Turbine low-pressure cylinder blade water erosion prevention system and method

Abstract

The present application relates to the technical field of steam turbine, and especially relates to a steam turbine low-pressure cylinder blade water erosion prevention system, which comprises a controller, an ultrasonic sensor for monitoring the liquid drop particle size and concentration of the low-pressure cylinder exhaust side, a temperature detector for monitoring the low-pressure cylinder exhaust temperature, a first nozzle group and a second nozzle group each having a plurality of nozzles arranged on the low-pressure cylinder exhaust side, and a first water injection pipeline and a second water injection pipeline respectively for conveying water to the first nozzle group and the second nozzle group, the number of nozzles of the second nozzle group is more than that of the first nozzle group, the first water injection pipeline and the second water injection pipeline are respectively provided with a first adjusting valve and a second adjusting valve, and the ultrasonic sensor, the temperature detector, the first adjusting valve and the second adjusting valve are all connected with the controller. The present application also relates to a steam turbine low-pressure cylinder blade water erosion prevention method using the system, which mainly comprises the following steps: controlling and adjusting the opening degree of the first adjusting valve and / or the second adjusting valve according to the liquid drop particle size and concentration by the controller, and controlling the water injection amount. The blade water erosion can be eliminated without processing the blade.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and in particular to a system for preventing water erosion of the blades in a low-pressure cylinder of a steam turbine and a method for preventing water erosion of the blades 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 system and method for preventing water erosion of turbine blades in low-pressure cylinders, which can eliminate water erosion of 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 turbine low-pressure cylinder blade erosion prevention system, comprising a controller, an ultrasonic sensor for monitoring the droplet size and concentration 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 and a second water spray pipe 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. 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 ultrasonic 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 preventing water erosion of turbine blades in a low-pressure cylinder. The method employs the turbine low-pressure cylinder blade water erosion prevention system described above. During low-load operation of the turbine low-pressure cylinder, a thermometer monitors the exhaust temperature on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. An ultrasonic sensor monitors the droplet size and concentration on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. When the exhaust temperature reaches a set temperature, the controller controls the opening of the first regulating valve. The controller controls and adjusts the opening degree of the first regulating valve and / or the second regulating valve according to the droplet size and concentration. If the droplet size and concentration are greater than the first set value, the controller adjusts the opening of the first regulating valve to keep the droplet size and concentration at the set safety value; if the droplet size and concentration are less than the first set value but greater than the second set value, the controller controls the second regulating valve to open and controls the first regulating valve to close, and the controller adjusts the opening of the second regulating valve to keep the droplet size and concentration at the set safety value; if the droplet size and concentration are less than the second set value, the controller controls the second regulating valve to open and simultaneously adjusts the opening of the first and second regulating valves to keep the droplet size and concentration at the set safety value.

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

[0016] It can precisely control the water spray volume based on the droplet size and concentration on the exhaust side of the low-pressure cylinder without replacing or treating the blades, without affecting the blade structure, or affecting stage efficiency. This ensures that the water spray droplets not only control the exhaust temperature within limits but also vaporize into steam in a timely manner. This minimizes the impact of droplets carried back from the exhaust side of the low-pressure cylinder on the last-stage blades, reducing water erosion caused by droplet impact. Through real-time monitoring of the exhaust temperature and droplet size and concentration on the exhaust side of the low-pressure cylinder and precise control of the water spray volume, it avoids water erosion caused by excessive water spray and excessive exhaust temperature caused by insufficient water spray. This improves the steam flow environment of the low-pressure cylinder, achieving the goal of eliminating water erosion of the low-pressure cylinder blades and controlling the exhaust temperature on the exhaust side of the low-pressure cylinder within limits, ensuring the safe operation of the low-pressure cylinder under low load. The ultrasonic sensor monitors the droplet size and concentration on the exhaust side of the low-pressure cylinder without needing to insert into the flow path of the low-pressure cylinder, thus not interfering with the steam flow field inside the low-pressure cylinder and enabling long-term dynamic real-time monitoring. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the turbine low-pressure cylinder blade erosion prevention system 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 spray pipe

[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 invention provides an embodiment of a turbine low-pressure cylinder blade erosion prevention system. During turbine operation, 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 (e.g., the low-pressure cylinder 12 is shut down). The turbine low-pressure cylinder blade erosion prevention system of this embodiment is used to eliminate blade erosion of the low-pressure cylinder 12 during low-load operation, while simultaneously controlling the exhaust steam temperature on the exhaust side of the low-pressure cylinder 12 to not exceed the limit.

