Adjustable turbine low-pressure cylinder active anti-corrosion steam supplementing system and control method thereof

Abstract

The invention relates to the technical field of steam turbines, and discloses an adjustable steam turbine low-pressure cylinder active anti-corrosion steam supplementing system and a control method thereof. The system comprises a low-pressure cylinder, a steam cooler, a steam supplementing pipeline, a first steam inlet pipeline, a condensed water pipeline and an isolating valve. The steam cooler is provided with a steam channel and a cooling water channel; the steam supplementing pipeline is connected with a steam source and connected into a steam channel inlet through a first adjusting valve. The first steam inlet pipeline is connected with an outlet of the steam channel, and an outlet of the first steam inlet pipeline is formed in the front area of an inlet of the penultimate-stage moving blade in the low-pressure cylinder. Steam can be obtained from a steam source, the pressure and the superheat degree of the steam are adjusted, and the steam is injected into a water erosion risk area. When the load is low, the steam dryness can be improved, the volume flow is increased, and water erosion on the steam inlet side of the low-pressure last-stage moving blade is restrained; during cylinder switching heat supply, accurate cooling is provided, extensive water spraying is replaced, and water erosion on the steam outlet side is avoided. A blade body does not need to be changed, and the water erosion problem of the low-pressure cylinder last-stage blade under deep peak regulation is solved through active system intervention.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, specifically to an adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system and its control method. Background Technology

[0002] With the energy structure shifting towards cleaner and more diversified production, thermal power units participating in deep peak shaving has become the norm. When units frequently operate under low-load (small volumetric flow rate) conditions or switch to low-pressure cylinder heating mode, severe water erosion occurs in the last-stage blades of the low-pressure cylinder. During low-load operation, the steam volumetric flow rate within the low-pressure cylinder decreases, while humidity increases. Steam condenses on the surface of the last-stage stationary blades, forming a water film that tears at the outlet edge, producing large-diameter secondary water droplets. These droplets impact the top of the last-stage moving blades at high speed on the inlet side, causing severe erosion damage. When the load further decreases to forced draft conditions, the exhaust steam temperature rises. Water spraying in the low-pressure cylinder, used to control temperature, may again cause water erosion in the root region of the last-stage moving blades on the outlet side due to poor atomization and flow eddies.

[0003] In related technologies, water erosion protection measures mainly focus on improving the water erosion resistance of materials, such as embedding Stellite alloy hard sheets on the inlet side of the moving blades, or applying supersonic flame spraying coatings on the outlet side; or structural improvements, such as designing the last-stage stator blade as a hollow blade with drainage grooves to drain condensate. However, material protection is a passive response and cannot actively eliminate the root cause of water erosion, and alloy sheets are at risk of detachment. Structural improvements are limited by complex manufacturing processes, are costly, and have potential impacts on the strength and reliability of the blades, thus preventing their widespread adoption. Summary of the Invention

[0004] In view of this, the present invention provides an adjustable steam turbine low-pressure cylinder active anti-corrosion steam replenishment system and its control method to solve the problems mentioned in the background art.

[0005] In a first aspect, the present invention provides an adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system, comprising a low-pressure cylinder, wherein a second-stage moving blade, a final-stage stationary blade, and a final-stage moving blade are sequentially arranged within the low-pressure cylinder along the steam flow direction; the system further comprises: A steam cooler, wherein the steam cooler is provided with mutually isolated steam passages and cooling water passages; The steam supply pipeline has its inlet connected to a steam source and its outlet connected to the steam channel inlet of the steam cooler via a first regulating valve. The first steam inlet pipe has its inlet connected to the steam passage outlet of the steam cooler and its outlet connected to the low-pressure cylinder. The outlet position of the first steam inlet pipe is configured to deliver steam to the area before the inlet of the second-to-last stage moving blade. The condensate pipeline has an inlet suitable for cooling water to cool steam, and an outlet connected to the cooling water channel inlet of the steam cooler via a second regulating valve. And an isolation valve, which is installed on the first steam inlet pipe.

[0006] Beneficial Effects: This application, through the installation of a steam cooler, a steam injection pipeline, a condensate pipeline, a first regulating valve, and a second regulating valve, enables the system to obtain steam from the steam source and actively regulate its superheat. The controllable steam is then accurately injected into the area before the inlet of the second and final stage moving blades via the first steam inlet pipeline, directly acting on the area where water erosion occurs. Under low-load conditions, the injected steam effectively increases the overall dryness of the steam from the second and final stage moving blades to the final stage stationary blades, thereby significantly reducing the amount of secondary water droplets generated on the surface of the final stage stationary blades and preventing water erosion at the blade tips on the steam inlet side. Simultaneously, the additional steam flow directly increases the volumetric flow rate through the final stage moving blades, improving their aerodynamic environment and allowing them to escape unfavorable low-flow-rate operating conditions. In situations such as cylinder cutting heating leading to excessively high exhaust temperatures, the anti-corrosion steam injection system can serve as a precise source of cooling medium, avoiding or reducing coarse low-pressure cylinder water spraying, thereby preventing water erosion at the blade roots on the steam outlet side due to poor water atomization. The technical solution provided in this application does not require modification of the material of the blade body or its complex internal structure. It achieves the technical objective of reducing water erosion through active and adjustable intervention.

