Steam turbine system and temperature control method thereof

Abstract

The invention relates to the technical field of steam turbines, and particularly discloses a steam turbine system and a temperature control method thereof. The steam turbine system comprises a steam turbine high-pressure module and a steam turbine medium-pressure starting module and further comprises a heat insulation device. The thermal insulation device can improve the working condition of a cylinder by adjusting the working temperature of a cylinder area, and improves the running safety and stability of a steam turbine. The heat insulation devices are respectively arranged in any one or both of the steam turbine high-pressure module and the steam turbine medium-pressure module; the turbine system is an ultra-supercritical turbine system, and a turbine high-pressure module is composed of a high-pressure outer cylinder upper half part, a high-pressure outer cylinder lower half part, a high-pressure inner cylinder upper half part, a high-pressure inner cylinder lower half part and a high-pressure rotor. The steam turbine medium-pressure module is composed of a medium-pressure outer cylinder upper half part, a medium-pressure outer cylinder lower half part, a medium-pressure inner cylinder upper half part, a medium-pressure inner cylinder lower half part and a medium-pressure rotor. The temperature can be adjusted, so that the outer cylinder temperature field of the steam turbine is more uniform, and the service life of the steam turbine is prolonged.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, specifically a steam turbine system and a temperature control method for the steam turbine system. Background Technology

[0002] With the continuous development of steam turbine technology, ultra-supercritical reheat units, which offer excellent economic efficiency, have become the mainstay of thermal power generation. Due to the high operating parameters (pressure and temperature) of ultra-supercritical units, key components require control during operation to prevent operating temperatures from exceeding the allowable limits of equipment materials. During turbine operation, the temperature field in the high-pressure and intermediate-pressure outer cylinders is uneven, and significant stress and deformation exist, which can severely impact the service life of the turbine.

[0003] Existing ultra-supercritical steam turbines with separate high- and medium-pressure cylinders (each with an independent module) lack thermal insulation devices; their main structure is as follows: Figure 1 As shown. The high-pressure module of the steam turbine mainly consists of the upper half of the high-pressure outer cylinder 1, the lower half of the high-pressure outer cylinder 2, the upper half of the high-pressure inner cylinder 3, the lower half of the high-pressure inner cylinder 4, and the high-pressure rotor 5; wherein, a high-pressure inner and outer cylinder sandwich layer is formed between the high-pressure outer cylinder and the high-pressure inner cylinder – namely, the upper half of the high-pressure inner and outer cylinder sandwich layer 15 and the lower half of the high-pressure inner and outer cylinder sandwich layer 16. The intermediate-pressure module of the steam turbine mainly consists of the upper half of the intermediate-pressure outer cylinder 6, the lower half of the intermediate-pressure outer cylinder 7, the upper half of the intermediate-pressure inner cylinder 8, the lower half of the intermediate-pressure inner cylinder 9, and the intermediate-pressure rotor 10; wherein, a intermediate-pressure inner and outer cylinder sandwich layer is formed between the intermediate-pressure outer cylinder and the intermediate-pressure inner cylinder – namely, the upper half of the intermediate-pressure inner and outer cylinder sandwich layer 17 and the lower half of the intermediate-pressure inner and outer cylinder sandwich layer 18. During operation of this type of steam turbine, the main steam enters the high-pressure inner cylinder from the high-pressure outer cylinder inlet through the connecting pipe between the inner and outer cylinders. Most of the steam enters the turbine's flow path to perform work, while a small portion leaks into the high-pressure inner and outer cylinder interlayer through the steam seal on the inner cylinder's inlet side. Additionally, some steam also leaks into the high-pressure inner and outer cylinder interlayer through the connecting pipe. After performing work in the high-pressure cylinder, the high-pressure steam is discharged into the high-pressure exhaust chamber—specifically, the upper half (19) and lower half (20) of the high-pressure exhaust chamber (where the steam temperature and pressure decrease). It then exits through the high-pressure exhaust port and enters the boiler reheater, where it is reheated to form reheated steam. Reheated steam enters the intermediate-pressure inner cylinder from the inlet of the intermediate-pressure outer cylinder through the connecting pipe between the inner and outer cylinders. Most of it enters the turbine flow path to do work. After doing work, the steam is discharged from the intermediate-pressure exhaust. A small portion leaks into the intermediate-pressure inner and outer cylinder interlayer and the three-stage extraction chamber - the upper half 21 and the lower half 22 of the three-stage extraction chamber - through the steam seal on the steam inlet side of the inner cylinder. In addition, there is also some steam leakage into the intermediate-pressure inner and outer cylinder interlayer through the connecting pipe between the intermediate-pressure inner and outer cylinders.

