Extraction steam turbine and its operation method

Abstract

The present application provides an extraction steam turbine and its operation method, which can achieve multiple functions, operate more flexibly, and have higher economy. The extraction steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, a first low-pressure cylinder, and a second low-pressure cylinder; a high-pressure exhaust steam flow path and a low-pressure exhaust steam flow path are provided in the intermediate-pressure cylinder, as well as a high-pressure exhaust steam cavity communicating with the exhaust side of the high-pressure exhaust steam flow path and a low-pressure exhaust steam cavity communicating with the exhaust side of the low-pressure exhaust steam flow path; the steam inlet side of the first low-pressure cylinder communicates with the low-pressure exhaust steam cavity, and the steam inlet side of the second low-pressure cylinder communicates with the high-pressure exhaust steam cavity; a first exhaust steam flow path is provided in the first low-pressure cylinder, and a second exhaust steam flow path is provided in the second low-pressure cylinder. The flow area of the steam inlet side of the first exhaust steam flow path is larger than the flow area of the steam inlet side of the second exhaust steam flow path, and the flow area of the exhaust side of the first exhaust steam flow path is smaller than the flow area of the exhaust side of the second exhaust steam flow path.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbines, and particularly relates to an extraction steam turbine and an operation method thereof. Background Art

[0002] In order to simplify the body structure and the extraction steam adjustment strategy of a high-power cogeneration steam turbine, usually only one-stage extraction steam is provided, that is, one path of steam is extracted from the steam turbine for use. However, there are also steam turbines with two-stage extraction steam, that is, two paths of steam are extracted from the steam turbine for use. At this time, the structure of the steam turbine is relatively complex, the extraction steam pressure control logic is relatively complex, and it is difficult to improve the flexibility. Summary of the Invention

[0003] The purpose of the present application is to provide an extraction steam turbine and an operation method thereof, which can realize multiple functions, operate more flexibly, and have higher economy.

[0004] The extraction steam turbine provided by the present application includes a high-pressure cylinder, an intermediate-pressure cylinder, a first low-pressure cylinder, and a second low-pressure cylinder; a high-pressure exhaust steam flow path and a low-pressure exhaust steam flow path are arranged in the intermediate-pressure cylinder, and a high-pressure exhaust steam cavity communicating with the exhaust side of the high-pressure exhaust steam flow path and a low-pressure exhaust steam cavity communicating with the exhaust side of the low-pressure exhaust steam flow path; the inlet side of the first low-pressure cylinder is communicated with the low-pressure exhaust steam cavity, and the inlet side of the second low-pressure cylinder is communicated with the high-pressure exhaust steam cavity;

[0005] A first exhaust steam flow path is arranged in the first low-pressure cylinder, and a second exhaust steam flow path is arranged in the second low-pressure cylinder. The flow area of the inlet side of the first exhaust steam flow path is larger than the flow area of the inlet side of the second exhaust steam flow path, and the flow area of the exhaust side of the first exhaust steam flow path is smaller than the flow area of the exhaust side of the second exhaust steam flow path.

[0006] In a specific embodiment, the inlet side of the second low-pressure cylinder is further communicated with the low-pressure exhaust steam cavity, and a first regulating valve is arranged on the path between the first regulating valve and the inlet side of the second low-pressure cylinder; a cooling device is further arranged between the first regulating valve and the inlet side of the second low-pressure cylinder.

[0007] In a specific embodiment, pressure regulating valves are arranged between the inlet side of the first low-pressure cylinder and the low-pressure exhaust steam cavity, and between the inlet side of the second low-pressure cylinder and the high-pressure exhaust steam cavity.

[0008] In a specific embodiment, the number of moving blades in the first exhaust steam flow path is less than the number of moving blades in the second exhaust steam flow path; the length of the last-stage moving blade in the first exhaust steam flow path is less than the length of the last-stage moving blade in the second exhaust steam flow path.

[0009] In a specific embodiment, the number of moving blades in the low-pressure exhaust flow path is more than that in the high-pressure exhaust flow path.

[0010] In a specific embodiment, it further includes a first condenser and a second condenser. The exhaust side of the first low-pressure cylinder is connected to the first condenser, and the exhaust side of the second low-pressure cylinder is connected to the second condenser. The first condenser is used to connect to heat users.

