Zero-intrusive blade tip timing sensing method and measurement system

Abstract

This invention discloses a zero-intervention blade tip timing sensing method and measurement system, belonging to the field of rotating machinery vibration testing technology. The method includes: S1 placing an electromagnetic sensing device on the outside of a metal casing; S2 applying low-frequency AC electromagnetic excitation, utilizing the penetrating power of the low-frequency field to overcome the electromagnetic shielding of the casing; S3 introducing a permanent magnet to form a strong magnetic bias field; S4 the composite magnetic field modulation change caused by the blade sweeping past, transmitted to the outside via the casing's electromagnetic diffusion channel; S5 an externally attached sensing element sensing the magnetic flux change and converting it into an induced voltage signal; and extracting the blade arrival time series through signal processing. This invention eliminates the need for casing openings, meets structural integrity requirements, and possesses advantages such as strong penetration, high sensitivity, and calibrability. It is suitable for blade tip timing measurement and vibration monitoring of high-speed rotating blade systems such as aero-engines and gas turbines.

Description

Technical Field

[0001] This invention belongs to the field of rotating machinery vibration testing and condition monitoring technology, specifically relating to a zero-intervention blade tip timing sensing method and measurement system. Background Technology

[0002] Blade tip timing technology is a non-contact measurement method that obtains the blade's arrival time sequence by sensing the instantaneous event of a rotating blade passing through a sensor, thereby inverting the blade's vibration state.

[0003] Existing blade tip timing sensing methods widely used in engineering mainly include fiber optic and capacitive types. Their common characteristic is the need to create openings in the casing to place the sensor inside the flow channel, forming direct optical or electric field coupling with the blade. However, in aero-engine testing and engineering applications, openings in the casing are generally not permitted. Such openings would compromise the structural integrity of the casing, affecting aerodynamic performance and safety, thus severely limiting the widespread application of traditional blade tip timing technology in engineering.

[0004] Therefore, a new method for achieving blade tip timing sensing without openings or intervention is urgently needed. Without openings, the sensor can only be placed on the outside of the casing, and the blade must indirectly sense events by penetrating the metal casing through an electromagnetic field.

[0005] Because the metal casing has a significant electromagnetic shielding effect, conventional high-frequency electromagnetic or weak magnetic sensing methods are difficult to penetrate effectively. The external signal amplitude is low and the noise is high, making it difficult to form a reliable blade tip timing pulse signal.

[0006] Currently, there is a lack of a zero-intervention leaf-end timing sensing method and measurement system that utilizes the penetrating power of low-frequency electromagnetic fields and combines strong magnetic bias to enhance sensing sensitivity. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to overcome the defects of existing blade tip timing technology, which requires openings in the casing and is difficult to implement in engineering applications. The invention proposes a method that uses a composite electromagnetic field of low-frequency AC excitation and strong magnetic bias to realize blade passage event sensing without openings or intervention, providing a reliable arrival time input for subsequent blade vibration measurement and condition monitoring.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A zero-intervention blade tip timing sensing method, which obtains the arrival time of rotating blades through low-frequency strong magnetic composite electromagnetic sensing without opening holes and while maintaining the structural integrity of the casing, includes the following steps:

[0010] S1, The electromagnetic sensing device is placed on the outside of the metal casing so that it forms an indirect sensing relationship with the area swept by the rotating blades;

[0011] S2, apply low-frequency AC electromagnetic excitation to the electromagnetic sensing device to form a low-frequency electromagnetic field in the casing area, and use the penetration ability of the low-frequency electromagnetic field to overcome the electromagnetic shielding effect of the casing.

[0012] S3, on the basis of the low-frequency electromagnetic field, a permanent magnet or equivalent magnetic source is introduced to form a strong magnetic bias field, so that a composite magnetic field is formed in the local area of ​​the casing, thereby improving the detectability of magnetic field disturbances caused by blade passage events under weak coupling conditions.

[0013] S4, when the rotating blade sweeps across the corresponding area, the blade material and motion state cause modulation changes in the local composite magnetic field and transient changes in magnetic flux. These changes are transmitted to the outside of the casing through the electromagnetic diffusion channel formed by the casing.

