Steam cooling system and regulation method for low-pressure cylinder of steam turbine

Abstract

This invention relates to the field of steam turbine technology, and more particularly to a steam cooling system for a low-pressure cylinder of a steam turbine. The system includes a controller, a pressure sensor for monitoring the exhaust pressure on the exhaust side of the low-pressure cylinder, a thermometer for monitoring the exhaust temperature of the low-pressure cylinder, first and second nozzle groups, each having a plurality of nozzles located on the exhaust side of the low-pressure cylinder, and first and second water spray pipes for supplying water to the first and second nozzle groups, respectively. The second nozzle group has more nozzles than the first nozzle group. First and second regulating valves are respectively installed on the first and second water spray pipes. The pressure sensor, thermometer, first regulating valve, and second regulating valve are all connected to the controller. The invention also relates to a method for regulating the steam cooling of the low-pressure cylinder of a steam turbine using this system. This method primarily involves the controller controlling and adjusting the opening of the first regulating valve and / or the second regulating valve according to the required water spray volume, thereby precisely controlling the water spray volume. This method can eliminate blade erosion without requiring blade treatment.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and in particular to a steam cooling system for a low-pressure cylinder of a steam turbine and a method for regulating steam cooling in a low-pressure cylinder of a steam turbine. Background Technology

[0002] With increasingly stringent national requirements for energy conservation, emission reduction, and clean heating, achieving thermal-electric decoupling and deep peak shaving in thermal power units has become a crucial performance indicator for many power plants in China. In response to national demands to tap the peak-shaving potential of thermal power units, improve their operational flexibility, and enhance the absorption capacity of new energy sources, many power plants in northern China have implemented turbine-to-cylinder conversions to enable low-load operation. While eliminating the low-pressure cylinder for heating offers significant economic advantages, the low-pressure cylinder operates under low-volume flow conditions during this conversion, resulting in extremely complex flow patterns on the last-stage blades. Desulfurization, backflow, and reverse suction occur at the blade root region, and the returning steam carries liquid droplets that impact the blades, causing water erosion. Blade water erosion affects blade vibration performance and stage efficiency, and in severe cases, can lead to blade breakage and major accidents. The droplets in the steam flow come from two sources: firstly, the increased humidity of the exhaust steam from the last few stages of the low-pressure blades causes the exhaust steam to condense into water droplets; secondly, to control the exhaust steam temperature during cylinder cutting, the water spray device needs to be turned on to cool it down. However, if the amount of water sprayed is excessive and the water cannot be vaporized in time, it will be carried back and hit the exhaust edge of the blades, causing water erosion.

[0003] Patent application CN109944646A discloses a method for mitigating blade risks during zero-power retrofitting of the low-pressure cylinder of a thermal power turbine unit. The method includes the following steps: Step 1, selecting blades for the zero-power retrofit of the low-pressure cylinder based on three indicators: static stress distribution, dynamic stress magnitude, and operating frequency; Step 2, real-time monitoring of blade vibration during the zero-power retrofit; Step 3, increasing the water injection volume of the thermal power turbine unit and introducing steam into the bypass of the unit; Step 4, applying a coating to the blade surface; Step 5, mitigating blade risks during the zero-power retrofit of the low-pressure cylinder using the methods described in steps 1 to 4. This method requires blade replacement and surface coating to improve water erosion resistance. Replacing blades increases retrofit costs. Spraying the blade surface affects the blade structure and stage efficiency. Furthermore, the improvement in water erosion resistance from spraying is limited, and there is a risk of the coating peeling off. Once the coating peels off, water erosion may worsen. Therefore, it is necessary to regularly open the cylinder to check the blade coating. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a steam cooling system and adjustment method for a low-pressure cylinder of a steam turbine, which can eliminate water erosion of the blades without replacing or treating the blades, thereby overcoming the above-mentioned defects of the prior art.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a steam cooling system for a low-pressure cylinder of a steam turbine, comprising a controller, a pressure sensor for monitoring the exhaust pressure on the exhaust side of the low-pressure cylinder, a thermometer for monitoring the exhaust temperature on the exhaust side of the low-pressure cylinder, a first nozzle group and a second nozzle group each having a plurality of nozzles disposed on the exhaust side of the low-pressure cylinder, and a first water spray pipe and a second water spray pipe respectively supplying water to the first nozzle group and the second nozzle group. The second nozzle group has more nozzles than the first nozzle group. A first regulating valve is provided on the first water spray pipe, and a second regulating valve is provided on the second water spray pipe. The pressure sensor, the thermometer, the first regulating valve, and the second regulating valve are all connected to the controller.

