Synchronous decoupling measurement method for vibration displacement and blade top clearance of shrouded blade

Abstract

The invention discloses a synchronous decoupling measurement method for vibration displacement and blade top clearance of a shrouded blade, and relates to the field of energy power engineering, and the method comprises the following steps: 1, calibrating the axial vibration displacement and blade top clearance of the shrouded blade; step 2, installing an eddy current sensor; 3, the rotor is made to operate normally, the vibration state of the shrouded blade is measured in the rotating process of the shrouded blade, and a measurement signal is obtained; step 4, carrying out preprocessing on the measurement signal; 5, the sensing area variation of the sensor and the measurement distance variation from the sensor to the shroud are measured; and 6, calculating the vibration displacement and the blade top clearance of the shrouded blade. According to the method, the defects of the prior art can be overcome, synchronous and decoupling measurement on the vibration displacement and the blade top clearance of the shrouded blade can be realized, the measurement accuracy and credibility can be effectively improved, and the measurement requirement can be effectively met.

Description

Technical Field

[0001] This invention relates to the field of energy and power engineering, and in particular to a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade. Background Technology

[0002] As a core component of modern energy conversion systems, steam turbines are widely used in thermal power generation, nuclear power generation, and some geothermal power generation systems, and are an important part of the stable operation of the power system. The blades, as the power-generating elements in the steam turbine that directly interact with high-temperature, high-pressure steam, play a decisive role in the overall operational safety and energy conversion efficiency of the turbine.

[0003] In the operation of large turbomachinery, the rotor is often at a high linear velocity, and the blades, as key components, bear high loads. Based on their structural characteristics, blades can be divided into free blades and shrouded blades. Compared to the relatively mature measurement methods for free blades, vibration measurement methods for shrouded blades are currently lacking. Shrouded blades mainly face the following technical challenges during operation: 1. Rotor deformation and centrifugal extension during rotation will cause dynamic changes in blade tip clearance, which will affect aerodynamic performance and may also cause blade rubbing risks. 2. Complex loads under non-design conditions can easily induce abnormal vibration phenomena such as flutter and instability; 3. Degradation of material properties caused by harsh working environments can alter the natural frequency of the blades and increase the risk of resonance.

[0004] Because the measurement environment of large turbomachinery such as steam turbines is complex, sensors are required to perform stable measurements under special conditions. Currently, most measurement methods are based on eddy current sensors. The working principle of an eddy current sensor is that when the sensor measures a conductor, the equivalent impedance Z of the probe coil under the influence of the induced current can be expressed as... From the formula, we can see that the magnitude of the coil impedance is related to several parameters: For excitation current, The resistivity of the measured object. The magnetic permeability of the measured object. The frequency of the excitation current. The relative area between the coil and the object being measured. Let Z be the distance between the coil and the object being measured. If other parameters remain constant, changing one parameter in the impedance expression will result in the sensor coil impedance Z being a function of that parameter.

[0005] The following are existing solutions that are similar to this invention: 1. A non-contact measurement method for crowned blades based on an eddy current sensor (Invention Application No. 201910688307.8) can meet the requirement of measuring the vibration displacement amplitude of crowned blades. Based on the characteristic that crowned blades mainly generate axial vibration, this invention constructs a single-valued function of the sensor coil impedance with respect to the sensing area, and captures the change in the sensing area according to the change in the sensor signal, thereby achieving the measurement of vibration displacement.

[0006] 2. A blade tip clearance calibration and measurement system and method based on the coupling characteristics of crowned blades (Invention Application No. 201910571820.9) can meet the requirements for measuring the blade tip clearance of crowned blades. In this invention, the sensor coil impedance is expressed as a bivariate function of clearance and size factor, expressed as... By utilizing the impedance values ​​of the sensor as it passes through the leaf crown coupling point and the crowned blade, and based on the condition that the size factor remains constant at the two measurement points on each leaf crown, the impedance change can be constructed. To the size of the gap A single-valued function is used to measure the tip gap.

[0007] 3. A calibration system for vibration measurement of crowned blades (Invention Application No. 201921088181.2) describes a calibration system for crowned blades. By using a three-dimensional displacement stage to drive the crowned blade to move in the x, y, and z directions, the system simulates the circumferential rotation direction, vibration displacement direction, and tip clearance change of the crowned blade under actual conditions, thereby calibrating and obtaining the size factor for use in tip-time-based measurement methods.