[0004] Steam leakage from the steam seal or inlet connection pipe can enter the high-pressure or medium-pressure inner and outer cylinder interlayer. The interlayer temperature is relatively high, resulting in a higher operating temperature for the outer cylinder. If the installation is improper or components deform after operation, the amount of steam leaking into the high-pressure or medium-pressure inner and outer cylinder interlayer may increase, leading to excessively high interlayer temperatures and adversely affecting the outer cylinder.

[0005] In the prior art, CN114483223A discloses a temperature balancing structure for a steam turbine cylinder, which can reduce steam leakage, reduce the flow difference of leaking steam between the upper and lower halves of the cylinder, and mitigate the deformation difference between the upper and lower halves of the outer cylinder; CN116025428A discloses a sealing structure for the intermediate-pressure reheat steam inlet of a steam turbine, which is designed for the special characteristics of the intermediate-pressure reheat steam inlet of high-power steam turbine units. It effectively prevents the leakage of high-quality reheat steam at the reheat steam inlet by means of steam sealing, making the sealing effect of the intermediate-pressure reheat steam inlet reliable, avoiding the waste of high-quality reheat steam, and also reducing the steam temperature directly acting on the intermediate-pressure outer cylinder; CN115929422A discloses a temperature balancing structure between the interlayers of a high-power steam turbine cylinder, which takes into account both controlling the flow difference of high and low temperature steam within the interlayer and preventing the backflow of leaking steam between stages within the interlayer, thereby reducing the expansion difference of the steam turbine cylinder. To prevent deformation and fatigue damage to the inner and outer cylinders, CN106917648A discloses a cylinder heat insulation structure for a steam turbine, in which the outer cylinder covers the entire flow passage, and the inner cylinder has an inlet chamber. Steam flows from the inlet chamber through the flow passage to the exhaust area. A heat insulation cover is provided between the outer and inner cylinders and is fixed to the outer cylinder. The heat insulation cover isolates the outer cylinder from the interlayer temperature, thus achieving cylinder heat insulation. CN106089334A discloses a high- and medium-pressure combined cylinder unit with an inner and outer cylinder interlayer seal, mainly providing a sealing method between the inner and outer cylinders. CN206860242U discloses a heat insulation cover device and an ultra-high pressure intermediate reheat steam turbine including the same, providing a heat insulation device between the inner and outer cylinders. The heat insulation cover isolates the outer cylinder from the interlayer temperature, which helps to reduce the thermal stress of the medium and low pressure cylinder and improve the service life of the medium and low pressure cylinder. However, the aforementioned prior art does not solve the defects in the prior art, and the structural principles and functions adopted are different from those of the present invention. There are also no literature reports related to the present invention. Summary of the Invention

[0006] The technical objective of this invention is to overcome the shortcomings of the prior art and address the technical problem of uneven temperature fields and significant stress and deformation in the high-pressure and intermediate-pressure outer cylinders of a steam turbine system during turbine unit operation, which can severely impact the service life of the turbine. This invention provides an adjustable temperature insulation system for the high-temperature regions of the high- and intermediate-pressure cylinders, i.e., a steam turbine system and a temperature control method for this system. By employing this invention, the operating conditions of the cylinders are improved and the safety and stability of the steam turbine operation are enhanced during unit operation by adjusting the operating temperature of the high-temperature regions.

[0007] The technical objective of this invention is achieved through the following technical solution: a steam turbine system, comprising a high-pressure module and a medium-pressure module; The turbine system also includes a heat insulation device; The heat insulation device can improve the working conditions of the cylinder by adjusting the working temperature of the cylinder area, thereby enhancing the safety and stability of the turbine operation.

[0008] Furthermore, the heat insulation device is installed in the high-voltage module or the medium-voltage module; The turbine system is an ultra-supercritical turbine system, and the high-pressure module consists of an upper high-pressure outer cylinder, a lower high-pressure outer cylinder, an upper high-pressure inner cylinder, a lower high-pressure inner cylinder, and a high-pressure rotor. The medium-pressure module consists of an upper half of a medium-pressure outer cylinder, a lower half of a medium-pressure outer cylinder, an upper half of a medium-pressure inner cylinder, a lower half of a medium-pressure inner cylinder, and a medium-pressure rotor.