[0007] Preferably, a first shut-off valve is provided on the first water spray pipe before the first regulating valve, and a second shut-off valve is provided on the second water spray pipe before the second regulating valve.

[0008] Preferably, a first throttle valve is provided on the first water spray pipe after the first regulating valve, and a second throttle valve is provided on the second water spray pipe after the second regulating valve.

[0009] Preferably, a first pressure gauge is provided on the first water spray pipe after the first throttle valve, and a second pressure gauge is provided on the second water spray pipe after the second throttle valve. Both the first and second pressure gauges are connected to the controller.

[0010] Preferably, a third shut-off valve is provided before the first pressure gauge, and a fourth shut-off valve is provided before the second pressure gauge.

[0011] Preferably, it also includes a main pipeline, one end of which is connected to a condensate pump and the other end is connected to a first spray pipe and a second spray pipe. A flow meter is installed on the main pipeline and is connected to a controller.

[0012] Preferably, a filter screen is installed on the main pipeline.

[0013] Preferably, the main pipeline is also connected to the original water spray valve station.

[0014] This invention also provides a method for regulating steam cooling in the low-pressure cylinder of a steam turbine. Using the steam cooling system for the low-pressure cylinder described above, when the low-pressure cylinder is operating at low load, a thermometer monitors the current exhaust temperature on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. A pressure sensor monitors the current exhaust pressure on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. The controller calculates the saturated steam temperature corresponding to the current exhaust pressure and determines the target exhaust temperature as the sum of the saturated steam temperature and a set superheat. Based on the difference between the current exhaust temperature and the target exhaust temperature, the controller calculates the required water spray volume to achieve the target exhaust temperature. The controller then controls and adjusts the first regulating valve according to the required water spray volume. And / or the opening degree of the second regulating valve: If the required water spray volume is less than the first set value, the controller controls the first regulating valve to open and adjusts the opening degree of the first regulating valve so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value; if the required water spray volume is greater than the first set value and less than the second set value, the controller controls the second regulating valve to open and adjusts the opening degree of the second regulating valve so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value; if the required water spray volume is greater than the second set value, the controller controls both the first regulating valve and the second regulating valve to open and simultaneously adjusts the opening degrees of the first regulating valve and the second regulating valve so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value.

[0015] Compared with the prior art, the present invention has significant progress:

[0016] It can determine a target exhaust temperature with a certain degree of superheat based on the current exhaust pressure on the low-pressure cylinder exhaust side without replacing, treating, or affecting the blade structure or stage efficiency. By comparing the current exhaust temperature with the target exhaust temperature, it accurately calculates the amount of water spray required to achieve the target exhaust temperature. Based on the required water spray volume, it controls and adjusts the opening of the first regulating valve and / or the second regulating valve, realizing three-stage water spray logic regulation. This allows for continuous adjustment of the water spray volume, ensuring precise control of the water spray volume. It not only ensures that the exhaust temperature varies within a safe range but also avoids the risks of excessive or insufficient water spray. Furthermore, by maintaining a certain degree of superheat in the exhaust temperature, the water droplets generated by the spray can be vaporized into steam in a timely manner. This prevents water erosion caused by water spraying from the last stage blades impacting the steam outlet edge during low-load operation of the low-pressure cylinder due to backflow. Thus, it can actively prevent blade water erosion and reduce the requirements for blade water erosion resistance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the steam cooling system of the low-pressure cylinder of a steam turbine according to an embodiment of the present invention.