[0008] The operational stability of crowned blades has a decisive impact on equipment safety and performance efficiency. The crowned structure significantly improves the overall rigidity of the blade assembly through circumferential coupling, while effectively suppressing blade vibration amplitude. However, under high-speed rotation, crowned blades are still subjected to complex periodic excitation forces, resulting in significant vibration responses and dynamic stresses. Long-term operation can lead to risks such as material fatigue, crack propagation, and even fracture failure. Blade vibration displacement and tip clearance are core parameters for evaluating the operational status of crowned blades, and their real-time synchronous measurement is crucial for equipment condition monitoring and fault early warning. Existing measurement methods rely on single sensors to measure individual operating parameters, failing to distinguish the coupling effects of vibration displacement and tip clearance on the measurement signals. This leads to cross-interference in parameter measurements and generally suffers from insufficient sensitivity and accuracy. Existing measurement methods require multiple sensors to be placed at different circumferential positions to monitor vibration displacement and tip clearance separately, which introduces significant measurement errors. For example, when the rotor experiences radial movement, the clearance values ​​measured by sensors at different circumferential positions will show significant deviations, resulting in inconsistent measurement results.

[0009] Therefore, in response to the above-mentioned technical challenges, those skilled in the art are dedicated to developing a measurement method that can adapt to the special structural characteristics of crowned blades, realize the synchronous decoupled measurement of vibration displacement and blade tip clearance, and provide a reliable technical means for condition monitoring and fault diagnosis of rotating machinery. Summary of the Invention

[0010] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is how to perform synchronous and decoupled measurement of the vibration displacement and tip clearance of crowned blades.

[0011] To achieve the above objectives, the present invention provides a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade, characterized in that the method includes the following steps: Step 1: Set up a calibration test bench in a laboratory environment to calibrate the axial vibration displacement and tip clearance of the crowned blade; Step 2: Install the first eddy current sensor and the second eddy current sensor; Step 3: Run the rotor normally and measure its vibration state during the rotation of the crowned blades to obtain the measurement signals from the first eddy current sensor and the second eddy current sensor. Step 4: Preprocess the measurement signal; Step 5: Measure the change in the sensor's sensing area and the change in the measurement distance from the sensor to the leaf crown; Step 6: Calculate the vibration displacement and tip gap of the crowned blade using the change in sensing area and the change in measurement distance.

[0012] Furthermore, in step 1, the calibration includes curves showing the change in the modulus of the output signals from the sensing area and the measurement distance to the output signals of the first and second eddy current sensors.

[0013] Furthermore, in step 2, the first eddy current sensor and the second eddy current sensor are mounted by opening holes in the casing.

[0014] Furthermore, step 2 also includes: determining the measurement distance and sensing area of ​​the crown portion of the crowned blade by the first eddy current sensor and the second eddy current sensor in the initial measurement state when the crowned blade is stationary.

[0015] Furthermore, in step 4, the preprocessing of the measurement signal includes periodic truncation and smoothing filtering of the signal to extract effective signal components.

[0016] Further, in step 5, the measurement signals of the first eddy current sensor and the second eddy current sensor are represented as follows:

[0017] in, These are the components that affect the signal amplitude under the initial measurement conditions, such as the measurement distance and the sensing area. , These are correction functions that measure the impact of changes in the measurement distance and sensing area on the signal amplitude compared to the initial conditions.

[0018] Furthermore, step 5 also includes: Step 5.1: Under circumferential observation, the crowned blade vibrates during operation. When the blade crown moves from a stationary position to a vibrating position, the change in the measured signals of the first and second eddy current sensors from the initial measurement state to the blade vibration displacement is expressed as follows: By solving the inverse function The change in the sensing area is obtained.

[0019] Furthermore, step 5 also includes: Step 5.2: Under tangential observation, the crowned blade vibrates during operation. When the blade crown moves from a stationary position to a vibrating position, the change in the measured signals of the first and second eddy current sensors from the initial measurement state to the blade vibration displacement is expressed as follows: By solving the inverse function The change in the measured distance is obtained.

[0020] Furthermore, in step 6, the bivariate equation is solved by extracting the change in sensing area and the change in measurement distance of the first eddy current sensor and the second eddy current sensor, thereby achieving the decoupled extraction of the vibration displacement of the crowned blade and the blade tip clearance.

[0021] Furthermore, the method also includes: Step 7: Process the blade vibration displacement sequence to achieve overall vibration analysis of the bladed disk.

