Turboelectric power generation machine that uses coolant extracted from the rotor cavity

Abstract

The turbomachinery comprises a casing (51) and a rotor (43) housed to rotate within the casing. A high-pressure region (71) and a low-pressure region (73) are located adjacent to the rotor shaft and separated by a high-pressure package seal (75) around the rotor shaft. The high-pressure package seal separates the high-pressure region from the low-pressure region, with the high-pressure region positioned on the side facing forward of the high-pressure package seal and the low-pressure region positioned on the side facing rear of the high-pressure package seal. A first rotor cavity (77) is fluid-coupled to the high-pressure region and adapted to provide coolant flow to the upstream section of the rotor. A second rotor cavity (83) is fluid-coupled to the low-pressure region and adapted to provide coolant flow to the downstream section of the rotor. A sealing member (85) separates the first rotor cavity from the second rotor cavity.

Description

Technical Field

[0001] The present disclosure relates to power generation turbomachinery such as expanders and gas turbines.

Background Art

[0002] Turbomachinery is generally used to generate mechanical power by the expansion of a high-pressure, high-temperature process fluid. The process fluid flows through a flow path that extends through a plurality of turbomachinery stages. Each stage includes an annular array of stationary blades, also known as stator vanes, and an annular array of rotor blades disposed downstream of the annular array of stationary blades in the direction of flow of the expanding process fluid. The rotor blades are attached around respective rotor disks and together form a rotor wheel of the rotor. The rotor is housed within a casing and is adapted to rotate about a rotor shaft upon receiving the thrust of the expanding gas flowing along the flow path. A wheel space is formed between the radially inwardly oriented ends of the stationary blades of each annular array and the rotor wheel.

[0003] To prevent thermal damage to the rotor wheel and extend its useful life, it is common practice to purge the wheel space with a cooling process fluid flow at an appropriate pressure. The cooling process fluid prevents the high-temperature process fluid from leaking from the flow path into the wheel space. Additionally or alternatively, a low-temperature pressurized process fluid is used to cool the rotor blades. Cooling fluid cavities or ducts are disposed within the rotor from which the cooling process fluid is supplied to the wheel space and / or blade cooling ducts through appropriate holes, slots, and calibrated passages.

[0004] The cooling process fluid must be at an appropriate pressure to reach the wheel space and / or blades at several locations along the turbomachinery flow path, overcoming head loss through the duct and the pressure of the process fluid within the flow path. The pressure of the process fluid along the flow path decreases from upstream to downstream, i.e., from front to back, following expansion in the continuously arranged stages of the turbomachinery.

[0005] Providing an appropriate pressure level for the cooling fluid, particularly in the upstream stage of the flow path, becomes challenging in turbomachinery operating at high pressure levels, such as supercritical expanders commonly used in Aram cycles and similar thermodynamic cycles.

[0006] Providing adequate cooling and / or purging, while simultaneously reducing the amount of cooling fluid, is crucial for improving the overall efficiency of turbomachinery and preventing thermal damage to rotor components, especially when turbomachinery operates under high temperature and high pressure conditions.

[0007] In some known turbomachinery, such as gas turbine engines, process fluids are drawn from different stages of the gas turbine engine's air compressor at different pressure levels and supplied to different parts of the turbine rotor. This arrangement is not possible in turbomachinery that does not include an inline compressor, such as the expander in an oxygen fuel combustion cycle, and in turbomachinery with a central tie rod.

[0008] Therefore, a more efficient arrangement for supplying cooling process gases within the wheel space of a power-generating turbomachinery would be welcome in the art. [Overview of the Initiative]

[0009] In one embodiment, this specification discloses a power-generating turbomachine, such as an expander, comprising a casing and a number of stages. Each stage comprises an annular row of fixed blades fixedly arranged within the casing and an annular row of rotor blades forming part of a rotor. Each annular row of rotor blades can be mounted on its respective rotor wheel or integrated with part of a rotor shaft. The rotor shaft includes a front shaft portion and a rear shaft portion. The annular row of rotor blades is positioned between the front shaft portion and the rear shaft portion and can be mounted directly to these portions and / or to discs stacked on top of each other between the front shaft portion and the rear shaft portion. The turbomachine stages are arranged sequentially from the upstream stage to the downstream stage in a front-to-rear direction, defining an expansion passage extending from the intake side to the exhaust side of the turbomachine.

[0010] As used herein, “upstream” and “downstream” are terms indicating the direction of the process fluid flowing through the expansion channel of a turbomachinery, or the flow of coolant through one of the turbomachinery components.

[0011] As used herein, “forward” and “rear” refer to the direction of the process gas flow through the expander 3. Specifically, “forward” refers to the intake side of the turbomachinery, and “rear” refers to the exhaust side of the turbomachinery. Therefore, as used herein, the direction from “forward to rear” is the direction from the intake end to the exhaust end of the turbomachinery, that is, the direction of the process gas flow expanding through the turbomachinery.

[0012] The turbomachinery further comprises a high-pressure region adjacent to the rotor shaft, more specifically adjacent to or around the forward shaft portion of the rotor shaft. The turbomachinery further comprises a low-pressure region adjacent to the rotor shaft, more specifically adjacent to or around the forward shaft portion. The low-pressure region is located downstream of the high-pressure region in the forward-to-rear direction, i.e., in the direction of the process fluid flow across the turbomachinery. The high-pressure and low-pressure regions are located upstream of the stationary blades and rotor blades that form the expansion stage of the turbomachinery with respect to the flow direction of the process fluid expanding within the turbomachinery.