[0014] S5, the change in magnetic flux is sensed by an external sensing coil or magnetic sensitive element, and converted into an induced voltage signal corresponding to the blade passage event;

[0015] S6, process the induced voltage signal, extract the blade arrival time sequence, and realize blade tip timing sensing under zero intervention conditions.

[0016] As a preferred embodiment of the above technical solution, the frequency range of the low-frequency AC electromagnetic excitation in step S2 is determined by the skin depth based on the casing material parameters and thickness. To achieve effective penetration of the metal casing, the following was determined: It is the low-frequency AC electromagnetic excitation angular frequency. ; The permeability of the casing; The electrical conductivity of the casing; It is the low-frequency AC electromagnetic excitation frequency.

[0017] As a preferred embodiment of the above technical solution, the strong magnetic bias field in step S3 is generated by a permanent magnet, an excitation coil, or a combination of both, to establish a stable magnetic field operating point on the outside of the casing, forming a composite magnetic field for sensing. .

[0018] As a preferred embodiment of the above technical solution, the external sensing element includes one or more of an induction coil, a magnetoresistive sensor, a Hall sensor, or a fluxgate sensor.

[0019] As a preferred embodiment of the above technical solution, it further includes establishing a physical mapping model between blade passage events, the casing electromagnetic diffusion channel, and external observation signals, wherein the physical mapping model includes at least the following relationships:

[0020] A. The externally observed electrical signal satisfies or is equivalent to satisfying:

[0021] ,

[0022] in Let be the ideal induced voltage corresponding to the blade passage event under casing-less conditions. This represents the impulse response of the electromagnetic diffusion channel in the casing. Noise term;

[0023] B. The ideal induced voltage satisfies or is equivalent to the following:

[0024] ,

[0025] in For the receiving end magnetic flux, The number of turns of the receiving coil. For the receiving end magnetic flux;

[0026] C. Characterization of the magnetic flux mutual inductance: ,in To incentivize and receive equivalent mutual inductance, This refers to the static flux linkage term formed by strong magnetic bias;

[0027] D. The change in mutual inductance of the blade caused by the event satisfies or is equivalent to the following:

[0028] ,

[0029] in The baseline mutual inductance when no blades pass by. The amplitude of the mutual inductance change caused by the event to the blade Let be the normalized time shape function for the events passing through the blade. This represents the time when the blade arrives.

[0030] The complex transfer function of the electromagnetic diffusion channel in the frequency domain satisfies or is equivalent to satisfying:

[0031] ,

[0032] in, The imaginary unit; skin depth , The permeability of the casing, For the casing conductivity, For the thickness of the casing, It is the low-frequency AC electromagnetic excitation angular frequency. , This is the low-frequency AC electromagnetic excitation frequency; and it is used to quantitatively characterize the amplitude attenuation. Phase lag This is used to compensate for or correct for arrival time offsets.

[0033] As a preferred embodiment of the above technical solution, the blade arrival time in step S6 is obtained by analyzing the waveform characteristics of the broadened weak signal, including peak position, zero-crossing point, inflection point, or energy center; or by obtaining it through cross-correlation, satisfying or equivalently satisfying:

[0034] ,

[0035] in, The reference template signal was obtained by calibrating the sampling alignment and the average / median. For the relevant calculation window; This refers to the original induced voltage signal sensed by the sensor on the outside of the casing; For the time coordinates of the sampling system, This represents the time when the blade arrives.

[0036] As a preferred embodiment of the above technical solution, the method is applicable to the timing measurement and vibration monitoring of the blade tips of aero-engines, gas turbines, or other high-speed rotating blade systems.

[0037] On the other hand, the present invention further discloses an blade tip timing measurement system for implementing the zero-intervention blade tip timing sensing method, comprising:

[0038] The strong magnetic bias module is used to generate a strong magnetic bias field on the outside of the metal casing to regulate the magnetic state of a local area of ​​the casing.

