A multi-stage extraction low-pressure cylinder and steam turbine

Abstract

The present application provides a multi-stage extraction low-pressure cylinder and steam turbine, including a first inner shell, a steam inlet pipe, and a second inner shell. The inlet of the steam inlet pipe is connected to the medium-pressure cylinder, and the first inner shell is connected to the outlet of the steam inlet pipe. A first-stage extraction chamber and a first extraction flow channel are provided on the main body of the first inner shell. The extraction port of the first extraction flow channel is close to the outlet of the steam inlet pipe. The first-stage extraction chamber is integrally formed with the first inner shell and extracts primary steam through the first extraction flow channel. The second inner shell is connected to the other end of the first inner shell, and together with the first inner shell and the steam inlet pipe, encloses a second-stage extraction chamber located on the periphery of the steam inlet pipe; the first inner shell is provided with a second extraction flow channel connected to the second-stage extraction chamber to extract secondary steam. The present application ensures the stability of the structure and can improve the deformation resistance of the inner shell. It reduces the life loss of high-stress components in the steam inlet area, ensures the safe, stable and reliable operation of the steam turbine unit, and is conducive to its popularization and use.

Description

Technical Field

[0001] The present application relates to the technical field of power plant steam turbines, and in particular to a multi-stage extraction low-pressure cylinder and a steam turbine. Background Art

[0002] In high-power, high-parameter power plant steam turbines, the low-pressure cylinder usually continues to expand and perform work after receiving steam discharged from the intermediate-pressure cylinder. In addition, engineering practices often extract a suitable amount of steam from the intermediate-pressure cylinder exhaust for heating or various industrial process needs. At this time, the low-pressure cylinder's steam inlet parameters are usually around 0.6MPa(a) / 300°C. If higher extraction parameters are required, the steam parameters are generally increased by adjusting the opening of the regulating valve arranged on the connecting pipe, such as increasing the steam pressure to 1.2MPa and the temperature to 420°C. At this time, the structural requirements for the low-pressure cylinder will be increased, especially in the low-load stage, where the low-pressure cylinder may experience short-term operation at a temperature of 450°C.

[0003] In the prior art, multiple extraction chambers are formed by welding together multiple steel plates. These extraction chambers are then welded to the inner casing of the low-pressure cylinder (LPC) to extract steam of varying parameters. However, as the inlet steam parameters increase, the steel plate welds weaken their ability to resist deformation after receiving high-parameter steam. This can lead to deformation due to significant thermal stress, affecting the overall structural stability of the LPC and increasing the lifespan of high-stress components, thus impacting the safe operation of the steam turbine. Summary of the Invention

[0004] The first purpose of the embodiment of the present application is to provide a multi-stage extraction low-pressure cylinder, which can solve the problem of low-pressure cylinder structural stability under high-parameter steam inlet conditions and ensure that the unit can operate safely, stably and reliably.

[0005] A second object of an embodiment of the present application is to provide a steam turbine comprising the above-mentioned multi-stage extraction low-pressure cylinder.

[0006] In a first aspect, a multi-stage steam extraction low-pressure cylinder is provided, comprising:

[0007] Steam inlet pipe, whose inlet is connected to the medium pressure cylinder.

[0008] The first inner shell has one end connected to the outlet of the steam inlet pipe. The main body of the first inner shell is provided with a first-stage steam extraction chamber and a first steam extraction flow channel. The steam extraction port of the first steam extraction flow channel is close to the outlet of the steam inlet pipe. The first-stage steam extraction chamber is integrally formed with the first inner shell and extracts primary steam through the first steam extraction flow channel.

[0009] The second inner shell is connected to the other end of the first inner shell, and together with the first inner shell and the steam inlet pipe, encloses a secondary steam extraction chamber located on the periphery of the steam inlet pipe; the first inner shell is provided with a second steam extraction flow channel connected to the secondary steam extraction chamber, and the second steam extraction flow channel is arranged downstream of the first steam extraction flow channel; the secondary steam extraction chamber extracts secondary steam through the second steam extraction flow channel, and the flow direction of the secondary steam entering the secondary steam extraction chamber is parallel or approximately parallel to the axial direction of the steam inlet pipe.