[0018] The reference numerals in the attached figures are explained as follows:

[0019] 100 First spray pipe

[0020] 200 Second water spray line

[0021] 300 main pipeline

[0022] 1a First regulating valve

[0023] 1b Second regulating valve

[0024] 2. Reducing tee

[0025] 3. Reduction

[0026] 4a First shut-off valve

[0027] 4b Second shut-off valve

[0028] 5a First throttle valve

[0029] 5b Second throttle valve

[0030] 6a First pressure gauge

[0031] 6b Second pressure gauge

[0032] 7a Third shut-off valve

[0033] 7b Fourth shut-off valve

[0034] 8 Condensate Pump

[0035] 9. Flow meter

[0036] 10 filters

[0037] 11 Original water spray valve station

[0038] 12 Low-pressure cylinder Detailed Implementation

[0039] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] like Figure 1 As shown, this is an embodiment of the steam cooling system for the low-pressure cylinder of a steam turbine according to the present invention. During the operation of the steam turbine, when the inlet steam pressure of the low-pressure cylinder 12 is lower than a set characteristic value, the low-pressure cylinder 12 enters a low-load operation state (small volume flow condition operation, such as shutting down the low-pressure cylinder 12). The steam cooling system for the low-pressure cylinder of the steam turbine in this embodiment is used to eliminate water erosion of the blades of the low-pressure cylinder 12 when the low-pressure cylinder 12 is running under low load, while controlling the exhaust steam temperature on the exhaust side of the low-pressure cylinder 12 to not exceed the limit.

[0044] The steam cooling system for the low-pressure cylinder of the steam turbine in this embodiment includes a controller, a pressure sensor, a temperature sensor, a first nozzle group, a second nozzle group, a first water spray pipe 100, and a second water spray pipe 200.

[0045] The pressure sensor is used to monitor the exhaust pressure on the exhaust side of the low-pressure cylinder 12. The pressure sensor is installed inside the low-pressure cylinder 12 and is used to monitor the current exhaust pressure on the exhaust side of the low-pressure cylinder 12 in real time.

[0046] The temperature sensor is used to monitor the exhaust temperature on the exhaust side of the low-pressure cylinder 12. The temperature sensor is installed on the exhaust side of the low-pressure cylinder 12 and located after the last stage moving vanes of the low-pressure cylinder 12. It is used to monitor the current exhaust temperature on the exhaust side of the low-pressure cylinder 12 in real time. Preferably, the temperature sensor is a thermocouple.

[0047] The first nozzle group and the second nozzle group each have a number of nozzles located on the exhaust side of the low-pressure cylinder 12, used to spray water onto the exhaust side of the low-pressure cylinder 12 when needed to reduce the exhaust temperature. The second nozzle group has more nozzles than the first nozzle group, resulting in a larger water spray volume. To ensure uniform water spraying, preferably, the nozzles of both the first and second nozzle groups are evenly distributed circumferentially along the exhaust side of the low-pressure cylinder 12. When the low-pressure cylinder 12 is a dual-flow low-pressure cylinder with central steam inlet and two-sided exhaust, one exhaust side is the regulating valve end, and the other exhaust side is the motor end. The nozzles of both nozzle groups are evenly distributed at the regulating valve end and the motor end of the low-pressure cylinder 12. The number of nozzles in the first nozzle group and the second nozzle group are not limited and can be designed according to the performance parameters of the low-pressure cylinder 12 in actual application. For example, in this embodiment, the first nozzle group can have 8 nozzles, with 4 nozzles arranged at the valve end and 4 nozzles at the motor end of the low-pressure cylinder 12. Each nozzle serves as a water spray point, and the water spray points are arranged at equal intervals along the circumference of the exhaust side of the low-pressure cylinder 12. The second nozzle group can have 16 nozzles, with 8 nozzles arranged at the valve end and 8 nozzles at the motor end of the low-pressure cylinder 12. Every two nozzles serve as a water spray point, and the water spray points are arranged at equal intervals along the circumference of the exhaust side of the low-pressure cylinder 12. Preferably, the nozzles are hollow conical nozzles with small nozzle diameter and good atomization effect. Such nozzles can produce a circular spray shape with a droplet size of about 0.2 mm, a spray angle of about 70°, uniform spray distribution, and a wide range of applicable pressure and flow rates, achieving the effect of uniformly spraying water from the exhaust area of ​​the low-pressure cylinder 12 in all directions.