[0039] The low-frequency excitation module is used to output a low-frequency AC excitation current or a pulse / encoded excitation dominated by a low-frequency component to form a low-frequency AC magnetic field in a local area of ​​the casing.

[0040] The sensing and receiving module, including a receiving coil or magnetic field sensor, is used to sense the transient magnetic flux caused by the sweeping of the blade and output the observed electrical signal;

[0041] The signal processing module is used to amplify, filter, synchronize demodulate, perform correlation detection, or match filtering on the observed electrical signals.

[0042] The arrival time extraction module is used to determine the time position of the blade passage event based on waveform features or cross-correlation, and output the blade arrival time result.

[0043] The signal processing module is further used to compensate or correct the arrival time offset caused by the phase lag introduced by the casing, based on the complex transfer function of the casing's electromagnetic diffusion channel.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] (1) Achieve zero openings and maintain structural integrity

[0046] This invention places the electromagnetic sensing device entirely on the outside of the metal casing, eliminating the need for any mounting holes or structural modifications on the casing. This completely avoids the damage to the casing's structural integrity, aerodynamic performance, and safety caused by traditional blade tip timing technology, and meets the stringent requirements for structural integrity in aero-engine testing and engineering applications.

[0047] (2) Low-frequency strong magnetic composite, achieving strong penetration and high sensitivity.

[0048] By utilizing low-frequency AC electromagnetic excitation and the strong penetrating power of the low-frequency electromagnetic field through the metal casing, the electromagnetic shielding effect of the casing is effectively overcome, achieving stable diffusion of the electromagnetic field from the outside to the inside of the casing. Based on this, a permanent magnet or equivalent magnetic source is introduced to form a strong magnetic bias field, significantly improving the detectability of magnetic field disturbances caused by blade passage events under weak coupling conditions. This composite design of low frequency and strong magnetism fundamentally solves the problem of "weak signal and high noise" in external sensing.

[0049] 3) Establish a physical mapping model to achieve signal interpretability and time offset correction.

[0050] For the first time, a physical mapping model of "blade passage event - casing electromagnetic diffusion channel - external observation signal" was established, and the complex transfer function of the casing channel was explicitly given. The quantitative relationship between the model and material parameters (electrical conductivity, magnetic permeability, thickness) can be established. Based on this model, the amplitude attenuation introduced by the casing can be accurately characterized. Phase lag This allows for effective compensation or correction of arrival time offsets, significantly improving measurement accuracy.

[0051] (4) Multi-mode signal processing to ensure robust time extraction under low signal-to-noise ratio.

[0052] To address the signal broadening and amplitude attenuation caused by casing diffusion, a dual-mode time-of-arrival (TOA) extraction method is supported, based on waveform characteristics (peaks, inflection points, energy centers) and cross-correlation / matched filtering. By constructing a reference template signal and performing cross-correlation peak localization, the TOA can be stably extracted under extremely low signal-to-noise ratio conditions, exhibiting excellent noise immunity.

[0053] (5) It has strong applicability and supports engineering applications.

[0054] This invention is applicable to various metal casing materials such as titanium alloy and high-temperature alloy, and is compatible with various sensing elements such as induction coil, magnetoresistive sensor, Hall sensor, and fluxgate sensor. It can be flexibly adapted to the blade tip timing measurement and vibration monitoring needs of aero engines, gas turbines and other high-speed rotating blades, and has good engineering promotion value. Attached Figure Description

[0055] Figure 1 A flowchart illustrating the zero-intervention leaf tip timing sensing method provided in an embodiment of the present invention;

[0056] Figure 2 A schematic diagram of a measurement system based on zero-intervention leaf tip timing sensing provided in an embodiment of the present invention;

[0057] Figure 3 A schematic diagram illustrating the principle of low-frequency strong magnetic composite zero-intervention leaf-end timing sensing provided in an embodiment of the present invention;

[0058] Among them, 1. Eddy current coil; 2. Permanent magnet; 3. Thin-walled metal casing; 4. Rotor blade; 5. Alternating magnetic field; 6. Static magnetic field; 7. Blade arrival pulse; 8. Low-frequency AC excitation;

[0059] Figure 4 A schematic diagram of the pulse signal obtained by the zero-intervention blade tip timing sensing in an embodiment of the present invention;

[0060] Figure 5 A three-dimensional electromagnetic simulation model of the casing, blades, outer excitation / receiving coils, and permanent magnet bias is established for the embodiments of the present invention.