[0009] Furthermore, the heat insulation device is simultaneously installed in both the high-voltage module and the medium-voltage module; The heat insulation device installed in the high-pressure module is located between the high-pressure outer cylinder and the high-pressure inner cylinder, forming a high-pressure inner and outer cylinder interlayer. A high-pressure connecting pipe is installed between the high-pressure outer cylinder and the high-pressure inner cylinder. The high-pressure connecting pipe allows the main steam to enter the high-pressure inner cylinder from the high-pressure outer cylinder inlet through the connecting pipe between the high-pressure inner and outer cylinders, thus completing the work. The heat insulation device installed in the medium-pressure module is located between the medium-pressure outer cylinder and the medium-pressure inner cylinder, forming a medium-pressure inner and outer cylinder interlayer. A medium-pressure connecting pipe is installed between the medium-pressure outer cylinder and the medium-pressure inner cylinder. The medium-pressure connecting pipe allows reheat steam to enter the medium-pressure inner cylinder from the inlet of the medium-pressure outer cylinder through the connecting pipe between the medium-pressure inner and outer cylinders.

[0010] Furthermore, the main steam enters the high-pressure inner cylinder from the high-pressure outer cylinder inlet through the high-pressure connecting pipe between the high-pressure inner and outer cylinders. Most of it enters the turbine flow path to do work, while a small portion leaks into the high-pressure inner and outer cylinder interlayer through the steam seal on the steam inlet side of the high-pressure inner cylinder. At the same time, there is also some steam leakage into the high-pressure inner and outer cylinder interlayer through the high-pressure inner and outer cylinder connecting pipe. After the high-pressure steam finishes its work in the high-pressure cylinder, it is discharged into the high-pressure exhaust chamber (at this time, the steam temperature and pressure decrease), and then discharged from the high-pressure exhaust port. It enters the boiler reheater and is then reheated by the boiler to form reheated steam. Reheated steam enters the intermediate-pressure inner cylinder from the inlet of the intermediate-pressure outer cylinder through the intermediate-pressure connecting pipe between the intermediate-pressure inner and outer cylinders. Most of it enters the turbine flow path to do work. After doing work, the steam is discharged through the intermediate-pressure exhaust. A small portion leaks into the intermediate-pressure inner and outer cylinder interlayer through the steam seal on the steam inlet side of the intermediate-pressure inner cylinder. At the same time, there is also some steam leakage into the intermediate-pressure inner and outer cylinder interlayer through the intermediate-pressure inner and outer cylinder connecting pipe.

[0011] Furthermore, the heat insulation device of the high-pressure module is installed in the interlayer between the high-pressure outer cylinder and the high-pressure inner cylinder, separating the high-pressure outer cylinder from the interlayer. The heat insulation device and the high-pressure outer cylinder form a steam flow channel, which is the high-pressure heat insulation layer. The inlet of the high-pressure heat insulation layer is connected to the high-pressure exhaust chamber (this is the cooling steam inlet). The heat insulation device of the medium-pressure module is set in the interlayer between the medium-pressure outer cylinder and the medium-pressure inner cylinder, separating the high-pressure outer cylinder from the interlayer. The heat insulation device and the medium-pressure outer cylinder form a steam flow channel, which is the medium-pressure heat insulation layer. The inlet of the medium-pressure heat insulation layer is connected to the three-stage steam extraction chamber (this is the cooling steam outlet).

[0012] Furthermore, the turbine system also has a steam regulation system located outside the cylinder; The steam regulation system installed outside the cylinder mainly consists of pipes and four valves: a, b, c, and d. The pipe inlet is connected to the high-pressure insulation layer, and the pipe outlet is connected to the medium-pressure insulation layer. When the steam turbine unit is running, the valves are opened, and the steam from the high-pressure insulation layer flows to the medium-pressure insulation layer. The opening of the four valves a, b, c, and d can be adjusted.

[0013] Furthermore, the insulation layer is provided with dividing plates along the circumferential direction, dividing it into N independent chambers, where N is an integer greater than or equal to 2; Valves a and c are electrically adjustable valves; Valves b and d are electrically operated shut-off valves.

