A method, system and device for monitoring the radial displacement of a steam turbine low pressure cylinder blade

Abstract

This invention relates to the field of displacement measurement technology, specifically to a method, system, and equipment for monitoring the radial displacement of turbine low-pressure cylinder blades. The method includes: acquiring multi-source monitoring data during the operation of the turbine low-pressure cylinder; determining a synchronous deviation characteristic based on steam moisture content data and the instantaneous blade clearance value; determining a propagation attenuation characteristic based on the changing waveform characteristics of the measurement signal generated by the same blade passing through the measurement position in different rotation cycles; determining a dynamic correction coefficient based on the synchronous deviation characteristic and the propagation attenuation characteristic; and correcting the monitored radial displacement value of the blade based on the dynamic correction coefficient to obtain the corrected radial displacement of the blade. This invention improves the accuracy of monitoring the radial displacement of turbine low-pressure cylinder blades under wet steam medium disturbance conditions.

Description

Technical Field

[0001] This invention relates to the field of displacement measurement technology, specifically to a method, system, and equipment for monitoring the radial displacement of low-pressure cylinder blades in a steam turbine. Background Technology

[0002] Steam turbines are the core power equipment in large-scale thermal power and nuclear power units. Their low-pressure cylinder is the final stage where steam expands and performs work, and it contains multiple stages of long blades. During operation, the last-stage blades of the low-pressure cylinder are subjected to the combined effects of high temperature, high humidity, high speed, and strong steam disturbances. Their radial displacement directly affects the safety margin of the blade tip clearance and the unit's operating efficiency. Therefore, accurate monitoring of the blade radial displacement is a crucial foundation for ensuring the safe and economical operation of the steam turbine.

[0003] Currently, the monitoring of radial displacement of low-pressure cylinder blades in steam turbines typically employs non-contact displacement sensors (such as eddy current sensors or capacitive displacement sensors) positioned near the blade tip on the low-pressure cylinder casing. Radial displacement information is indirectly obtained by measuring the change in the gap between the blade tip and the sensor probe. This method can achieve basic displacement monitoring under normal operating conditions and has been applied to some extent in engineering practice.

[0004] However, in the actual operating environment of the last stage blades of the low-pressure cylinder, the steam humidity is high and the flow field has obvious unsteady characteristics. Periodically changing wet steam boundary layers and micro-scale droplet groups will form around the blades. The dynamic changes of these wet steam media will disturb the measurement field of the sensor, resulting in additional fluctuation components that are unrelated to the actual radial displacement of the blade superimposed on the sensor output signal. This makes the accuracy of the blade radial displacement monitoring results obtained directly based on the sensor output signal insufficient. Summary of the Invention

[0005] To address the technical problem of insufficient accuracy in monitoring the radial displacement of turbine low-pressure cylinder blades under turbulent wet steam conditions, the present invention aims to provide a method, system, and equipment for monitoring the radial displacement of turbine low-pressure cylinder blades. The specific technical solution adopted is as follows: Firstly, a method for monitoring the radial displacement of a turbine low-pressure cylinder blade is provided. This method includes: acquiring multi-source monitoring data during the operation of the turbine low-pressure cylinder, including the instantaneous blade clearance value generated by each blade passing through a measurement position and steam moisture content data; determining a synchronization deviation characteristic quantity based on the steam moisture content data and the blade instantaneous clearance value, the synchronization deviation characteristic quantity being used to characterize the degree of synchronization deviation between changes in the wet steam state and the response change in the blade instantaneous clearance value; determining a propagation attenuation characteristic quantity based on the changing characteristics of the measurement signal waveform generated by the same blade passing through a measurement position in different rotation cycles, the propagation attenuation characteristic quantity being used to characterize the degree of influence on the propagation stability of the measurement field in the wet steam medium; determining a dynamic correction coefficient based on the synchronization deviation characteristic quantity and the propagation attenuation characteristic quantity; and correcting the blade radial displacement monitoring value based on the dynamic correction coefficient to obtain the corrected blade radial displacement.

[0006] In one possible design, acquiring multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine includes: circumferentially arranging displacement sensors near the top of the last-stage blades on the low-pressure cylinder casing to collect the raw electrical signals generated by the sensor probes of each blade as it passes the displacement sensors; acquiring the rotor speed and rotor angular position through a speed sensor or shaft encoder, and simultaneously recording the timestamp of each blade passing the measurement position; determining the instantaneous blade gap value corresponding to each blade passing the measurement position based on the raw electrical signals and rotor angular position; and acquiring steam moisture content data through a wet steam moisture content monitoring device in the last-stage steam passage of the low-pressure cylinder.

[0007] In one possible design, the synchronization deviation characteristic quantity is determined based on steam moisture content data and blade instantaneous clearance value. This includes: determining the signal baseline offset based on the degree of deviation of the blade instantaneous clearance value relative to the operating reference value within a single rotation cycle; the signal baseline offset characterizing the overall offset level of the measurement field within a single rotation cycle; determining the signal fluctuation dispersion based on the variation amplitude of the signal baseline offset between all adjacent cycle pairs in multiple consecutive rotation cycles; the signal fluctuation dispersion characterizing the fluctuation amplitude of the blade instantaneous clearance value between different rotation cycles; determining the wet steam state fluctuation degree based on the signal fluctuation dispersion degree and the degree of deviation of the steam moisture content data relative to the operating reference value; and determining the synchronization deviation characteristic quantity based on the degree of difference in the changing trend between the steam moisture content data and the blade instantaneous clearance value, as well as the wet steam state fluctuation degree.

[0008] In one possible design, the signal baseline offset is determined based on the degree of deviation of the blade instantaneous clearance value relative to the operating reference value within a single rotation cycle. This includes: determining the operating reference value based on the blade instantaneous clearance value obtained during the initial operation of the turbine; and determining the average deviation of the blade instantaneous clearance values ​​corresponding to all blades within a single rotation cycle relative to the operating reference value to obtain the signal baseline offset.