[0013] In some embodiments, the high-pressure region and the low-pressure region can extend around the rotor shaft, for example, in the form of annular plenums.

[0014] The high-pressure and low-pressure regions are separated from each other by a high-pressure package seal around the rotor shaft. The high-pressure region is located upstream of the high-pressure package seal in the front-to-rear direction, i.e., on the side facing the front of the high-pressure package seal. The low-pressure region is located downstream of the high-pressure package seal in the front-to-rear direction, i.e., on the side facing the rear of the high-pressure package seal.

[0015] The first rotor cavity is fluid-coupled to the high-pressure region and adapted to provide a coolant flow, i.e., a flow of cooling fluid, to the upstream section of the rotor.

[0016] The second rotor cavity is fluid-coupled to a low-pressure region and adapted to provide a coolant flow, i.e., a flow of cooling fluid, to the downstream section of the rotor. The coolant may be a side flow of the same process fluid expanding through an expansion channel. The process fluid used as the coolant flows from the high-pressure region into the first rotor cavity. The process fluid leaking through the high-pressure package seal enters the low-pressure region and from there is supplied to the second rotor cavity at a lower pressure than the process fluid in the first rotor cavity. A sealing member separates the first and second rotor cavities from each other.

[0017] A low-pressure region adjacent to or around the rotor shaft can be fluid-coupled to a first wheel space located between the fixed blades of the first annular row and the rotor blades of the first annular row, i.e., the rotor blades of the first expansion stage, when viewed from front to rear along the expansion flow path. In some embodiments, the low-pressure region and the first wheel space are at substantially the same pressure. As understood herein, “at substantially the same pressure” means that there is no separating seal between the low-pressure region and the first wheel space, such that the first wheel space forms part of the low-pressure region. The first wheel space receives coolant flow from the low-pressure region adjacent to or around the rotor shaft.

[0018] Therefore, the coolant leaking through the high-pressure package seal is divided into a first flow directed towards the first wheel space and used to purge the first wheel space between the fixed blades and rotor blades of the first (i.e., the most upstream) stage of the turbomachinery, and a second flow directed towards the second rotor cavity and used to cool and / or purge the downstream section of the rotor. Higher pressure coolant from the high-pressure region adjacent to or around the rotor shaft is supplied into the first rotor cavity and used to cool or purge the upstream section of the rotor where higher pressure coolant is required. The upstream section of the rotor comprises rotor components such as rotor blades and wheel space between the first annular row of rotor blades and the downstream rotor section.

[0019] Therefore, the flow rate of coolant leaking through the high-pressure package seal can be greater than the flow rate required to purge or cool the first wheel space, because some of the coolant leaking through the high-pressure package seal is used to purge the downstream section of the rotor where a lower coolant pressure is sufficient.

[0020] Therefore, the entire coolant flow rate leaking through the high-pressure package seal is actively utilized for purging purposes, resulting in particularly efficient operation of the turbomachinery. High-performance seals downstream of the high-pressure region are not required because the coolant leaking through them is used for purging or cooling purposes. Since the high-pressure package seal does not need to provide a complete seal against coolant leakage, its axial dimensions can be reduced, resulting in a smaller overall footprint for the turbomachinery. [Brief explanation of the drawing]

[0021] Here, we will briefly refer to the attached diagram. [Figure 1] This is a cross-sectional view of the expander of the present disclosure along a plane containing the rotor's axis of rotation. [Figure 2] Figure 1 shows an enlarged view of the flow path of the expander. [Figure 3] An enlarged view of the flow path of the expander in a further embodiment is shown. [Figure 4] This disclosure shows an oxygen fuel combustion circuit including an expander. [Modes for carrying out the invention]

[0022] To mitigate the shortcomings and limitations of current technology as outlined above, according to this disclosure, the cooling or purging process fluid is drawn directly from a first wheel space, i.e., from the wheel space between the fixed blades of the first row and the rotor blades of the first row that form the first expansion stage of the turbomachinery. The pressure in the first wheel space is lower than the maximum available pressure of the process fluid at the intake of the turbomachinery. Therefore, the coolant at the pressure of the first wheel space can be used to cool the downstream section of the rotor, reducing overall coolant consumption.

[0023] In the embodiments disclosed herein, a high-pressure region and a low-pressure region are formed around the front shaft portion. The high-pressure region contains a process fluid at the highest pressure available in the thermodynamic cycle, while the low-pressure region can be fluid-coupled to the first wheel space of the turbomachine. A seal around the rotor shaft (hereinafter referred to as the high-pressure package seal) separates the high-pressure region from the low-pressure region. The process gas leaks through the high-pressure package seal from the high-pressure region towards the low-pressure region. The high-pressure region is fluid-coupled to the first rotor cavity, and the low-pressure region is fluid-coupled to the second rotor cavity. In the first rotor cavity, a cooling fluid exists at a higher pressure than in the second rotor cavity, and the two cavities are separated by a seal member. The coolant from the first rotor cavity is used to cool or purge a more upstream section of the rotor where a higher coolant pressure is required, and the coolant from the second rotor cavity is used to cool or purge a more downstream section of the rotor.

[0024] Thus, in contrast to current technology cooling and purge systems that use coolants from different compressor stages, e.g., different pressure sources, in the turbomachine of the present disclosure, the high-pressure coolant and the low-pressure coolant are diverted from the high-pressure region and the low-pressure region, respectively, and these regions are arranged around the front shaft portion of the rotor and separated from each other by the high-pressure package seal. The low-pressure region is fluid-coupled to the first wheel space or forms part of the first wheel space. Thus, the process gas leaking through the high-pressure package seal along the front shaft portion is used to purge the first wheel space and the downstream section of the rotor, while the intermediate section of the rotor arranged between the first wheel space and the downstream section of the rotor is purged with the cooling process gas taken from the high-pressure region upstream of the high-pressure package seal.