[0007] In some embodiments, the anti-corrosion steam injection system further includes a first pressure gauge disposed on the low-pressure cylinder, the first pressure gauge being used to detect the steam pressure before the inlet of the secondary and final stage moving blades.

[0008] Beneficial effect: The steam pressure before the inlet of the second and final stage moving blades is monitored by the first pressure gauge. In the actual implementation stage, the operator or control system can accurately set or adjust the target pressure at the outlet of the steam passage of the steam cooler based on the real-time pressure value here.

[0009] In some embodiments, the anti-corrosion steam injection system further includes a first thermometer disposed on the last stage moving blade, the first thermometer being used to detect the temperature of the last stage moving blade.

[0010] Beneficial Effects: The first thermometer directly monitors the metal temperature of the final-stage moving blades, providing direct and reliable data on the system's operating conditions. The metal temperature of the final-stage moving blades is a crucial indicator of the severity of their working environment; excessively high temperatures indicate that the blades are under forced-air friction, leading to decreased material strength and necessitating water spray cooling. This solution monitors the temperature of the final-stage moving blades in real time to determine when to activate the anti-cavitation and cooling mode on the steam outlet side, and controls the supplementary steam until the temperature falls below a safe threshold. This design improves the overall operational safety of the anti-cavitation and supplementary steam system.

[0011] In some embodiments, the anti-corrosion steam supply system further includes a second pressure gauge and a second thermometer, both of which are disposed on the steam passage of the steam cooler. The second pressure gauge is used to detect the steam pressure in the steam passage, and the second thermometer is used to detect the steam temperature in the steam passage.

[0012] Beneficial effects: By directly monitoring the steam pressure and temperature at the steam outlet of the steam channel in the steam cooler using a second pressure gauge and a second thermometer, the system can calculate the superheat of the supplementary steam in real time. This method of determining the supplementary steam based on superheat effectively improves dryness without introducing excessively high enthalpy values ​​that could affect efficiency. This application, combined with the reference pressure provided by the first pressure gauge, allows the system to independently control the steam pressure and superheat of the supplementary steam by adjusting the first and second regulating valves, ensuring that the injected steam is always in the preset desired state, thereby maximizing its anti-corrosion effect and ensuring process controllability.

[0013] In some embodiments, the anti-corrosion steam supply system further includes a controller, which is signal-connected to the first pressure gauge, the first thermometer, the second pressure gauge, the second thermometer, the first regulating valve, the second regulating valve, and the isolation valve, respectively.

[0014] Beneficial effects: Based on the detection elements, a controller is introduced, which interconnects all detection elements and valves in the actuator section to achieve intelligent automatic control and enhance the system's rapid response capability. The controller acquires load, pressure, and temperature signals from the detection elements in real time to automatically determine the unit's operating mode and automatically executes operations such as mode switching, valve linkage adjustment, and gas supply control according to preset programs. This reduces reliance on operator experience, enabling the system to make optimal responses and proactively intervene with appropriate gas supply parameters, thereby maximizing corrosion prevention and optimizing operational safety while reducing the workload of operators.

[0015] In some embodiments, multiple first steam inlet pipes are provided, and the multiple first steam inlet pipes are connected in parallel between the isolation valve and the low-pressure cylinder; the outlets of the multiple first steam inlet pipes are evenly distributed in a ring around the low-pressure cylinder.

[0016] Beneficial effects: By configuring the first steam inlet pipeline as multiple parallel lines evenly distributed around the circumference of the low-pressure cylinder, the makeup steam is uniformly input across the entire annular flow cross-section of the low-pressure cylinder. A single makeup steam injection point may lead to uneven steam distribution within the cylinder, resulting in localized undercooling or flow disturbance, affecting the uniformity of the corrosion prevention effect. The design of multiple parallel pipelines evenly distributed around the circumference allows the treated steam to enter the chamber before the secondary and final stage moving blades evenly and stably, thus achieving rapid and uniform mixing with the mainstream steam; ensuring that all areas of the final stage blades and secondary and final stages receive the same dryness enhancement and flow increase effect, making the active corrosion prevention effect more synchronous and reliable.

[0017] In some embodiments, the anti-corrosion steam supply system further includes a second steam inlet pipe, the inlet of which is connected to the steam channel outlet of the steam cooler, and the outlet is connected to an external low-pressure heater.

