Dynamic adjustment method for through-flow steam seal clearance of steam turbine

Abstract

The invention relates to the field of steam turbines, and discloses a dynamic adjustment method for a through-flow steam seal gap of a steam turbine, which comprises the following steps: acquiring parameters such as unit load, rotating speed, temperature, vibration and the like, judging the current working condition stage (starting, stable operation, shutdown and abnormity), and dynamically adjusting the steam seal gap based on preset logic. And meanwhile, a differential control strategy is adopted by combining the characteristics of the sub-cylinders (a high-medium-pressure cylinder and a low-pressure cylinder). Through a real-time working condition parameter accurate judgment stage, a target steam seal gap is dynamically matched, the gap is increased to guarantee safety during starting / stopping and abnormal working conditions, the gap is reduced to reduce gas leakage during stable operation, and balance of safety and efficiency is achieved; and meanwhile, all-working-condition adaptability is achieved, the control precision is high, different cylinder bodies can be adapted in a differentiated mode, the abnormal response is fast, compatibility is high, and compared with the prior art, the operation economical efficiency and safety of the steam turbine are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of steam turbines, and more specifically to a method for dynamically adjusting the steam seal gap in a steam turbine. Background Technology

[0002] As the core power equipment in a power plant, the efficiency of the steam turbine directly determines the plant's energy consumption and economy. During the operation of the steam turbine, the energy conversion efficiency of steam in the flow path is a key factor affecting the overall performance of the unit, and the steam seal clearance is one of the core factors restricting the flow efficiency.

[0003] Traditional steam turbines use rigid comb-tooth steam seals, whose clearance must be set once during unit installation or maintenance (usually 0.8-1.2mm) and cannot be adjusted during operation. This fixed clearance design presents an irreconcilable contradiction: during high-load stable operation, theoretically the clearance needs to be reduced to minimize steam leakage, but the fixed clearance cannot be further optimized, resulting in higher heat consumption of the steam seals in the high- and intermediate-pressure cylinder stages, directly reducing unit efficiency; during startup, shutdown, or low-load conditions, the rotor and cylinder experience relative displacement due to differences in thermal expansion. If the clearance is too small, the steam seal teeth are prone to rubbing against the rotor, which may lead to rotor bending, equipment damage, or even shutdown accidents in severe cases.

[0004] In existing technologies, some adjustable steam seals attempt to adjust the clearance through springs or hydraulic mechanisms, but they have the following limitations: poor adaptability to operating conditions, only able to achieve two-level adjustment of "fully open / fully closed", and cannot be continuously adjusted according to dynamic parameters such as unit load, speed, and temperature; the high-pressure and medium-pressure cylinders use a unified adjustment logic, without differentiated design for the operating characteristics of different cylinders, thus limiting the optimization effect; and the lack of real-time monitoring and correction of actual clearance, vibration, and temperature makes it difficult to guarantee stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for dynamically adjusting the steam seal gap of a steam turbine. This solves the problem that the traditional fixed steam seal gap cannot adapt to different operating conditions, resulting in large air leakage losses at high loads and easy rubbing during low loads or start-up and shutdown.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for dynamically adjusting the steam seal clearance of a steam turbine includes the following steps: The operating parameters of the steam turbine are obtained, including at least the unit load, speed, steam seal area temperature and vibration amplitude. Based on the operating condition parameters, the current operating condition stage of the steam turbine is determined. The operating condition stages include the startup stage, stable operation stage, shutdown stage, and abnormal operating condition stage. determine the target steam seal gap value in the current working condition based on a preset correspondence between working condition stages and target steam seal gaps; adjust the steam seal gap to the target steam seal gap value through a steam seal actuator according to the steam seal gap value corresponding to the current working condition.

[0007] Optionally, the operating condition parameters further include high and intermediate pressure cylinder inlet steam pressure, low pressure cylinder exhaust steam pressure, and steam seal steam chamber pressure.