[0048] A first water spray pipe 100 supplies water to a first nozzle group. A first regulating valve 1a is installed on the first water spray pipe 100, and the opening degree of the first regulating valve 1a is continuously adjustable. The opening and closing of the first regulating valve 1a controls the on / off state of the first water spray pipe 100, i.e., controls whether the first nozzle group sprays water. When the first regulating valve 1a is open, adjusting the opening degree of the first regulating valve 1a controls the amount of water supplied by the first water spray pipe 100 to the first nozzle group, thereby controlling the water spray volume of the first nozzle group. In this embodiment, the end of the first water spray pipe 100 is divided into two branches. The two branches are respectively connected to the four nozzles (four water spray points) arranged at the regulating valve end of the low-pressure cylinder 12 and the four nozzles (four water spray points) arranged at the motor end of the low-pressure cylinder 12 in the first nozzle group. Each of the two branches is connected to the corresponding four nozzles in sequence through a reducing tee 2 and a reducing joint 3, thereby making the pipe diameter of the branch connected to each nozzle consistent, thus ensuring that the water spray volume of each nozzle is consistent and ensuring that the water spray of the first nozzle group is uniform.

[0049] The second water spray pipe 200 supplies water to the second nozzle group. The second water spray pipe 200 is equipped with a second regulating valve 1b, the opening of which is continuously adjustable. The opening and closing of the second regulating valve 1b controls the on / off state of the second water spray pipe 200, i.e., whether the second nozzle group sprays water. When the second regulating valve 1b is open, adjusting its opening degree controls the amount of water supplied from the second water spray pipe 200 to the second nozzle group, thereby controlling the water spray volume of the second nozzle group. In this embodiment, the end of the second water spray pipe 200 is divided into two branches. The two branches are respectively connected to the eight nozzles (four spray points) arranged at the regulating valve end of the low-pressure cylinder 12 and the eight nozzles (four spray points) arranged at the motor end of the low-pressure cylinder 12 in the second nozzle group. Each of the two branches is connected to the corresponding four spray points in sequence through a reducing tee 2 and a reducing joint 3, thereby making the diameter of the branch pipes connected to each spray point consistent, thus ensuring that the water spray volume of each spray point is consistent and ensuring that the water spray of the second nozzle group is uniform.

[0050] The pressure sensor, thermometer, first regulating valve 1a, and second regulating valve 1b are all connected to the controller. The controller type is not limited; existing controllers such as PLC controllers or microcontrollers can be used. The pressure sensor transmits the measured exhaust pressure signal from the exhaust side of the low-pressure cylinder 12 to the controller, and the thermometer transmits the measured exhaust temperature signal from the exhaust side of the low-pressure cylinder 12 to the controller. The controller receives the monitoring signals from the pressure sensor and thermometer, and controls the opening of the first regulating valve 1a and / or the second regulating valve 1b and adjusts the opening degree of the first regulating valve 1a and / or the second regulating valve 1b according to the received monitoring signals.