[0025] In the following description, as an exemplary embodiment of a power generation turbomachine according to the present disclosure, specifically, an expander, more specifically, a supercritical carbon dioxide (sCO2) expander is referred to. Those skilled in turbomachinery will nevertheless understand that the novel features disclosed herein can be advantageously used in expanders that use fluids different from carbon dioxide or carbon dioxide in a non-supercritical state, or in other power generation turbomachines such as gas turbines, or in a gas turbine engine including a compressor section, a combustor, and a turbine section.

[0026] The novel features disclosed herein are particularly beneficial, for example, in expanders operating at high pressures where the available maximum pressure in the thermodynamic cycle is 50 barA or more, for example 300 barA or more.

[0027] In some embodiments, the expander 3 includes an outer casing 41 that houses a combustor 7, for example, a can-type combustor, an annular combustor, a can-annular combustor (also known as a cannular combustor). The combustor can include a plurality of combustor chambers 7A arranged around the axis A-A of the expander 3.

[0028] In other embodiments not shown, the combustor can be arranged outside the expander. In yet another embodiment, the expander may not include a combustor and can be used in a closed thermodynamic cycle, in which case heat is transferred to the process fluid, for example, through a heat exchanger.

[0029] In some embodiments, the outer casing 41 includes a body 41.1, which is referred to herein as the high-pressure casing, and a closure 41.2, which is referred to herein as the low-pressure exhaust casing.

[0030] The low-pressure exhaust casing 41.2 can be positioned on the discharge side of the expander 3, that is, the rear side, that is, on the opposite side of the combustor 7 located on the front side of the expander 3.

[0031] The high-pressure casing 41.1 and the low-pressure exhaust casing 41.2 can be connected to each other along a plane P perpendicular to the axis of rotation AA of the rotor 43, which is supported to rotate within the outer casing 41. Thus, the expander 3 is a vertical split expander. In other embodiments, the expander may be a horizontal split expander, comprising a casing with two casing portions connected to each other along a plane containing the axis of rotation AA of the rotor 43.

[0032] In some embodiments, the low-pressure exhaust casing 41.2 forms an exhaust volute or exhaust plenum 41.3 through which the exhausted flue gas is discharged from the expander 3.

[0033] Reference numerals 45 and 47 indicate bearing devices that rotatably support the rotor 43. For example, the bearing device 45 on the opposite side from the combustor 7, i.e., the rear side, may include an axial bearing or thrust bearing combined with a radial bearing, or a bearing having axial-radial bearing capability. The bearing device 47 on the combustor side, i.e., the front side, may include a radial bearing. The reverse arrangement is also possible, with a bearing having axial load capacity located on the combustor side. The bearing devices 45 and 47 can be housed in bearing casings not shown in detail.

[0034] In some embodiments, the rotor 43 is housed in an inner casing 51 and fixedly housed in an outer casing 41.

[0035] In the embodiments of Figures 1 and 2, the expander 3 includes multiple stages. As merely an example, the expander in Figures 1 and 2 includes eight stages. However, those skilled in the art will understand that the novel features disclosed herein may also be beneficial in expanders having different numbers of stages, specifically at least two stages, or three stages, or more stages. Each stage includes an annular row of fixed vanes or fixed blades 53 fixedly arranged within the outer casing 41. In the exemplary embodiment of Figure 1, the annular row of fixed blades 53 is housed in the inner casing 51. Each expansion stage further includes each annular row of rotor blades 55 positioned downstream of each annular row of fixed blades 53 along an expansion flow path extending from front to rear through the multiple expansion stages of the expander from the combustor 7 to the exhaust plenum 41.3. Specifically, each annular row of fixed blades in the i-th stage is labeled 53.i, and each annular row of rotor blades in the i-th stage is labeled 55.i, where i=1 to 8 in this exemplary embodiment. In this specification, reference numeral 53 is used to indicate a general annular row of fixed blades or individual fixed blades. Reference numeral 55 is used to indicate a general annular row of rotor blades or individual rotor blades.

[0036] In some embodiments, the first, i.e., the upstream, annular row of fixed blades 53.1 may be located at the discharge end of the combustor 7, forming an array of nozzles that guide the high-temperature, high-pressure process fluid from the combustor chamber 7A of the combustor 7 to the first annular row of rotor blades. The first annular row of rotor blades 55.1 is located immediately downstream of the first annular row of fixed blades 53.1. The last, i.e., downstream, annular row of fixed blades 53.8 may be located upstream of the last, i.e., downstream annular row of rotor blades 55.8, near the discharge plenum 41.3.

[0037] The rotor blades 55 constitute part of the rotor 43, i.e., they are connected to rotate with the rotor shaft. In the embodiment, each annular row of rotor blades 55 (i.e., each row 55.i where i=1 to 8 in the exemplary embodiment shown) is mounted on a respective rotor disk. The rotor disks are labeled 57.i, i=1 to 8. Reference numeral 57 indicates a typical rotor disk.

[0038] A unit comprising a rotor disc 57 and annular rows of rotor blades 55 is also referred to herein as a rotor wheel and is labeled 58, where 58.1 (Figure 2) is the first rotor wheel in the upstream direction, i.e., from front to back, and 58.8 is the last rotor wheel in the downstream direction, i.e., from front to back.