[0010] In one embodiment, the first-stage steam extraction cavity is an annular cavity, and the annular cavity is arranged around the circumference of the rotor.

[0011] In one embodiment, the cross-sectional shape of the first-stage steam extraction cavity is circular or elliptical.

[0012] In one embodiment, the first-stage steam extraction chamber includes two annular cavities, and the two annular cavities are respectively arranged on both sides of the steam inlet pipe.

[0013] In one embodiment, a plurality of first steam extraction flow channels are provided on the inner wall of the first inner shell, and each of the first steam extraction flow channels is communicated with the first-stage steam extraction cavity.

[0014] In one embodiment, a first exhaust passage is provided on the outer wall of the first inner shell, one end of the first exhaust passage is communicated with the first-stage steam extraction chamber, and the other end of the first exhaust passage is connected to the heat recovery pipe.

[0015] In one embodiment, a steam extraction pipe is provided between the first exhaust steam flow channel and the heat recovery pipe.

[0016] In one embodiment, a sealing ring is provided at the connection between the first inner shell and the second inner shell.

[0017] In one embodiment, an expansion joint assembly is provided between the second inner casing and the steam inlet pipe.

[0018] According to a second aspect of the present application, a steam turbine is further provided, comprising the multi-stage extraction low-pressure cylinder as described in the first aspect.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] In the technical solution of this application, a first-stage steam extraction chamber is integrally formed on the first inner casing, through which high-parameter primary steam is extracted, ensuring structural stability. By locating the first and second-stage steam extraction chambers around the steam inlet pipe, contact between the low-parameter steam in the exhaust chamber and the high-temperature steam inlet pipe is prevented. This prevents thermal stress caused by excessive temperature and pressure gradients between the chambers, reduces the lifespan of high-stress components in the steam inlet area, and ensures safe, stable, and reliable operation of the steam turbine unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 Schematic diagram of a multi-stage steam extraction low-pressure cylinder structure according to an embodiment of the present application;

[0023] Figure 2 Schematic diagram of a cannula structure according to an embodiment of the present application.

[0024] The description of the accompanying drawings is as follows:

[0025] 1. First inner shell 2. First stage steam extraction chamber

[0026] 3. Second steam extraction flow channel 4. First steam extraction flow channel

[0027] 5. Secondary steam extraction chamber 6. Steam inlet pipe

[0028] 7. Second inner shell 8. Sealing ring

[0029] 9. Expansion joint assembly 10. Outer shell

[0030] 11. Connecting pipe 12. Rotor

[0031] 13. Reinforced rib support rod 14. First steam extraction pipe

[0032] 15. First steam extraction pipe 16. Second steam extraction pipe

[0033] 17. Angle seal ring 18. Threaded ring

[0034] 19. Interface DETAILED DESCRIPTION

[0035] The following is a further detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0038] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0039] According to the first aspect of this application, see Figure 1First, a multi-stage steam extraction low-pressure cylinder is provided, including a steam inlet pipe 6, a first inner shell 1, and a second inner shell 7. The inlet of the steam inlet pipe 6 is connected to the intermediate-pressure cylinder, and the steam parameters discharged from the intermediate-pressure cylinder are 1.2MPa(a) and 420℃. The steam inlet pipe 6 transports the steam discharged from the intermediate-pressure cylinder to the rotor 12 of the low-pressure cylinder for expansion and work. One end of the first inner shell 1 is connected to the outlet of the steam inlet pipe 6. By adopting a casting molding process for the first inner shell 1 and the steam inlet pipe 6, the deformation resistance of the first inner shell 1 is improved. A first-stage steam extraction chamber 2 and a first steam extraction flow channel 4 are provided on the main body of the first inner shell 1. The steam extraction port of the first steam extraction flow channel 4 is close to the outlet of the steam inlet pipe 6. The first-stage steam extraction chamber 2 is integrally formed with the first inner shell 1 and extracts primary steam through the first steam extraction flow channel 4. The first extraction flow channel 4 is provided at the second-stage moving blade, so the primary steam is the steam after the second-stage expansion and work, and the first-stage extraction chamber 2 can extract primary steam with steam parameters of 0.58MPa(a) and 332°C. However, the structure in the prior art cannot extract steam with such high parameters. The present application can extract primary steam by setting the first-stage extraction chamber 2. The first-stage extraction chamber 2 and the first inner shell 1 are integrated by casting, and the original low-pressure stationary blade holding ring component is eliminated, making the structure between the extraction flow channel and the extraction chamber simpler, making the extraction flow channel and flow field smoother, reducing the resistance loss on the extraction flow channel, and having a positive effect.