[0061] Figure 6 The interface diagram for setting and developing simulation model parameters;

[0062] Figure 7 This is a top view of the simulation geometric model;

[0063] Figure 8 This is a comparison diagram of the induced voltage waveforms with and without strong magnetic bias. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0066] To clearly understand the technical solution of this invention, the core terms used therein are defined as follows:

[0067] Electromagnetic diffusion path: refers to the equivalent transmission path of low-frequency electromagnetic waves as they pass through a conductive metal casing, where amplitude attenuation and phase lag occur due to eddy current effects. The characteristics of this path are determined by the conductivity, permeability, and thickness of the casing material, and can be quantitatively characterized using a complex transfer function.

[0068] Composite magnetic field: refers to the combined magnetic field formed by the superposition of a low-frequency AC excitation magnetic field and a strong magnetic bias magnetic field in a local area of ​​the casing, denoted as... .in, It is a strong magnetic bias field (usually generated by a permanent magnet). This represents the amplitude of a low-frequency alternating magnetic field.

[0069] Physical mapping model: refers to a mathematical model that describes the quantitative relationship between "blade passage event → casing electromagnetic diffusion → external observation signal", including the complex transfer function of the casing, mutual inductance change function, etc., and is used to realize the interpretability of the signal and time offset correction.

[0070] like Figure 1 As shown, a zero-intervention blade tip timing sensing method acquires the arrival time of rotating blades through low-frequency strong magnetic composite electromagnetic sensing without opening holes and while maintaining the structural integrity of the casing. The method includes the following steps:

[0071] S1, The electromagnetic sensing device is placed on the outside of the metal casing so that it forms an indirect sensing relationship with the area swept by the rotating blades;

[0072] S2, apply low-frequency AC electromagnetic excitation to the electromagnetic sensing device to form a low-frequency electromagnetic field in the casing area, wherein the low-frequency excitation current satisfies or is equivalent to satisfying ,in , To achieve the excitation frequency, the electromagnetic shielding effect of the casing is overcome by utilizing the penetrating power of low-frequency electromagnetic fields through the metal casing.

[0073] S3, based on the low-frequency alternating magnetic field, a permanent magnet or equivalent magnetic source is introduced to form a strong magnetic bias field, causing a composite magnetic field to form in a local area of ​​the casing. The composite magnetic field satisfies or is equivalent to satisfying To improve the detectability of magnetic field disturbances caused by blade passage events under weak coupling conditions;

[0074] S4, when the rotating blade sweeps across the corresponding area, the blade material and motion state cause modulation changes in the local composite magnetic field and transient changes in magnetic flux. These changes are transmitted to the outside of the casing through the electromagnetic diffusion channel formed by the casing.

[0075] S5, the change in magnetic flux is sensed by an external sensing coil or magnetic sensitive element, and converted into an induced voltage signal corresponding to the blade passage event;

[0076] S6, process the induced voltage signal, extract the blade arrival time sequence, and realize blade tip timing sensing under zero intervention conditions.

[0077] This invention places the electromagnetic sensing device entirely on the outside of the metal casing, eliminating the need for any mounting holes or structural modifications on the casing. This completely avoids the damage to the casing's structural integrity, aerodynamic performance, and safety caused by traditional blade tip timing technology, and meets the stringent requirements for structural integrity in aero-engine testing and engineering applications.