[0018] Beneficial effects: The second steam inlet pipeline can serve as an auxiliary path; during the initial startup or commissioning of the supplementary steam system, steam can be first introduced to the low-pressure heater for warm-up and parameter adjustment. Once the steam quality is stable, it can then be switched to the low-pressure cylinder, making the steam introduction process smoother and safer. When the low-pressure cylinder does not require supplementary steam for a short period, the system can still maintain low-flow operation, with steam entering the external thermal system through the second steam inlet pipeline for heat recovery, avoiding frequent start-ups and shutdowns. Furthermore, the second steam inlet pipeline can provide stable back pressure for the steam cooler, which is beneficial for stable control of the internal steam pressure of the steam cooler.

[0019] In some embodiments, the steam source is configured as one of the following: intermediate pressure cylinder exhaust, auxiliary steam header, or low pressure cylinder extraction pipeline.

[0020] Beneficial effects: Due to the differences in thermal system configuration and operation modes among different power plants, this solution provides multiple optional steam sources, with specific configuration designs tailored to actual site conditions, enabling the system to flexibly adapt to the pipeline conditions of various existing power plants. For example, utilizing the intermediate-pressure cylinder exhaust provides stable steam source parameters and short distance; utilizing the auxiliary steam header ensures a reliable and independent steam source; and utilizing the low-pressure cylinder extraction enables better energy matching.

[0021] Secondly, the present invention also provides a control method applied to the above-mentioned adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system, comprising the following steps: When the unit load is lower than the preset load threshold, the steam inlet side water erosion prevention mode is activated: By opening the second regulating valve to introduce condensate, the first regulating valve is adjusted to stabilize the steam pressure in the steam cooler at the first target pressure, while the second regulating valve is adjusted to stabilize the steam superheat at the first target superheat. Open the isolation valve to introduce steam that meets the requirements for steam pressure and steam superheat into the inlet of the secondary and final stage moving blades through the first steam inlet pipeline; In addition, when the unit is in the low-pressure cylinder heating operation mode and the temperature of the last-stage moving blades is higher than the preset temperature threshold, the supplementary steam anti-steam-side water cavitation and cooling mode is executed: Open the second regulating valve, adjust the first regulating valve to make the steam pressure in the steam cooler the same as the pressure before the inlet of the second and last stage moving blades, and at the same time adjust the second regulating valve to stabilize the steam superheat at the first target superheat. Open the isolation valve, and while maintaining the steam superheat, increase the opening of the first regulating valve to increase the steam injection pressure, and introduce steam into the low-pressure cylinder to reduce the temperature of the last stage moving blades to below the preset temperature threshold.

[0022] Beneficial Effects: This control method provides two operating modes: prevention of water erosion on the inlet side and prevention of water erosion on the outlet side, along with cooling. Specifically, in the inlet side water erosion prevention mode, the goal is to maintain a fixed injection pressure and low superheat, aiming to stably provide steam with suitable dryness and dilute wet steam. In the outlet side water erosion prevention mode, a method of first smoothly implementing pressure matching, and then increasing the pressure based on the blade metal temperature, aims to provide effective cooling. This control method enables the system to actively adjust according to different water erosion principles to achieve the technical objective of reducing water erosion.

[0023] In some embodiments, the preset load threshold is 35% of the unit's rated load; the first target pressure is the steam pressure before the inlet of the second and last stage moving blades when the unit load is 35%; the first target superheat is set to 3°C~5°C; and the preset temperature threshold is set to 70°C. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the adjustable steam turbine low-pressure cylinder active anti-corrosion steam replenishment system according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the anti-inlet water erosion mode of the adjustable steam turbine low-pressure cylinder active anti-corrosion steam replenishment system according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the process for preventing water erosion on the steam outlet side and cooling mode of the adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. Low-pressure cylinder; 2. Last stage moving vane; 3. Last stage stationary vane; 4. Secondary last stage moving vane; 5. Steam cooler; 6. Make-up steam pipeline; 7. First steam inlet pipeline; 8. Second steam inlet pipeline; 9. Condensate pipeline; 10. First regulating valve; 11. Second regulating valve; 12. Isolation valve; 13. First pressure gauge; 14. First thermometer; 15. Second pressure gauge; 16. Second thermometer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The following is combined with Figures 1 to 3 The following describes embodiments of the present invention.

[0029] This embodiment addresses the increasingly urgent need for deep peak shaving and flexible operation by providing a technical solution that proactively intervenes at the source of the thermal system, reducing and suppressing water erosion by adjusting steam parameters.

[0030] According to an embodiment of the present invention, an adjustable steam turbine low-pressure cylinder active anti-corrosion steam injection system and its control method are provided. The active anti-corrosion steam injection system introduces a stream of steam with controllable parameters from an external steam source and injects it into a specific location within the low-pressure cylinder 1, thereby actively improving the steam flow environment in the last-stage blade region and reducing the risk of water erosion at its source.