[0039] Each rotor blade 55 in each stage can be manufactured separately from each rotor disk 57 and mechanically mounted thereon, as schematically shown in Figures 1 and 2. In other embodiments, each rotor blade 55 and rotor disk 57 in each stage can be manufactured as a monolithic body, for example by additive manufacturing. In yet another embodiment, two design options can be combined. One or more stages may include each monolithically manufactured component, including the rotor blades and disks, while one or more stages may include a rotor disk and separately manufactured rotor blades mechanically coupled to the rotor disk.

[0040] In some embodiments, the rotor discs 57 are stacked and connected to each other by tie rods. In the exemplary embodiments shown in Figures 1 and 2, the tie rods include a plurality of tie rods 61 positioned at a certain distance from the rotation axis AA, and a central tie rod 63 that is coaxial with the rotor 43.

[0041] In other embodiments, different arrangements of tie rods can be provided, for example, only a single tie rod in the center coaxial with the rotor 43, or only a set of tie rods arranged around axis AA at radial distances from it. In yet another embodiment, tie rods can be provided at different distances from the rotating axis AA.

[0042] In some embodiments, the rotor 43 further comprises a front shaft portion 65 and a rear shaft portion 67. Each of the front shaft portion 65 and the rear shaft portion 67 may include one or more sections connected to each other, for example by tie rods, as shown in the example for the front shaft portion 65.

[0043] In the embodiments shown in Figures 1, 2, and 3, all rotor blades are mounted on rotor discs, which are stacked on top of each other between the front shaft portion 65 and the rear shaft portion 67. In other embodiments not shown, one or more annular rows of rotor blades may be mounted directly on (or manufactured integrally with) the front shaft portion, and / or one or more annular rows of rotor blades may be mounted directly on (or manufactured integrally with) the rear shaft portion. In some embodiments, the rotor may include a front shaft portion and a rear shaft portion connected to each other by tie rods or the like, and all stages of rotor blades may be mounted on either the front shaft portion or the rear shaft portion, or partially on the front shaft portion and partially on the rear shaft portion, without intermediate rotor discs (or manufactured integrally with the rear shaft portion).

[0044] In some embodiments, the combustor 7 extends around the front shaft portion 65. In some embodiments, the exhaust plenum 41.3 extends around the rear shaft portion 67.

[0045] In some embodiments, referring to Figure 1, the front shaft portion 65 and the rear shaft portion 67 are connected to the rotor disc 57 in a stacked arrangement by the tie rod arrangement described above.

[0046] In some embodiments, each rotor disc 57 is provided with front teeth on both its front-facing and rear-facing sides. The front teeth are provided for torsional engagement of adjacent components of the rotor 43. In the embodiments of Figures 1 and 2, the front-facing side of the upstream rotor disc 57.1 engages with the front shaft portion 65, and the rear-facing side of the downstream rotor disc engages with the rear shaft portion 67.

[0047] In some embodiments, each sealing disc 68, also known as a spacing disc or spacer, is positioned between each pair of consecutive (i.e., adjacent) rotor discs 57. When the sealing discs 68 are scattered between pairs of rotor discs 57, each sealing disc 68 has front teeth on both sides, and the consecutively arranged rotor discs 57 are twisted together via the interposed sealing discs 68, forming hearth joints between both sides of each rotor disc 57 and each sealing disc 68.

[0048] As used herein, the term “torsion-connected” means a connection adapted to transmit torque between torsion-connected components so that the torsion-connected components rotate individually around the rotor’s axis of rotation AA.

[0049] Each sealing disc or spacer 68 features an annular seal 68A adapted to cooperate with the radially inward-facing end of the fixed blade 53. In some embodiments, an annular shroud may be provided to connect the radially inward-facing end of the fixed blade, in which case the annular seal 68A cooperates with the shroud, although this is not mandatory.

[0050] In Figures 1 and 2, the sealing disc or spacer 68 extends radially inward between adjacent rotor discs 57, but in other embodiments, the rotor discs 57 may be stacked in direct contact with each other and each may have front teeth of a hearth joint that directly transmit torque from one rotor disc 57 to an adjacent rotor disc 57. In this case, the annular seal can engage between adjacent rotor wheels near the feet of each rotor blade 55 in an arrangement that cooperates with the ends of the radially inward-facing fixed blades 53.

[0051] In either case, the annular seal or sealing disc 68 provides a seal to the radially inward-facing end of the stationary blade, preventing the expanding process fluid from leaking toward the rotor axis from the expansion passage defined by the scattered rows of stationary and rotor blades, which carries the risk of thermal damage to the rotor disc.

[0052] During operation, when the expander 3 is operating in an oxygen-fuel cycle, a pressurized process fluid, such as a mixture of oxygen and carbon dioxide, is supplied to the combustor 7, mixed with fuel, and burned to produce a high-temperature pressurized process fluid, i.e., a high-temperature pressurized flue gas, which expands along the expansion channel formed by an annular array of continuously arranged fixed vanes and annular arrays of rotor blades, generating mechanical power, which becomes available on the rotor shaft at either the rear end, the front end, or both the rear and front ends. The mechanical power is converted into electricity by a generator drivably coupled to the shaft of the rotor 43 and / or can be used to drive loads such as compressors, pumps, or other rotating equipment. A gearbox can be provided along the axis between the expander and the load connected to it so that the load can rotate at a speed different from the rotational speed of the expander.

[0053] If the expander does not include a combustor and is located in a closed thermodynamic cycle, the compressed process fluid may be heated, for example, by heat exchange in a heat exchanger before expansion.