[0011] This application also provides an operating method for a extraction steam turbine, which is used to operate the extraction steam turbine described in the sixth item above, and includes:

[0012] When the extraction steam turbine is in a low-load condition or the extraction steam volume in the high-pressure exhaust cavity is large, close the passage between the high-pressure exhaust cavity and the second low-pressure cylinder to make the second low-pressure cylinder operate at zero power.

[0013] In a specific embodiment, connect the low-pressure exhaust cavity and the second low-pressure cylinder, introduce part of the steam in the low-pressure exhaust cavity, and after cooling, enter the second low-pressure cylinder.

[0014] In a specific embodiment, when the extraction steam turbine is in a high-load condition or the extraction steam volume in the low-pressure exhaust cavity is small, reduce the vacuum value of the first condenser to make the first condenser operate in a low-vacuum state, or increase the vacuum value of the first condenser to make the first condenser operate in a condensing state; when the extraction steam turbine is in a low-load condition or the extraction steam volume in the low-pressure exhaust cavity is large, increase the vacuum value of the first condenser to make the first condenser operate in a condensing state.

[0015] In a specific embodiment, always keep the second condenser operating in a high-vacuum state.

[0016] This extraction steam turbine can achieve more functions and has more flexible operation control:

[0017] Part of the low-pressure steam in the intermediate-pressure cylinder enters the first low-pressure cylinder. The first low-pressure cylinder is suitable for operating under a higher condenser pressure and a smaller steam flow rate. For example, when operating under a higher condenser steam pressure, it can achieve the function of low-vacuum heat supply, thereby increasing the heat supply; when the load of the extraction steam turbine decreases or the extraction steam volume of the low-pressure steam in the intermediate-pressure cylinder is large, the steam flow rate entering the first low-pressure cylinder will become smaller. At this time, since the first low-pressure cylinder has a smaller exhaust-side flow area, it is thus suitable for operating under smaller steam flow rate conditions, improving the economy of the extraction steam turbine at low loads.

[0018] A part of the high-pressure steam in the intermediate-pressure cylinder enters the second low-pressure cylinder. The second low-pressure cylinder is suitable for operating under lower condenser pressure and larger steam flow conditions, and has better economy. If the load of the extraction steam turbine decreases or the extraction steam volume of the high-pressure steam in the intermediate-pressure cylinder is large, the steam volume in the second low-pressure cylinder decreases. At this time, the second low-pressure cylinder can be controlled to operate at zero power, that is, the high-pressure exhaust cavity of the intermediate-pressure cylinder is disconnected from the second low-pressure cylinder, and the high-pressure steam in the intermediate-pressure cylinder no longer enters the second low-pressure cylinder, which is beneficial to improving economy. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of the steam turbine system in the embodiment of the present application.

[0020] The descriptions of the reference numerals in the drawings are as follows:

[0021] 100 - Boiler;

[0022] 201 - High-pressure cylinder; 202 - Intermediate-pressure cylinder; 2021 - High-pressure exhaust flow path; 2022 - Low-pressure exhaust flow path; 2023 - Thrust balance drum; 2023a - First pressure balance cavity; 2024 - Reverse thrust balance drum; 2024a - Second pressure balance cavity; 202a - Low-pressure exhaust cavity; 202b - High-pressure exhaust cavity; 203 - First low-pressure cylinder; 2031 - First exhaust flow path; 2031a - First last-stage moving blade; 204 - Second low-pressure cylinder; 2041 - Second exhaust flow path; 2041a - Second last-stage moving blade;

[0023] 300 - Generator;

[0024] 401 - High-pressure heat exchanger; 402 - Low-pressure heat exchanger;

[0025] 501 - First condenser; 502 - Second condenser;

[0026] 600 - Water pump;

[0027] 11 - First pressure regulating valve; 12 - First regulating valve; 13 - Cooling device; 14 - Second pressure regulating valve; 15 - Intermediate-pressure main steam valve; 16 - Second regulating valve; 17 - High-pressure main steam valve; 18 - First regulating valve; 19 - Check valve; 21 - First passage; 22 - Second passage; 23 - Third passage; 24 - Fourth passage; 25 - Fifth passage; 26 - Sixth passage; 27 - Seventh passage; 28 - Eighth passage; 29 - Ninth passage; 210 - Tenth passage; 211 - Eleventh passage. Detailed Embodiment

[0028] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0029] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the steam turbine system in the embodiment of the present application.