[0040] The second inner casing 7 is connected to the other end of the first inner casing 1. Due to its lower operating parameters, the second inner casing 7 is formed using a steel plate assembly welding process. Therefore, this application selects different forming processes based on the service environment of different components, allowing for simultaneous and parallel processing of different components. This further optimizes the overall manufacturing and processing of the low-pressure cylinder, further shortening product preparation cycles and improving work efficiency. The second inner casing 7, together with the first inner casing 1 and the steam inlet pipe 6, encloses a secondary steam extraction chamber 5 located around the steam inlet pipe 6. The first inner casing 1 is provided with a second steam extraction channel 3, which communicates with the secondary steam extraction chamber and is located downstream of the first steam extraction channel 4. The secondary steam extraction chamber 5 extracts secondary steam through the second steam extraction channel 3. The secondary steam entering the secondary steam extraction chamber 5 flows parallel or approximately parallel to the axial direction of the steam inlet pipe 6. Secondary steam is steam that has undergone several pressure stages of further expansion and work. The steam parameters of the secondary steam are reduced to 0.25 MPa(a) and 235°C.

[0041] By arranging the first-stage extraction chamber 2 and the second-stage extraction chamber 5 as close as possible to the steam inlet axis of the steam inlet pipe, the axial span of the flow, that is, the axial span of the rotating axis of the rotor 12, is minimized, and the disadvantage of the increase in the axial span of the inner casing caused by the extraction chamber having to be arranged downstream of the extraction port under the welded component structure is avoided to the greatest extent.

[0042] It should be noted that the present application also includes an outer shell 10, which is arranged outside the first inner shell 1 and the second inner shell 7, and is formed by welding plate parts.

[0043] Specifically, the exhaust port of the first inner casing 1, the inner wall of the second inner casing 7, and the sealing ring 8 form a three-stage steam extraction chamber. The outer wall of the second inner casing 7 and the inner wall of the outer casing 10 form an exhaust chamber. The steam parameters in the exhaust chamber are 11kPa(a) and 50°C. The exhaust steam from the entire low-pressure cylinder is ultimately fed to the condensing device through the exhaust chamber.

[0044] In the prior art, the exhaust chamber of the low-pressure cylinder is formed between the outer shell, the outside of multiple extraction chambers, and the steam inlet pipe, which has the disadvantage of being set close to the steam inlet pipe. Because the exhaust chamber is used to extract steam after the rotor has undergone multi-stage expansion and work, the parameters of the steam are relatively low, usually 11kpa(a) and 50°C, while the steam parameters in the steam inlet pipe are 1.2MPa and 420°C. Therefore, the temperature gradient and pressure gradient of the steam on both sides of the steam inlet pipe are too large, and the resulting thermal stress will also affect the stability of the low-pressure cylinder structure. However, the present application arranges the first-stage extraction chamber 2 and the second-stage extraction chamber 5 with higher-parameter steam close to the steam inlet pipe to avoid the exhaust chamber with low steam parameters from contacting the steam inlet pipe, thereby avoiding the situation where the temperature gradient and pressure gradient of the steam on both sides of the steam inlet pipe are too large, and the resulting thermal stress affects the stability of the low-pressure cylinder structure.