[0009] In one possible design, the degree of wet steam state fluctuation is determined based on the dispersion of signal fluctuations and the deviation of steam moisture content data from the operating reference value. This includes: setting an observation window containing multiple rotation cycles; determining the operating reference value based on the steam moisture content data acquired during the initial operation of the turbine; determining the average moisture content deviation based on the deviation of the steam moisture content data from the operating reference value within the observation window; and determining the degree of wet steam state fluctuation by multiplying the dispersion of signal fluctuations by the average moisture content deviation.

[0010] In one possible design, determining the degree of difference in the trend between steam moisture content data and blade instantaneous gap value includes: determining a first slope sequence of steam moisture content data changing over time within the observation window, and a second slope sequence of blade instantaneous gap value changing over time; and determining the degree of difference in the trend based on the first slope sequence and the second slope sequence.

[0011] In one possible design, the propagation attenuation characteristic is determined based on the variation characteristics of the measurement signal waveform generated by the same blade at different rotation cycles. This includes: determining the start time of each rotation cycle based on the pulse signal of the key phase sensor, and determining all measurement signal regions of the same blade in different rotation cycles by combining the preset distribution positions of each blade in the circumferential direction; using the signal peak point of each measurement signal region as the boundary, extracting the average rate of change of the signal rising segment to the left of the peak point and the average rate of change of the signal falling segment to the right of the peak point; determining the first difference and the second difference of the average rate of change of the signal rising segment between each pair of adjacent cycles of the same blade in multiple consecutive rotation cycles; determining the propagation attenuation metric of a single blade based on the first and second differences corresponding to all pairs of adjacent cycles; and determining the propagation attenuation characteristic based on the propagation attenuation metric of all blades.

[0012] In one possible design, the start time of each rotation cycle is determined based on the pulse signal from the key phase sensor, and combined with the preset distribution positions of each blade in the circumferential direction, all measurement signal regions of the same blade in different rotation cycles are determined. This includes: determining the start pulse signal of the rotation cycle by monitoring a preset phase marker using the key phase sensor, the preset phase marker being set on the turbine shaft; determining the time offset of each blade relative to the start pulse signal of the rotation cycle based on the preset distribution positions of each blade; and locating the measurement signal time interval corresponding to each blade in each rotation cycle based on the time offset, thereby obtaining all measurement signal regions of the same blade in different rotation cycles.

[0013] Secondly, a system for monitoring the radial displacement of turbine low-pressure cylinder blades is provided, comprising: a data acquisition unit for acquiring multi-source monitoring data during the operation of the turbine low-pressure cylinder, including the instantaneous blade clearance value generated by each blade passing through the measurement position and steam moisture content data; a first feature determination unit for determining a synchronization deviation feature quantity based on the steam moisture content data and the blade instantaneous clearance value, the synchronization deviation feature quantity characterizing the degree of synchronization deviation between changes in the wet steam state and changes in the blade instantaneous clearance value response; a second feature determination unit for determining a propagation attenuation feature quantity based on the changing characteristics of the measurement signal waveform generated by the same blade passing through the measurement position in different rotation cycles, the propagation attenuation feature quantity characterizing the degree of influence on the propagation stability of the measurement field in the wet steam medium; a correction coefficient determination unit for determining a dynamic correction coefficient based on the synchronization deviation feature quantity and the propagation attenuation feature quantity; and a displacement correction unit for correcting the blade radial displacement monitoring value based on the dynamic correction coefficient to obtain the corrected blade radial displacement.

[0014] Thirdly, a radial displacement monitoring device for low-pressure cylinder blades of a steam turbine is provided, comprising a displacement sensor, a speed sensor, a wet steam moisture content monitoring device, a key phase sensor, a processor, and a memory. The processor is communicatively connected to the displacement sensor, the speed sensor, the wet steam moisture content monitoring device, the key phase sensor, and the memory. The memory stores a computer program, and when the processor executes the computer program, it implements the radial displacement monitoring method for low-pressure cylinder blades of a steam turbine as provided in any possible design of the first aspect.

[0015] The present invention has the following beneficial effects: In the turbine low-pressure cylinder blade radial displacement monitoring method provided by this invention, the synchronization degree between the changing trends of steam moisture content data and blade instantaneous clearance value is analyzed to determine the synchronization deviation characteristic quantity. This is used to identify whether changes in the state of the wet steam medium have produced a substantial response in the measurement signal, thereby distinguishing whether the source of measurement signal fluctuations is the actual blade displacement change or external medium disturbance. Simultaneously, by analyzing the differences in the rise and fall rates of the measurement signal waveform in different rotation cycles of the same blade, a propagation attenuation characteristic quantity is determined to quantify the actual influence of the wet steam medium on the propagation characteristics of the sensor's measurement field. Based on this, a dynamic correction coefficient is determined by combining the two characteristic quantities to correct the blade radial displacement monitoring value. This ensures that the final obtained blade radial displacement effectively reduces the periodic fluctuations in the measurement signal caused by unsteady changes in the wet steam flow field, reduces the impact of changes in the propagation characteristics of the measurement field on the monitoring results, thereby improving the stability and accuracy of the monitoring data and making the corrected blade radial displacement closer to the actual blade motion state. Attached Figure Description

[0016] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a method for monitoring the radial displacement of a low-pressure cylinder blade in a steam turbine, provided in one embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a turbine low-pressure cylinder blade radial displacement monitoring system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a turbine low-pressure cylinder blade radial displacement monitoring device provided in one embodiment of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method, system, and device for monitoring the radial displacement of low-pressure cylinder blades of a steam turbine according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] In embodiments of the present invention, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in embodiments of the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0020] In the description of this invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, "at least one" and "more than one" refer to two or more. The terms "first," "second," etc., do not limit the quantity or order of execution, and "first," "second," etc., do not necessarily imply differences.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The following description, in conjunction with the accompanying drawings, details the specific scheme of a method, system, and equipment for monitoring the radial displacement of low-pressure cylinder blades in a steam turbine provided by the present invention.