[0008] Optionally, the method for determining the working condition stage in which the steam turbine is currently located includes: when the unit speed increases from 0 to 80% of the rated speed and the stable warm-up temperature is not reached, it is determined to be the start-up stage; when the unit load is stable at 70%-100% of the rated load, the vibration amplitude is ≤50 μm, and the temperature fluctuation is ≤5 ℃ / min, it is determined to be the stable operation stage; when the unit load decreases to below 30% of the rated load and the speed gradually decreases, it is determined to be the shutdown stage; when the vibration amplitude is >75 μm or the steam seal area temperature is >400 ℃, it is determined to be the abnormal working condition stage.

[0009] Optionally, the preset correspondence between working condition stages and target steam seal gaps includes: the target steam seal gap in the start-up stage is the maximum design gap to ensure that the steam seal and the rotor are not in contact, and the maximum design gap is 1.2-1.5 mm; in the stable operation stage, the target steam seal gap of the high and intermediate pressure cylinder is 0.4-0.6 mm, and the target steam seal gap of the last stage of the low pressure cylinder is 0.6-0.8 mm, and the gap linearly decreases as the load increases; the target steam seal gap in the shutdown stage gradually increases from the stable operation value to the maximum design gap, and the gap increases by 0.1 mm for every 10% decrease in load; the target steam seal gap in the abnormal working condition stage immediately increases to 0.8-1.0 mm and is maintained until the abnormality is resolved.

[0010] Optionally, in the abnormal working condition stage, if the vibration amplitude exceeds 75 μm for 3 s or the temperature exceeds 400 ℃ for 5 s, an emergency adjustment mechanism is triggered, the steam seal gap is increased to 80% of the maximum design gap within 0.5 s, and the unit load is reduced by 5%-10%.

[0011] Optionally, in the shutdown stage, when the unit speed decreases to below 1000 r / min, the steam seal gap is forced to return to the maximum design gap until the rotor completely stops rotating and the temperature decreases to below 100 ℃.

[0012] Optionally, in the stable operation stage, differential logic is adopted for adjusting the steam seal gap of the high and low pressure cylinders, the high pressure cylinder aims to reduce the steam seal heat consumption, when the steam inlet pressure increases by 5%, the steam seal gap is additionally reduced by 0.03mm; the low pressure cylinder aims to reduce the leakage of the last stage partition, when the exhaust pressure increases by 3%, the steam seal gap is additionally reduced by 0.02mm.

[0013] Optionally, in the starting stage, when the rotating speed increases from 0 to 1500r / min, the steam seal gap keeps the maximum design gap; when the rotating speed increases from 1500r / min to 3000r / min, if the vibration amplitude is less than or equal to 50μm, the gap can be gradually reduced to 1.5 times of the stable operation value.

[0014] Optionally, in the step of controlling the action of the steam seal actuator, the actual value of the steam seal gap is further monitored, when the deviation between the actual value and the target value exceeds 0.1mm, an adjustment correction signal is sent.

[0015] Compared with the prior art, the present application has the following beneficial effects: In the present application, through the real-time working condition parameter accurate determination stage, the target steam seal gap is dynamically matched, which not only increases the gap to ensure safety during starting / stoppage and abnormal working conditions, but also reduces the gap to reduce leakage during stable operation, achieving the balance between safety and efficiency; at the same time, it has full working condition adaptability, high control accuracy, can be differentially adapted to different cylinder bodies, and has fast abnormal response and strong compatibility, which significantly improves the economic efficiency and safety of the steam turbine compared with the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the flowchart of the steam turbine through-flow steam seal gap dynamic adjustment method in the embodiment of the present application. DETAILED DESCRIPTION

[0017] The present application will now be further described in detail with reference to the accompanying drawings and embodiments, which are all simplified schematic diagrams, and only schematically show the basic structure of the present application, and therefore only show the configurations related to the present application.