[0031] In this embodiment, as Figure 1 As shown, the active anti-corrosion steam replenishment system includes a low-pressure cylinder 1, a steam cooler 5, a steam replenishment pipeline 6, a first steam inlet pipeline 7, a condensate pipeline 9, and an isolation valve 12. The low-pressure cylinder 1 is provided with a secondary and final stage moving blade 4, a final stage stationary blade 3, and a final stage moving blade 2 in sequence along the steam flow direction. The isolation valve 12 is installed on the first steam inlet pipeline 7 and is used to control the on / off of steam replenishment to the low-pressure cylinder 1.

[0032] This embodiment analyzes the causes of water erosion in the final stage of low-pressure cylinder 1 and actively intervenes from thermodynamic and fluid dynamic perspectives. The main objectives are: first, to increase steam dryness by injecting dry steam with controllable superheat, diluting the humidity of the wet steam from the outlet of the secondary stage to the final stage stationary blade 3, thereby reducing the amount of water film formed on the surface of the final stage stationary blade 3 and the size and number of secondary water droplets, thus suppressing water erosion on the inlet side from the source; second, to increase volumetric flow rate, as the supplemented steam directly increases the steam flow through the final stage moving blade 2, moving it away from low volumetric flow rate conditions, improving the flow state within the blade passage, reducing the blower effect and backflow risk, and enhancing aerodynamic stability; and third, to provide precise cooling, replacing the traditional coarse water spraying of low-pressure cylinder 1 with steam with controllable steam pressure and superheat in conditions such as cylinder cutting heating, achieving uniform and gentle cooling of the final stage region, and avoiding water erosion on the outlet side caused by large water droplets directly impacting the blades. The solution provided in this embodiment avoids modification of the blade body and implements active intervention and control based on system integration.

[0033] The steam cooler 5 serves as a heat exchange device, equipped with isolated steam and cooling water channels to achieve non-contact heat exchange between the two media. The inlet of the make-up steam pipeline 6 is connected to the steam source, and the outlet is connected to the steam channel inlet of the steam cooler 5 via the first regulating valve 10; the inlet of the first steam inlet pipeline 7 is connected to the steam channel outlet of the steam cooler 5, and the outlet is connected to the low-pressure cylinder 1.

[0034] The outlet of the first steam inlet pipe 7 is configured to deliver steam to the area before the inlet of the second-to-last stage moving blade 4. The inlet of the condensate pipe 9 is adapted to cool the steam with cooling water, and the outlet is connected to the cooling water passage inlet of the steam cooler 5 via the second regulating valve 11.

[0035] The system, consisting of the steam cooler 5, the make-up steam pipeline 6, the condensate pipeline 9, the first regulating valve 10, and the second regulating valve 11, forms a complete steam parameter regulation path. The system can obtain steam from the steam source and actively regulate its superheat; then, the first steam inlet pipeline 7 accurately injects controllable steam into the area before the inlet of the secondary final stage moving blade 4, directly acting on the area where water erosion occurs.

[0036] For low-load operating conditions, injecting steam with appropriate superheat can effectively increase the overall dryness of the steam in the chamber from the second-to-last stage moving blade 4 to the front of the last-stage stationary blade 3, thereby significantly reducing the amount of secondary water droplets generated on the surface of the last-stage stationary blade 3 and preventing water erosion at the blade tip on the steam inlet side. At the same time, the additional steam flow can directly increase the volumetric flow rate through the last-stage moving blade 2, improve its aerodynamic environment, and allow it to escape the unfavorable low-flow-rate operating state, thereby improving operating efficiency and safety.

[0037] For situations where excessively high exhaust temperatures are caused by cylinder cutting heating, the anti-corrosion steam injection system can serve as a precise source of cooling medium. By injecting moderately cooled steam into the final stage region, the exhaust temperature can be effectively reduced, thereby avoiding or significantly reducing the input of water injection into the coarse low-pressure cylinder 1. This avoids water erosion damage to the root region of the final stage moving blade 2 on the exhaust side caused by large water droplets due to poor water atomization and uneven distribution, while also making the cooling process more uniform and gentle.

[0038] The technical solution provided in this embodiment does not require modification of the blade material or complex internal structure. It achieves the technical objective of reducing water erosion through active and adjustable intervention. It has the advantages of relatively small modification workload, wide applicability, and flexible control.

[0039] In specific embodiments, such as Figure 1 As shown, the anti-corrosion steam injection system also includes a first pressure gauge 13, which is installed on the low-pressure cylinder 1. The first pressure gauge 13 is used to detect the steam pressure before the inlet of the second-to-last stage moving blade 4. The steam pressure before the inlet of the second-to-last stage moving blade 4 is monitored by the first pressure gauge 13. In the specific implementation phase, the operator or control system can accurately set or adjust the target pressure at the outlet of the steam channel of the steam cooler 5 based on the real-time pressure value at this location. For example, in the anti-inlet side water erosion mode, the injection steam pressure needs to be matched with the pressure under low-load healthy operating conditions; in the initial stage of the cylinder-cutting heating mode, the injection steam pressure needs to be equal to the pressure at this location to achieve stable operation.