[0023] Please see Figure 1 The diagram illustrates a flowchart of a method for monitoring the radial displacement of a low-pressure cylinder blade of a steam turbine, provided by an embodiment of the present invention, including the following steps S101-S105.

[0024] S101. Acquire multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine.

[0025] The multi-source monitoring data includes the instantaneous blade gap value generated by each blade passing through the measurement position and the steam moisture content data.

[0026] Optionally, a displacement sensor is circumferentially arranged on the low-pressure cylinder casing of the turbine near the tip of the last-stage blade. The displacement sensor is a non-contact sensor, such as an eddy current sensor or a capacitive displacement sensor. A preset initial gap is maintained between the sensor probe and the tip of the blade (e.g., an empirical value of 2 mm). After the low-pressure cylinder of the turbine is started, the sensor is zero-point calibrated, and the raw electrical signal generated when the blade passes the sensor probe is continuously collected.

[0027] The rotor speed and rotor angular position are synchronously acquired by a speed sensor or shaft encoder, and the timestamp of each blade passing the measurement position is recorded synchronously.

[0028] Furthermore, based on the original electrical signal and rotor angular position, the instantaneous blade gap value corresponding to the measurement position of each blade is determined.

[0029] It should be noted that, due to the physical width of the blade, a single blade does not pass by the sensor probe instantaneously, but rather undergoes a complete process from the blade approaching to the blade leaving. Therefore, the event of a single blade passing by corresponds to a signal waveform containing multiple consecutive sampling points in the original electrical signal.

[0030] In some embodiments, the time interval for each blade passing through the measurement area is identified based on the rotor angular position, resulting in the original signal waveform corresponding to each blade passage. A sliding window scan is performed on the original signal waveform, calculating the signal variation amplitude within a window consisting of several consecutive sampling points. An exemplary value for the window size is 10 to 20 consecutive sampling points. When the signal variation amplitude within the window is lower than a preset amplitude threshold (e.g., 0.5% of the full-scale signal amplitude), it indicates that the signal variation within that time interval is relatively smooth, and the relative position change between the blade and the sensor probe is small. This time interval is then defined as a stable sampling interval. The average voltage value within the stable sampling interval is calculated, and the average voltage value is converted into the corresponding blade instantaneous gap value using a sensor calibration relationship. This sensor calibration relationship is the correspondence between the voltage value and the blade instantaneous gap value obtained through a pre-calibration experiment.

[0031] Steam moisture content data is obtained through a wet steam moisture content monitoring device in the last stage steam channel of the low-pressure cylinder. The steam moisture content data is continuously collected and recorded by the wet steam moisture content monitoring device at a fixed sampling frequency. An example value of the fixed sampling frequency is 1000 Hz.

[0032] Optionally, after acquiring the instantaneous blade gap value and steam moisture content data, normalization processing is performed on them respectively. For the instantaneous blade gap value, the ratio of the acquired instantaneous blade gap value to the pre-calibrated maximum gap value can be used as the normalization result, mapping the instantaneous blade gap value to the interval between 0 and 1. For the steam moisture content data, the ratio of the acquired steam moisture content data to the maximum range of the wet steam moisture content monitoring device can be used as the normalization result, mapping the steam moisture content data to the interval between 0 and 1. It should be noted that in subsequent calculations based on the instantaneous blade gap value and steam moisture content data, the corresponding normalized values ​​are used in the calculations.

[0033] Finally, the instantaneous blade gap value and steam moisture content data are time-aligned to generate an aligned steam moisture content data sequence with the same length as the instantaneous blade gap value sequence. The two are matched one-to-one according to the blade passing events, and together they form a multi-source monitoring data set, thus completing the acquisition of multi-source monitoring data.

[0034] Optionally, since the blade instantaneous gap value is a discrete sequence generated each time a blade passes the measurement position, with each value corresponding to a timestamp of a blade passing event, while the steam moisture content data is a time series continuously collected at a preset fixed sampling frequency, the sampling mechanisms and data lengths of the two are different. To achieve subsequent point-by-point comparative analysis of the changing trends of the two, the following alignment rule is adopted: using the timestamps of each blade passing event in the blade instantaneous gap value sequence as the alignment benchmark, for each blade passing event, all steam moisture content sampling values ​​within the time interval corresponding to the passing event are extracted from the steam moisture content data, and their arithmetic mean is calculated as the steam moisture content data aligned with the blade instantaneous gap value. The time interval is a window centered on the signal peak time of the blade passing event, with preset time lengths taken before and after it. This preset time length is determined based on the signal duration of a single blade passing event, and is not less than half of the signal duration and does not exceed that duration; for example, it can be taken as 0.3 milliseconds to 1 millisecond.

[0035] S102. Determine the synchronous deviation characteristic quantity based on the steam moisture content data and the instantaneous blade gap value.

[0036] Among them, the synchronous deviation characteristic is used to characterize the degree of synchronous deviation between the change of wet steam state and the change of blade instantaneous gap value. The larger the value of the synchronous deviation characteristic, the more asynchronous the two changes are.

[0037] As one possible approach, firstly, the signal baseline offset is determined based on the degree of deviation of the blade instantaneous clearance value relative to the operating reference value within a single rotation cycle. This signal baseline offset is used to characterize the overall offset level of the measurement field within a single rotation cycle.

[0038] In some embodiments, an operating reference value is determined based on the instantaneous blade clearance values ​​acquired during the initial operation of the turbine. Optionally, the average value of all instantaneous blade clearance values ​​acquired during the initial operation is used as the operating reference value. Then, for a single rotation cycle, the offset of the instantaneous blade clearance value of each blade within the rotation cycle from the operating reference value is determined (this offset can be the absolute value of the difference between the two, reflecting the degree of deviation of the instantaneous blade clearance value relative to the operating reference value under the current measurement state). The offsets corresponding to all blades are then averaged to obtain the average offset of the instantaneous blade clearance values ​​of all blades relative to the operating reference value. The obtained average offset is the signal baseline offset for that rotation cycle.