[0045] In one embodiment, the first-stage steam extraction chamber 2 is an annular chamber arranged circumferentially around the rotor 12. Because the inner casing adopts an upper and lower half structure and is connected and fixed at the center plane by flanges and bolts, the two semi-annular chambers on the upper and lower halves are spliced at the center plane to form an annular chamber, which serves as the first-stage steam extraction chamber 2.

[0046] In one embodiment, the cross-sectional shape of the first-stage steam extraction chamber 2 is circular or elliptical. It is considered that the circular or elliptical cross-sectional setting makes the inner wall of the steam extraction chamber smooth so that the extracted steam parameters are stable.

[0047] It should be noted that the radius of the circular cross section or the size of the elliptical cross section is set according to the volume flow of the extracted steam and the selected calculated flow rate.

[0048] In one embodiment, the first-stage steam extraction chamber 2 includes two annular cavities, which are respectively arranged on both sides of the steam inlet pipe 6 .

[0049] It should be noted that the two annular cavities are independent of each other and are not connected. By adjusting the position of the first steam extraction channel 4, steam with the same parameters or steam with different parameters can be extracted respectively.

[0050] The two annular cavities are arranged symmetrically or asymmetrically based on the flow design parameters. In this embodiment, a symmetrical steam extraction is used, with the steam extraction flow path located behind the second-stage moving blades. An asymmetrical steam extraction structure can also be used, such as one side located behind the second-stage moving blades and the other side located behind the first-stage moving blades.

[0051] In one embodiment, a plurality of first steam extraction flow channels 4 are provided on the inner wall of the first inner shell 1 , and each first steam extraction flow channel 4 is communicated with the first-stage steam extraction chamber 2 .

[0052] It should be noted that the structural form of the steam extraction flow channel is ultimately determined based on the volume flow rate and design flow rate corresponding to the steam extraction. Several evenly or unevenly arranged circular holes or groove structures can be used within the entire circumference. Each steam extraction flow channel can be arranged vertically or non-vertically. The steam extraction flow channel can also adopt several arc-shaped groove structures that are divided into the entire circle.

[0053] Specifically, this embodiment prefers a uniformly distributed, circular, vertically arranged flow channel. This simple structure allows for smoother steam extraction while also ensuring overall structural rigidity in the flow channel area. For areas with high steam extraction volume flow rates and limited structural and spatial constraints, a non-uniformly distributed, channeled, or segmented arcuate channel flow channel structure may be considered.

[0054] In one embodiment, a first exhaust passage is provided on the outer wall of the first inner shell 1 , one end of the first exhaust passage is connected to the first-stage steam extraction chamber 2 , and the other end of the first exhaust passage is connected to the heat recovery pipe through a pipe structure.

[0055] Specifically, the first exhaust passage is provided on the lower half structure of the first inner shell 1, such as Figure 2 As shown, the intubation structure is specifically as follows:

[0056] A first steam extraction pipe 14 and a first steam extraction intubation pipe 15 are provided between the first exhaust flow channel and the heat recovery pipe to lead out the steam in the first-stage steam extraction chamber 2. The interface area between the first steam extraction pipe 14 and the first steam extraction intubation pipe 15 is sealed and connected by an angled sealing ring 17 and a threaded ring 18. The other end of the first steam extraction intubation pipe 15 is connected to the heat recovery steam extraction pipe. A second steam extraction intubation pipe 16 is provided on the outside of the first steam extraction intubation pipe 15, and the second steam extraction intubation pipe 16 is used to lead out the secondary steam. The flange of the first steam extraction intubation pipe 15 and the flange of the second steam extraction intubation pipe 16 are connected and fixed by a fourth circle of bolts. By providing the first steam extraction intubation pipe 15 and the sealing ring assembly, the isotropic thermal displacement between the inner shell and the heat recovery steam extraction pipe is balanced. A water-draining interface 19 is arranged on the first steam extraction intubation pipe 15 to recover condensed water from the second-stage steam extraction chamber 5 during startup, shutdown, and other stages.