[0030] The steam turbine system in this embodiment includes a extraction steam turbine and a generator. The extraction steam turbine includes a high-pressure cylinder 201, a middle-pressure cylinder 202, a first low-pressure cylinder 203, and a second low-pressure cylinder 204. The above cylinders and the generator 300 are arranged in series in sequence, that is, the rotor shafts of each cylinder are coaxially arranged and connected to the rotor shaft of the generator 300. The steam entering each cylinder drives the shaft to rotate, so as to drive the shaft of the generator 300 to rotate for power generation. The steam turbine system also includes a boiler 100. There are two flow paths in the boiler 100. In one flow path, high-temperature and high-pressure steam is generated and can flow to the steam inlet side of the high-pressure cylinder 201 through a high-pressure steam pipeline. The high-pressure steam pipeline is Figure 1 the sixth passage 26 shown. The high-pressure steam does work in the high-pressure cylinder 201. A high-pressure main steam valve 17 and a first regulating valve 18 are arranged in the sixth passage 26 to regulate the flow rate and pressure of the high-temperature and high-pressure steam. The steam that has done work flows back to the boiler 100 through a high-pressure exhaust pipeline connecting the exhaust side of the high-pressure cylinder 201. The high-pressure exhaust pipeline is Figure 1 the tenth passage 210 shown. A check valve 19 is arranged in the tenth passage 210, which only allows one-way flow to the boiler 100. The steam flowing back to the boiler 100 is reheated in another flow path of the boiler 100. The reheated steam enters the middle-pressure cylinder 202 through a middle-pressure steam pipeline, a middle-pressure main steam valve 15, and a second regulating valve 16. The middle-pressure steam pipeline is Figure 1 the eighth passage 28 shown.

[0031] It should be noted that the middle-pressure cylinder 202 in this embodiment is an asymmetric double-flow structure, that is, two groups of exhaust flow paths are arranged in the middle-pressure cylinder 202. The exhaust flow path is a channel assembly composed of a plurality of stationary blades and moving blades. The two groups of exhaust flow paths are different, forming an asymmetric structure. As Figure 1 shown, the two groups of exhaust flow paths arranged in the middle-pressure cylinder 202 are respectively defined as a high-pressure exhaust flow path 2021 and a low-pressure exhaust flow path 2022. Correspondingly, a high-pressure exhaust cavity 202b connecting the exhaust side of the high-pressure exhaust flow path 2021 and a low-pressure exhaust cavity 202a connecting the exhaust side of the low-pressure exhaust flow path 2022 are arranged in the middle-pressure cylinder 202. When the steam of the boiler 100 enters the middle-pressure cylinder 202, it is divided into two groups of exhaust flow paths. One part enters the high-pressure exhaust flow path 2021, and one part enters the low-pressure exhaust flow path 2022. Through the arrangement of the high-pressure exhaust flow path 2021 and the low-pressure exhaust flow path 2022, the steam pressure discharged from the high-pressure exhaust flow path 2021 is greater than the steam pressure discharged from the low-pressure exhaust flow path 2022. The high-pressure exhaust cavity 202b and the low-pressure exhaust cavity 202a described here are also defined according to the high and low steam pressures of the two.

[0032] The extraction steam turbine is also provided with a high-pressure extraction steam pipeline and a low-pressure extraction steam pipeline, which are respectively Figure 1 the third passage 23 and the fourth passage 24 shown in the figure. The high-pressure exhaust steam chamber 202b of the intermediate-pressure cylinder 202 is communicated with the third passage 23 to introduce the high-pressure steam in the high-pressure exhaust steam chamber 202b into the high-pressure heat exchanger 401 or the heat user. The low-pressure exhaust steam chamber 202a of the intermediate-pressure cylinder 202 is communicated with the fourth passage 24 to introduce the low-pressure steam in the low-pressure exhaust steam chamber 202a into the low-pressure heat exchanger 402 or the heat user, that is, the steam discharged from the intermediate-pressure cylinder 202 can be thermally utilized.