[0051] Specifically, when the low-pressure cylinder 12 of the steam turbine is running at low load, the temperature sensor monitors the current exhaust temperature t1 on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller. The pressure sensor monitors the current exhaust pressure p on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller, thus achieving real-time monitoring of the current exhaust temperature t1 and current exhaust pressure p on the exhaust side of the low-pressure cylinder 12. The controller calculates the saturated steam temperature t2 corresponding to the current exhaust pressure p in real time based on the water and steam property charts. Combined with the preset superheat Δt set before turbine startup, the target exhaust temperature t3 is determined to be the sum of the saturated steam temperature t2 and the preset superheat Δt: t3 = t2 + Δt, meaning the target exhaust temperature t3 has a certain degree of superheat. The controller precisely calculates the required water spray volume to reach the target exhaust temperature t3 based on the difference between the current exhaust temperature t1 and the target exhaust temperature t3. Then, the controller controls and adjusts the opening of the first regulating valve 1a and / or the second regulating valve 1b according to the calculated required water spray volume, realizing the following three-level water spray logic control: If the required water spray volume is less than the first set value, the controller controls the first regulating valve 1a to open and adjust the opening of the first regulating valve 1a, so that the exhaust temperature on the low-pressure cylinder exhaust side reaches and is maintained at the target exhaust temperature t3. This is the first-level water spray logic. For cases where the required water spray volume is small, the first water spray pipeline 100 and the first nozzle group alone can provide a small amount of water spray to reduce the exhaust side temperature so that it does not exceed the limit, while precisely controlling the water spray volume so that the sprayed water can be vaporized into steam in time to eliminate blade water erosion; If the required water spray volume is greater than the first set value and less than the second set value, the controller controls the second regulating valve 1b to open and adjust the opening of the second regulating valve 1b, so that the exhaust temperature on the low-pressure cylinder exhaust side reaches and is maintained at the target exhaust temperature t3. When the exhaust temperature on the low-pressure cylinder exhaust side reaches and remains at the target exhaust temperature value t3, this is the second-level water injection logic. For cases requiring a moderate water injection volume, the second water injection pipe 200 and the second nozzle group alone provide a moderate water injection volume to reduce the exhaust side temperature to prevent it from exceeding limits. Simultaneously, precise control of the water injection volume ensures the water can be vaporized into steam in a timely manner to eliminate blade erosion. If the required water injection volume is greater than the second set value, the controller controls both the first regulating valve 1a and the second regulating valve 1b to open and simultaneously adjusts their opening degrees to ensure the exhaust temperature on the low-pressure cylinder exhaust side reaches and remains at the target exhaust temperature value t3. This is the third-level water injection logic. For cases requiring a larger water injection volume, the first water injection pipe 100 and the first nozzle group, and the second water injection pipe 200 and the second nozzle group together provide a larger water injection volume to reduce the exhaust side temperature to prevent it from exceeding limits. Simultaneously, precise control of the water injection volume ensures the water can be vaporized into steam in a timely manner to eliminate blade erosion. The second setting value is greater than the first setting value. The first and second setting values ​​are the required water volume values ​​set according to the range of the required water volume.

[0052] Therefore, the steam cooling system of the turbine low-pressure cylinder in this embodiment can determine the target exhaust temperature t3 with a certain superheat Δt based on the current exhaust pressure p on the exhaust side of the low-pressure cylinder 12 without replacing the blades, without processing the blades, without affecting the blade structure, and without affecting the stage efficiency. By comparing the current exhaust temperature t1 with the target exhaust temperature t3, the required amount of water sprayed to achieve the target exhaust temperature t3 is accurately calculated. The opening of the first regulating valve 1a and / or the second regulating valve 1b is controlled and adjusted according to the required amount of water sprayed, which can realize three-stage water spray logic regulation. This allows the amount of water sprayed to be continuously adjusted, achieving precise control of the amount of water sprayed. This ensures that the exhaust temperature is within a safe range of variation and avoids the risks caused by excessive or insufficient water spraying. Furthermore, by maintaining a certain superheat in the exhaust temperature, the droplets generated by the water spray can be vaporized into steam in time. This avoids water erosion caused by the water sprayed from the last stage blades impacting the steam outlet edge during low-load operation of the low-pressure cylinder 12, thus actively preventing blade water erosion and reducing the requirements for the blade's water erosion resistance.

[0053] In this embodiment, the first regulating valve 1a is arranged as close as possible to the low-pressure cylinder 12 on the first water spray pipe 100 and the second regulating valve 1b is arranged on the second water spray pipe 200 to reduce pressure loss caused by the pipe arrangement.

[0054] In this embodiment, preferably, a first shut-off valve 4a is provided on the first water spray pipe 100 before the first regulating valve 1a. When the first regulating valve 1a needs maintenance, the first shut-off valve 4a is closed, allowing for disassembly, installation, and replacement of the first regulating valve 1a. A second shut-off valve 4b is provided on the second water spray pipe 200 before the second regulating valve 1b. When the second regulating valve 1b needs maintenance, the second shut-off valve 4b is closed, allowing for disassembly, installation, and replacement of the second regulating valve 1b.