[0040] In terms of selection, the first pressure gauge 13 can be a high-performance piezoresistive or capacitive pressure transmitter with a range covering vacuum to micro-positive pressure, such as -100kPa ~ 500kPa; the diaphragm material of the sensor must be resistant to moisture vapor corrosion, such as Hastelloy.

[0041] In specific embodiments, such as Figure 1 As shown, the anti-corrosion steam injection system also includes a first thermometer 14, which is installed on the last-stage moving blade 2. The first thermometer 14 is used to detect the temperature of the last-stage moving blade 2. The first thermometer 14 serves as the direct basis for determining whether the last-stage blade is overheating and whether the cooling mode needs to be activated.

[0042] The metal temperature of the final-stage moving blade 2 is directly monitored via the first thermometer 14, providing direct and reliable data on the system's operating conditions. The metal temperature of the final-stage moving blade 2 is a crucial indicator of the severity of its working environment; excessively high temperatures indicate that the blade is under forced-air friction, leading to decreased material strength and necessitating water spray cooling. This design uses real-time monitoring of the final-stage moving blade 2's temperature to determine when to activate the anti-cavitation and cooling mode on the steam outlet side, and controls the steam supply until the temperature falls below a safe threshold. This design enhances the overall operational safety of the anti-cavitation steam supply system.

[0043] In terms of selection, the first thermometer 14 can be a wear-resistant thermocouple or a resistance thermometer.

[0044] In specific embodiments, such as Figure 1 As shown, the anti-corrosion steam supply system also includes a second pressure gauge 15 and a second thermometer 16. Both the second pressure gauge 15 and the second thermometer 16 are installed on the steam passage of the steam cooler 5. The second pressure gauge 15 is used to detect the steam pressure in the steam passage, and the second thermometer 16 is used to detect the steam temperature in the steam passage.

[0045] The steam pressure and temperature at the steam outlet of the steam channel in the steam cooler 5 are directly monitored by the second pressure gauge 15 and the second thermometer 16, allowing the system to calculate the superheat of the supplementary steam in real time. This method of determining the supplementary steam based on superheat effectively improves dryness without introducing excessively high enthalpy values ​​that could affect efficiency. This application, combined with the reference pressure provided by the first pressure gauge 13, enables the system to independently control the steam pressure and superheat of the supplementary steam by adjusting the first regulating valve 10 and the second regulating valve 11, ensuring that the injected steam is always in the preset desired state, thereby maximizing its anti-corrosion effect and ensuring process controllability.

[0046] For the selection of gauges, the first pressure gauge 13 can also be a pressure transmitter, and the range needs to be determined according to the highest pressure of the steam source. The second thermometer 16 should be a resistance temperature detector with a protective sleeve, and its measurement range should cover the lowest to the highest temperature of the steam source.

[0047] In an optional embodiment, a flow meter, such as a vortex flow meter or a differential pressure flow meter, is installed on the first steam inlet pipe 7 to monitor the amount of supplementary steam; a thermometer and a flow meter are installed on the condensate pipe 9 to monitor the cooling water conditions.

[0048] In a specific embodiment, the corrosion prevention and steam replenishment system also includes a controller (not shown in the figure). The controller is connected to the first pressure gauge 13, the first thermometer 14, the second pressure gauge 15, the second thermometer 16, the first regulating valve 10, the second regulating valve 11, and the isolation valve 12, respectively. Based on the aforementioned detection elements, a controller is introduced, which interconnects all detection elements and valves in the execution section to achieve intelligent automatic control and enhance the system's rapid response capability. The controller acquires load, pressure, and temperature signals from the detection elements in real time to automatically determine the unit's operating mode and, according to a preset program, automatically executes operations such as mode switching, valve linkage adjustment, and steam replenishment control. This reduces reliance on operator experience, enabling the system to make optimal responses and proactively intervene with appropriate steam replenishment parameters, thereby maximizing the corrosion prevention effect, optimizing operational safety, and reducing the workload of operators.

[0049] In a specific embodiment, the controller is configured as follows: a. When the unit load is detected to be lower than the preset load threshold, the unit is determined to have entered a low-load risk condition, and the anti-steam-side water erosion mode is triggered: like Figure 2 As shown, in this mode, the controller first outputs a command to open the second regulating valve 11, introducing condensate into the cooling water passage of the steam cooler 5. Simultaneously, the controller receives a feedback signal from the second pressure gauge 15 and, by adjusting the opening of the first regulating valve 10, stabilizes the steam pressure at the outlet of the steam passage of the steam cooler 5 at a preset first target pressure. The first target pressure is set to the typical steam pressure value before the inlet of the second and last stage moving blades 4 when the unit is operating at a healthy low load (e.g., 35% of rated load).