[0018] Embodiment one, as shown in a steam turbine through-flow steam seal gap dynamic adjustment method, by acquiring unit load, rotating speed, temperature, vibration and other parameters, determining the current working condition stage (starting, stable operation, stopping, abnormality), and dynamically adjusting the steam seal gap based on the preset logic, and adopting differential control strategy combined with the characteristics of the split cylinder (high and low pressure cylinders). Figure 1

[0019] ​The method can reduce the leakage loss, stabilize the operation gap, reduce the steam seal heat consumption in the high and medium pressure cylinder by ≥63.73 kJ / kWh, and reduce the steam seal leakage by nearly 50%; can improve the safety, increase the gap during start and stop and abnormal conditions, avoid the collision between the rotor and the steam seal, and reduce the vibration amplitude by ≥20%; and can improve the efficiency, and the efficiencies of the high and medium pressure cylinders are increased from 80.45%, 91.32% to 81.92%, 92.41% respectively.

[0020] Specifically, first, the operation condition parameters of the steam turbine are acquired, then the current condition stage of the steam turbine is determined according to the operation condition parameters, then the target steam seal gap value in the current condition is determined based on the preset corresponding relationship between the condition stage and the target steam seal gap, finally the steam seal actuator is controlled to act, the steam seal gap is adjusted to the target steam seal gap value, and the actual value of the steam seal gap is monitored in real time; when the deviation between the actual value and the target value exceeds 0.1 mm, an adjustment correction signal is sent to correct the actuator action parameters; when the deviation does not exceed 0.1 mm, the current gap is maintained.

[0021] The condition stage includes a start stage, a stable operation stage, a stop stage and an abnormal condition stage, and the operation condition parameters at least include the unit load, the rotating speed, the steam seal area temperature and the vibration amplitude, and further include the high and medium pressure cylinder inlet steam pressure, the low pressure cylinder exhaust steam pressure and the steam seal steam chamber pressure.

[0022] As to the start stage of the steam turbine, when the unit rotating speed increases from 0 to 80% of the rated rotating speed and the stable warming temperature is not reached, it is determined as the start stage; the target steam seal gap in the start stage is the maximum design gap to ensure that the steam seal and the rotor are not in contact, and the maximum design gap is 1.2-1.5 mm.

[0023] In the start stage, when the rotating speed increases from 0 to 1500 r / min, the steam seal gap keeps the maximum design gap; when the rotating speed increases from 1500 r / min to 3000 r / min, if the vibration amplitude is ≤50 μm, the gap can be gradually reduced to 1.5 times of the stable operation value.

[0024] As to the stable operation stage of the steam turbine, when the unit load is stable at 70%-100% of the rated load, the vibration amplitude is ≤50 μm and the temperature fluctuation is ≤5 ℃ / min, it is determined as the stable operation stage; in the stable operation stage, the target gap of the steam seal in the high and medium pressure cylinder is 0.4-0.6 mm, the target gap of the last stage steam seal in the low pressure cylinder is 0.6-0.8 mm, and the gap linearly decreases with the increase of the load, i.e. the gap decreases by 0.05 mm when the load increases by 10%.

[0025] In the stable operation stage, differential logic is adopted for adjusting the steam seal gap of the high-pressure cylinder and the low-pressure cylinder. The high-pressure cylinder aims to reduce the steam seal heat consumption, and when the steam inlet pressure increases by 5%, the steam seal gap is additionally reduced by 0.03 mm. The low-pressure cylinder aims to reduce the leakage of the last-stage partition, and when the exhaust pressure increases by 3%, the steam seal gap is additionally reduced by 0.02 mm.

[0026] Regarding the shutdown stage of the steam turbine, when the unit load decreases to below 30% of the rated load and the rotating speed gradually decreases, the shutdown stage is determined. The target steam seal gap gradually increases from the stable operation value to the maximum design gap in the shutdown stage, and the gap increases by 0.1 mm when the load decreases by 10%. In the shutdown stage, when the rotating speed of the unit decreases to below 1000 r / min, the steam seal gap is forced to return to the maximum design gap until the rotor completely stops rotating and the temperature decreases to below 100℃.

[0027] Regarding the abnormal working condition stage of the steam turbine, when the vibration amplitude is greater than 75 μm or the temperature in the steam seal area is greater than 400℃, the abnormal working condition stage is determined. The target steam seal gap immediately increases to 0.8-1.0 mm in the abnormal working condition stage, and is maintained until the abnormality is removed.