[0055] In this embodiment, preferably, a first throttle valve 5a is provided on the first water spray pipeline 100 after the first regulating valve 1a. The first throttle valve 5a is used to adjust the downstream pressure of the first water spray pipeline 100 to a set set value before the turbine unit starts. A second throttle valve 5b is provided on the second water spray pipeline 200 after the second regulating valve 1b. The second throttle valve 5b is used to adjust the downstream pressure of the second water spray pipeline 200 to a set set value before the turbine unit starts.

[0056] Furthermore, a first pressure gauge 6a is installed on the first water spray line 100 after the first throttle valve 5a, and the first pressure gauge 6a is used to measure the pressure after the first throttle valve 5a. A second pressure gauge 6b is installed on the second water spray line 200 after the second throttle valve 5b, and the second pressure gauge 6b is used to measure the pressure after the second throttle valve 5b. Both the first pressure gauge 6a and the second pressure gauge 6b are connected to the controller to transmit the measured pressure signals after the first throttle valve 5a and the second throttle valve 5b to the controller. Before the turbine unit starts, the first throttle valve 5a and the second throttle valve 5b are adjusted according to the readings of the first pressure gauge 6a and the second pressure gauge 6b to adjust the pressure after the valves of the first water spray line 100 and the second water spray line 200 to the set values.

[0057] Furthermore, a third shut-off valve 7a is provided before the first pressure gauge 6a. When the first pressure gauge 6a needs maintenance, the third shut-off valve 7a can be closed to allow for disassembly, installation, and replacement of the first pressure gauge 6a. A fourth shut-off valve 7b is provided before the second pressure gauge 6b. When the second pressure gauge 6b needs maintenance, the fourth shut-off valve 7b can be closed to allow for disassembly, installation, and replacement of the second pressure gauge 6b.

[0058] Preferably, the steam cooling system for the low-pressure cylinder of the steam turbine in this embodiment further includes a main pipeline 300. One end of the main pipeline 300 is connected to a condensate pump 8, and the other end of the main pipeline 300 is connected to a first spray pipe 100 and a second spray pipe 200. The first spray pipe 100 and the second spray pipe 200 are connected in parallel to the main pipeline 300, and water is supplied from the main pipeline 300 to the first spray pipe 100 and the second spray pipe 200, with the water supply to the main pipeline 300 originating from the condensate pump 8. A flow meter 9 is provided on the main pipeline 300 to measure the flow rate in the main pipeline 300, which is the spray flow rate. The flow meter 9 is connected to a controller to transmit the measured flow rate signal of the main pipeline 300 to the controller.

[0059] Preferably, a filter screen 10 is provided on the main pipeline 300. The filter screen 10 is used to filter the cooling water from the condensate pump 8 to prevent impurities from contaminating or clogging the nozzles.

[0060] In this embodiment, preferably, the main pipeline 300 is also connected to the original water spray valve station 11, meaning the main pipeline 300 can also supply water to the original water spray valve station 11. The original water spray valve station 11 is a water spray valve station provided by the turbine unit itself for start-up, shutdown, and emergency operation. When the low-pressure cylinder 12 enters a low-load operating state and the turbine low-pressure cylinder steam cooling system of this embodiment is put into use, the original water spray valve station 11 is closed, and the main pipeline 300 supplies water to the first water spray pipeline 100 and / or the second water spray pipeline 200.

[0061] Based on the above-mentioned steam cooling system for the low-pressure cylinder of a steam turbine, this embodiment also provides a method for regulating the steam cooling of the low-pressure cylinder of a steam turbine. The method for regulating the steam cooling of the low-pressure cylinder of a steam turbine in this embodiment is implemented using the steam cooling system for the low-pressure cylinder of a steam turbine in this embodiment, which is also the working method of the steam cooling system for the low-pressure cylinder of a steam turbine in this embodiment.