[0014] Furthermore, the insulation layer is divided into N independent chambers along the circumferential direction, with N being an integer equal to 8; there are 4 chambers in each of the upper and lower halves (the high-pressure and medium-pressure insulation layers are arranged in the same way). Each chamber of the insulation layer is connected to a pipe. The four pipes in the upper half are combined into one pipe, and the pipes connecting the high-pressure upper half and the medium-pressure upper half insulation layers are interconnected. The four pipes in the lower half are combined into one pipe, and the pipes connecting the high-pressure lower half and the medium-pressure lower half insulation layers are interconnected. By dividing the insulation layer evenly, cooling steam can flow uniformly within the insulation layer, ensuring uniform cooling of the cylinder.

[0015] A temperature control method for the above-mentioned steam turbine system, the temperature control method comprising: When the unit is running, open the electric shut-off valves b and d, and gradually open the electric regulating valves a and c; At the same time, the low-temperature steam in the high-pressure exhaust chamber can enter the high-pressure insulation layer to cool the high-pressure outer cylinder; Then it enters the medium-pressure insulation layer through the pipeline to cool the medium-pressure outer cylinder, and finally is discharged into the three-stage extraction chamber; Adjust the opening of valves a and c according to the actual external cylinder temperature to achieve cylinder temperature regulation.

[0016] Furthermore, the insulation layer is evenly distributed circumferentially, and each independent chamber is connected to a steam pipe, which can ensure that the cylinder is cooled evenly circumferentially, so that the cylinder temperature field is evenly distributed and the temperature stress caused by the circumferential temperature difference is reduced.

[0017] The beneficial technical effects of this invention are: 1. The heat insulation device structure of the present invention can reduce the working temperature of the high-temperature area of ​​the high-pressure and medium-pressure outer cylinder during unit operation, thereby reducing the temperature difference along the axial direction of the outer cylinder, making its temperature field more uniform, which is conducive to reducing the deformation of the outer cylinder, and improving the service life of the outer cylinder and its fasteners such as bolts, thus improving the safe and stable operation of the steam turbine. 2. By adopting the heat insulation device structure of the present invention, during unit operation, the temperature of the high-pressure and medium-pressure outer cylinders can be reduced while the temperature of the high-pressure and medium-pressure interlayer can be maintained at a high level (without directly reducing the interlayer temperature), which is beneficial to reducing the temperature difference between the inner and outer walls of the high-pressure and medium-pressure inner cylinders, thereby reducing the deformation of the inner cylinder. 3. The insulation layer is evenly distributed along the circumference, and each independent chamber is connected to a steam pipe, which can ensure uniform cooling of the cylinder along the circumference, make the cylinder temperature field uniformly distributed, and reduce the temperature stress caused by the circumferential temperature difference. 4. With the heat insulation device structure described in this invention, the upper and lower halves are equipped with separate heat insulation devices, which is beneficial for the independent adjustment of the temperature of the upper and lower halves of the cylinder. Adjustments can be made according to the temperature difference between the upper and lower halves of the cylinder to maintain the temperature difference between the upper and lower halves within a reasonable range. 5. By adopting this invention, the operating temperature of the outer cylinder is reduced, which helps to lower manufacturing costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the existing technology.

[0019] Figure 2 This is a schematic diagram of the structure of the present invention.

[0020] Figure 3 This is a schematic cross-sectional view of the heat insulation device arrangement structure at the high-voltage module of the present invention.

[0021] The symbols in the diagram have the following meanings: 1—Upper half of the high-pressure outer cylinder; 2—Lower half of the high-pressure outer cylinder; 3—Upper half of the high-pressure inner cylinder; 4—Lower half of the high-pressure inner cylinder; 5—High-pressure rotor; 6—Upper half of the medium-pressure outer cylinder; 7—Lower half of the medium-pressure outer cylinder; 8—Upper half of the medium-pressure inner cylinder; 9—Lower half of the medium-pressure inner cylinder; 10—Medium-pressure rotor; 11—Upper half of the high-pressure heat insulation device; 12—Lower half of the high-pressure heat insulation device; 13—Upper half of the medium-pressure heat insulation device; 14—Lower half of the medium-pressure heat insulation device; 15—Upper half of the high-pressure inner and outer cylinder interlayer; 16—Lower half of the high-pressure inner and outer cylinder interlayer; 17—Upper half of the medium-pressure inner and outer cylinder interlayer; 18—Lower half of the medium-pressure inner and outer cylinder interlayer; 19—Upper half of the high-pressure exhaust chamber; 20—Lower half of the high-pressure exhaust chamber; 21—Upper half of the three-stage extraction chamber; 22—Lower half of the three-stage extraction chamber; a—Electric regulating valve; b—Electric shut-off valve; c—Electric regulating valve; d—Electric shut-off valve. Detailed Implementation