[0039] Optionally, a preset phase mark is provided on the turbine shaft, which is a groove or a reflective point on the shaft. The preset phase mark is monitored by a key phase sensor. When the rotor rotates to the position of the preset phase mark, the key phase sensor outputs the start pulse signal of the rotation cycle. The time interval between the start pulse signals of two adjacent rotation cycles is a complete rotation cycle.

[0040] It should be noted that the initial operating period refers to a pre-defined time interval from turbine startup to reaching a stable operating state, such as the 20th to 30th rotational cycles after turbine startup. During this initial operating period, the turbine components have not yet been affected by thermal deformation, wear, or fouling caused by prolonged high-temperature and high-pressure operation. The boundary layer state and droplet distribution in the wet steam flow field have not yet significantly deteriorated, and the measurement field propagation conditions between the displacement sensor and the blades basically maintain the initial calibration state. The instantaneous blade clearance value collected at this time can approximately reflect the true clearance characteristics of the blades under conditions without significant wet steam medium disturbance. Therefore, the operating benchmark value determined by the instantaneous blade clearance value collected during this stage is used as the reference benchmark for calculating the degree of deviation of the instantaneous blade clearance value in subsequent rotational cycles, possessing reference and comparison value that objectively reflects the starting point of the measurement field state change. Similarly, when determining the degree of wet steam state fluctuation, the operating reference value is determined based on the steam moisture content data obtained by the turbine during the initial operating period. The steam moisture content data collected during this stage represents the moisture content level when the wet steam flow field is in a relatively stable state, and also has reference and comparison value.

[0041] Furthermore, the signal fluctuation dispersion is determined based on the variation amplitude of the signal baseline offset between all adjacent cycle pairs in multiple consecutive rotation cycles. This signal fluctuation dispersion is used to characterize the fluctuation amplitude of the blade instantaneous gap value between different rotation cycles.

[0042] Optionally, an observation window containing multiple rotation cycles is set, with an example window size of 5 to 20 rotation cycles. The multiple rotation cycles within the observation window are then divided into multiple adjacent cycle pairs, and the signal fluctuation dispersion within the observation window is determined according to the following calculation formula.

[0043] In the formula, The degree of dispersion of signal fluctuations within the observation window. This refers to the number of rotation periods included within the observation window, with exemplary values ​​ranging from 5 to 20. Greater than zero, For the first Signal baseline offset per rotation cycle For the first Signal baseline offset per rotation cycle For the first The signal baseline offset of the first rotation cycle and the first The absolute value of the difference between the signal baseline offsets of each rotation cycle, that is, the magnitude of the change in signal baseline offset between adjacent cycle pairs.

[0044] in, It not only focuses on the variation amplitude between adjacent rotation cycles, but also considers the overall offset level of the measurement field in the current rotation cycle. When the wet steam disturbance is weak, even if there are small changes between adjacent rotation cycles, due to... The product term remains at a low level even when the inherent properties are relatively small; however, when the wet steam disturbance is strong... It is inherently large and its fluctuations during the week are also significant. The value increases accordingly, meaning that the stability of the measurement field decreases under strong disturbance conditions.

[0045] Subsequently, the degree of fluctuation in the wet steam state is determined based on the dispersion of signal fluctuations and the degree of deviation of steam moisture content data from the operating reference value.

[0046] Optionally, the average value of the steam moisture content data acquired during the initial operation of the steam turbine is first determined as the operating reference value. Then, the deviation of each steam moisture content data point collected within the observation window from the operating reference value is determined (this deviation can be the absolute value of the difference between the two, reflecting the degree of deviation of the droplet content in the steam at the current moment relative to the initial operation). The deviations corresponding to all steam moisture content data are then averaged to obtain the average moisture content deviation. Finally, the product of the signal fluctuation dispersion and the average moisture content deviation is determined as the degree of wet steam state fluctuation.

[0047] It should be noted that the degree of fluctuation in the state of wet steam is used to characterize the influence of disturbances in the wet steam medium on the measurement signal. By multiplying the degree of dispersion of the signal fluctuation by the average deviation of the moisture content, a coupling amplification relationship between changes in environmental state and the response of the measurement signal is established. Only when the environmental disturbance is significant and the measurement signal simultaneously exhibits periodic fluctuations will the value of the degree of fluctuation in the state of wet steam increase significantly.

[0048] Furthermore, the degree of difference in the changing trends between steam moisture content data and blade instantaneous gap values ​​was determined.

[0049] Optionally, for the steam moisture content data, a slope calculation window is formed by data points from two adjacent sampling times. The slope value within each slope calculation window is determined using the first-order difference method. All adjacent sampling time pairs in the steam moisture content data within the observation window are traversed to obtain a first slope sequence composed of the slope values ​​of each slope calculation window arranged sequentially. Similarly, for the blade instantaneous gap value, a second slope sequence composed of the slope values ​​of each slope calculation window arranged sequentially is obtained using the same first-order difference method. Since the aforementioned steam moisture content data and blade instantaneous gap value have been synchronously marked and stored according to a unified time reference, the lengths of the first slope sequence and the second slope sequence are the same. Then, based on the absolute value of the slope calculation difference at the same position of the two sequences, the mean of all calculated absolute values ​​is determined as the degree of difference in the trend between the steam moisture content data and the blade instantaneous gap value.

[0050] Finally, based on the degree of difference in the changing trends between the steam moisture content data and the instantaneous blade gap value, as well as the degree of fluctuation in the wet steam state, the synchronous deviation characteristic quantity is determined.