[0028] In the abnormal working condition stage, if the vibration amplitude continuously exceeds 75 μm for 3 s or the temperature continuously exceeds 400℃ for 5 s, an emergency adjustment mechanism is triggered, the steam seal gap increases to 80% of the maximum design gap within 0.5 s, and the unit load is reduced by 5%-10%.

[0029] In the second embodiment, on the basis of the first embodiment, the application further provides a device system for implementing the above method, which comprises a parameter acquisition system, a control unit, a steam seal actuator, and a monitoring and feedback system.

[0030] The parameter acquisition system comprises pressure sensors, temperature sensors, rotating speed sensors, and vibration sensors. The pressure sensors are installed on the high-pressure cylinder steam inlet pipe, the low-pressure cylinder exhaust port, and the steam seal steam chamber to monitor the steam pressure in real time (accuracy ±0.01 MPa), and a Rosemount 3051 pressure transmitter can be used.

[0031] The temperature sensors are distributed on the back of the steam seal segment and the surface of the rotor to measure the temperature change (accuracy ±1℃), and an armored thermocouple or a Pt100 thermal resistor can be used. The rotating speed sensors are installed on the main shaft of the steam turbine to monitor the rotating speed (accuracy ±1 r / min), and a magneto-optical or photoelectric rotating speed sensor can be selected. The vibration sensors are arranged on the bearing seat and the steam seal shell to measure the vibration amplitude (accuracy ±0.1 μm), such as a piezoelectric acceleration sensor.

[0032] The control unit includes a PLC controller, an industrial computer, and a communication module. The PLC controller uses a Siemens S7-1500 or ABBAC500 series to receive sensor data and execute control algorithms. The industrial computer calculates the target gap value based on real-time parameters, while the communication module supports protocols such as Modbus and Profibus to enable data interaction between the sensors and the actuators.

[0033] The steam seal actuator includes an adjustable steam seal with helical springs and a steam inlet groove, and an electric actuator. The adjustable steam seal consists of a steam seal arc block, four helical springs, and a steam inlet groove. The steam seal arc block is made of 1Cr13 stainless steel. The four helical springs are installed on the end face of the arc block, with a stiffness coefficient of 50 N / mm. The steam inlet groove is located on the steam inlet side of the back of the arc block. The springs provide the opening force, and the steam pressure in the steam inlet groove provides the closing force; the gap is adjusted by balancing these two forces. The electric actuator is connected to the steam seal arc block and receives control signals to drive the arc block to move radially (stroke accuracy ±0.02 mm), such as a Pepperl+Fuchs electric actuator.

[0034] The monitoring and feedback system includes a displacement sensor, a data acquisition card, and a human-machine interface (HMI). The displacement sensor is installed on the back of the gas seal arc block to monitor the actual gap in real time (accuracy ±0.01mm), such as a laser displacement sensor. The data acquisition card converts the sensor signal into a digital signal and transmits it to the controller. The HMI displays the operating parameters, gap value, and alarm information, and supports manual intervention.

[0035] Equipment collaboration workflow: Each sensor acquires load, speed, temperature, pressure, and vibration data, which is transmitted to the PLC. The PLC uploads the data to an industrial computer, which determines the current operating condition stage using a preset algorithm. The industrial computer calculates the target clearance value based on the correspondence between the operating condition and the clearance. The PLC sends a control signal to the electric actuator, driving the steam seal block to move to the target position. The displacement sensor monitors the actual clearance in real time and compares it with the target value. If the deviation is >0.1mm, a correction command is triggered. When the vibration is >75μm or the temperature is >400℃, the system automatically increases the clearance and triggers an alarm.

[0036] Example 3: The method for dynamic adjustment of steam seal gap based on operating conditions proposed in this invention.

[0037] The following parameters are obtained through sensors: unit load (0-100% rated load), speed (0-3000 r / min), temperature of the high and medium pressure cylinder steam seal area (200-450℃), low pressure cylinder exhaust pressure (0.005-0.015 MPa), and rotor vibration amplitude (0-100 μm).

