of the expander.

[0068] When the cooling or purging fluid has a high density, such as when condensed, pressurized, and recirculated carbon dioxide is used as the cooling or purging medium, it is particularly beneficial to control and minimize the flow rate of the cooling or purging fluid, because the high density and high Reynolds number of the recirculated carbon dioxide being cooled and compressed means a high heat transfer coefficient through convection on the thermally stationary components (blades 17 and shroud 19) of the expander.

[0069] Additionally, controlled cooling or purging fluid leakage is also beneficial to the overall efficiency of the expander, as less power is lost through compression and recirculation of the combustion gas; the higher flow rate of the recirculated combustion gas can be used for power generation purposes.

[0070] Although in the embodiments described so far, each ring array of fixed blades is carried by only one ring, in other embodiments, the array of fixed blades may be carried by two adjacent rings, and / or the same ring may support two or more ring arrays of fixed blades.

[0071] Figure 3An enlarged cross-sectional view of the upstream stage of the expander is illustrated, wherein fixed blades 17.2 are mounted on two adjacent rings labeled 18A and 18B. Similarly, fixed blades 17.3 are mounted on two adjacent rings 18B and 18C. In this embodiment, ring 18A also supports shroud 19.1, and ring 18B supports shroud 19.2.

[0072] Now for reference Figure 4 The enlarged view will describe one embodiment of the means for mechanically attaching the fixed blade 17 to the ring 18. Generally referring to any fixed blade 17 starting from the second expansion stage, each fixed blade or fixed impeller 17 includes an outer platform 71 and may also include an inner platform. The outer platform 71 has coupling members for connecting 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 forward edge 71.3 and a backward edge 71.4, as well as mechanical coupling features suitable for mechanically attaching the external platform 71 to a supporting structure in which... Figure 4 The middle is characterized by support ring 18.

[0075] Each external platform 71 may be integrally formed with a single fixed blade 17, meaning 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 blades 17 may be configured as arcuate segments, wherein each segment includes two or more fixed blades 17 integrally formed with a single external platform 71. The fixed blades integrally formed with the common external platform 71 also have a common internal platform 73.

[0076] Typically, the inner platform 71 and the outer platform are shaped such that when the annular fixed blades 17 are assembled with the corresponding rings 18, the multiple platforms 71 and 73 are arranged circumferentially around the axis of rotation AA and form corresponding circular bands, with multiple airfoils formed 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 1As shown in Figure 2, the mechanical coupling feature (through which each fixed blade 17 is coupled to a ring 18 or other support structure housed in the housing) includes a forward hook 77 that protrudes from the radially outer surface 71.1 of the outer platform 71 and is oriented toward the rearward edge 71.4 of the outer platform 71. More specifically, in Figure 4 In one embodiment, the forward 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 forward hook 77, the protrusion 77.2 being oriented in a rearward direction, i.e. towards the rearward edge 71.2 of the outer platform 71.

[0079] The forward hook 77 is positioned midway between the forward edge 71.3 and the rearward edge 71.4 of the outer platform 71. Considering the geometric plane PP, which is orthogonal to the axis of rotation AA and equidistant from the forward edge 71.3 and the rearward edge 71.4, dividing the outer platform 71 into a forward platform portion 71F and a rearward platform portion 71A, the forward hook 77 is preferably constrained to the outer platform 71 within its forward portion 71F. Therefore, similar to... Figure 1 As in the embodiment of Figure 2, the forward hook 77 is arranged on the side of the outer platform 71 closer to its forward edge 71.1. In some embodiments, the distal protrusion 77.2 may protrude beyond the midline plane PP toward the rearward 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, adapted to abut against the corresponding ring 18. The rib 71.5 extends adjacent to the rearward edge 71.4 of the outer platform 71 and... Figure 4 In one embodiment, rib 71.5 contacts the cylindrical inner surface 18C of ring 18. The diameter of the inner cylindrical surface 18C allows each fixed blade 17 to be mounted on ring 18 via forward-to-backward insertion.

[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 or directly to the housing 5. 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 rearward platform portion 71A extending from the forward hook 77 to the rearward edge 71.4 has a smaller thickness in the radial direction than the thickness of the forward 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 may be located between the forward hook 77 and the rearward edge 71.4 of the outer platform 71, and more precisely between the foot of the forward hook 77 and the rib 71.5, and may extend substantially parallel to the forward edge 71.3 and the rearward edge 71.4 of the outer platform 71. (As in...) Figure 1 In the embodiment of Figure 2, the recess 71.6 provides a reduction in the thickness of the rearward portion 71A of the outer platform 71.

[0083] Each forward hook 77 engages with a circular forward 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 forward hook 77 (and more specifically, its distal protrusion 77.2) into the outer platform 71.