[0044] The turbine low-pressure cylinder anti-blade water erosion system of this embodiment includes a controller, an ultrasonic sensor, a thermometer, a first nozzle group, a second nozzle group, a first water spray pipe 100, and a second water spray pipe 200.

[0045] The ultrasonic sensor is used to monitor the droplet size and concentration on the exhaust side of the low-pressure cylinder 12. The ultrasonic sensor is installed on the inner cylinder of the low-pressure cylinder 12 and located near the outlet of the last-stage moving blade. It is used to monitor the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 in real time. The ultrasonic sensor includes an ultrasonic transmitter and an ultrasonic receiver, which are arranged at a relative interval, avoiding the rotor of the low-pressure cylinder 12. This ensures that there is no metal obstruction between the ultrasonic transmitter and receiver; only steam and water droplets pass through the relative space between them. Therefore, the droplet size and concentration can be measured using the ultrasonic attenuation method. Monitoring the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 using the ultrasonic sensor does not require insertion into the flow path of the low-pressure cylinder 12, thus avoiding interference with the steam flow field inside the low-pressure cylinder 12 and enabling long-term dynamic real-time monitoring. Preferably, multiple ultrasonic sensors can be used to simultaneously measure the droplet size and concentration on the exhaust side of the low-pressure cylinder 12, ensuring the accuracy of the monitoring results. In this embodiment, preferably, three sets of ultrasonic transmitters and ultrasonic receivers are arranged opposite to each other on the inner cylinder of the low-pressure cylinder 12 near the outlet of the last stage moving blade of the low-pressure cylinder 12.

[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, for real-time monitoring of the exhaust temperature on the exhaust side of the low-pressure cylinder 12. 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 provided on the first water spray pipe 100. The opening and closing of the first regulating valve 1a controls the flow of water in the first water spray pipe 100, thus controlling whether the first nozzle group sprays water. When the first regulating valve 1a is open, the amount of water supplied by the first water spray pipe 100 to the first nozzle group can be controlled by adjusting the opening degree of the first regulating valve 1a, 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 four nozzles (four spray points) arranged at the regulating valve end of the low-pressure cylinder 12 and four nozzles (four spray points) arranged at the motor end of the low-pressure cylinder 12. Each branch is connected to the corresponding four nozzles sequentially through a reducing tee 2 and a reducing joint 3, thereby ensuring that the pipe diameter of the branch connected to each nozzle is consistent, thus ensuring that the water spray volume of each nozzle is consistent and 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. A second regulating valve 1b is provided on the second water spray pipe 200. 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, the amount of water supplied by the second water spray pipe 200 to the second nozzle group can be controlled by adjusting the opening degree of the second regulating valve 1b, 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 lead 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, respectively. Each branch is connected to the corresponding four spray points sequentially through a reducing tee 2 and a reducing joint 3, thereby ensuring that the pipe diameter of the branch connected to each spray point is consistent, thus ensuring that the water spray volume of each spray point is consistent and that the water spray of the second nozzle group is uniform.