[0078] In the method described, the frequency range of the low-frequency AC electromagnetic excitation is a low-frequency band that can effectively penetrate the metal casing, and the frequency band is determined based on the casing material parameters and thickness. Through skin depth To achieve effective penetration of the metal casing, the following was determined: It is the low-frequency AC electromagnetic excitation angular frequency. ; The permeability of the casing; The electrical conductivity of the casing; This refers to the low-frequency AC electromagnetic excitation frequency. For example, a titanium alloy casing has an electrical conductivity of 1.7 × 10⁶ s / m and a magnetic permeability of 1.2566 × 10⁻⁶, with an excitation frequency of 5 kHz. Substituting this into the formula, it is approximately equal to 5.45 mm.

[0079] By utilizing low-frequency AC electromagnetic excitation and the strong penetrating power of the low-frequency electromagnetic field through the metal casing, the electromagnetic shielding effect of the casing is effectively overcome, achieving stable diffusion of the electromagnetic field from the outside to the inside of the casing. Based on this, a permanent magnet or equivalent magnetic source is introduced to form a strong magnetic bias field, significantly improving the detectability of magnetic field disturbances caused by blade passage events under weak coupling conditions. This composite design of low frequency and strong magnetism fundamentally solves the problem of "weak signal and high noise" in external sensing.

[0080] Preferably, the strong magnetic bias field is generated by a permanent magnet, an excitation coil, or a combination of both, and is used to establish a stable magnetic field operating point on the outside of the casing.

[0081] Preferably, the metal casing is a titanium alloy casing, a high-temperature alloy casing, or other conductive metal casing.

[0082] Preferably, the external sensing element includes one or more of an induction coil, a magnetoresistive sensor, a Hall sensor, or a fluxgate sensor. Differentiated selection is made based on specific operating conditions: for high-speed rotation scenarios with rotation speeds greater than 10000 RPM, an induction coil is used to obtain a high-amplitude voltage signal using a high flux change rate; for thick-walled casings or high-shielding materials with a thickness greater than 5 mm, the high sensitivity of a magnetoresistive sensor compensates for signal attenuation; for strong magnetic bias field environments greater than 0.5 T, the wide linear region and non-saturation characteristics of a Hall sensor ensure signal integrity; for deep penetration requirements caused by extremely low-frequency excitations less than 100 Hz, the extremely high static magnetic field resolution of a fluxgate sensor stably extracts weak fundamental magnetic field modulation features.

[0083] In the method described above, the external observation signal transmitted through the electromagnetic diffusion channel of the casing exhibits amplitude attenuation and time-domain bandwidth characteristics.

[0084] The blade arrival time is obtained by analyzing the waveform characteristics of the broadened weak signal, including peak position, zero crossover point, inflection point or energy center.

[0085] The method further includes establishing a physical mapping model between blade passage events, the casing electromagnetic diffusion channel, and external observation signals. This physical mapping model includes at least the following relationships:

[0086] (1) The externally observed electrical signal satisfies or is equivalent to satisfying ,in Let be the ideal induced voltage corresponding to the blade passage event under casing-less conditions. This represents the impulse response of the electromagnetic diffusion channel in the casing. Noise term;

[0087] (2) The ideal induced voltage satisfies or is equivalent to satisfy ,in For the receiving end magnetic flux, The number of turns of the receiving coil. For the receiving end magnetic flux;

[0088] (3) Characterization of the magnetic flux mutual inductance: ,in To incentivize and receive equivalent mutual inductance, This refers to the static flux linkage term formed by strong magnetic bias;

[0089] (4) The blades satisfy or are equivalent to satisfy the mutual inductance changes caused by the event. ,in, The baseline mutual inductance when no blades pass through; The amplitude of the mutual inductance change in the blade caused by the event; The normalized time shape function for the events passing through the blade; For the time of leaf arrival, This represents the time coordinate of the sampling system.

[0090] (5) The arrival time of the blades is obtained through cross-correlation, and satisfies or is equivalent to satisfying ,in The reference template signal was obtained by calibrating the sampling alignment and the average / median. For the relevant calculation window; This refers to the original induced voltage signal sensed by the sensor on the outside of the casing; For the time coordinates of the sampling system, This represents the time when the blade arrives.