[0050] Next, the controller calculates the steam superheat based on the real-time steam pressure and temperature values ​​measured by the second pressure gauge 15 and the second thermometer 16. The controller adjusts the second regulating valve 11 to change the cooling water flow rate, precisely controlling the heat exchange intensity to stabilize the steam superheat within the lower first target superheat range of 3℃ to 5℃. This lower superheat ensures that the steam is dry, avoiding the introduction of liquid water, and also prevents excessively high superheat from causing excessively high enthalpy and affecting the unit's thermal economy.

[0051] Once the steam pressure and superheat have stabilized at the target values, the controller issues a command to slowly open the isolation valve 12, smoothly introducing the required supplementary steam into the designated position of the low-pressure cylinder 1.

[0052] b. Judgment and execution of steam outlet side water erosion prevention and cooling mode: like Figure 3 As shown, when the controller detects that the unit is operating in the low-pressure cylinder 1 heating mode, and the metal temperature of the final stage moving blade 2 fed back by the first thermometer 14 exceeds the preset temperature threshold (e.g., 70°C), it determines that it enters the anti-steam-side water erosion and cooling mode.

[0053] In this mode, the controller first opens the second regulating valve 11 to introduce cooling water. Then, the controller reads the real-time pressure before the final stage moving blade 4 measured by the first pressure gauge 13 as the target pressure. By adjusting the first regulating valve 10, the controller ensures that the steam pressure at the outlet of the steam cooler 5 matches this target pressure, achieving pressure matching between the supplementary steam and the steam in the cylinder, ensuring a smooth and shock-free injection process. Simultaneously, the controller adjusts the second regulating valve 11 to maintain the steam superheat within a suitable range of 3°C to 5°C.

[0054] After completing the parameter matching, the controller opens isolation valve 12. Subsequently, the controller's control strategy shifts to using the temperature of the final stage moving blade 2 as the ultimate control target. While maintaining a constant steam superheat, the controller gradually increases the opening of the first regulating valve 10, thereby increasing the supplementary steam pressure and flow rate to enhance the cooling effect. This process continues until the metal temperature fed back by the first thermometer 14 decreases and stabilizes below the preset temperature threshold (70°C). Afterward, the system enters a maintenance state, dynamically adjusting the supplementary steam quantity to keep the blade temperature within a safe range.

[0055] In a specific embodiment, to further optimize the steam replenishment effect, multiple first steam inlet pipes 7 are provided, and multiple first steam inlet pipes 7 are connected in parallel between the isolation valve 12 and the low-pressure cylinder 1; the outlets of multiple first steam inlet pipes 7 are evenly distributed in a ring around the low-pressure cylinder 1.

[0056] The first steam inlet pipe 7 is configured as multiple parallel lines evenly distributed around the circumference of the low-pressure cylinder 1, ensuring uniform input of make-up steam across the entire annular flow cross-section of the low-pressure cylinder 1. A single make-up steam injection point may lead to uneven steam distribution within the cylinder, resulting in localized undercooling or flow disturbance, affecting the uniformity of the corrosion prevention effect. The design of multiple parallel lines evenly distributed around the circumference allows the treated steam to enter the chamber before the secondary final stage moving blade 4 uniformly and stably, achieving rapid and uniform mixing with the mainstream steam. This ensures that all areas of the final stage blades and the secondary final stage receive the same dryness enhancement and flow increase effect, making the active corrosion prevention effect more synchronous and reliable.

[0057] In an optional embodiment, the multiple outlets of the first steam inlet pipe 7 are grouped to form independent injection rings (not shown in the figure). For example, they can be divided into upper and lower half-rings, or into four quadrants. Each group is controlled by an independent branch pipe regulating valve. The controller identifies areas with excessive humidity or uneven cooling based on feedback from multi-point humidity monitoring probes or temperature measuring points inside the low-pressure cylinder 1; for example, the lower half of the cylinder typically has higher humidity due to gravity. Based on this, precise zoned control is implemented, increasing the amount of steam supplied to areas with high humidity and decreasing the amount of steam supplied to areas with low humidity. This targeted steam supply method can provide the most accurate intervention at the most needed locations, achieving better corrosion prevention with a smaller total amount of steam supplied, and also helps optimize the thermal economy of the unit.