[0054] The flow of cooling or purging process fluid is diverted from the main cycle at the highest available pressure in the cycle, i.e., upstream of the expander, and at lower temperatures, i.e., upstream of the combustor 7 or heat exchanger. The cooling process fluid is supplied to the rotor 43 of the expander 3 and extracted from a cavity provided therein to purge the wheel space of the rotor and / or cool the rotor blades, particularly the uppermost stage rotor blades. The cooling process fluid prevents or limits leakage of the expanding process fluid from the expansion passage toward the rotor disk 57, thus improving the efficiency of expansion and preventing thermal damage to the rotor disk 57. Additionally or alternatively, cooling fluid supplied to the cooling system, particularly within the first stage rotor blades, prevents thermal damage thereto and allows the expander 3 to operate with higher temperature process fluids, thereby increasing the efficiency of the thermodynamic cycle.

[0055] For effective cooling or purging of the rotor 43, the present disclosure provides a novel arrangement of cooling ducts and cavities, which can reduce the consumption of process fluid for cooling or purging purposes, increase cooling or purging efficiency, and simplify the structure of the machine.

[0056] Specifically, the expander 3 includes a high-pressure region 71 adjacent to the rotor 43. In some embodiments, the high-pressure region 71 unfolds in an annular shape around a portion of the rotor 43. In some embodiments, the high-pressure region 71 surrounds the front shaft portion 65 of the rotor 43. The high-pressure region 71 may be defined on the side facing forward by the balance drum 72 of the turbo expander.

[0057] The high-pressure region 71 is adapted to be fluid-coupled to a process fluid path upstream of the combustor 7, where, during operation, the process fluid reaches the highest pressure available in the thermodynamic cycle performed by the process fluid. Therefore, when in use, the high-pressure region 71 contains high-pressure process fluid. For example, the high-pressure region 71 can be fluid-coupled to the supply side of a process fluid compressor (not shown). The fluid pressure in the high-pressure region 71 is typically slightly higher than the pressure in the combustor 7 to prevent combustion gases from leaving the combustor and entering the high-pressure region 71.

[0058] The process fluid supplied to the high-pressure region 71 is at a low temperature, i.e., close to the temperature on the supply side of the process fluid compressor.

[0059] The expander 3 further comprises a low-pressure region 73 adjacent to the rotor 43. In some embodiments, the low-pressure region 73 extends around the rotor shaft and forms an annular portion around it. In some embodiments, the low-pressure region 73 extends around the front shaft portion 65.

[0060] In some embodiments, the low-pressure region 73 includes a first wheel space 73A located between the first stage nozzle, i.e., the fixed blades 53.1 of the first annular row and the first rotor wheel 58.1, when viewed from front to rear.

[0061] The low-pressure regions 73 and 73A are separated from the high-pressure region 71 by an annular seal 75 (see Figure 2), referred to herein as the high-pressure package seal 75, which surrounds the rotor shaft, specifically the forward shaft portion 65 of the rotor shaft. Specifically, the high-pressure region 71 is located on the side of the high-pressure package seal 75 facing the front end of the expander 3, and the low-pressure region 73 is located on the side of the high-pressure package seal facing the rear end of the expander 3.

[0062] The pressure of the process gas leaking through the high-pressure package seal 75 (arrow fL in Figure 2), i.e., the pressure in the low-pressure region 73, is lower than the maximum usable pressure of the process fluid present in the high-pressure region 71. Specifically, in the illustrated embodiment, the pressure in the low-pressure region 73, including the first wheel space 73A, is set by the expansion within the fixed blades 53.1 of the first annular row. As will become apparent from the following description, the low-pressure process fluid contained in the low-pressure region 73 is at a pressure sufficient to cool or purge the stage of expander 3 located downstream of the first expander stage.

[0063] The rotor 43 includes a first rotor cavity 77 that is fluidly coupled to a high-pressure region 71 via one or more high-pressure coolant ducts 79 (Figure 2). In some embodiments, the first rotor cavity 77 may be coaxial with the rotor axis AA.

[0064] In some embodiments, multiple high-pressure coolant ducts 79 are provided around the rotation axis AA of the rotor 43. Each high-pressure coolant duct 79 extends from an inlet end 79.1 fluidly coupled to a high-pressure region 71 to an outlet end 79.2 fluidly coupled to a first rotor cavity 77.

[0065] In the exemplary embodiments of Figures 1 and 2, the first rotor cavity 77 is adapted to provide coolant flow to at least the second wheel space between the first rotor wheel 58.1, the second rotor wheel 58.2, and the second row of fixed blades 53.2. In the embodiments of Figures 1 and 2, the coolant flow, indicated by arrow C (Figure 2), flows from the first rotor cavity 77 through slots, holes and / or calibrated passages to the cavity 81 between the first rotor wheel 57.1, the second rotor wheel 57.2, and the annular seal 68A of the sealing disc 68 between them.

[0066] From the cavity 81, the coolant flow C leaks between the spacer 68 and the mutually opposing surfaces of the rotor wheels 58.1 and 58.2, preventing the expanding process fluid from flowing into the wheel space and towards the rotor discs 57.1 and 57.2 within the cavity 81.

[0067] To properly purge the cavity 81 and the second wheel space between the first rotor wheel 58.1, the second rotor wheel 58.2, and the fixed blades 53.2 of the second stage, the coolant in the first rotor cavity 77 must be at a pressure sufficient to overcome the head loss along the coolant passage from the first rotor cavity 77 to the second wheel space. The maximum available pressure of the process fluid in the high-pressure region 71 is sufficient to provide a proper flow of purging coolant toward the second wheel space. In some embodiments, the coolant flow C1 may be provided between the cavity 81 and the cooling system in the rotor blades 55.1 of the first rotor wheel 58.1.