[0038] Operating condition determination and clearance adjustment logic: Start-up phase: When the speed is 0-1500 r / min, the gap remains at the maximum design gap of 1.2 mm (spring preload 80 N, steam pressure not yet established, spring dominates opening); when the speed is 1500-3000 r / min, if the vibration is ≤50 μm, the gap gradually decreases to 0.8 mm (steam pressure rises to 0.5 MPa, providing partial closing force).

[0039] During stable operation (load ≥ 80% of rated load): the clearance of the high and medium pressure cylinders is adjusted to 0.5mm (steam pressure 1.2MPa, shut-off force dominant), and the clearance is further reduced by 0.03mm for every 5% increase in inlet steam pressure; the clearance of the low pressure cylinder is adjusted to 0.7mm, and the clearance is further reduced by 0.02mm for every 3% increase in exhaust steam pressure.

[0040] During shutdown: When the load drops from 100% to 30%, the clearance gradually increases from 0.5mm to 1.0mm (0.15mm for every 10% decrease in load); when the speed is <1000r / min, the clearance is forcibly restored to 1.2mm until the rotor stops and the temperature is <100℃.

[0041] Abnormal operating conditions: When vibration > 75μm or temperature > 400℃, increase the gap to 1.0mm within 0.5s; if the abnormality lasts for 3s, increase the gap to 1.2mm and reduce the load by 5%.

[0042] Feedback correction: The actual gap is monitored by a displacement sensor (accuracy ±0.01mm). When the deviation from the target value is >0.1mm, the spring preload or steam pressure is corrected.

[0043] Based on the above methods, during stable operation, the heat consumption of the internal steam seal in the high- and medium-pressure cylinder stage is reduced by 63.73 kJ / kWh, and the leakage of the bridge steam seal is reduced from 33.97 t / h to 17.43 t / h (a decrease of 50%); the maximum vibration amplitude during the start-up phase is 55 μm (without rubbing), which is 25% lower than that of Comparative Example 1.

[0044] Example 4: Differentiated Adjustment Logic for Differentiated Cylinders. Based on Example 3, this invention adopts more refined differentiated control for high-pressure and low-pressure cylinders.

[0045] High and medium pressure cylinder: When the inlet steam pressure increases from 10MPa to 10.5MPa (an increase of 5%), the steam seal gap decreases by an additional 0.03mm from 0.5mm (to 0.47mm), and the internal heat consumption is further reduced by 2.1kJ / kWh; Low-pressure cylinder: When the exhaust pressure increases from 0.01MPa to 0.0103MPa (an increase of 3%), the steam seal gap decreases by an additional 0.02mm from 0.7mm (to 0.68mm), and the final stage leakage is reduced by 1.2t / h.

[0046] Compared with Example 3, the heat consumption of the high and medium pressure cylinder is reduced to 64.2 kJ / kWh, the leakage of the last stage of the low pressure cylinder is reduced to 17.2 t / h, and the overall efficiency is improved by 0.2%.

[0047] In summary, this invention proposes a method that can dynamically adjust the steam seal clearance based on real-time operating conditions and differentiate control for different cylinder characteristics. It has the following advantages and is of great significance for balancing the safety and economy of steam turbines.

[0048] Dynamic clearance adjustment, balancing safety and efficiency: Increases clearance during start-up, shutdown, and abnormal situations to prevent collisions and wear; reduces clearance during stable operation to reduce air leakage; adaptable to all working conditions: Accurately determines working conditions based on real-time parameters, covering various load and speed scenarios; precise and stable control: Closed-loop feedback correction, clearance deviation ≤0.1mm, avoiding loss of control; cylinder optimization: Differentiated adjustments for high-pressure, medium-pressure, and low-pressure cylinders to improve overall efficiency; rapid response to abnormal situations: Quickly adjusts clearance to avoid risks and reduce accident losses when vibration or temperature exceeds limits.

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0050] 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for dynamically adjusting the steam seal clearance of a steam turbine, characterized in that, Includes the following steps: The operating parameters of the steam turbine are obtained, including at least the unit load, speed, steam seal area temperature and vibration amplitude. Based on the operating condition parameters, the current operating condition stage of the steam turbine is determined. The operating condition stages include the startup stage, stable operation stage, shutdown stage, and abnormal operating condition stage. Based on the pre-defined correspondence between operating conditions and target steam seal clearance, the target steam seal clearance value under the current operating condition is determined. Based on the current operating condition and the corresponding steam seal gap value, the steam seal gap is adjusted to the target steam seal gap value through the steam seal actuator.