[0058] In an optional embodiment, a steam-water separator and a preheater are added to the pipeline before the steam inlet of the steam channel of the steam cooler 5, and an automatic steam trap is installed at the lowest point of the steam cooler 5 and the make-up steam pipeline 6. The steam-water separator ensures that the steam from the steam source is as dry as possible, preventing liquid water from entering the subsequent system. The preheater can utilize low-grade heat sources such as low-pressure extraction steam to preheat the make-up steam during the initial startup or when the steam source temperature is low, preventing condensation of steam in the cooler. The automatic steam trap can promptly drain any condensate that may accumulate in the pipeline and cooler, ensuring that the finally injected steam is pure dry steam. This arrangement helps improve the quality of the make-up steam and enhances system reliability.

[0059] In a specific embodiment, the anti-corrosion steam injection system also includes a second steam inlet pipe 8. The inlet of the second steam inlet pipe 8 is connected to the steam channel outlet of the steam cooler 5, and the outlet is connected to an external low-pressure heater. The second steam inlet pipe 8 can serve as an auxiliary path; during the initial startup or commissioning of the steam injection system, steam can first be introduced to the low-pressure heater for warm-up and parameter adjustment. Once the steam quality is stable, it can then be introduced into the low-pressure cylinder 1, making the steam injection process smoother and safer. When the low-pressure cylinder 1 does not require steam injection for a short period, the system can still maintain low-flow operation, with steam entering the external thermal system through the second steam inlet pipe 8 to recover heat, avoiding frequent start-ups and shutdowns. In addition, the second steam inlet pipe 8 can also provide a stable back pressure for the steam cooler 5, which is beneficial for the stable control of the internal steam pressure of the steam cooler 5.

[0060] Although this embodiment emphasizes active intervention, it does not preclude its use in conjunction with traditional passive protection measures to form a dual protection system combining active and passive approaches, suitable for units with high water erosion risk. In an optional embodiment, a Stellite alloy sheet can be embedded in the top of the inlet side of the last-stage rotor blade 2, while HVOF coating is applied to the root of the outlet side. This supplementary steam system serves as primary protection, significantly reducing the erosion energy and frequency of water droplets; the alloy material and blade coating serve as secondary protection, resisting the impact of residual micro-droplets. This combined approach maximizes blade life and can meet the needs of units with frequent deep peak shaving and unstable steam source quality.

[0061] In specific embodiments, the steam source offers flexible options, selectable based on the actual thermal system layout and operating mode of the power plant. It is typically configured as one of the following: intermediate-pressure cylinder exhaust pipe, auxiliary steam header, or low-pressure cylinder 1 extraction pipe. Providing multiple steam source options enhances the system's flexibility for on-site adaptation. For example, using intermediate-pressure cylinder exhaust as the steam source offers advantages such as relatively stable steam pressure and temperature, proximity of the pipe to low-pressure cylinder 1, and rapid system response. Using the auxiliary steam header provides an independent and reliable steam source, unaffected by drastic fluctuations in main unit load, making it suitable as a cooling steam source during cylinder-to-heat switching. Using low-pressure cylinder 1 extraction as the steam source achieves better system energy matching and partially recovers steam energy, but places specific requirements on extraction parameters and system design. In specific designs, the stability, availability, economy, and impact on main unit efficiency of the steam source parameters must be comprehensively considered.

[0062] This embodiment also provides a control method applied to the above-mentioned adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system, including the following steps: When the unit load is lower than the preset load threshold, the steam inlet side water erosion prevention mode is activated: By opening the second regulating valve 11 to introduce condensate, the first regulating valve 10 is adjusted to stabilize the steam pressure in the steam cooler 5 at the first target pressure, and the second regulating valve 11 is adjusted to stabilize the steam superheat at the first target superheat. Open the isolation valve 12 to introduce steam that meets the requirements of steam pressure and steam superheat into the inlet of the secondary final stage moving blade 4 through the first steam inlet pipe 7; In addition, when the unit is in the low-pressure cylinder 1 heating operation mode and the temperature of the last stage moving blade 2 is higher than the preset temperature threshold, the supplementary steam anti-steam-side water cavitation and cooling mode is executed: Open the second regulating valve 11, adjust the first regulating valve 10 to make the steam pressure in the steam cooler 5 the same as the pressure before the inlet of the secondary and final stage moving blades 4, and at the same time adjust the second regulating valve 11 to stabilize the steam superheat at the first target superheat. Open the isolation valve 12, and while maintaining the steam superheat, increase the opening of the first regulating valve 10 to increase the steam injection pressure, and introduce steam into the low-pressure cylinder 1 so that the temperature of the last stage moving blade 2 drops below the preset temperature threshold.

[0063] This control method provides two operating modes: prevention of water erosion on the inlet side and prevention of water erosion on the outlet side, along with cooling. Specifically, in the inlet side water erosion prevention mode, the goal is to maintain a fixed injection pressure and low superheat, aiming to stably provide steam with appropriate dryness and dilute wet steam. In the outlet side water erosion prevention mode, a method of first smoothly introducing pressure matching, and then increasing the pressure based on the blade metal temperature, aims to provide effective cooling. This control method enables the system to actively adjust according to different water erosion principles to achieve the technical objective of reducing water erosion.