[0057] In one embodiment, a sealing ring 8 is provided at the connection between the first inner shell 1 and the second inner shell 7 to prevent the secondary steam from overflowing and causing the parameters to fail to meet the design requirements.

[0058] It should be noted that at the connection between the first inner shell 1 and the second inner shell 7, a connector extends outward from the first inner shell 1, and the thickness of the connector matches that of the second inner shell 7. Because the first inner shell 1 is a casting, and the first-stage steam extraction chamber 2, the first steam extraction flow channel 4, and the second steam extraction flow channel 3 are cast on the first inner shell 1, the thickness of the first inner shell 1 is much greater than that of the second inner shell 7. The provision of the connector facilitates the connection between the first inner shell 1 and the second inner shell 7. This prevents the initiation and propagation of weld cracks caused by high-temperature service environments, ensuring the sealing performance of the chamber.

[0059] In one embodiment, an expansion joint assembly 9 is provided between the second inner casing 7 and the steam inlet pipe 6 .

[0060] Specifically, the second inner shell 7 and the expansion joint assembly 9 are fixed by a first circle of bolts, and the connecting pipe 11 and the steam inlet pipe 6 are fixed by a second circle of bolts. The outer shell 10 and the expansion joint assembly 9 are fixed by a third circle of bolts. The expansion joint assembly 9 includes four expansion joints, which are used to absorb the thermal expansion differences from the outer shell 10, the first inner shell 1, and the second inner shell 7, to ensure that the relative positions of the components after thermal expansion are appropriate. In addition, the specific number of inner ring expansion joints and outer ring expansion joints that make up the expansion joint assembly 9 can be comprehensively considered in combination with the structural dimensions of each shell of the low-pressure cylinder, the thermal expansion difference, and the on-site installation operation space, and can be adjusted according to the requirements. Figure 1 The shown configuration is 2 expansion joints in the inner ring + 2 expansion joints in the outer ring, which is a "2+2" configuration. Combinations in various configurations, such as "1+1", "1+2", and "2+1", are also possible.

[0061] Preferably, the type of expansion joint is a bellows-type expansion joint.

[0062] In one embodiment, the bottom of the steam inlet pipe 6 is tapered, with an inlet guide ring assembly and stiffener struts 13 positioned on the inner wall of the tapered opening. The stiffener struts 13 ensure the overall strength and rigidity requirements of the low-pressure first inner casing 1. The inlet guide ring assembly ensures that the flow field of the steam inlet cavity matches the flow vanes.

[0063] According to a second aspect of the present application, a steam turbine is further provided, comprising the multi-stage extraction low-pressure cylinder provided in the first aspect.

[0064] In summary, in the multi-stage extraction low-pressure cylinder and steam turbine provided by this application, steam with increased parameters flows in through the steam inlet pipe, the steam that has expanded and worked through the two-stage rotor is extracted into the first-stage extraction chamber through the first extraction flow channel, and the steam that has expanded and worked through the multi-stage rotor is extracted into the second-stage extraction chamber through the second extraction flow channel. This application reduces the pressure difference of the steam inlet chamber from 1.189MPa to 0.95MPa, a decrease of 20%, and reduces the temperature difference from 370℃ to 185℃, a decrease of 50%. The temperature difference and pressure difference load between the high-parameter low-pressure cylinder steam inlet chamber and the extraction chamber are optimized to the greatest extent.