[0033] In addition, the steam inlet side of the first low-pressure cylinder 203 is communicated with the low-pressure exhaust steam chamber 202a of the intermediate-pressure cylinder 202, and the steam inlet side of the second low-pressure cylinder 204 is communicated with the high-pressure exhaust steam chamber 202b of the intermediate-pressure cylinder 202. That is, the steam with relatively lower pressure in the intermediate-pressure cylinder 202 enters the first low-pressure cylinder 203, and the steam with relatively higher pressure enters the second low-pressure cylinder 204. The steam turbine system also includes a first condenser 501 communicated with the exhaust side of the first low-pressure cylinder 203 and a second condenser 502 communicated with the exhaust side of the second low-pressure cylinder 204. The steam discharged from the two low-pressure cylinders becomes condensate water after passing through the corresponding condensers and flows to the boiler 100 through the feed water pipeline. The feed water pipeline is Figure 1 the seventh passage 27 shown in the figure. A water pump 600 can be arranged in the seventh passage 27 to provide sufficient return water power. The seventh passage 27 is communicated with the high-temperature and high-pressure steam circuit for communicating with the high-pressure cylinder 201 in the boiler 100, that is, the condensate water is introduced into the boiler 100 for reheating and entering the recirculation.

[0034] In the first low-pressure cylinder 203 of this embodiment, a first exhaust steam flow path 2031 is arranged, and in the second low-pressure cylinder 204, a second exhaust steam flow path 2041 is arranged. Then look Figure 1 , both the first low-pressure cylinder 203 and the second low-pressure cylinder 204 adopt a double-flow structure. However, different from the intermediate-pressure cylinder 202, the two low-pressure cylinders are symmetric double-flow structures, and two groups of the same exhaust steam flow paths are arranged in each low-pressure cylinder. It can be seen that the two low-pressure cylinders can also be single-flow structures, but the double-flow structure is more suitable for the steam volume usage requirements of the extraction steam turbine. The high-pressure cylinder 201 in this embodiment can be a single-flow structure.

[0035] It should be emphasized that although both low-pressure cylinders are symmetric double-flow structures, there are differences between the two low-pressure cylinders. Among them, the flow area on the steam inlet side of the first exhaust steam flow path 2031 is larger than that on the steam inlet side of the second exhaust steam flow path 2041, and the flow area on the steam exhaust side of the first exhaust steam flow path 2031 is smaller than that on the steam exhaust side of the second exhaust steam flow path 2041. That is to say, the first low-pressure cylinder 203 is relatively "large in and small out" to adapt to the low-pressure steam from the intermediate-pressure cylinder 202, and the second low-pressure cylinder 204 is relatively "small in and large out" to adapt to the high-pressure steam from the intermediate-pressure cylinder 202. The pressure of the low-pressure steam is relatively low, entering from a relatively large inlet and flowing out from a relatively small outlet, while the pressure of the high-pressure steam is relatively high, entering from a relatively small inlet and flowing out from a relatively large outlet. This can enhance the functional adaptability of the unit and achieve better economy.

[0036] With such a setting, the extraction steam turbine operates more flexibly:

[0037] A part of the low-pressure steam in the intermediate-pressure cylinder 202 enters the first low-pressure cylinder 203, and the first low-pressure cylinder 203 is suitable for operating under a relatively high condenser pressure and a relatively small steam flow rate. For example, when operating under a relatively high condenser steam pressure, the function of low-vacuum heat supply can be realized, thereby increasing the heat supply. That is, the first condenser 501 can be connected to heat users to provide hot water, achieving better economy; when the load of the extraction steam turbine decreases or the low-pressure extraction steam volume of the low-pressure steam in the intermediate-pressure cylinder 202 is relatively large, the steam flow rate entering the first low-pressure cylinder 203 will become smaller. At this time, due to the relatively small flow area on the steam exhaust side of the first low-pressure cylinder 203, it is thus suitable for operating under relatively small steam flow conditions, improving the economy of the extraction steam turbine at low loads.

[0038] A part of the high-pressure steam in the intermediate-pressure cylinder 202 enters the second low-pressure cylinder 204, and the second low-pressure cylinder 204 is suitable for operating under a relatively low condenser pressure and a relatively large steam flow rate, with better economy. When the load of the extraction steam turbine is relatively high or the extraction steam volume of the high-pressure steam in the intermediate-pressure cylinder 202 is relatively small, the steam flow rate entering the second low-pressure cylinder 204 becomes larger. At this time, the relatively large flow area on the steam exhaust side can improve the economy of the extraction steam turbine.