[0064] In a specific embodiment, the preset load threshold is 35% of the unit's rated load; the first target pressure is the steam pressure before the inlet of the second and last stage moving blades 4 when the unit load is 35%; the first target superheat is set to 3℃~5℃; and the preset temperature threshold is set to 70℃.

[0065] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system, comprising a low-pressure cylinder (1), wherein the low-pressure cylinder (1) is provided with a secondary and final stage moving blade (4), a final stage stationary blade (3), and a final stage moving blade (2) sequentially along the steam flow direction; characterized in that, The system also includes: A steam cooler (5) is provided with a steam passage and a cooling water passage that are isolated from each other; Steam supply pipeline (6), the inlet of which is connected to a steam source, and the outlet is connected to the steam passage inlet of the steam cooler (5) through a first regulating valve (10); The first steam inlet pipe (7) is connected to the steam passage outlet of the steam cooler (5) and the outlet is connected to the low-pressure cylinder (1). The outlet position of the first steam inlet pipe (7) is configured to deliver steam to the area in front of the inlet of the secondary final stage moving blade (4). Condensate pipe (9), the inlet of which is suitable for cooling water to cool steam, and the outlet is connected to the cooling water channel inlet of the steam cooler (5) through a second regulating valve (11); And an isolation valve (12), which is installed on the first steam inlet pipe (7).

2. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 1, characterized in that, It also includes a first pressure gauge (13), which is installed on the low-pressure cylinder (1) and is used to detect the steam pressure before the inlet of the secondary final stage moving blade (4).

3. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 2, characterized in that, It also includes a first thermometer (14), which is disposed on the last stage moving blade (2) and is used to detect the temperature of the last stage moving blade (2).

4. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 3, characterized in that, It also includes a second pressure gauge (15) and a second thermometer (16), both of which are installed on the steam passage of the steam cooler (5). The second pressure gauge (15) is used to detect the steam pressure of the steam passage, and the second thermometer (16) is used to detect the steam temperature of the steam passage.

5. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 4, characterized in that, It also includes a controller, which is signal connected to the first pressure gauge (13), the first thermometer (14), the second pressure gauge (15), the second thermometer (16), the first regulating valve (10), the second regulating valve (11), and the isolation valve (12), respectively.

6. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 1, characterized in that, Multiple first steam inlet pipes (7) are provided, and multiple first steam inlet pipes (7) are arranged in parallel between the isolation valve (12) and the low-pressure cylinder (1); the outlets of multiple first steam inlet pipes (7) are evenly distributed in a ring around the low-pressure cylinder (1).

7. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 1, characterized in that, It also includes a second steam inlet pipe (8), the inlet of which is connected to the steam channel outlet of the steam cooler (5), and the outlet is connected to an external low-pressure heater.

8. The adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to claim 1, characterized in that, The steam source is set to one of the following: exhaust steam from the medium-pressure cylinder, auxiliary steam header, or extraction steam from the low-pressure cylinder (1).

9. A control method applied to the adjustable steam turbine low-pressure cylinder active anti-corrosion steam supply system according to any one of claims 1-8, characterized in that, Includes the following steps: When the unit load is lower than the preset load threshold, the steam inlet side water erosion prevention mode is activated: By opening the second regulating valve (11) to introduce condensate, the first regulating valve (10) is adjusted to stabilize the steam pressure in the steam cooler (5) at the first target pressure, and the second regulating valve (11) is adjusted to stabilize the steam superheat at the first target superheat. Open the isolation valve (12) and introduce steam that meets the requirements of steam pressure and steam superheat into the inlet of the secondary final stage moving blade (4) through the first steam inlet pipe (7); In addition, when the unit is in the low-pressure cylinder (1) heating operation mode and the temperature of the last stage moving blade (2) is higher than the preset temperature threshold, the supplementary steam anti-steam-side water cavitation and cooling mode is executed: Open the second regulating valve (11), adjust the first regulating valve (10) to make the steam pressure in the steam cooler (5) the same as the pressure before the inlet of the second-to-last stage moving blade (4), and at the same time adjust the second regulating valve (11) to make the steam superheat stabilize at the first target superheat. Open the isolation valve (12), and while maintaining the superheat of the steam, increase the opening of the first regulating valve (10) to increase the steam replenishment pressure, and introduce steam into the low-pressure cylinder (1) so that the temperature of the last stage moving blade (2) drops below the preset temperature threshold.

10. The control method according to claim 9, characterized in that, The preset load threshold is 35% of the rated load of the unit; the first target pressure is the steam pressure before the inlet of the second and last stage moving blades (4) when the unit load is 35%; the first target superheat is set to 3℃~5℃; the preset temperature threshold is set to 70℃.

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