2. The method for dynamically adjusting the steam turbine flow seal clearance according to claim 1, characterized in that, The operating parameters also include the inlet steam pressure of the high-pressure cylinder, the exhaust steam pressure of the low-pressure cylinder, and the steam seal chamber pressure.

3. The method for dynamically adjusting the steam turbine flow seal clearance according to claim 1, characterized in that, Methods for determining the current operating stage of a steam turbine include: When the unit speed increases from 0 to 80% of the rated speed and has not reached a stable warm-up temperature, it is determined to be in the start-up phase. When the unit load is stable at 70%-100% of the rated load, the vibration amplitude is ≤50μm and the temperature fluctuation is ≤5℃ / min, it is judged to be in the stable operation stage. When the unit load drops below 30% of the rated load and the speed gradually decreases, it is determined to be in the shutdown phase. When the vibration amplitude is greater than 75μm or the temperature in the steam seal area is greater than 400℃, it is determined to be an abnormal operating condition.

4. The method for dynamically adjusting the steam seal clearance of a steam turbine according to claim 3, characterized in that, The pre-defined operating conditions and their correspondence with the target steam seal clearance include: The target steam seal clearance during the startup phase is the maximum design clearance to ensure no contact between the steam seal and the rotor, and the maximum design clearance is 1.2-1.5 mm. During the stable operation phase, the target gap of the steam seal of the high-pressure cylinder is 0.4-0.6 mm, and the target gap of the final stage steam seal of the low-pressure cylinder is 0.6-0.8 mm, and the gap decreases linearly with the increase of load. During the shutdown phase, the target steam seal clearance gradually increases from the stable operating value to the maximum design clearance, with the clearance increasing by 0.1 mm for every 10% decrease in load. The target steam seal gap immediately increases to 0.8-1.0 mm during the abnormal operating condition phase and remains thereafter until the abnormality is resolved.

5. The method for dynamically adjusting the steam turbine flow seal clearance according to claim 4, characterized in that, During the abnormal operating condition phase, if the vibration amplitude exceeds 75μm for 3 seconds or the temperature exceeds 400℃ for 5 seconds, the emergency adjustment mechanism will be triggered. The steam seal gap will increase to 80% of the maximum design gap within 0.5 seconds, and the unit load will be reduced by 5%-10%.

6. The method for dynamically adjusting the steam seal gap of a steam turbine according to claim 5, characterized in that, During the shutdown phase, when the unit speed drops below 1000 r / min, the steam seal gap is forcibly restored to the maximum design gap until the rotor completely stops rotating and the temperature drops below 100°C.

7. The method for dynamically adjusting the steam seal clearance of a steam turbine according to claim 6, characterized in that, During the stable operation phase, a differentiated logic is adopted for adjusting the steam seal gap between the high-pressure cylinder and the low-pressure cylinder. The high-pressure cylinder aims to reduce the heat consumption of the steam seal within the stage. When the inlet steam pressure increases by 5%, the steam seal gap is reduced by an additional 0.03mm. The low-pressure cylinder aims to reduce the leakage of the last stage diaphragm. When the exhaust steam pressure increases by 3%, the steam seal gap is reduced by an additional 0.02mm.

8. The method for dynamically adjusting the steam seal clearance of a steam turbine according to claim 7, characterized in that, During the startup phase, when the speed increases from 0 to 1500 r / min, the steam seal gap remains at the maximum design gap; when the speed increases from 1500 r / min to 3000 r / min, if the vibration amplitude is ≤50 μm, the gap can be gradually reduced to 1.5 times the stable operating value.

9. The method for dynamically adjusting the steam turbine flow seal clearance according to any one of claims 1-8, characterized in that, The steps for controlling the operation of the steam seal actuator also include real-time monitoring of the actual value of the steam seal gap. When the deviation between the actual value and the target value exceeds 0.1 mm, an adjustment and correction signal is issued.

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