[0022] This invention relates to the field of steam turbine technology, specifically a steam turbine system and a temperature control method for the steam turbine system, particularly to an ultra-supercritical reheat unit system. The steam turbine system of this invention includes a temperature-adjustable steam turbine cylinder insulation system, capable of regulating temperature and extending the service life of the steam turbine, and making the external cylinder temperature field of the steam turbine more uniform. The technical solution of this invention will be clearly and thoroughly explained below with reference to the accompanying drawings. See Figure 2 and Figure 3 As shown, this invention relates to a steam turbine system, particularly an ultra-supercritical reheat unit system, which includes a temperature-adjustable steam turbine cylinder heat insulation device. The main structure and system are as follows: Figure 2 As shown, the specific description is as follows.

[0023] The high-pressure module of the steam turbine comprises an upper half of a high-pressure outer cylinder (1), a lower half of a high-pressure outer cylinder (2), an upper half of a high-pressure inner cylinder (3), a lower half of a high-pressure inner cylinder (4), and a high-pressure rotor (5). The upper half of the high-pressure inner-outer cylinder interlayer (15) is formed between the upper half of the high-pressure outer cylinder (1) and the upper half of the high-pressure inner cylinder (3), while the lower half of the high-pressure inner cylinder interlayer (2) and the lower half of the high-pressure inner cylinder (4) form the lower half of the high-pressure inner-outer cylinder interlayer (16). A heat insulation device is installed in the space formed by the upper half of the high-pressure inner-outer cylinder interlayer (15) and the lower half of the high-pressure inner-outer cylinder interlayer (16). This device consists of an upper half (11) of the high-pressure heat insulation device located within the upper half (15) and a lower half (12) of the high-pressure inner-outer cylinder interlayer (16). The high-pressure heat insulation device separates the high-pressure outer cylinder from the interlayer, forming a steam flow channel, which is the high-pressure heat insulation layer. The inlet of the high-pressure heat insulation layer communicates with the high-pressure exhaust chamber (this is the cooling steam inlet).

[0024] The intermediate-pressure module of the steam turbine includes an upper half of the intermediate-pressure outer cylinder (6), a lower half of the intermediate-pressure outer cylinder (7), an upper half of the intermediate-pressure inner cylinder (8), a lower half of the intermediate-pressure inner cylinder (9), and an intermediate-pressure rotor (10). Among them, the upper half of the intermediate-pressure outer cylinder (6) and the upper half of the intermediate-pressure inner cylinder (8) form an upper half of the intermediate-pressure inner and outer cylinder interlayer (17), and the lower half of the intermediate-pressure outer cylinder (7) and the lower half of the intermediate-pressure inner cylinder (9) form a lower half of the intermediate-pressure inner and outer cylinder interlayer (18). In the space between the intermediate-pressure outer cylinder and the intermediate-pressure inner cylinder—that is, the space formed by the upper half 17 and the lower half 18 of the intermediate-pressure inner and outer cylinder interlayer—a heat insulation device is installed. Specifically, the upper half 13 of the intermediate-pressure heat insulation device is located in the upper half 17 of the intermediate-pressure inner and outer cylinder interlayer, and the lower half 14 of the intermediate-pressure heat insulation device is located in the lower half 18 of the intermediate-pressure inner and outer cylinder interlayer. The intermediate-pressure heat insulation device separates the outer cylinder from the interlayer. The heat insulation device and the outer cylinder form a steam flow channel, which is the intermediate-pressure heat insulation layer. The inlet of the intermediate-pressure heat insulation layer is connected to the three-section steam extraction chamber (this is the cooling steam outlet).

[0025] A steam regulation system is also installed outside the cylinder, mainly consisting of pipes and four valves: a, b, c, and d. Valves a and b are electrically operated regulating valves, while valves c and d are electrically operated shut-off valves. The pipe inlet connects to the high-pressure insulation layer, and the pipe outlet connects to the medium-pressure insulation layer. When the unit is running, the valves are opened, and steam flows from the high-pressure insulation layer to the medium-pressure insulation layer.