[0022] The beneficial technical effects of the present invention are as follows: 1. The vibration displacement of crowned blades directly reflects the operational safety of turbomachinery, while the radial tip clearance directly reflects its efficiency. Both are important indicators that need to be monitored to measure the operating status of the equipment. Current technologies for measuring the vibration displacement and tip clearance of crowned blades suffer from asynchronous problems. For example, when the rotor experiences radial axial movement, the clearance values ​​measured by sensors at different circumferential positions will show significant deviations, leading to inconsistent measurement results and insufficient accuracy, failing to meet measurement requirements. This invention designs a method for synchronously measuring the vibration displacement and tip clearance of crowned blades. When a crowned blade is working, it mainly generates vibration displacement in the axial direction, with the vibration mode primarily being pitch diameter vibration; simultaneously, in the radial direction, due to centrifugal force and thermal expansion, the blade undergoes stretching, manifested as changes in the tip clearance. If measured using an eddy current sensor, these two changes will cause variations in the sensor's measurement area and distance, leading to changes in the probe coil impedance, thus affecting the amplitude of the eddy current sensor's output signal. As an alternative, the eddy current sensor can be replaced with other field sensors for measurement. Therefore, the output signal of the eddy current sensor can be expressed as... , in These are the components that affect the signal amplitude under the initial measurement conditions, namely the measurement distance and the relative measurement area. , These are correction functions representing the impact of changes in measurement distance and measurement area on signal amplitude compared to the initial state. The specific expression of these functions needs to be determined through calibration experiments. Since the sensor signal is a bivariate function, at least two signals are required to simultaneously measure two measurands. Based on this principle, this invention designs a dual-sensor arrangement for synchronously measuring blade vibration displacement and tip clearance of crowned blades of arbitrary shapes. Taking a parallel straight-plate-shaped crown as an example, this invention arranges two eddy current sensors to measure the upper and lower edges of the crown respectively. Initially, the output signal amplitude of the sensors is not zero. Two eddy current sensors are arranged in a special configuration at the same position in the circumferential direction, constructing a system of two equations that meets the requirements of decoupling analysis. This overcomes the shortcomings of existing technologies, enabling synchronous and decoupled measurement of vibration displacement and tip clearance of crowned blades, effectively meeting measurement needs.

[0023] 2. Existing methods for measuring the vibration displacement of crowned blades suffer from low sensitivity when using a single sensor due to the small axial vibration displacement of the blade. This invention proposes a differential measurement scheme based on the collaborative operation of two sensors. When the crowned blade vibrates during operation, the axial vibration displacement causes the crown position in the circumferential observation to shift from its static position to its vibrating position. This increases the sensing area of ​​the first eddy current sensor and decreases the sensing area of ​​the second eddy current sensor. The change in the sensing area of ​​the two sensors in this measurement scenario is... The absolute values ​​are the same, but the signs are opposite, therefore the two sensor signals produce changes with opposite trends. The signal modulus describing this change is expressed as... By solving the inverse function The change in the sensing area can be calculated. Under tangential observation, compared to the position of the blade crown in a static state, the position of the blade crown when it sweeps past the sensor probe during actual operation is at the position of the blade crown in a vibrating state. The blade tip clearance changes synchronously with the rotor's operation. At this time, the change in the measurement distance from the first and second eddy current sensors to the blade crown is... Since the absolute values ​​and signs are the same, the signals from the two sensors produce changes with the same trend. The signal modulus describing this change is expressed as... By solving the inverse function The change in measurement distance can be calculated. The sensing area and the change in measurement distance can respectively reflect the vibration displacement of the crowned blade and the size of the blade tip clearance, enabling decoupling of the two measurands from the equation system. This invention achieves differential and decoupled measurement by introducing two sensor signals, effectively improving measurement accuracy and reliability, and enhancing the sensitivity when measuring vibration displacement. This is the most important supporting element of the synchronous measurement scheme.

[0024] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0025] Figure 1 This is a flowchart of a preferred embodiment of the present invention, showing a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade. Figure 2 This is a top view of the differential synchronous measurement scheme of a preferred embodiment of the present invention, which is a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade. Figure 3 This is a side view of the principle of a differential synchronous measurement scheme for a preferred embodiment of the present invention, which is a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade. Figure 4This is a schematic diagram of a preferred embodiment of the present invention, illustrating the principle of a method for synchronously decoupling the vibration displacement and tip clearance of a crowned blade. Wherein, 1-first eddy current sensor, 2-second eddy current sensor, 3-blade crown position under vibration, 4-blade crown position under static state, 5-blade crown, 6-casing, 7-change in sensing area of ​​first eddy current sensor, 8-change in sensing area of ​​second eddy current sensor. Detailed Implementation

[0026] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0027] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0028] like Figure 1 As shown, this invention addresses the insufficient measurement accuracy of existing crowned blade measurement methods by using a dual-sensor measurement method to synchronously decouple vibration displacement and blade tip clearance signals based on signal change characteristics. The specific implementation process of this invention is as follows: A calibration test bench was set up in a laboratory environment to calibrate the axial vibration displacement and tip clearance of the crowned blade. Curves were calibrated showing the correlation between the sensing area, measurement distance, and the modulus of the output signals from the two sensors. A suitable working area was then selected as the installation location for the eddy current sensor. The purpose of this step is to use the calibration results as the basis for subsequent measurements based on the measured signal modulus.