[0039] It can be seen from this that after the intermediate-pressure cylinder 202 of the extraction steam turbine is asymmetrically designed, the steam in the intermediate-pressure cylinder 202 can be separated into high-pressure steam and low-pressure steam, enabling the simultaneous implementation of high-pressure regulated extraction and low-pressure regulated extraction. In addition, the high-pressure steam and low-pressure steam can be respectively introduced into their corresponding low-pressure cylinders. When the load of the extraction steam turbine and the extraction steam condition of the intermediate-pressure cylinder 202 change, there is always a low-pressure cylinder suitable for the working condition, so as to improve the operating flexibility and economy of the extraction steam turbine.

[0040] The second low-pressure cylinder 204 is used to admit high-pressure steam from the intermediate-pressure cylinder 202. As mentioned above, the second low-pressure cylinder 204 is suitable for operating conditions with a large amount of steam. If the load of the extraction steam turbine decreases or the extraction amount of high-pressure steam in the intermediate-pressure cylinder 202 is large, the amount of steam in the second low-pressure cylinder 204 decreases. At this time, the second low-pressure cylinder 204 can be controlled to operate at zero power, that is, the high-pressure exhaust cavity 202b of the intermediate-pressure cylinder 202 is disconnected from the second low-pressure cylinder 204, and the high-pressure steam in the intermediate-pressure cylinder 202 no longer enters the second low-pressure cylinder 204, which is beneficial to improving economy.

[0041] At this time, although high-pressure steam does not enter the second low-pressure cylinder 204, the moving blades of the second exhaust flow path 2041 will rotate with the rotating shaft of the extraction steam turbine. If no steam enters completely, the moving blades are prone to heat up. As Figure 1 shown, the steam inlet side of the second low-pressure cylinder 204 is also connected to the low-pressure exhaust cavity 202a, specifically through Figure 1 the eleventh passage 211 in it, and a third regulating valve 12 is provided on the eleventh passage 211 of the steam inlet side of the second low-pressure cylinder 204 and the low-pressure exhaust cavity 202a. That is, when the second low-pressure cylinder 204 operates at zero power, although the high-pressure steam in the intermediate-pressure cylinder 202 does not enter the second low-pressure cylinder 204, a part of the low-pressure steam can be introduced into the second low-pressure cylinder 204 through the third passage 23. When the second low-pressure cylinder 204 is connected to the high-pressure exhaust cavity 202b, the third regulating valve 12 can be closed. In addition, a cooling device 13 is provided between the third regulating valve 12 and the steam inlet side of the second low-pressure cylinder 204. The cooling device 13 is used to cool the low-pressure steam introduced from the intermediate-pressure cylinder 202. The cooling device 13 is, for example, a spray desuperheating device, which can further cool down the low-pressure steam from the intermediate-pressure cylinder 202. In this way, the steam cooled by the cooling device 13 can enter the second low-pressure cylinder 204, thereby cooling the second exhaust flow path 2041 in the second low-pressure cylinder 204 and preventing the exhaust flow path from overheating due to drum wind when no high-pressure steam is introduced.

[0042] Figure 1Among them, pressure regulating valves are provided between the steam inlet side of the first low-pressure cylinder 203 and the low-pressure exhaust cavity 202a, and between the steam inlet side of the second low-pressure cylinder 204 and the high-pressure exhaust cavity 202b, which can be respectively defined as the first pressure regulating valve 11 and the second pressure regulating valve 14. Specifically, the first low-pressure cylinder 203 and the low-pressure exhaust cavity 202a are connected through the first passage 21, the second low-pressure cylinder 204 and the high-pressure exhaust cavity 202b are connected through the second passage 22, the first pressure regulating valve 11 is arranged in the first passage 21, and the second pressure regulating valve 14 is arranged in the second passage 22. The pressure regulating valve can specifically be a pressure regulating butterfly valve. Of course, the pressure regulating valve is not limited to the pressure regulating butterfly valve, as long as it can regulate the pressure. By adjusting the opening degree of the pressure regulating valve, the pressure on the exhaust side of the intermediate-pressure cylinder 202 can be adjusted, so that the pressure entering the low-pressure heat exchanger 402 or the high-pressure heat exchanger 401 or the heat user can be adjusted. In addition, as mentioned above, when controlling the second low-pressure cylinder 204 to operate at zero power, it is necessary to control the disconnection between the second low-pressure cylinder 204 and the intermediate-pressure cylinder 202, and then directly close the second pressure regulating valve 14. At this time, the eleventh passage 211 is arranged upstream of the first pressure regulating valve 11 to ensure that when the second low-pressure cylinder 204 operates at zero power, a portion of the steam can be diverted into the second low-pressure cylinder 204.