[0062] The steam cooling regulation method for the low-pressure cylinder of the steam turbine in this embodiment is as follows: When the low-pressure cylinder 12 of the steam turbine is running at low load, the current exhaust temperature t1 on the exhaust side of the low-pressure cylinder 12 is monitored by a temperature sensor and the monitoring signal is transmitted to the controller. The current exhaust pressure p on the exhaust side of the low-pressure cylinder 12 is monitored by a pressure sensor and the monitoring signal is transmitted to the controller, thereby realizing real-time monitoring of the current exhaust temperature t1 and the current exhaust pressure p on the exhaust side of the low-pressure cylinder 12. The controller calculates the saturated steam temperature t2 corresponding to the current exhaust pressure p in real time according to the water and steam property chart, and combines it with the preset superheat Δt before the steam turbine starts up to determine the target exhaust temperature t3 as the sum of the saturated steam temperature t2 and the preset superheat Δt: t3 = t2 + Δt, that is, the target exhaust temperature t3 has a certain superheat. The controller accurately calculates the required water spray volume to reach the target exhaust temperature t3 based on the difference between the current exhaust temperature t1 and the target exhaust temperature t3. Then, the controller controls and adjusts the opening of the first regulating valve 1a and / or the second regulating valve 1b according to the calculated required water spray volume to achieve the following three-level water spray logic control.

[0063] If the required water spray volume is less than the first set value, the controller controls the first regulating valve 1a to open and adjust the opening degree of the first regulating valve 1a so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature t3. This is the first-level water spray logic. When the required water spray volume is small, the first water spray pipeline 100 and the first nozzle group can provide a small amount of water spray to reduce the exhaust side temperature so that it does not exceed the limit. At the same time, the water spray volume is precisely controlled so that the water spray can be vaporized into steam in time to eliminate blade water erosion.

[0064] If the required water spray volume is greater than the first set value and less than the second set value, the controller controls the second regulating valve 1b to open and adjust the opening degree of the second regulating valve 1b so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature t3. This is the secondary water spray logic. For the case where the required water spray volume is moderate, the second water spray pipeline 200 and the second nozzle group can provide a moderate water spray volume to reduce the exhaust side temperature so that it does not exceed the limit. At the same time, the water spray volume can be precisely controlled so that the sprayed water can be vaporized into steam in time to eliminate blade water erosion.

[0065] If the required water spray volume is greater than the second set value, the controller controls both the first regulating valve 1a and the second regulating valve 1b to open and simultaneously adjust the opening degree of the first regulating valve 1a and the second regulating valve 1b, so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value t3. This is the three-stage water spray logic. In the case of a large required water spray volume, the first water spray pipeline 100 and the first nozzle group, and the second water spray pipeline 200 and the second nozzle group jointly provide a large water spray volume, which can reduce the exhaust side temperature so that it does not exceed the limit. At the same time, the water spray volume is precisely controlled so that the sprayed water can be vaporized into steam in time to eliminate blade water erosion.

[0066] The second setting value is greater than the first setting value. The first and second setting values ​​are the required water volume values ​​set according to the range of the required water volume.

[0067] Therefore, the steam cooling regulation method for the low-pressure cylinder of the steam turbine in this embodiment can determine the target exhaust temperature t3 with a certain superheat Δt based on the current exhaust pressure p on the exhaust side of the low-pressure cylinder 12 without replacing the blades, without processing the blades, without affecting the blade structure, and without affecting the stage efficiency. It then accurately calculates the amount of water spray required to reach the target exhaust temperature t3 by comparing the current exhaust temperature t1 with the target exhaust temperature t3, and controls and adjusts the first regulating valve 1a and / or the second regulating valve 1b according to the required water spray amount. The opening size allows for three-stage water spray logic adjustment, enabling continuous adjustment of the water spray volume and precise control. This ensures that the exhaust steam temperature remains within a safe range while avoiding the risks associated with excessive or insufficient water spray. Furthermore, maintaining a certain degree of superheat in the exhaust steam temperature ensures that the water droplets generated by the spray can be vaporized into steam in a timely manner. This prevents water erosion caused by water spraying from the last stage blades impacting the steam outlet edge during low-load operation of the low-pressure cylinder 12, thus proactively preventing blade water erosion and reducing the requirements for blade water erosion resistance.