[0050] The ultrasonic 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 ultrasonic sensor transmits the measured droplet size and concentration signals from the exhaust side of the low-pressure cylinder 12 to the controller. 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 ultrasonic sensor and thermometer, and controls the opening of the first regulating valve 1a and / or the second regulating valve 1b and adjusts their opening degrees 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 exhaust temperature on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller. The ultrasonic sensor monitors the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller, thereby realizing real-time monitoring of the exhaust temperature, droplet size and concentration on the exhaust side of the low-pressure cylinder 12. When the exhaust steam temperature reaches the set temperature, water spraying is required to cool the exhaust side of the low-pressure cylinder 12. At this time, the controller controls the first regulating valve 1a to open, and water is delivered from the first water spraying pipeline 100 to the first nozzle group. The first nozzle group sprays water onto the exhaust side of the low-pressure cylinder 12. The water spraying will produce different degrees of vaporization depending on the current exhaust steam temperature. Therefore, the size and concentration of droplets on the exhaust side of the low-pressure cylinder 12 after water spraying reflect the current exhaust steam temperature. When the exhaust steam temperature is high, the water spraying vaporizes immediately, resulting in smaller droplet size and concentration, and vice versa. Therefore, if the ultrasonic sensor measures a larger droplet size and concentration on the exhaust side of the low-pressure cylinder 12, it indicates that the current exhaust steam temperature is low, and less water spraying is required; if the ultrasonic sensor measures a smaller droplet size and concentration on the exhaust side of the low-pressure cylinder 12, it indicates that the current exhaust steam temperature is high, and more water spraying is required.Based on this, after the ultrasonic sensor monitors and obtains the droplet size and concentration on the exhaust side of the low-pressure cylinder 12, the controller can control and adjust the opening of the first regulating valve 1a and / or the second regulating valve 1b according to the droplet size and concentration to achieve the following three-level water spray logic control: If the droplet size and concentration are greater than the first set value, the controller adjusts the opening of the first regulating valve 1a to keep the droplet size and concentration at the set safe value. This is the first-level water spray logic, corresponding to the case where the exhaust temperature is low and the required water spray volume is small. The first water spray pipeline 100 and the first nozzle group alone provide a small amount of water spray to reduce the exhaust side temperature so that it does not exceed the limit, while accurately controlling the water spray volume so that the spray water can be vaporized into steam in time to eliminate blade water erosion; If the droplet size and concentration are less than the first set value and greater than the second set value, the controller controls the second regulating valve 1b to open and controls the first regulating valve 1a to close. The controller adjusts the opening of the second regulating valve 1b to keep the droplet size and concentration at the set safe value. The droplet size and concentration are maintained at a set safe value. This is the second-level water spray logic, which corresponds to a moderate exhaust temperature and a moderate required water volume. The second water spray pipe 200 and the second nozzle group alone provide a moderate water volume to reduce the exhaust temperature to prevent it from exceeding the limit. At the same time, the water volume is precisely controlled so that the water can be vaporized into steam in time to eliminate water erosion on the blades. If the droplet size and concentration are less than the second set value, the controller controls the second regulating valve 1b to open and simultaneously adjusts the opening of the first regulating valve 1a and the second regulating valve 1b to maintain the droplet size and concentration at the set safe value. This is the third-level water spray logic, which corresponds to a higher exhaust temperature and a larger required water volume. The first water spray pipe 100 and the first nozzle group, and the second water spray pipe 200 and the second nozzle group together provide a larger water volume to reduce the exhaust temperature to prevent it from exceeding the limit. At the same time, the water volume is precisely controlled so that the water can be vaporized into steam in time to eliminate water erosion on the blades. The set temperature is the allowable exhaust temperature limit of the low-pressure cylinder 12 exhaust side determined according to the actual situation. The exhaust temperature of the low-pressure cylinder 12 exhaust side should be controlled below the set temperature. The first set value and the second set value are droplet size and concentration values ​​set according to the range of water spray volume required corresponding to droplet size and concentration, and the second set value is less than the first set value. The set safety value is the droplet size and concentration value that can eliminate blade water erosion determined according to the actual situation. The set safety value can be a specific value or a range of values.

[0052] Therefore, the turbine low-pressure cylinder blade erosion prevention system of this embodiment can precisely control the water spray volume based on the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 without replacing the blades, treating the blades, affecting the blade structure, or affecting the stage efficiency. This ensures that the water spray droplets can both control the exhaust temperature and vaporize into steam in time, thereby minimizing the impact of droplets carried back from the exhaust side of the low-pressure cylinder on the last stage blades. This reduces water erosion caused by water spray droplets impacting the blades. Through real-time monitoring of the exhaust temperature and droplet size and concentration on the exhaust side of the low-pressure cylinder 12 and precise control of the water spray volume, it avoids blade erosion caused by excessive water spray and excessive exhaust temperature caused by insufficient water spray. This improves the steam flow environment of the low-pressure cylinder 12, achieving the goal of eliminating blade erosion of the low-pressure cylinder 12 and controlling the exhaust temperature on the exhaust side of the low-pressure cylinder 12 to ensure safe operation of the low-pressure cylinder 12 under low load.