[0043] Please continue to refer to Figure 1 , the last-stage moving blade in the first exhaust flow path 2031 is the first last-stage moving blade 2031a, and the last-stage moving blade in the second exhaust flow path 2041 is the second last-stage moving blade 2041a. The length of the first last-stage moving blade 2031a is less than the length of the second last-stage moving blade 2041a. The last-stage moving blade is the moving blade on the exhaust side in the exhaust flow path. The longer the last-stage moving blade is, the larger the corresponding flow area is. In this way, the flow area on the exhaust side is larger, which can ensure that the flow area on the exhaust side of the second low-pressure cylinder 204 is larger than that of the first low-pressure cylinder 203, so that the two low-pressure cylinders can better adapt to the steam inlet conditions of low-pressure steam and high-pressure steam.

[0044] In addition, in this embodiment, the number of stages of the moving blades in the first exhaust steam flow path 2031 in the first low-pressure cylinder 203 is less than the number of stages of the moving blades in the second exhaust steam flow path 2041 in the second low-pressure cylinder 204. This is because the inlet steam pressure of the first exhaust steam flow path 2031 is lower than the inlet steam pressure of the second exhaust steam flow path 2041. Correspondingly, the volume flow rate of the inlet steam of the first exhaust steam flow path 2031 is greater than the volume flow rate of the inlet steam of the second exhaust steam flow path 2041. Therefore, when designing the flow path size, the inlet flow area of the first exhaust steam flow path 2031 is set to be larger than the inlet flow area of the second exhaust steam flow path 2041. In this embodiment, in order for the first exhaust steam flow path 2031 to adapt to high back-pressure heat supply operation, the first last-stage moving blade 2031a is designed to be relatively short; the second exhaust steam flow path 2041 operates under high vacuum conditions for a long time, and the second last-stage moving blade 2041a is designed to be relatively long. At the same time, in order to ensure reasonable enthalpy drop distribution for each stage of the flow path and smooth and reasonable expansion of the flow path, the number of stages of the second exhaust steam flow path 2041 is configured to be relatively more. In this way, the above-mentioned situation where the first exhaust steam flow path 2031 is relatively "large at the inlet and small at the outlet" and the second exhaust steam flow path 2041 is relatively "small at the inlet and large at the outlet" appears.

[0045] Looking further Figure 1 , in this embodiment, the number of stages of the moving blades in the low-pressure exhaust steam flow path 2022 in the intermediate-pressure cylinder 202 is more than the number of stages of the moving blades in the high-pressure exhaust steam flow path 2021; the flow area on the inlet side of the low-pressure exhaust steam flow path 2022 is equal to the flow area on the inlet side of the high-pressure exhaust steam flow path 2021. Since the flow areas on the inlet side are equal, after the steam from the boiler 100 enters the intermediate-pressure cylinder 202, it can be relatively evenly divided into two streams and flow to the low-pressure exhaust steam flow path 2022 and the high-pressure exhaust steam flow path 2021 respectively. Since the number of stages of the moving blades in the low-pressure exhaust steam flow path 2022 is relatively large and the inlet flow area of the first exhaust steam flow path 2031 is relatively large, the pressure of the steam flowing and discharging in the low-pressure exhaust steam flow path 2022 will be relatively small, realizing the distinction between the high-pressure exhaust steam cavity 202b and the low-pressure exhaust steam cavity 202a, and the setting is relatively simple. It can be seen that the intermediate-pressure cylinder 202 is not limited to such a setting, and the distribution of the steam in the two groups of exhaust steam flow paths entering the intermediate-pressure cylinder 202 can also be unequal. For example, if the flow area on the inlet side of the low-pressure exhaust steam flow path 2022 is larger, the amount of steam entering the low-pressure exhaust steam flow path 2022 will be more, or if the flow area on the inlet side of the high-pressure exhaust steam flow path 2021 is larger, the amount of steam entering the high-pressure exhaust steam flow path 2021 will be more, that is, by adjusting the size of the inlet flow area of the high-pressure exhaust steam cavity 202b and the low-pressure exhaust steam cavity 202a of the intermediate-pressure cylinder 202, the distribution of the steam flow rate in the two groups of flow paths is realized. Then, according to the amount of steam inlet of the steam entering the two groups of exhaust steam flow paths, the length of each stage of the blade is designed to ensure that the pressure in the high-pressure exhaust steam cavity 202b and the pressure in the low-pressure exhaust steam cavity 202a meet the design requirements.