[0026] Taking the high-pressure module of a steam turbine as an example, the cross-section of the heat insulation device layout structure is as follows: Figure 3 As shown, the specific description is as follows (the insulation structure settings are the same for high pressure and medium pressure).

[0027] The high-pressure insulation device is welded to the high-pressure outer cylinder, forming an insulation layer. The insulation layer is divided into eight independent chambers along its circumference by a dividing plate: four chambers in the upper half and four in the lower half. Each chamber is connected to a pipe. The four pipes in the upper half are combined into one pipe, connecting the high-pressure and medium-pressure upper half of the insulation layer. Similarly, the four pipes in the lower half are combined into one pipe, connecting the high-pressure and medium-pressure lower half of the insulation layer. This equal division of the insulation layer ensures uniform flow of cooling steam within the insulation layer, guaranteeing uniform cooling of the cylinder.

[0028] The system workflow of this invention is as follows: During unit operation, open the electric shut-off valves c and d, and gradually open the electric regulating valves a and b. At this time, the low-temperature steam from the high-pressure exhaust chamber—namely, the upper half 19 and the lower half 20 of the high-pressure exhaust chamber—can enter the high-pressure insulation layer to cool the high-pressure outer cylinder; then it enters the intermediate-pressure insulation layer through pipelines to cool the intermediate-pressure outer cylinder, and finally exits into the three-stage extraction chamber—namely, the upper half 21 and the lower half 22 of the three-stage extraction chamber. Adjust the opening of valves a and b according to the actual outer cylinder temperature to achieve cylinder temperature regulation.

[0029] The above specific technical solutions are only used to illustrate the present invention, and are not intended to limit it.

[0030] Although the present invention has been described in detail with reference to the specific technical solutions described above, those skilled in the art should understand that modifications can still be made to the specific technical solutions described above, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the present invention.

Claims

1. A steam turbine system, comprising a high-pressure module and a medium-pressure module; Its features are: The turbine system also includes a heat insulation device; The heat insulation device can improve the working conditions of the cylinder by adjusting the working temperature of the cylinder area, thereby enhancing the safety and stability of the turbine operation.

2. The steam turbine system according to claim 1, characterized in that: The heat insulation device is installed in the high-voltage module or the medium-voltage module; The turbine system is an ultra-supercritical turbine system, and the high-pressure module consists of an upper high-pressure outer cylinder, a lower high-pressure outer cylinder, an upper high-pressure inner cylinder, a lower high-pressure inner cylinder, and a high-pressure rotor. The medium-pressure module consists of an upper half of a medium-pressure outer cylinder, a lower half of a medium-pressure outer cylinder, an upper half of a medium-pressure inner cylinder, a lower half of a medium-pressure inner cylinder, and a medium-pressure rotor.

3. The steam turbine system according to claim 2, characterized in that: The heat insulation device is installed in both the high-voltage module and the medium-voltage module; The heat insulation device installed in the high-pressure module is located between the high-pressure outer cylinder and the high-pressure inner cylinder, forming a high-pressure inner and outer cylinder interlayer. A high-pressure connecting pipe is installed between the high-pressure outer cylinder and the high-pressure inner cylinder. The high-pressure connecting pipe allows the main steam to enter the high-pressure inner cylinder from the high-pressure outer cylinder inlet through the connecting pipe between the high-pressure inner and outer cylinders, thus completing the work. The heat insulation device installed in the medium-pressure module is located between the medium-pressure outer cylinder and the medium-pressure inner cylinder, forming a medium-pressure inner and outer cylinder interlayer. A medium-pressure connecting pipe is installed between the medium-pressure outer cylinder and the medium-pressure inner cylinder. The medium-pressure connecting pipe allows reheat steam to enter the medium-pressure inner cylinder from the inlet of the medium-pressure outer cylinder through the connecting pipe between the medium-pressure inner and outer cylinders.