[0051] In some embodiments, the formula for determining the synchronization deviation characteristic is as follows: In the formula, For synchronous deviation characteristic quantity; The value represents the degree of fluctuation in the state of wet steam, used to characterize the impact of disturbances in the wet steam medium on the measurement signal. The larger the value, the more significant the environmental disturbance. The value represents the degree of difference between the changing trends of steam moisture content data and blade instantaneous gap values. It is used to measure the degree of difference between the changing trends of steam moisture content data and blade instantaneous gap values. The larger the value, the greater the difference between the slope of environmental change and the slope of signal change, and the more asynchronous the two changes are. This indicates normalization processing, such as using the maximum-minimum normalization method to normalize... The calculated values ​​are mapped to [0,1], where the maximum and minimum values ​​are obtained by calibration using sample data covering historical extreme disturbance conditions. When the calculated result is greater than the maximum value, the normalization result is forced to 1. When the calculated result is less than the minimum value, the normalization result is forced to 0.

[0052] Among them, when Smaller or A smaller value indicates weaker environmental disturbances or that the signal response is more consistent with environmental changes. The product is smaller. A smaller value indicates a lower degree of synchronization deviation between changes in the wet steam state and changes in the instantaneous blade clearance; when Larger and A larger value indicates significant environmental disturbance and a large difference between the signal response and environmental changes. The product is large. A larger value indicates a higher degree of synchronization deviation, meaning the changes between the two are less synchronized.

[0053] S103. Determine the propagation attenuation characteristic quantity based on the changing characteristics of the measurement signal waveform generated by the same blade passing through the measurement position in different rotation cycles.

[0054] Among them, the propagation attenuation characteristic is used to characterize the degree to which the propagation stability of the measurement field is affected in the wet steam medium.

[0055] First, the start time of each rotation cycle is determined based on the pulse signal of the key phase sensor, and combined with the preset distribution position of each blade in the circumferential direction, all measurement signal areas of the same blade in different rotation cycles are determined.

[0056] Optionally, based on the rotation cycle determined in step S102 above, the timestamp when the position corresponding to the preset phase mark passes the measurement position can be determined to correspond to the start time of the rotation cycle (or the end time of the previous rotation cycle). Further, according to the position corresponding to the preset phase mark and the preset distribution position of each blade, the angle between each blade and the preset phase mark can be obtained. Based on the angle corresponding to the blade and the current rotor speed, the time offset of the starting pulse signal of each blade relative to the rotation cycle when it passes the measurement position can be obtained. Thus, according to the start time of each rotation cycle and the time offset corresponding to each blade, the measurement signal time interval of each blade can be located in each rotation cycle, thereby obtaining all measurement signal regions of the same blade in different rotation cycles.

[0057] Secondly, taking the signal peak point of each measurement signal region as the boundary, the average rate of change of the signal rising segment to the left of the peak point and the average rate of change of the signal falling segment to the right of the peak point are extracted respectively.

[0058] It should be noted that as the blade gradually approaches the sensor probe of the displacement sensor, the measurement signal gradually rises from the baseline; as the blade moves away from the sensor probe of the displacement sensor, the measurement signal gradually decreases.

[0059] In some embodiments, the measurement signal region is divided into a left rising segment and a right falling segment, with the signal peak point of each measurement signal region as the boundary. Optionally, a differential operation is performed on the left rising segment to obtain the average rate of change of the signal rising segment, denoted as . ,in, Indicates the same blade on the first The average rate of change of the signal during the rising segment as it passes the sensor probe is the rate at which the energy coupling of the measurement field intensifies when the blade enters the measurement field. This is the rate at which the signal decreases due to differential calculations on the right-hand falling segment, denoted as [missing information]. ,in, Indicates the same blade on the first The average rate of change of the signal during the descent phase when the blade passes the sensor probe is the rate at which the energy coupling of the measurement field weakens when the blade leaves the measurement field.

[0060] Furthermore, the first difference in the average rate of change of the signal rising segment and the second difference in the average rate of change of the signal falling segment between each adjacent pair of cycles in multiple consecutive rotation cycles of the same blade are determined, wherein multiple consecutive rotation cycles correspond to multiple rotation cycles within the observation window.

[0061] Optionally, the first difference is The second difference is , For the blade in the first The average rate of change of the signal during the rise of the signal each time it passes the sensor probe. For the blade in the first The average rate of change of the signal during the descent phase as it passes the sensor probe. If the measurement field propagation is stable, the average rate of change of the signal during the ascent phase and the average rate of change of the signal during the descent phase should remain consistent across different rotation cycles for the same blade; that is, both the first and second differences should be small. Conversely, if the dynamic disturbance of the wet steam medium causes fluctuations in the propagation characteristics of the measurement field, the first and second differences will increase.

[0062] Subsequently, the propagation attenuation metric for a single blade is determined based on the first and second differences corresponding to all adjacent period pairs.

[0063] In some embodiments, the formula for determining the propagation attenuation metric of a single blade is as follows: In the formula, This represents the number of consecutive rotation cycles (i.e., the number of rotation cycles included within the observation window), with exemplary values ​​ranging from 5 to 20. Greater than zero, For the blade in the first The average rate of change of the signal during the rise of the signal each time it passes the sensor probe. For the blade in the first The average rate of change of the signal during the rise of the signal each time it passes the sensor probe. This is the first difference; For the blade in the first The average rate of change of the signal during the descent phase when the sensor probe passes through it once. For the blade in the first The average rate of change of the signal during the descent phase when the sensor probe passes through it once. The second difference; The propagation attenuation metric for a single blade represents the average difference in the rate of change of the signal waveform over multiple rotation cycles of the same blade. The larger the value, the more significant the propagation attenuation of the measurement field corresponding to that blade.

[0064] Finally, the mean of the propagation attenuation measures of all blades is determined as the propagation attenuation characteristic quantity, denoted as . .

[0065] It should be noted that, since the disturbance of the wet steam medium is usually temporally random, the propagation attenuation metric of all blades is averaged, and the maximum and minimum values ​​are normalized to map the mean to [0,1]. The maximum and minimum values ​​are obtained by calibration from historical sample data covering extreme disturbance conditions. Thus, the normalized value is determined as the overall propagation attenuation characteristic of the entire blade tip measurement area. The larger the value, the greater the impact on the stability of the measurement field propagation in the wet steam medium.