[0046] As shown in Figure 1 , in this embodiment, if the flow path of the intermediate pressure cylinder 202 adopts the reaction type technology, a thrust balance drum 2023 and a first pressure balance chamber 2023a are provided at the tail of the high-pressure exhaust chamber 202b, and the first pressure balance chamber 2023a behind the thrust balance drum 2023 is connected to the low-pressure exhaust chamber 202a through a pressure balance pipe. The pressure balance pipe is the Figure 1 shown ninth passage 209. By adjusting the diameter of the thrust balance drum 2023, the magnitude and direction of the axial thrust of the rotor of the intermediate pressure cylinder 202 can be changed. In this way, it can be ensured that when a failure occurs in the high-pressure extraction steam or low-pressure extraction steam alone or simultaneously, the axial thrust of the rotor of the intermediate pressure cylinder 202 will not change significantly. If the flow path of the intermediate pressure cylinder 202 adopts the impulse type technology, the thrust balance drum 2023 and the first pressure balance chamber 2023a do not need to be provided.

[0047] If it is difficult to achieve due to the excessive diameter of the thrust balance drum 2023 on the high-pressure exhaust flow 2021 side, a reverse thrust balance drum 2024 and a second pressure balance chamber 2024a can be added on the low-pressure exhaust flow 2022 side, and the second pressure balance chamber 2024a behind the reverse thrust balance drum 2024 is connected to the high-pressure exhaust chamber 202b through a pressure balance pipe. The pressure balance pipe here is the fifth passage 25. By adjusting the diameter of the reverse thrust balance drum 2024, the magnitude and direction of the axial thrust of the rotor of the intermediate pressure cylinder 202 are adjusted.

[0048] This embodiment also provides an operating method for a steam extraction turbine for operating the above-mentioned steam extraction turbine, including:

[0049] When the steam extraction turbine is in a low-load condition or the steam extraction amount of the high-pressure exhaust chamber 202b is large, the passage between the high-pressure exhaust chamber 202b and the second low-pressure cylinder 204 is closed, so that the second low-pressure cylinder 204 operates at zero power.

[0050] As described above, the second low-pressure cylinder 204 is suitable for operating under lower condenser pressure and larger steam flow conditions. When the load of the steam turbine is high or the steam extraction amount is small, the steam flow rate entering the second low-pressure cylinder becomes larger, and the second low-pressure cylinder 204 has higher economy. When the load of the steam turbine decreases or the high-pressure steam extraction amount is large, the steam amount entering the second low-pressure cylinder 204 decreases. At this time, the connection between the second low-pressure cylinder 204 and the high-pressure exhaust chamber 202b can be disconnected, so that the second low-pressure cylinder 204 operates at zero power to achieve better economy.

[0051] Based on the zero-power operation of the second low-pressure cylinder 204, the following operation controls can also be included:

[0052] Connect the low-pressure exhaust cavity 202a and the second low-pressure cylinder 204, introduce a part of the steam in the low-pressure exhaust cavity 202a, and after cooling, enter the second low-pressure cylinder 204.

[0053] As described above, the introduced cooling steam can cool the moving blades in the flow path of the second low-pressure cylinder 204 to prevent overheating due to blowing. The cooling is carried out, for example, Figure 1 by the cooling device 13 shown.

[0054] When the steam turbine is in a high-load condition or the extraction steam volume of the low-pressure exhaust cavity 202a is small, reduce the vacuum value of the first condenser 501 to make the first condenser 501 operate in a low-vacuum state, or increase the vacuum value of the first condenser 501 to make the first condenser 501 operate in a condensing state, that is, high-vacuum operation. In this embodiment, the low-vacuum heat supply operation of the first low-pressure cylinder 203 and the zero-power operation of the second low-pressure cylinder 204 can be carried out simultaneously without interference. When the steam turbine is in a high-load condition or the extraction steam volume of the low-pressure exhaust cavity 202a is small, reducing the vacuum value of the first condenser 501 can make the first condenser 501 operate in a low-vacuum state. The first condenser 501 can be connected to the heat user for low-vacuum heat supply operation, which can increase the exhaust temperature and exhaust pressure and improve the heat supply effect. When the steam turbine is in a low-load condition or the extraction steam volume of the low-pressure exhaust cavity 202a is large, the steam volume entering the first low-pressure cylinder 203 decreases. At this time, if the steam flow rate is too small to support low-vacuum heat supply, increase the vacuum value of the first condenser 501 to ensure the economy under the current working condition.