[0068] Preferably, in the steam cooling regulation method for the low-pressure cylinder of the steam turbine in this embodiment, before the steam turbine unit is started, the first throttle valve 5a and the second throttle valve 5b are adjusted according to the readings of the first pressure gauge 6a and the second pressure gauge 6b to adjust the downstream pressure of the first water spray pipeline 100 and the second water spray pipeline 200 to the set set value. During the operation of the steam turbine unit, when the steam inlet pressure of the low-pressure cylinder 12 is lower than the set characteristic value, the low-pressure cylinder 12 enters a low-load operation state, the steam cooling system of the low-pressure cylinder of the steam turbine is put into use, and the original water spray valve station 11 is closed.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A steam cooling system for a low-pressure cylinder of a steam turbine, characterized in that, The device includes a controller, a pressure sensor for monitoring the exhaust pressure on the exhaust side of the low-pressure cylinder, a thermometer for monitoring the exhaust temperature on the exhaust side of the low-pressure cylinder, a first nozzle group and a second nozzle group each having a plurality of nozzles located on the exhaust side of the low-pressure cylinder, and a first water spray pipe (100) and a second water spray pipe (200) for supplying water to the first nozzle group and the second nozzle group respectively. The second nozzle group has more nozzles than the first nozzle group. The first water spray pipe (100) is provided with a first regulating valve (1a), and the second water spray pipe (200) is provided with a second regulating valve (1b). The pressure sensor, the thermometer, the first regulating valve (1a), and the second regulating valve (1b) are all connected to the controller. When the low-pressure cylinder of the steam turbine is running at low load, the temperature sensor monitors the current exhaust temperature on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. The pressure sensor monitors the current exhaust pressure on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. The controller calculates the saturated steam temperature corresponding to the current exhaust pressure and determines the exhaust temperature target value as the sum of the saturated steam temperature and the set superheat. Based on the difference between the current exhaust temperature and the exhaust temperature target value, the controller calculates the required water injection amount to reach the exhaust temperature target value. The controller controls and adjusts the opening of the first regulating valve (1a) and / or the second regulating valve (1b) according to the required water injection amount. If the required water injection amount is less than the first set value, the controller controls the first regulating valve (1a) to open and adjust the opening of the first regulating valve (1a) so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the exhaust temperature target value. If the required water spray volume is greater than the first set value and less than the second set value, the controller controls the second regulating valve (1b) to open and adjust the opening degree of the second regulating valve (1b) so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value. If the required water spray volume is greater than the second set value, the controller controls both the first regulating valve (1a) and the second regulating valve (1b) to open and simultaneously adjust the opening degree of the first regulating valve (1a) and the second regulating valve (1b) so that the exhaust temperature on the exhaust side of the low-pressure cylinder reaches and is maintained at the target exhaust temperature value.

2. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 1, characterized in that, The first water spray pipe (100) is provided with a first shut-off valve (4a) before the first regulating valve (1a), and the second water spray pipe (200) is provided with a second shut-off valve (4b) before the second regulating valve (1b).

3. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 1, characterized in that, The first water spray pipe (100) is provided with a first throttle valve (5a) after the first regulating valve (1a), and the second water spray pipe (200) is provided with a second throttle valve (5b) after the second regulating valve (1b).

4. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 3, characterized in that, A first pressure gauge (6a) is provided on the first water spray line (100) after the first throttle valve (5a), and a second pressure gauge (6b) is provided on the second water spray line (200) after the second throttle valve (5b). Both the first pressure gauge (6a) and the second pressure gauge (6b) are connected to the controller.

5. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 4, characterized in that, A third shut-off valve (7a) is provided before the first pressure gauge (6a), and a fourth shut-off valve (7b) is provided before the second pressure gauge (6b).

6. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 1, characterized in that, It also includes a main pipeline (300), one end of which is connected to a condensate pump (8), and the other end is connected to the first spray pipe (100) and the second spray pipe (200). A flow meter (9) is provided on the main pipeline (300), and the flow meter (9) is connected to the controller.

7. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 6, characterized in that, A filter screen (10) is provided on the main pipeline (300).

8. The steam cooling system for the low-pressure cylinder of a steam turbine according to claim 6, characterized in that, The main pipeline (300) is also connected to the original water spray valve station (11).

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