[0066] S104. Determine the dynamic correction coefficient based on the synchronization deviation characteristic and the propagation attenuation characteristic.

[0067] In some embodiments, the formula for calculating the dynamic correction coefficient is as follows: In the formula, This is a dynamic correction coefficient. This is a synchronous deviation characteristic quantity, used to characterize the degree of synchronous deviation between changes in the wet steam state and changes in the instantaneous blade clearance value. The larger the value, the greater the degree of synchronization deviation, meaning the less synchronized the changes of the two. This is a propagation attenuation characteristic quantity, used to characterize the degree to which the propagation stability of the measurement field is affected in a wet steam medium. The larger the value, the more significant the influence of the wet vapor medium disturbance on the propagation of the measurement field. Used for Normalization was performed because and The maximum value is 1, therefore the numerator The maximum value is Through this fraction, we can The value of is limited to the range of 0 to 1.

[0068] Among them, when the synchronous deviation characteristic quantity The smaller the propagation attenuation characteristic value The smaller the value, the lower the degree of synchronization deviation between the change in the wet steam state and the change in the instantaneous clearance value of the blades, and the less the stability of the measurement field is affected. In this case, the dynamic correction coefficient... The closer the value is to 0, the lower the unreliability of the wet steam medium disturbance on the blade radial displacement monitoring value. When the synchronous deviation characteristic value... Larger or propagation attenuation characteristic When it is larger, the dynamic correction coefficient The closer the value is to 1, the higher the unreliability of the radial displacement monitoring values ​​of the blades due to the disturbance of the wet steam medium. Dynamic correction coefficient. Used to characterize the degree of unreliability caused by wet steam medium disturbance to the radial displacement monitoring values ​​of the blades. The larger the value, the greater the proportion of error caused by the disturbance of the wet steam medium in the original monitoring value, and the greater the correction required.

[0069] S105. The monitored value of the blade radial displacement is corrected based on the dynamic correction coefficient to obtain the corrected blade radial displacement.

[0070] First, obtain the radial displacement monitoring values ​​of the blade.

[0071] Optionally, the instantaneous blade clearance value obtained from the above steps is converted using the sensor calibration relationship to obtain the blade radial displacement monitoring value, denoted as... ,in, This represents the radial displacement monitoring value of the blade corresponding to a single blade pass event. The sensor calibration relationship is the correspondence between the instantaneous blade clearance value and the blade radial displacement obtained through pre-calibration experiments. (The last part, "blade radial displacement monitoring value," appears to be an unrelated fragment and is omitted from the translation.) It contains two parts: one part is the actual radial displacement of the blade, and the other part is the measurement error caused by the disturbance of the wet steam medium, with a dynamic correction coefficient. Its function is to estimate and reduce the error component in the radial displacement monitoring value of the blade.

[0072] Secondly, based on the radial displacement monitoring values ​​of the blades and dynamic correction coefficient Determine the corrected radial displacement of the blade, denoted as . Optional In the formula, The radial displacement monitoring value of the blade is obtained by collecting data through a displacement sensor and converting it according to a calibration relationship. This is a reference value for the radial displacement of the blades, obtained by converting the instantaneous blade clearance value acquired during the initial operation of the steam turbine through calibration relationships. It is used to reflect the steady-state clearance level of the blades under conditions without significant disturbance from the wet steam medium. This is a dynamic correction factor used to characterize the degree of unreliability caused by wet steam medium disturbance to the monitored values ​​of blade radial displacement.

[0073] In this correction formula, the current blade radial displacement monitoring value is used. Relative to the blade radial displacement reference value offset As an estimation benchmark for errors caused by disturbances in the wet steam medium, and with a dynamic correction coefficient The confidence weights used for error estimation are discarded. When When the value approaches 0, it indicates that the degree of unreliability caused by disturbances in the wet steam medium is extremely low. The corrected blade radial displacement is mainly determined by the blade radial displacement monitoring values. Decision. When When the value approaches 1, it indicates that the degree of unreliability caused by the disturbance of the wet steam medium is extremely high. The corrected blade radial displacement returns to the blade radial displacement reference value. The system no longer accepts the radial displacement monitoring values ​​of the blades. Instead, it uses the steady-state clearance level of the turbine during the initial stage of operation as the best estimate of the true radial displacement of the blades, avoiding the physical anomaly of the correction result returning to zero due to extreme disturbances. When the value is between 0 and 1, the corrected radial displacement of the blade is a linear interpolation result between the original monitored value and the operating reference value. The larger the value, the greater the correction range, and the closer the correction result is to the operating baseline value.

[0074] It should be noted that in the actual operating environment of the last-stage blades of the low-pressure cylinder, the wet steam boundary layer tends to form an additional steam droplet medium layer between the sensor probe and the blade tip. This medium layer alters the effective operating distance of the sensor's measurement field, thereby affecting the monitored radial displacement values ​​of the blade. The offset relative to the actual gap is related to the change in the dielectric properties of the dielectric layer, which can be expressed as the radial displacement monitoring value of the blade. An excessively large value can also be reflected in the radial displacement monitoring value of the blade. The value is too small. Therefore, the radial displacement value of the blade is used as the reference value. The additive compensation method, which is used as a reference, can adaptively handle measurement errors in different directions.

[0075] Optionally, to avoid overcorrection under extreme disturbances and significant changes in the actual radial displacement of the blades, the dynamic correction coefficient can be adjusted. The value of is subject to constraints: when calculated based on the synchronization deviation characteristic and the propagation attenuation characteristic. The value exceeds the preset correction upper limit threshold. At that time, with It participates in the correction calculation as a dynamic correction coefficient. Preset correction upper limit threshold. An exemplary value is 0.5 to 0.8. By setting a correction upper limit, some information from the original monitoring values ​​is retained even when the disturbance is highly unreliable, avoiding over-reliance on the blade radial displacement reference value. This masks the actual changes in the radial displacement of the blades.