[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 turbine low-pressure cylinder blade erosion prevention system of 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 blade erosion prevention 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 turbine low-pressure cylinder blade erosion prevention system, this embodiment also provides a method for preventing turbine low-pressure cylinder blade erosion. The turbine low-pressure cylinder blade erosion prevention method of this embodiment is implemented using the above-mentioned turbine low-pressure cylinder blade erosion prevention system, which is also the working method of the above-mentioned turbine low-pressure cylinder blade erosion prevention system of this embodiment.

[0062] The method for preventing blade water erosion in 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, a thermometer monitors the exhaust temperature on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller. An ultrasonic sensor monitors the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 and transmits the monitoring signal to the controller, thereby realizing real-time monitoring of the exhaust temperature, droplet size, and concentration on the exhaust side of the low-pressure cylinder 12. The ultrasonic sensor includes an ultrasonic transmitter and an ultrasonic receiver. The ultrasonic transmitter and the ultrasonic receiver are arranged at a relative interval, avoiding the rotor of the low-pressure cylinder 12, so that there is no metal obstruction between the ultrasonic transmitter and the ultrasonic receiver. Only steam and water droplets pass through the relative space between the ultrasonic transmitter and the ultrasonic receiver. Therefore, the droplet size and concentration can be measured by using the ultrasonic attenuation method. By monitoring the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 with an ultrasonic sensor, it is not necessary to extend into the flow path of the low-pressure cylinder 12, and it will not interfere with the steam flow field inside the low-pressure cylinder 12, enabling long-term dynamic real-time monitoring.

[0063] When the exhaust steam temperature reaches the set temperature, water spraying is required to cool the exhaust side of the low-pressure cylinder 12. At this time, the controller controls the first regulating valve 1a to open, and water is delivered from the first water spraying pipeline 100 to the first nozzle group. The first nozzle group sprays water onto the exhaust side of the low-pressure cylinder 12. The water spraying will produce different degrees of vaporization depending on the current exhaust steam temperature. Therefore, the size and concentration of droplets on the exhaust side of the low-pressure cylinder 12 after water spraying reflect the current exhaust steam temperature. When the exhaust steam temperature is high, the water spraying vaporizes immediately, resulting in smaller droplet size and concentration, and vice versa. Therefore, if the ultrasonic sensor measures a larger droplet size and concentration on the exhaust side of the low-pressure cylinder 12, it indicates that the current exhaust steam temperature is low, and less water spraying is required; if the ultrasonic sensor measures a smaller droplet size and concentration on the exhaust side of the low-pressure cylinder 12, it indicates that the current exhaust steam temperature is high, and more water spraying is required. Based on this, after the ultrasonic sensor monitors and obtains the droplet size and concentration on the exhaust side of the low-pressure cylinder 12, the controller controls and adjusts the opening of the first regulating valve 1a and / or the second regulating valve 1b according to the droplet size and concentration, and performs the following three-level water spray logic control.

[0064] If the droplet size and concentration exceed the first set value, the controller adjusts the opening of the first regulating valve 1a to keep the droplet size and concentration at the set safe value. This is the first-level water spraying logic, which corresponds to the case where the exhaust steam temperature is low and the required water spray volume is small. The first water spraying pipeline 100 and the first nozzle group can provide a small amount of water spray to reduce the exhaust steam 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.

[0065] If the droplet size and concentration are less than the first set value and greater than the second set value, the controller controls the second regulating valve 1b to open and the first regulating valve 1a to close. The controller adjusts the opening of the second regulating valve 1b to keep the droplet size and concentration at the set safe values. This is a two-stage water spraying logic, corresponding to situations where the exhaust temperature is moderate and the required water spray volume is moderate. The second water spraying pipeline 200 and the second nozzle group can provide a moderate water spray volume to reduce the exhaust temperature to prevent it from exceeding the limit, while precisely controlling the water spray volume to ensure that the sprayed water can be vaporized into steam in time to eliminate blade water erosion.