[0091] Step 1: Parameter Initialization and Skin Depth Calculation

[0092] Based on the casing material parameters and thickness Through skin depth To achieve effective penetration of the metal casing, the following was determined: It is the low-frequency AC electromagnetic excitation angular frequency. ; The permeability of the casing; The electrical conductivity of the casing; It is the low-frequency AC electromagnetic excitation frequency.

[0093] Step 2: Establish the casing diffusion channel model

[0094] Give the complex transfer function of the casing channel. ;

[0095] This formula originates from the solution of the diffusion equation for the propagation of harmonic electromagnetic waves in a good conductor in classical electromagnetism. When a low-frequency electromagnetic field passes through a conductive metal casing, the electromagnetic energy attenuates and lags due to the eddy current effect. This physical process is abstracted as an "electromagnetic diffusion channel," and the complex transfer function is used to quantitatively characterize the influence of the casing material properties on the signal.

[0096] Step 3: Calculate the phase lag and theoretical offset

[0097] This model can accurately characterize the amplitude attenuation introduced by the casing. Phase lag .

[0098] Step 4: Extract the original observation time

[0099] For induced voltage signal Perform correlation detection or matched filtering using the reference template signal. Perform relevant calculations , obtained It is the "performance arrival time" that includes the casing delay effect.

[0100] Step 5: Perform time offset compensation

[0101] Using the physical correction factor calculated in the third step, the actual blade arrival time is inverted. , This compensation step eliminates systematic errors introduced by casing material and thickness, outputting a high-precision blade arrival time series.

[0102] In the method described, the complex transfer function of the electromagnetic diffusion channel of the casing in the frequency domain satisfies or is equivalent to satisfying ,in, The imaginary unit; skin depth , The permeability of the casing, For the casing conductivity, For the thickness of the casing, It is the low-frequency AC electromagnetic excitation angular frequency. , It is the low-frequency AC electromagnetic excitation frequency.

[0103] This is used to quantitatively characterize amplitude decay. Phase lag It is used to compensate for or correct for arrival time offset.

[0104] This invention is the first to systematically establish a physical mapping model of "blade passage event - casing electromagnetic diffusion channel - external observation signal", and explicitly gives the complex transfer function of the casing channel. The quantitative relationship between this model and material parameters (electrical conductivity, magnetic permeability, thickness) can be established. Based on this model, the amplitude attenuation introduced by the casing can be accurately characterized.

[0105] Phase lag This allows for effective compensation or correction of arrival time offsets, significantly improving measurement accuracy.

[0106] To address the signal broadening and amplitude attenuation caused by casing diffusion, a dual-mode time-of-arrival (TOA) extraction method is supported, based on waveform characteristics (peaks, inflection points, energy centers) and cross-correlation / matched filtering. By constructing a reference template signal and performing cross-correlation peak localization, the TOA can be stably extracted under extremely low signal-to-noise ratio conditions, exhibiting excellent noise immunity.

[0107] The method described herein is applicable to timing measurement and vibration monitoring of blade tips in aero-engines, gas turbines, or other high-speed rotating blade systems. This invention is applicable to various metal casing materials such as titanium alloys and high-temperature alloys, and is compatible with various sensing elements such as induction coils, magnetoresistive sensors, Hall effect sensors, and fluxgate sensors. It can flexibly adapt to the timing measurement and vibration monitoring needs of blade tips in aero-engines, gas turbines, and other high-speed rotating blades, and has significant engineering application value.

[0108] The present invention also provides a zero-intervention blade tip timing measurement system for implementing the above method, comprising:

[0109] A strong magnetic bias module is used to generate a strong magnetic bias field on the outside of the metal casing. The strong magnetic bias module can be composed of one or more neodymium iron boron permanent magnets and is placed inside the sensor housing, behind the coil.

[0110] The low-frequency excitation module is used to output low-frequency AC excitation current. To create a low-frequency alternating magnetic field in a localized area of ​​the casing;

[0111] The sensing and receiving module, including a receiving coil or magnetic field sensor, is used to sense the transient magnetic flux caused by the sweeping of the blades and output the observed electrical signal. ;

[0112] The signal processing module is used to amplify, filter, and perform correlation detection or matched filtering on the observed electrical signals.