[0084] and Figure 1 , Figure 2A , Figure 2B The implementation plans are different, in 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 to backward direction (…). Figure 4 Arrow f71) is mounted on its support ring 18. Therefore, the fixing blade 17 can be mounted on the 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 at both ends of the corresponding expansion stage, and also prevents leakage.

[0085] In the embodiments described so far, each ring 18 is integral, or in some cases may be divided into two symmetrical half-rings, each half-ring unfolding, for example, around 180°, to facilitate the mounting of the fixed blades. However, in other embodiments, one, some, or all of the rings may be divided into two partial rings, namely a first ring component and a second ring component, which are easier to manufacture and can be coupled to each other by an interference fit, preferably by a shrink fit. A shield 19 may be installed between the two partial rings or ring components. Each shield 19 may be formed of a plurality of shield segments that are installed between and held between the two ring components. Figure 5 An example of one of the rings 18 of an expander is shown, which is divided into two partial rings or ring components 18A and 18B, which are coupled to each other by a contraction fit. The two ring components are coaxial, and each ring component 18A and 18B is a one-piece integral piece extending around 360°.

[0086] In all embodiments disclosed herein, ring 18 is axially held in the housing by pressure contact between adjacent rings and / or between the ring and the housing, without requiring additional or separate locking or retaining devices, such as bolts, to provide axial holding force. Only anti-rotation features may be added to prevent the ring from rotating within the housing.

[0087] 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. An expander, the expander comprising: -Outer casing; - An inner housing, which is housed within the outer housing; - A plurality of fixed blades in a ring array, the plurality of fixed blades in a ring array being housed in the inner housing; - A rotor, which is housed within the inner housing for rotation therein; the rotor includes a rotation axis and rotor blades arranged in a plurality of annular arrays around the rotation axis; The rotor blades of each annular array are arranged downstream of a corresponding fixed blade of the fixed blades of the annular array, and form a corresponding expander stage therewith; wherein the fixed blades of each annular array are mounted on at least one corresponding ring housed in the inner housing; Each ring is in pressure contact with at least one adjacent ring or at least with the inner housing; Wherein: at least the intermediate ring is in pressure contact with its upstream ring at the forward contact surface and with its downstream ring at the backward contact surface; and the forward contact surface is further from the axis of rotation than the backward contact surface; such that, in operation, the reaction forces applied to the backward and forward contact surfaces generate a torque on the intermediate ring in the opposite direction to the torque applied by the fixed blade supported by the ring; and / or Wherein: at least one of the rings includes an annular groove forming a forward contact surface that is in pressure contact with the upstream ring; and the upstream ring has a rearward end forming a rearward contact surface that engages in the annular groove and is surrounded by the ring.

2. The expander according to claim 1, wherein the forward contact surface formed by the annular groove is cylindrical, and the backward contact surface is cylindrical.

3. The expander according to claim 1 or 2, wherein a gap for pressurizing, cooling, or purging fluid is formed between the ring and the inner housing.

4. The expander according to any one of the preceding claims, wherein the fixed blades of at least one annular array are mounted on a single ring.

5. The expander according to any one of the preceding claims, wherein the fixed blades of at least one annular array are mounted on two adjacent rings.

6. The expander according to any one of the preceding claims, wherein the ring is configured to transmit only the axial reaction force generated by the fluid flow through the respective fixed blades to the inner housing.

7. The expander according to any one of the preceding claims, wherein at least one of the rings supports a shroud, the shroud surrounding the rotor blades of the annular array, the rotor blades of the annular array being arranged downstream or upstream of fixed blades of the annular array mounted on the at least one ring of the rings.

8. The expander according to any one of the preceding claims, wherein at least one of the rings includes a channel for pressurizing, cooling, or purging fluid.

9. The expander according to any one of the preceding claims, wherein at least some of the rings include a forward contact surface that contacts the upstream ring or the inner housing, and a backward contact surface that contacts the downstream ring or the inner housing.

10. The expander of claim 9, wherein the forward contact surface, the rearward contact surface, or both the forward contact surface and the rearward contact surface are flat and orthogonal to the axis of rotation.

11. The expander according to any one of the preceding claims, wherein each ring is a single-piece ring having an integral extension of about 360°.

12. The expander according to any one of the preceding claims, wherein the inner housing is horizontally divided.

13. The expander according to any one of the preceding claims, wherein the outer housing is vertically segmented.

14. The expander according to any one of the preceding claims, the expander further comprising a burner located on the forward side of the expander, upstream of the fixed blades of the most upstream annular array.

15. The expander according to any one of the preceding claims, wherein at least one of the rings is formed by a first ring component and a second ring component coupled to each other.

16. The expander of claim 15, wherein the first ring component and the second ring component are coupled to each other by an interference fit, specifically by a shrink fit.

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