[0076] Finally, the radial displacement monitoring values ​​of all blades are corrected within each rotation cycle. For each blade pass event in each rotation cycle, the corresponding radial displacement monitoring value is acquired. Based on the dynamic correction coefficients determined in the preceding steps and blade radial displacement reference value According to the above correction formula Correction calculations are performed one by one to obtain the corrected radial displacement of each blade in each passing event. The corrected radial displacements of all blades in multiple consecutive rotation cycles are arranged in chronological order to form a time series of blade radial displacements, thus completing the output of the monitoring results of the radial displacement of the turbine low-pressure cylinder blades.

[0077] Understandably, in the turbine low-pressure cylinder blade radial displacement monitoring method provided in this embodiment of the invention, the synchronization degree between the changing trends of steam moisture content data and blade instantaneous clearance value is analyzed to determine the synchronization deviation characteristic quantity. This is used to identify whether changes in the state of the wet steam medium have produced a substantial response in the measurement signal, thereby distinguishing whether the source of measurement signal fluctuations is the actual blade displacement change or external medium disturbance. Simultaneously, by analyzing the differences in the rise and fall rates of the measurement signal waveform in different rotation cycles of the same blade, a propagation attenuation characteristic quantity is determined to quantify the actual influence of the wet steam medium on the propagation characteristics of the sensor's measurement field. Based on this, a dynamic correction coefficient is determined by combining the two characteristic quantities to correct the blade radial displacement monitoring value. This ensures that the final obtained blade radial displacement can effectively reduce the periodic fluctuations caused by unsteady changes in the wet steam flow field on the measurement signal, reduce the impact of changes in the propagation characteristics of the measurement field on the monitoring results, thereby improving the stability and accuracy of the monitoring data, and making the corrected blade radial displacement closer to the actual blade motion state.

[0078] Please see Figure 2 The diagram illustrates a structural schematic of a turbine low-pressure cylinder blade radial displacement monitoring system according to an embodiment of the present invention. Figure 2 As shown, the turbine low-pressure cylinder blade radial displacement monitoring system 20 includes a data acquisition unit 21, a first feature determination unit 22, a second feature determination unit 23, a correction coefficient determination unit 24, and a displacement correction unit 25.

[0079] The data acquisition unit 21 is used to acquire multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine. The multi-source monitoring data includes the instantaneous blade gap value generated by each blade passing through the measurement position and the steam moisture content data.

[0080] The first feature determination unit 22 is used to determine the synchronous deviation feature quantity based on the steam moisture content data and the blade instantaneous gap value. The synchronous deviation feature quantity is used to characterize the degree of synchronous deviation between the change in wet steam state and the response change in the blade instantaneous gap value.

[0081] The second feature determination unit 23 is used to determine the propagation attenuation feature quantity based on the change characteristics of the measurement signal waveform generated by the same blade passing through the measurement position in different rotation cycles. The propagation attenuation feature quantity is used to characterize the degree to which the propagation stability of the measurement field is affected in the wet steam medium.

[0082] The correction coefficient determination unit 24 is used to determine the dynamic correction coefficient based on the synchronization deviation characteristic and the propagation attenuation characteristic.

[0083] The displacement correction unit 25 is used to correct the monitored value of the blade radial displacement based on the dynamic correction coefficient to obtain the corrected blade radial displacement.

[0084] It should be noted that the turbine low-pressure cylinder blade radial displacement monitoring system 20 provided in the above embodiments is only an example of the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the computer equipment can be divided into different functional modules to complete all or part of the functions described above.

[0085] Please see Figure 3 The diagram illustrates a structural schematic of a turbine low-pressure cylinder blade radial displacement monitoring device according to an embodiment of the present invention. Figure 3 As shown, the turbine low-pressure cylinder blade radial displacement monitoring device 30 includes a displacement sensor 31, a speed sensor 32, a wet steam moisture content monitoring device 33, a key phase sensor 34, a processor 35, and a memory 36.

[0086] The processor 35 is communicatively connected to the displacement sensor 31, the speed sensor 32, the wet steam moisture content monitoring device 33, the key phase sensor 34, and the memory 36. The memory 36 stores a computer program, and the processor 35 can execute the computer program to implement the aforementioned method for monitoring the radial displacement of the turbine low-pressure cylinder blades.

[0087] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0088] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method of monitoring the radial displacement of a blade in a low pressure cylinder of a steam turbine, characterised in that, The method includes: Acquire multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine. The multi-source monitoring data includes the instantaneous blade clearance value generated when each blade passes the measurement position and the steam moisture content data. Based on the steam moisture content data and the blade instantaneous gap value, a synchronization deviation characteristic quantity is determined. The synchronization deviation characteristic quantity is used to characterize the degree of synchronization deviation between the change in wet steam state and the response change in the blade instantaneous gap value. Based on the variation characteristics of the measurement signal waveform generated by the same blade passing through the measurement position in different rotation cycles, the propagation attenuation characteristic is determined. The propagation attenuation characteristic is used to characterize the degree to which the propagation stability of the measurement field is affected in the wet steam medium. The dynamic correction coefficient is determined based on the synchronization deviation characteristic and the propagation attenuation characteristic. The monitored radial displacement of the blade is corrected based on the dynamic correction coefficient to obtain the corrected radial displacement of the blade.

2. The method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine according to claim 1, characterized in that, Acquire multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine, including: Displacement sensors are arranged circumferentially near the top of the last stage blades in the low-pressure cylinder casing of the steam turbine. The original electrical signals generated by the sensor probe of each blade as it passes through the displacement sensor are collected by the displacement sensors. The rotor speed and rotor angular position are obtained by a speed sensor or shaft encoder, and the timestamp of each blade passing the measurement position is recorded synchronously. Based on the original electrical signal and the rotor angular position, determine the instantaneous blade gap value corresponding to the measurement position of each blade; The moisture content of steam is obtained through a moisture content monitoring device in the final stage steam channel of the low-pressure cylinder.