[0113] Arrival time extraction module, used for based on Determine the time and location of the blade passage event and output the blade arrival time result.

[0114] Example:

[0115] This embodiment establishes a three-dimensional electromagnetic simulation model of the casing, blades, external excitation / receiving coils, and permanent magnet bias. The casing is a thick-walled metal cylinder (5 mm thick). Permanent magnets are arranged on the outside of the casing to provide strong magnetic bias, and a 500 Hz low-frequency AC excitation is applied. The blades sweeping across the measurement area are simulated by motion scanning to obtain the induced voltage signal of the receiving coil.

[0116] Simulation environment: COMSOL 6.2;

[0117] Coil position: The excitation coil is wound around the outside of the permanent magnet or close to the bottom of the permanent magnet (near the casing side).

[0118] Coil dimensions: Inner diameter: 2.5mm; Outer diameter: 5-8mm; Height: 4-6mm; Number of coil turns: 200-500 turns.

[0119] like Figures 5-7Simulation results show that with a strong magnetic bias, the magnetic flux transient event caused by the blade sweep is more clearly discernible. Without a strong magnetic bias, the magnetic field disturbance signal generated by the blade is extremely weak and submerged in background noise. After applying a 1.2T strong magnetic bias field, the amplitude of the magnetic flux density transient generated by the blade sweep is significantly increased to approximately 8.5mT, resulting in a sensor output signal-to-noise ratio better than 35dB. Processing the simulation signal using a cross-correlation peak localization algorithm shows that the standard deviation of the blade arrival time extraction is less than 0.1 microseconds.

[0120] The arrival time of the blade can be stably extracted by using cross-correlation peak location.

[0121] Finally, it should be noted that the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0122] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A zero-intervention leaf tip timing sensing method, characterized in that, Without opening any holes and maintaining the structural integrity of the casing, the arrival time of the rotating blades is obtained through low-frequency strong magnetic composite electromagnetic sensing. The method includes the following steps: S1, The electromagnetic sensing device is placed on the outside of the metal casing so that it forms an indirect sensing relationship with the area swept by the rotating blades; S2, apply low-frequency AC electromagnetic excitation to the electromagnetic sensing device to form a low-frequency electromagnetic field in the casing area, and use the penetration ability of the low-frequency electromagnetic field to overcome the electromagnetic shielding effect of the casing. S3, on the basis of the low-frequency electromagnetic field, a permanent magnet or equivalent magnetic source is introduced to form a strong magnetic bias field, so that a composite magnetic field is formed in the local area of ​​the casing, thereby improving the detectability of magnetic field disturbances caused by blade passage events under weak coupling conditions. S4, when the rotating blade sweeps across the corresponding area, the blade material and motion state cause modulation changes in the local composite magnetic field and transient changes in magnetic flux. These changes are transmitted to the outside of the casing through the electromagnetic diffusion channel formed by the casing. S5, the change in magnetic flux is sensed by an external sensing coil or magnetic sensitive element, and converted into an induced voltage signal corresponding to the blade passage event; S6, process the induced voltage signal, extract the blade arrival time sequence, and realize blade tip timing sensing under zero intervention conditions.

2. The zero-intervention leaf tip timing sensing method according to claim 1, characterized in that, The frequency range of the low-frequency AC electromagnetic excitation in step S2 is determined by the skin depth based on the casing material parameters and thickness. To achieve effective penetration of the metal casing, the following was determined: It is the low-frequency AC electromagnetic excitation angular frequency. , This is the low-frequency AC electromagnetic excitation frequency; The permeability of the casing; The conductivity of the casing.

3. The zero-intervention leaf tip timing sensing method according to claim 1, characterized in that, The strong magnetic bias field in step S3 is generated by a permanent magnet, an excitation coil, or a combination of both, and is used to establish a stable magnetic field operating point on the outside of the casing, forming a composite magnetic field for sensing. ,in It is a local composite magnetic field. It is a strong magnetic bias field. The amplitude of the low-frequency alternating magnetic field. It is the low-frequency AC electromagnetic excitation angular frequency. For time.