[0066] If the droplet size and concentration are less than the second set value, the controller controls the second regulating valve 1b to open and simultaneously adjusts the opening of the first regulating valve 1a and the second regulating valve 1b to keep the droplet size and concentration at the set safe value. This is a three-stage water spraying logic, corresponding to situations where the exhaust steam temperature is high and a large amount of water spraying is required. The first water spraying pipeline 100 and the first nozzle group, and the second water spraying pipeline 200 and the second nozzle group jointly provide a large amount of water spraying, which can reduce the exhaust steam temperature to prevent it from exceeding the limit, while precisely controlling the amount of water spraying so that the sprayed water can be vaporized into steam in time to eliminate blade water erosion.

[0067] The set temperature is the allowable exhaust temperature limit of the low-pressure cylinder 12 exhaust side determined according to the actual situation. The exhaust temperature of the low-pressure cylinder 12 exhaust side should be controlled below the set temperature. The first set value and the second set value are droplet size and concentration values ​​set according to the range of water spray volume required corresponding to droplet size and concentration, and the second set value is less than the first set value. The set safety value is the droplet size and concentration value that can eliminate blade water erosion determined according to the actual situation. The set safety value can be a specific value or a range of values.

[0068] Therefore, the turbine low-pressure cylinder blade erosion prevention method of this embodiment can precisely control the water spray volume based on the droplet size and concentration on the exhaust side of the low-pressure cylinder 12 without replacing the blades, treating the blades, affecting the blade structure, or affecting the stage efficiency. This ensures that the water spray droplets can both control the exhaust temperature and vaporize into steam in time, thereby minimizing the impact of droplets carried back on the exhaust side of the low-pressure cylinder on the last stage blades and reducing water erosion caused by droplet impact. Through real-time monitoring of the exhaust temperature and droplet size and concentration on the exhaust side of the low-pressure cylinder 12 and precise control of the water spray volume, excessive water spraying can prevent blade erosion, while insufficient water spraying can prevent the exhaust temperature from exceeding the limit. This improves the steam flow environment of the low-pressure cylinder 12, achieving the goal of eliminating blade erosion in the low-pressure cylinder 12 and controlling the exhaust temperature on the exhaust side of the low-pressure cylinder 12 to ensure safe operation of the low-pressure cylinder 12 under low load.

[0069] Preferably, in the turbine low-pressure cylinder blade erosion prevention method of this embodiment, before the 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 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 turbine low-pressure cylinder blade erosion prevention system is put into use, and the original water spray valve station 11 is closed.

[0070] 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 system for preventing water erosion of blades of a low pressure cylinder of a steam turbine, characterized in that, The device includes a controller, an ultrasonic sensor for monitoring the droplet size and concentration 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 ultrasonic 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 exhaust temperature on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. The ultrasonic sensor monitors the droplet size and concentration on the exhaust side of the low-pressure cylinder and transmits the monitoring signal to the controller. When the exhaust temperature reaches the set temperature, the controller controls the first regulating valve (1a) to open. The controller controls and adjusts the opening degree of the first regulating valve (1a) and / or the second regulating valve (1b) according to the droplet size and concentration. If the droplet size and concentration are greater than the first set value, the controller adjusts the opening of the first regulating valve (1a) to keep the droplet size and concentration at the set safe value. If the droplet size and concentration are less than the first set value and greater than the second set value, the controller controls the second regulating valve (1b) to open and controls the first regulating valve (1a) to close. The controller adjusts the opening of the second regulating valve (1b) to keep the droplet size and concentration at the set safe value. If the droplet size and concentration are less than the second set value, the controller controls the second regulating valve (1b) to open and simultaneously adjusts the opening degree of the first regulating valve (1a) and the second regulating valve (1b) so that the droplet size and concentration are maintained at the set safe value.

2. The steam turbine LP-prevention blade-erosion system of claim 1, wherein, 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 turbine LP-prevent-blade-erosion system of claim 1, wherein, 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 turbine LP casing anti-blade-erosion system of claim 3, wherein, 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 turbine LP-prevention blade-erosion system of claim 4, wherein, 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 turbine LP casing anti-blade-erosion system of claim 1, wherein, 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 pipeline (100) and the second spray pipeline (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 turbine LP-prevention blade-erosion system of claim 6, wherein, A filter screen (10) is provided on the main pipeline (300).

8. The turbine low-pressure cylinder blade erosion prevention system 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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