[0029] After calibration, install the measuring sensors on-site. For example... Figure 4 As shown, a first eddy current sensor 1 and a second eddy current sensor 2 are installed in holes drilled at the calibrated positions on the casing 6 to determine the initial measurement state of the blade crown 5. Considering that the two eddy current sensors may interfere with each other if they are installed too close together, a certain distance is maintained between the sensors during actual installation.

[0030] To ensure the rotor operates normally, its vibration state is measured during the rotation of the crowned blades, and measurement signals from the first eddy current sensor 1 and the second eddy current sensor 2 are obtained.

[0031] Before further analysis, the original signal needs to be preprocessed. The main steps are periodic truncation, smoothing filtering, and other operations to extract effective signal components, which will facilitate subsequent signal processing.

[0032] The measurement signal of the eddy current sensor can be expressed as: ,in These are the components that affect the signal amplitude under the initial measurement conditions, namely the measurement distance and the relative measurement area. , These are, respectively, correction functions that reflect the impact of changes in measurement distance and measurement area on signal amplitude compared to the initial conditions. The specific expression of these functions needs to be determined through calibration experiments. Since the sensor signal is a bivariate function, at least two signals are required to simultaneously measure two measurands.

[0033] like Figure 2 and Figure 3 As shown, when the crowned blade vibrates during operation, due to axial vibration displacement, the crown moves from position 4 (static state) to position 3 (vibrating state) under circumferential observation. The sensing area of ​​the first eddy current sensor 1 increases by 7, while the sensing area of ​​the second eddy current sensor 2 decreases by 8. The changes in the sensing areas of the two sensors under this measurement scenario are... The absolute values ​​are the same, but the signs are opposite, therefore the signals from the two sensors produce changes with opposite trends. For example, in the initial measurement, the upper and lower edges of the same blade are measured using the first eddy current sensor 1 and the second eddy current sensor 2. When the blade vibrates and displaces, the signals measured by the two sensors change. The signal modulus describing this change is expressed as... By solving the inverse function The change in the sensing area can be calculated.

[0034] Under tangential observation, compared to position 4 of the blade crown in a static state, position 3 of the blade crown is in a vibrating state when it sweeps past the sensor probe during actual operation. The blade tip clearance changes synchronously when the rotor is working. At this time, the change in the measurement distance from the first eddy current sensor 1 and the second eddy current sensor 2 to the blade crown is... Since the absolute values ​​and signs are the same, the signals from the two sensors produce changes with the same trend. For example, in the initial measurement scenario, the upper and lower edge signals of the same blade crown are measured using the first eddy current sensor 1 and the second eddy current sensor 2. When the blade vibrates and displaces, the signals measured by the two sensors change. The signal modulus describing this change is expressed as... By solving the inverse function The change in the measured distance can be obtained.

[0035] The above can be achieved. For the collaborative analysis of signals from two sensors, the decoupling extraction of the two measurands can be realized by extracting the signal modulus and solving the binary equation. The changes in sensing area and measurement distance can respectively reflect the vibration displacement of the crowned blade and the size of the blade tip gap, thus enabling the decoupling of the two measurands from the equation system.

[0036] Monitoring of the tip gap of the crowned blades has concluded. Further processing of the blade vibration displacement sequence will enable overall vibration analysis of the bladed disk.

[0037] Technical Advantages: The measurement method proposed in this invention has wide applicability. For leaf crown structures with smooth edges, direct measurement can be performed; for irregularly shaped leaf crown structures, signal processing methods can be used to convert them into equivalent leaf crown structures for measurement. Therefore, the method of this invention has no requirements on leaf crown characteristics and can measure crowned blades of any shape. The measurement method proposed in this invention achieves, for the first time, simultaneous and decoupled measurement of vibration displacement and tip gap of crowned blades, filling the gap in current technologies capable of achieving this effect.