4. The zero-intervention leaf-tip timing sensing method according to claim 1, characterized in that, The external sensing element includes one or more of an induction coil, a magnetoresistive sensor, a Hall sensor, or a fluxgate sensor.

5. The zero-intervention leaf tip timing sensing method according to claim 1, characterized in that, It also includes establishing a physical mapping model between blade passage events, the casing electromagnetic diffusion channel, and external observation signals, wherein the physical mapping model includes at least the following relationships: (1) The externally observed electrical signal satisfies or is equivalent to satisfying: ， in Let be the ideal induced voltage corresponding to the blade passage event under casing-less conditions. This represents the impulse response of the electromagnetic diffusion channel in the casing. Noise term; (2) The ideal induced voltage satisfies or is equivalent to satisfying: ， ， in For the receiving end magnetic flux, The number of turns of the receiving coil. For the receiving end magnetic flux; (3) Characterization of magnetic flux mutual inductance: ,in To incentivize and receive equivalent mutual inductance, For low-frequency excitation current, This refers to the static flux linkage term formed by strong magnetic bias; (4) The mutual inductance changes caused by the event by the blade satisfy or are equivalent to satisfy: ， in The baseline mutual inductance when no blades pass by. The magnitude of the mutual inductance change caused by the event affecting the blade. Let be the normalized time shape function for the events passing through the blade. For the time coordinates of the sampling system, This represents the time when the blade arrives.

6. The zero-intervention leaf tip timing sensing method according to claim 5, characterized in that, The complex transfer function of the electromagnetic diffusion channel in the frequency domain satisfies or is equivalent to satisfying: ， in, The imaginary unit; skin depth , The permeability of the casing, For the casing conductivity, For the thickness of the casing, It is the low-frequency AC electromagnetic excitation angular frequency. , This is the low-frequency AC electromagnetic excitation frequency; and it is used to quantitatively characterize the amplitude attenuation. Phase lag This is used to compensate for or correct for arrival time offsets.

7. The zero-intervention leaf tip timing sensing method according to claim 1 or 5, characterized in that, The blade arrival time in step S6 is obtained by analyzing the waveform characteristics of the broadened weak signal, including peak position, zero-crossing point, inflection point, or energy center; or by obtaining a satisfying or equivalent satisfying condition through cross-correlation. ， in, The reference template signal was obtained by calibrating the sampling alignment and the average / median. For the relevant calculation window; This refers to the original induced voltage signal sensed by the sensor on the outside of the casing; For the time coordinates of the sampling system, This represents the time when the blade arrives.

8. The zero-intervention leaf tip timing sensing method according to claim 1, characterized in that, The method is applicable to the timing measurement and vibration monitoring of blade tips in aero-engines, gas turbines, or other high-speed rotating blade systems.

9. A blade tip timing measurement system for implementing the zero-intervention blade tip timing sensing method according to any one of claims 1 to 8, characterized in that, include: The strong magnetic bias module is used to generate a strong magnetic bias field on the outside of the metal casing to regulate the magnetic state of a local area of ​​the casing. The low-frequency excitation module is used to output a low-frequency AC excitation current or a pulse / encoded excitation dominated by a low-frequency component to form a low-frequency AC magnetic field in a local area of ​​the casing. The sensing and receiving module, including a receiving coil or magnetic field sensor, is used to sense the transient magnetic flux caused by the sweeping of the blade and output the observed electrical signal; The signal processing module is used to amplify, filter, synchronize demodulate, perform correlation detection, or match filtering on the observed electrical signals. The arrival time extraction module is used to determine the time position of the blade passage event based on waveform features or cross-correlation, and output the blade arrival time result.

10. The blade tip timing measurement system according to claim 9, characterized in that, The signal processing module is further used to compensate or correct the arrival time offset caused by the phase lag introduced by the casing, based on the complex transfer function of the casing's electromagnetic diffusion channel.

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