[0068] The first rotor cavity 77 extends axially from the front shaft portion 65 to the intermediate rotor disk 57. In the embodiments shown in Figures 1 and 2, the first rotor cavity 77 extends to the second rotor disk 57.2 of the second rotor wheel 58.2. In other embodiments, the first rotor cavity 77 may have a larger axial extension and may terminate at a third rotor disk 57.3 or a fourth rotor disk 57.4, for example, as shown below with reference to further embodiments.

[0069] The rotor 43 further comprises a second rotor cavity 83 which can extend along the axis of rotation AA from the front shaft portion 65 toward the rear shaft portion 67. The second rotor cavity 83 is coaxial with the axis of rotation AA and can surround the tie rod 63.

[0070] The second rotor cavity 83 is fluidically separated from the first rotor cavity 77 by a sealing member 85. In some embodiments, the sealing member 85 may have a substantially cylindrical shape and may extend coaxially with the axis of rotation AA of the rotor 43 from the forward shaft portion 65 to the second rotor disk 57.2 (or, if the first rotor cavity 77 extends further downstream of the second rotor disk 58.2 as described above, to another further downstream rotor disk).

[0071] The second rotor cavity 83 is fluid-coupled to the low-pressure region 73 and, therefore, to the first wheel space 73A, which forms part of the low-pressure region 73. The low-pressure coolant flows into the first wheel space 73A (arrow f73 in Figure 2) and into the second rotor cavity 83 through one or more low-pressure coolant ducts 87 extending from the low-pressure region 73 to the second rotor cavity 83. The low-pressure coolant ducts 87 can extend radially or be inclined radially, as shown in Figures 1 and 2. The low-pressure coolant flow through the ducts 87 is illustrated by arrow f87, as shown in Figure 2.

[0072] Therefore, a coolant flow at a pressure lower than the maximum pressure available in the cycle is supplied into the second rotor cavity 83 (see arrow f83) and into the first wheel space 73A. As described above, the pressure in the low-pressure region 73, including the first wheel space 73A, is set by the expansion in the fixed blades 53.1 of the first annular row. Depending on the value of this pressure, the first rotor cavity 83 may extend further downstream of the second rotor wheel 58.2, as described above.

[0073] Specifically, each low-pressure coolant duct 87 has an inlet end 87.1 at a radially outward position within the low-pressure region 73 and an outlet end 87.2 at a radially inward position within the second rotor cavity 83.

[0074] In some embodiments, as best shown in Figure 2, the outlet end 87.2 of each low-pressure coolant duct 87 is positioned radially inward relative to the outlet end 79.2 of each duct 79. In other words, the outlet end 87.2 of each low-pressure coolant duct 87 is located at a distance less than the distance between the outlet end 79.2 of each high-pressure coolant duct 79 and the rotor axis AA. Thus, the low-pressure coolant ducts 87 and high-pressure coolant ducts 79 intersect each other.

[0075] In the embodiments shown in Figures 1 and 2, the pressure of the coolant in the second rotor cavity 83 is sufficient for the coolant to purge at least a portion of the wheel space downstream of the second rotor wheel 58.2. In the embodiments shown in Figures 1 and 2, the coolant pressure in the low-pressure region 73 is drawn from the second rotor cavity 83 and used to purge the wheel space downstream of the furthest downstream wheel space that has been cooled by the coolant from the first rotor cavity 77. In the illustrated embodiments, the coolant from the second rotor cavity 83 is used to purge and / or cool the wheel space from the second rotor wheel 58.3 to the last rotor wheel 58.8.

[0076] Generally, the first rotor cavity 77 can be fluid-coupled to a first group of the upstream wheel spaces, and the second rotor cavity 83 can be fluid-coupled to a second group of wheel spaces downstream of the first group of the upstream wheel spaces. In the embodiments of Figures 1 and 2, the first group of the upstream wheel spaces includes only the wheel spaces between the first, i.e., the upstream rotor wheel 58.1 and the second rotor wheel 58.2, but in other embodiments, one or more subsequent wheel spaces can also be purged by the coolant process fluid from the first rotor cavity 77.

[0077] In other words, in some embodiments, for example, depending on the pressure in the first wheel space 73A, the first rotor cavity 77 may extend further downstream, and the high-pressure coolant supplied therein can be used to purge the wheel space downstream of the second annular row of rotor blades 55.2.

[0078] The coolant from the second rotor cavity 83 can also be used to cool one or more rotor blades 55 of the rotor wheel downstream of the rotor wheel 58.1.

[0079] As a result of the above arrangement, separate high-pressure coolant flows (arrow f79 in Figure 2) and low-pressure coolant flows (arrow f87 in Figure 2) are supplied at different pressure levels into the first rotor cavity 77 and the second rotor cavity 83. From there, the coolant is supplied at different locations along the expansion flow path of the expander for purging and / or cooling purposes. In the second rotor cavity 83, a lower coolant pressure is available, which is sufficient for the purpose of cooling and purging the expansion stage further downstream.

[0080] In the exemplary embodiments shown in Figures 1 and 2, no sealing device is provided between the first wheel space 73A and the region immediately downstream of the high-pressure package seal 75, so the coolant pressure in the second rotor cavity 83 may be approximately the same as the pressure in the first wheel space 73A. In other embodiments, the option is not ruled out to position an additional seal surrounding the rotor between the low-pressure region 73 and the first wheel space 73A such that the coolant pressure in the second rotor cavity 83 is higher than the pressure in the first, i.e., the upstream wheel space.