4. The steam turbine system according to claim 3, characterized in that: The main steam enters the high-pressure inner cylinder from the high-pressure outer cylinder inlet through the high-pressure connecting pipe between the high-pressure inner and outer cylinders. Most of it enters the turbine flow path to do work, while a small portion leaks into the high-pressure inner and outer cylinder interlayer through the steam seal on the steam inlet side of the high-pressure inner cylinder. At the same time, there is also some steam leakage into the high-pressure inner and outer cylinder interlayer through the high-pressure inner and outer cylinder connecting pipe. After the high-pressure steam finishes its work in the high-pressure cylinder, it is discharged into the high-pressure exhaust chamber, exited through the high-pressure exhaust port, and enters the boiler reheater. After being reheated by the boiler, it forms reheated steam. Reheated steam enters the intermediate-pressure inner cylinder from the inlet of the intermediate-pressure outer cylinder through the intermediate-pressure connecting pipe between the intermediate-pressure inner and outer cylinders. Most of it enters the turbine flow path to do work. After doing work, the steam is discharged through the intermediate-pressure exhaust. A small portion leaks into the intermediate-pressure inner and outer cylinder interlayer through the steam seal on the steam inlet side of the intermediate-pressure inner cylinder. At the same time, there is also some steam leakage into the intermediate-pressure inner and outer cylinder interlayer through the intermediate-pressure inner and outer cylinder connecting pipe.

5. The steam turbine system according to claim 4, characterized in that: The heat insulation device of the high-pressure module is installed in the interlayer between the high-pressure outer cylinder and the high-pressure inner cylinder, separating the high-pressure outer cylinder from the interlayer. The heat insulation device and the high-pressure outer cylinder form a steam flow channel, which is the high-pressure heat insulation layer. The inlet of the high-pressure heat insulation layer is connected to the high-pressure exhaust chamber. The heat insulation device of the medium-pressure module is set in the interlayer between the medium-pressure outer cylinder and the medium-pressure inner cylinder, separating the high-pressure outer cylinder from the interlayer. The heat insulation device and the medium-pressure outer cylinder form a steam flow channel, which is the medium-pressure heat insulation layer. The inlet of the medium-pressure heat insulation layer is connected to the three-stage steam extraction chamber.

6. The steam turbine system according to any one of claims 1 to 5, characterized in that: The turbine system also has a steam regulation system located outside the cylinder; The steam regulation system installed outside the cylinder mainly consists of pipes and four valves: a, b, c, and d. The pipe inlet is connected to the high-pressure insulation layer, and the pipe outlet is connected to the medium-pressure insulation layer. When the steam turbine unit is running, the valves are opened, and the steam from the high-pressure insulation layer flows to the medium-pressure insulation layer. The opening of the four valves a, b, c, and d can be adjusted.

7. The steam turbine system according to claim 6, characterized in that: The insulation layer is divided into N independent chambers by a partition plate along the circumferential direction, where N is an integer greater than or equal to 2. Valves a and c are electrically adjustable valves; Valves b and d are electrically operated shut-off valves.

8. The steam turbine system according to claim 7, characterized in that: The insulation layer is divided into N independent chambers along the circumferential direction, with N being an integer equal to 8; there are 4 chambers in the upper half and 4 in the lower half. Each chamber of the insulation layer is connected to a pipe. The four pipes in the upper half are combined into one pipe, and the pipes connecting the high-pressure upper half and the medium-pressure upper half insulation layers are interconnected. The four pipes in the lower half are combined into one pipe, and the pipes connecting the high-pressure lower half and the medium-pressure lower half insulation layers are interconnected. By dividing the insulation layer evenly, cooling steam can flow uniformly within the insulation layer, ensuring uniform cooling of the cylinder.

9. A temperature control method for a steam turbine system according to claims 1 to 8, characterized in that, The temperature control method includes: When the unit is running, open the electric shut-off valves b and d, and gradually open the electric regulating valves a and c; At the same time, the low-temperature steam in the high-pressure exhaust chamber can enter the high-pressure insulation layer to cool the high-pressure outer cylinder; Then it enters the medium-pressure insulation layer through the pipeline to cool the medium-pressure outer cylinder, and finally is discharged into the three-stage extraction chamber; Adjust the opening of valves a and c according to the actual external cylinder temperature to achieve cylinder temperature regulation.

10. The temperature control method for a steam turbine system according to claim 9, characterized in that: The insulation layer is evenly distributed circumferentially, and each independent chamber is connected to a steam pipe, which can ensure that the cylinder is cooled evenly circumferentially, so that the cylinder temperature field is evenly distributed and the temperature stress caused by the circumferential temperature difference is reduced.

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