[0065] By integrally forming a first-stage extraction chamber on the first inner shell, high-parameter primary steam is extracted through the first-stage extraction chamber, ensuring structural stability and improving the inner shell's ability to resist deformation. By arranging the first-stage extraction chamber and the second-stage extraction chamber on the periphery of the steam inlet pipe, the low-parameter steam in the exhaust chamber is prevented from contacting the high-temperature steam inlet pipe, thereby avoiding thermal stress caused by excessive temperature and pressure gradients between the chambers, reducing the life loss of high-stress components in the steam inlet area, and ensuring safe, stable, and reliable operation of the steam turbine unit. In addition, by simultaneously arranging the first-stage extraction chamber and the second-stage extraction chamber in a direction parallel to the axis of the steam inlet pipe, the span of the first-stage extraction chamber and the second-stage extraction chamber along the rotor's rotation axis is reduced, fully utilizing space and providing space for arranging multi-stage, large-capacity extraction chambers in the low-pressure cylinder, so that the low-pressure cylinder can meet more diverse extraction requirements and reduce product costs.

[0066] This application addresses the issue of excessive deformation in the flow inlet area impacting the clearance setting and safe operation of the unit's static and dynamic components. By replacing welded components with castings, it avoids the structural weakness caused by excessive welding and weld defects. Therefore, while improving steam inlet parameters, it also meets the diverse needs of industrial steam extraction parameters, facilitating widespread adoption.

[0067] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A multi-stage steam extraction low-pressure cylinder, characterized in that: include: a steam inlet pipe (6), the inlet of which is connected to the intermediate pressure cylinder; A first inner shell (1), one end of which is connected to the outlet of the steam inlet pipe (6); a first-stage steam extraction chamber (2) and a first steam extraction flow channel (4) are provided on the main body of the first inner shell (1); a steam extraction port of the first steam extraction flow channel (4) is close to the outlet of the steam inlet pipe (6); the first-stage steam extraction chamber (2) and the first inner shell (1) are integrally cast and primary steam is extracted through the first steam extraction flow channel (4); The second inner shell (7) is connected to the other end of the first inner shell (1), and together with the first inner shell (1) and the steam inlet pipe (6), encloses a secondary steam extraction chamber (5) located on the periphery of the steam inlet pipe (6); the first inner shell (1) is provided with a second steam extraction flow channel (3) communicating with the secondary steam extraction chamber (5), and the second steam extraction flow channel (3) is arranged downstream of the first steam extraction flow channel (4); the secondary steam extraction chamber (5) extracts secondary steam through the second steam extraction flow channel (3), and the flow direction of the secondary steam entering the secondary steam extraction chamber (5) is parallel or approximately parallel to the axial direction of the steam inlet pipe (6); The first-stage steam extraction chamber (2) is an annular chamber, and the annular chamber is arranged around the circumference of the rotor (12); The cross-sectional shape of the first-stage steam extraction chamber (2) is circular or elliptical; An expansion joint assembly (9) is provided between the second inner casing (7) and the steam inlet pipe (6).

2. The multi-stage steam extraction low-pressure cylinder according to claim 1, characterized in that: The first-stage steam extraction chamber (2) comprises two annular chambers, and the two annular chambers are respectively arranged on both sides of the steam inlet pipe (6).

3. The multi-stage steam extraction low-pressure cylinder according to claim 1, characterized in that: A plurality of first steam extraction flow channels (4) are provided on the inner wall of the first inner shell (1), and each of the first steam extraction flow channels (4) is in communication with the first-stage steam extraction chamber (2).

4. The multi-stage steam extraction low-pressure cylinder according to claim 3, characterized in that: A first exhaust passage is provided on the outer wall of the first inner shell (1), one end of the first exhaust passage is communicated with the first-stage steam extraction chamber (2), and the other end of the first exhaust passage is connected to a heat recovery pipe.

5. The multi-stage steam extraction low-pressure cylinder according to claim 4, characterized in that: A steam extraction pipe and a steam extraction intubation pipe are provided between the first exhaust flow channel and the heat recovery pipe, and primary steam is led out into the heat recovery pipe through the steam extraction pipe and the steam extraction intubation pipe.

6. The multi-stage steam extraction low-pressure cylinder according to claim 1, characterized in that: A sealing ring (8) is provided at the connection between the first inner shell (1) and the second inner shell (7).

7. A steam turbine, characterized in that: The invention comprises a multi-stage steam extraction low-pressure cylinder according to any one of claims 1 to 6.

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