[0081] In some embodiments not shown, the fluid coupling between the low-pressure region 73 and the second rotor cavity 83 can be designed such that the pressure in the second cavity 83 is lower than the pressure in the low-pressure region 73. This may be necessary, for example, to reduce the flow rate of the purge cooling fluid flowing from the low-pressure region 73 to the inner cavity 83. This can be achieved, for example, by providing a coolant duct 87 designed to create a head loss between its respective inlet 87.1 and outlet 87.2. For example, the diameter of the coolant duct 87 can be designed to be narrow enough to establish a desired pressure drop through the coolant duct 87 such that the pressure in the second cavity 83 is lower (but not nearly the same as) the pressure in the low-pressure region 73.

[0082] In the embodiments of Figures 1 and 2, the first rotor cavity 77 provides coolant to the upstream section of the rotor and / or the respective rotor blades, including the second wheel space between rotor wheel 58.1 and rotor wheel 58.2. The second rotor cavity 83 provides coolant to the downstream section of the rotor, including the remaining stages of the expander, in the illustrated embodiment. However, this is not the only possible arrangement.

[0083] Depending on the pressure required for the coolant in the continuously arranged expander stages, the first rotor cavity 77 can be designed to provide coolant flow not only to the second wheel space between the first rotor wheel 58.1 and the second rotor wheel 58.2, but also to more.

[0084] Figure 3 shows a cross-sectional view of the expander 3 in another embodiment, in which the upstream section of the rotor has an additional wheel space. The same reference numerals in Figures 1 and 2 are used to indicate the same or equivalent parts described above and again will not be described in detail. In Figure 3, the first rotor cavity 77 extends from the forward shaft portion 85 to the third rotor disc 57.3 and provides coolant or purge fluid to the second wheel space and the third wheel space, i.e., the wheel space between the first rotor wheel 58.1 and the third rotor wheel 58.3, which represent the upstream section of the rotor. The sealing member 85 seals and separates the first rotor cavity 77 from the second rotor cavity 83, which provides coolant to the downstream section of the rotor at a lower pressure.

[0085] In some embodiments, the expander 3 may be a CO2 expander for an oxygen combustion cycle, such as an ARAM or NET-POWER thermodynamic cycle.

[0086] Referring further to Figures 1, 2, and 3, Figure 4 shows an exemplary power generation system based on an oxygen-fuel thermodynamic cycle, in which the expander 3 according to this disclosure can be used. The system in Figure 4 is shown as an exemplary and non-limiting embodiment, and it should be understood that the novel features disclosed above may be embodied in expanders for different thermodynamic cycles or in other power generation machines.

[0087] The combustor 7 of the expander 3 is supplied with an oxidizer stream provided by an oxidizer source. The oxidizer may contain oxygen (O2), oxygen and carbon dioxide (CO2), or a mixture mainly consisting of these. The oxidizer stream can be generated by an air separation unit 9 having an oxidizer source. The air separation unit 9 can remove nitrogen or nitrogen and carbon dioxide from the ambient air to generate the necessary oxidizer stream supplied to the combustor 7 of the expander 3 through the oxidizer line 11. In some embodiments, the latter may contain about 20 vol% oxygen and 80 vol% carbon dioxide for easier handling of the oxidizer stream. The above CO2 and O2 ratios are examples. Carbon dioxide can be added to the oxygen through a recirculation line 12, as will be described in detail below.

[0088] Reference numeral 13 indicates a fuel supply line adapted to supply natural gas, such as methane, to the combustor 7, specifically to each combustor chamber 7.1. The oxidizer and fuel are supplied under high pressure from the inlet side of the expander 3 to the combustor 7.

[0089] The mixture of oxidizer and fuel is burned in the combustor 7. The pressurized, high-temperature combustion gas produced by the combustion expands the passage of the expander 3, and the expanded exhaust flue gas is discharged to the discharge side of the expander 3 in the discharge line 15.

[0090] The circuit in Figure 4 further includes a regenerative heat exchanger 17, where the high-temperature flue gas flowing through the high-temperature side 17.1 of the regenerative heat exchanger 17 is cooled by heat exchange with the flow of cooled flue gas flowing through the low-temperature side 17.2 of the regenerative heat exchanger 17. The flue gas discharged from the high-temperature side 17.1 of the regenerative heat exchanger 17 is further cooled in a cooling heat exchanger 19 to a temperature that causes condensation of the vapor contained in the discharged flue gas. The condensed water is removed from the exhausted flue gas in a water / gas separator 21.

[0091] The dehydrated, exhausted, and cooled flue gas, consisting mainly or exclusively of carbon dioxide, is compressed in the flue gas compressor 23 to the pressure on the inlet side of the expander 3. The supply-side pressure of the compressor 23 is the maximum pressure of the thermodynamic cycle including the expander 3.

[0092] The compressed flue gas supplied by the flue gas compressor 23 is partially removed from the cycle through the discharge line 25. If the compressor 23 is characterized by multiple compression turbomachines arranged in series, the discharge line 25 may be connected between two consecutively arranged turbomachines and / or to the discharge side of the furthest downstream compression turbomachine.

[0093] The remaining compressed flue gas is sent through the low-temperature side 17.2 of the regenerative heat exchanger 17, heated by heat exchange with the high-temperature flue gas flowing through the high-temperature side 17.1 of the regenerative heat exchanger 17, and recirculated to the expander 3 through the recirculation line 25. The flue gas recirculated through the recirculation line 25 is mixed with the combustion gas produced in the combustor 7 or with the oxidizer stream from the oxidizer line 11.