3. The method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine according to claim 1, characterized in that, Based on the steam moisture content data and the instantaneous blade clearance value, the synchronization deviation characteristic quantity is determined, including: The signal baseline offset is determined based on the degree of deviation of the instantaneous blade clearance value relative to the operating reference value within a single rotation cycle. The signal baseline offset is used to characterize the overall offset level of the measurement field within a single rotation cycle. The signal fluctuation dispersion is determined based on the change magnitude of the signal baseline offset between all adjacent cycle pairs in multiple consecutive rotation cycles. The signal fluctuation dispersion is used to characterize the fluctuation magnitude of the blade instantaneous clearance value between different rotation cycles. The degree of fluctuation in the wet steam state is determined based on the dispersion of the signal fluctuation and the deviation of the steam moisture content data from the operating reference value. The synchronization deviation characteristic quantity is determined based on the degree of difference in the changing trend between the steam moisture content data and the instantaneous blade gap value, as well as the degree of fluctuation in the wet steam state.

4. The method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine according to claim 3, characterized in that, The signal baseline offset is determined based on the degree of deviation of the instantaneous blade clearance value relative to the operating reference value within a single rotation cycle, including: The operating reference value is determined based on the instantaneous blade clearance value obtained during the initial operation of the steam turbine. The signal baseline offset is obtained by determining the average offset of the instantaneous blade clearance value corresponding to all blades within a single rotation cycle relative to the operating reference value.

5. The method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine according to claim 3, characterized in that, The degree of fluctuation in the wet steam state is determined based on the dispersion of the signal fluctuations and the deviation of the steam moisture content data from the operating reference value, including: Set an observation window that includes multiple rotation cycles; The operating reference value is determined based on the steam moisture content data obtained during the initial operation of the steam turbine. The average deviation of the moisture content is determined based on the deviation of the steam moisture content data relative to the operating reference value within the observation window; The product of the signal fluctuation dispersion and the average deviation of the moisture content is determined as the degree of wet steam state fluctuation.

6. The method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine according to claim 5, characterized in that, Determining the degree of difference in the trend between the steam moisture content data and the instantaneous blade clearance value includes: Determine the first slope sequence of the steam moisture content data changing with time within the observation window, and the second slope sequence of the blade instantaneous gap value changing with time; The degree of difference in the trend of change is determined based on the first slope sequence and the second slope sequence.

7. The method for monitoring the radial displacement of low-pressure cylinder blades of a steam turbine according to claim 1, characterized in that, Based on the changing waveforms of the measurement signals generated by the same blade at different rotation cycles through the measurement positions, the propagation attenuation characteristic quantities are determined, including: The start time of each rotation cycle is determined based on the pulse signal of the key phase sensor, and the preset distribution position of each blade in the circumferential direction is combined to determine all measurement signal areas of the same blade in different rotation cycles. Using the signal peak point of each measured signal region as a boundary, the average rate of change of the signal rising segment to the left of the peak point and the average rate of change of the signal falling segment to the right of the peak point are extracted respectively. Determine a first difference in the average rate of change of the rising segment of the signal and a second difference in the average rate of change of the falling segment of the signal between each pair of adjacent cycles in multiple consecutive rotation cycles of the same blade; Based on the first and second differences corresponding to all adjacent period pairs, a propagation attenuation metric for a single blade is determined. The propagation attenuation characteristic is determined based on the propagation attenuation metric values ​​of all blades.

8. The method for monitoring the radial displacement of low-pressure cylinder blades of a steam turbine according to claim 7, characterized in that, The start time of each rotation cycle is determined based on the pulse signal from the key phase sensor. Combined with the preset distribution positions of each blade in the circumferential direction, all measurement signal regions for the same blade in different rotation cycles are determined, including: The starting pulse signal of the rotation cycle is determined by monitoring a preset phase marker using the key phase sensor, and the preset phase marker is set on the turbine shaft; Based on the preset distribution position of each blade, determine the time offset of each blade relative to the starting pulse signal of the rotation cycle at the measurement position. Based on the time offset, the measurement signal time interval corresponding to each blade is located in each rotation cycle, thus obtaining all measurement signal regions of the same blade in different rotation cycles.

9. A radial displacement monitoring system for low-pressure cylinder blades of a steam turbine, characterized in that, include: The data acquisition unit is used to acquire multi-source monitoring data during the operation of the low-pressure cylinder of the steam turbine. The multi-source monitoring data includes the instantaneous blade gap value generated by each blade passing the measurement position and the steam moisture content data. The first feature determination unit is used to determine the synchronization deviation feature quantity based on the steam moisture content data and the blade instantaneous gap value. The synchronization deviation feature quantity is used to characterize the degree of synchronization deviation between the change in wet steam state and the response change in the blade instantaneous gap value. The second feature determination unit is used to determine the propagation attenuation feature based on the change characteristics of the measurement signal waveform generated by the same blade passing through the measurement position in different rotation cycles. The propagation attenuation feature is used to characterize the degree to which the propagation stability of the measurement field is affected in the wet steam medium. The correction coefficient determination unit is used to determine the dynamic correction coefficient based on the synchronization deviation characteristic and the propagation attenuation characteristic. The displacement correction unit is used to correct the monitored value of the blade radial displacement based on the dynamic correction coefficient to obtain the corrected blade radial displacement.

10. A device for monitoring the radial displacement of low-pressure cylinder blades in a steam turbine, characterized in that, It includes a displacement sensor, a speed sensor, a wet steam moisture content monitoring device, a bonded phase sensor, a processor, and a memory. The processor is communicatively connected to the displacement sensor, the speed sensor, the wet steam moisture content monitoring device, the bonded phase sensor, and the memory. The memory stores a computer program, and when the processor executes the computer program, it implements the method for monitoring the radial displacement of the low-pressure cylinder blades of a steam turbine as described in any one of claims 1 to 8.

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