[0038] Performance Indicators: The measurement scheme proposed in this invention introduces signals from two sensors, solves a system of two equations, and measures the changes in the sensor sensing area and measurement distance during blade operation, thereby simultaneously capturing the vibration displacement of the crowned blade and the tip clearance. This method avoids the measurement errors introduced by existing measurement methods that assume the eddy current sensor signal is a univariate function, effectively improving measurement accuracy and sensitivity.

[0039] Taking a steam turbine as an example, in actual operation, the vibration displacement of the crowned blades and the tip clearance are important indicators affecting its performance. Therefore, simultaneous online monitoring of these two measurements is of great significance. If existing technologies are used for detection, vibration displacement and tip clearance measurement sensors need to be arranged separately in the circumferential direction. This requires multiple sensors at different positions in the circumferential direction. Because the measurement positions for the two measurements are different in the circumferential direction, errors will be introduced when applying them to the analysis of the same blade. This invention, however, can simultaneously measure the vibration displacement and tip clearance of the crowned blade at the same location, effectively improving the accuracy and reliability of the measurement.

[0040] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for measuring the vibration displacement of a shrouded blade and synchronously decoupling the tip clearance, characterized in that, The method comprises the following steps: Step 1, a calibration test bench is built in a laboratory environment to calibrate the axial vibration displacement and the tip clearance of the shrouded blade; Step 2, a first eddy current sensor and a second eddy current sensor are installed; Step 3, the rotor is normally operated, and the vibration state of the shrouded blade is measured during the rotation of the shrouded blade to obtain the measurement signals of the first eddy current sensor and the second eddy current sensor; Step 4, the measurement signals are preprocessed; Step 5, the change amount of the sensing area of the measurement sensor and the change amount of the measurement distance from the sensor to the blade shroud are measured; Step 6, the vibration displacement and the tip clearance of the shrouded blade are calculated through the change amount of the sensing area and the change amount of the measurement distance.

2. The method of claim 1, wherein the method is characterized by: In the step 1, the calibration includes the curve of the change amount of the output signal modulus of the first eddy current sensor and the second eddy current sensor to the sensing area and the measurement distance.

3. The method of claim 1, wherein the method is characterized by: In the step 2, the first eddy current sensor and the second eddy current sensor are installed on the casing through hole.

4. The method of claim 1, wherein the method is characterized by: The step 2 further comprises: in the static state of the shrouded blade, the measurement distance and the sensing area of the first eddy current sensor and the second eddy current sensor to the blade shroud part of the shrouded blade in the initial measurement state are determined.

5. The method of claim 1, wherein the method is characterized by: In the step 4, the preprocessing of the measurement signals comprises periodic truncation and smoothing filtering of the signals to extract effective signal components.

6. A method of shrouded blade vibration displacement and tip clearance synchronisation decoupling measurement as claimed in claim 1 characterised in that, In the step 5, the measurement signals of the first eddy current sensor and the second eddy current sensor are represented as: wherein, is a component of the measured distance, the sensing area affecting the signal amplitude in the initial measurement state; , are correction functions of the change in the measured distance, the sensing area, respectively, affecting the signal amplitude compared to the initial case.

7. A method of shroud-leaf vibration displacement and tip clearance synchronised decoupling measurement as claimed in claim 6, characterised in that, The step 5 further comprises: Step 5.

1. In the circumferential observation condition, the vibration of the shrouded blade in operation is generated, the first eddy current sensor and the second eddy current sensor measure the change of the signal from the initial measurement condition to the vibration displacement of the blade when the blade crown moves from the static state position to the vibration state position, and the signal modulus of the change is represented as The change of the sensing area is obtained by solving the inverse function .

8. A method of shroud-leaf vibration displacement and tip clearance synchronised decoupling measurement as claimed in claim 7, characterised in that, The step 5 further comprises: Step 5.2, in the tangential observation case, the vibration of the shrouded blade in operation, the first eddy current sensor and the second eddy current sensor measure the change of the signal from the initial measurement to the vibration displacement of the blade, and the signal modulus of the change is represented as The measured distance change is obtained by solving the inverse function .

9. The method of claim 1, wherein the method is a method of shrouded blade vibration displacement and tip clearance synchronisation decoupling measurement. In the step 6, a binary equation is solved by extracting the change amount of the sensing area and the change amount of the measurement distance of the first eddy current sensor and the second eddy current sensor to realize decoupling extraction of the vibration displacement and the tip clearance of the shrouded blade.

10. The method of claim 1, wherein the method is a method of shrouded blade vibration displacement and tip clearance synchronisation decoupling measurement. The method further comprises: Step 7, the blade vibration displacement sequence is processed to realize vibration analysis of the whole blade disc.

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