[0094] The mechanical power generated by the expansion of the combustion gas in the expander 3 is available at the output shaft end 31 for mechanical drive or power generation purposes. In the exemplary embodiment shown in Figure 4, the output shaft end 31 is drivable either directly to the generator 33 or via a gearbox, joint, or a combination thereof.

[0095] The side flow of cooled flue gas at the highest pressure of the thermodynamic cycle is supplied to the expander 3 through a cooling line 27 that bypasses the regenerative heat exchanger 17. The cooling line 27 is fluid-coupled to the high-pressure region 71 of the expander 3 and provides a flow of coolant that is distributed to the first rotor cavity 77, the low-pressure region 73, and the second rotor cavity 83 as described above.

[0096] The novel features of the coolant distribution system described with reference to Figures 1 to 3 can also be used in gas turbine engines.

[0097] Exemplary embodiments are disclosed above and shown in the accompanying drawings. Those skilled in the art will understand that various modifications, omissions, and additions may be made to those specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

1. It is a power generation turbomachine, Casing (41, 51) and A plurality of annular rows of fixed blades (53) arranged within the casing, A rotor (43) housed within the casing to rotate around a rotor axis (A-A), the rotor comprising a rotor shaft having a front shaft portion (65) and a rear shaft portion (67), and a plurality of annular rows of rotor blades (55), wherein the fixed blades (53) of each annular row and the rotor blades (55) downstream thereof form a turbomachinery stage, and the turbomachinery stage defines an expansion passage extending from front to rear from the uppermost stage to the lowermost stage, the rotor (43), The high-voltage region (71) adjacent to the front shaft portion (65), The low-pressure region (73) adjacent to the front shaft portion (65), A high-pressure package seal (75) around the front shaft portion, wherein the high-pressure package seal (75) has a side facing forward and a side facing rear, the high-pressure package seal (75) separates the high-pressure region (71) and the low-pressure region (73) from each other, the high-pressure region (71) is located on the side facing forward of the high-pressure package seal (75), and the low-pressure region (73) is located on the side facing rear of the high-pressure package seal (75), A first rotor cavity (77) is fluid-coupled to the high-pressure region (71) and adapted to provide a high-pressure coolant flow to the upstream section of the rotor, A second rotor cavity (83) is fluid-coupled to the low-pressure region (73) and adapted to provide a low-pressure coolant flow to the downstream section of the rotor, The rotor is housed in a sealing member (85) that separates the first rotor cavity (77) and the second rotor cavity (83) from each other, The low-pressure region (73) includes a first wheel space (73A) positioned between the first annular row fixed blades (53.1) and the first annular row rotor blades (55.1) of the uppermost stage, and during use, coolant leaking from the high-pressure region (71) to the low-pressure region (73) through the high-pressure package seal (75) flows through the low-pressure region, the first wheel space (73A), and the second rotor cavity, in a power-generating turbomachinery.

2. At least one high-pressure coolant duct (79) fluidly coupling the high-pressure region (71) to the first rotor cavity (77), the at least one high-pressure coolant duct (79) having an inlet end (79.1) in the high-pressure region (71) and an outlet end (79.2) in the first rotor cavity (77), the outlet end (79.2) being at a first distance from the rotor axis (A-A), The power generation turbomachinery according to claim 1, comprising: at least one low-pressure coolant duct (87) that fluidly couples the low-pressure region (73) with the second rotor cavity (83), the at least one low-pressure coolant duct (87) having an inlet end (87.1) in the low-pressure region (73) and an outlet end (87.2) in the second rotor cavity (83), wherein the outlet end is at a second distance from the rotor axis (A-A), the second distance being smaller than the first distance.

3. The power generation turbomachinery according to claim 2, wherein the outlet end (79.2) of the at least one high-pressure coolant duct (79) is located at a distance from the rotor shaft (A-A) that is less than the distance from the rotor shaft (A-A) of the inlet end (87.1) of the at least one low-pressure coolant duct (87).

4. The power generation turbomachinery according to any one of claims 1 to 3, wherein, during use, the coolant in the first wheel space and the coolant in the low-pressure region are at approximately the same pressure.

5. The power-generating turbomachine according to any one of claims 1 to 4, wherein the upstream section of the rotor comprises at least one of the first annular row of rotor blades (55), a first rotor wheel (57.1), and a second wheel space located downstream of the first wheel space in the front-to-rear direction.

6. The power generation turbomachinery according to any one of claims 1 to 5, wherein the downstream section of the rotor comprises at least one of a rotor wheel (57) downstream of the upstream section of the rotor, a rotor blade (55) downstream of the upstream section, and a wheel space downstream of the upstream section in the front-to-rear direction.

7. The power-generating turbomachine according to any one of claims 1 to 6, wherein the first rotor cavity (77) is coaxial with the second rotor cavity (83) and is arranged radially outward from the second rotor cavity (83).

8. The power generation turbomachinery according to claim 7, wherein the sealing member (85) is positioned coaxially with the first rotor cavity (77) and the second rotor cavity (83).

9. The power-generating turbomachine according to any one of claims 1 to 8, wherein the second rotor cavity (83) surrounds a central tie rod (63) that connects the front shaft portion (65) and the rear shaft portion (67) to each other.

10. The power generation turbomachinery according to any one of claims 1 to 9, wherein the sealing member (85) comprises a hollow cylindrical body coaxial with the rotor (43).

11. The power generation turbomachine according to any one of claims 1 to 10, further comprising a balance drum (72) twist-coupled to the rotor shaft, wherein the high-pressure region (71) is defined on the side facing forward by the balance drum (72).

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