[0055] In addition, the second condenser 502 is connected to the second low-pressure cylinder 204, and high-pressure steam in the intermediate-pressure cylinder 202 is introduced into the second low-pressure cylinder 204. The second condenser 502 can always operate in a high-vacuum state to ensure economy. The high vacuum and low vacuum described here can be determined according to the performance requirement values of the specific condenser.

[0056] In this article, specific examples are used to elaborate on the principle and implementation mode of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. Extraction steam turbine, characterized in that: It comprises a high-pressure cylinder, a medium-pressure cylinder, a first low-pressure cylinder and a second low-pressure cylinder; the medium-pressure cylinder is provided with a high-pressure exhaust steam flow and a low-pressure exhaust steam flow, and a high-pressure exhaust steam chamber connected to the exhaust side of the high-pressure exhaust steam flow, and a low-pressure exhaust steam chamber connected to the exhaust side of the low-pressure exhaust steam flow; the steam inlet side of the first low-pressure cylinder is connected to the low-pressure exhaust steam chamber, and the steam inlet side of the second low-pressure cylinder is connected to the high-pressure exhaust steam chamber; A first exhaust steam flow is provided in the first low-pressure cylinder, a second exhaust steam flow is provided in the second low-pressure cylinder, a flow area on the steam inlet side of the first exhaust steam flow is larger than a flow area on the steam inlet side of the second exhaust steam flow, and a flow area on the steam exhaust side of the first exhaust steam flow is smaller than a flow area on the steam exhaust side of the second exhaust steam flow; The steam inlet side of the second low-pressure cylinder is also connected to the low-pressure exhaust chamber, and a first regulating valve is arranged on the passage between the steam inlet side of the second low-pressure cylinder and the low-pressure exhaust chamber; a cooling device is also arranged between the first regulating valve and the steam inlet side of the second low-pressure cylinder.

2. The extraction steam turbine according to claim 1, characterized in that: Pressure regulating valves are provided between the steam inlet side of the first low-pressure cylinder and the low-pressure exhaust chamber, and between the steam inlet side of the second low-pressure cylinder and the high-pressure exhaust chamber.

3. The extraction steam turbine according to claim 1, characterized in that: The number of moving blades in the first exhaust steam flow is less than the number of moving blades in the second exhaust steam flow; the length of the last-stage moving blades in the first exhaust steam flow is less than the length of the last-stage moving blades in the second exhaust steam flow.

4. The extraction steam turbine according to any one of claims 1 to 3, characterized in that: The number of stages of the moving blades through which the low-pressure exhaust steam flows is greater than the number of stages of the moving blades through which the high-pressure exhaust steam flows.

5. The extraction steam turbine according to any one of claims 1 to 3, characterized in that: It also includes a first condenser and a second condenser. The exhaust side of the first low-pressure cylinder is connected to the first condenser, and the exhaust side of the second low-pressure cylinder is connected to the second condenser. The first condenser is used to connect to a heat user.

6. A method for operating an extraction steam turbine, characterized in that: For operating the extraction steam turbine according to claim 5, comprising: When the extraction steam turbine is in a low-load condition or the extraction amount of the high-pressure exhaust chamber is large, the passage between the high-pressure exhaust chamber and the second low-pressure cylinder is closed to enable the second low-pressure cylinder to achieve zero-power operation.

7. The method for operating an extraction steam turbine according to claim 6, characterized in that: The low-pressure exhaust chamber and the second low-pressure cylinder are connected, and part of the steam in the low-pressure exhaust chamber is introduced and enters the second low-pressure cylinder after being cooled.

8. The method for operating an extraction steam turbine according to claim 7, characterized in that: When the extraction steam turbine is in a high-load condition or the steam extraction amount of the low-pressure exhaust chamber is small, the vacuum value of the first condenser is reduced so that the first condenser is in a low-vacuum operation state, or the vacuum value of the first condenser is increased so that the first condenser is in a condensing operation state; when the extraction steam turbine is in a low-load condition or the steam extraction amount of the low-pressure exhaust chamber is large, the vacuum value of the first condenser is increased so that the first condenser is in a condensing operation state.

9. The method for operating an extraction steam turbine according to claim 7 or 8, characterized in that: The second condenser is always kept in a high vacuum operation state.

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