High-temperature-resistant through-shell eddy current tip clearance measurement device and method

Abstract

The application discloses to belong to the technical field of clearance measurement, and particularly relates to a high-temperature-resistant shell-penetrating eddy current blade tip clearance measuring device and method, the device comprises: a sensor probe module, a signal conditioning module, a data acquisition module and a data processing module; the sensor probe module is installed on the outer wall of the casing; the sensor probe module comprises: a permanent magnet excitation source, a soft magnetic core and a receiving coil; the signal conditioning module is electrically connected with the receiving coil, amplifies, filters and integrates the weak induction signal; the data acquisition module is electrically connected with the signal conditioning module, converts the analog signal into a digital signal; and the data processing module processes the collected digital signal and extracts the blade tip clearance information.

Description

Technical Field

[0001] This invention belongs to the field of gap measurement technology, and specifically relates to a high-temperature resistant through-shell type eddy current blade tip gap measurement device and method. Background Technology

[0002] Tip clearance refers to the radial clearance between the tip of a turbine blade and the inner wall of the casing in an aero-engine, and it is a critical parameter affecting engine performance, efficiency, and reliability. Excessive tip clearance can lead to airflow leakage, reducing engine efficiency and thrust; insufficient tip clearance can cause blade rubbing against the casing, resulting in blade damage or even catastrophic failure. Studies show that for every 0.25 mm increase in tip clearance, engine efficiency decreases by approximately 1%, and fuel consumption increases by approximately 1.5%. Therefore, accurate measurement of tip clearance is of great significance for engine performance optimization, condition monitoring, and fault diagnosis.

[0003] Existing technologies for blade tip clearance measurement mainly include: capacitive measurement methods: These methods utilize the principle that the capacitance formed between the blade and the sensor changes with the clearance. This requires drilling holes in the casing to install the sensor, which compromises the casing's structural integrity and is significantly affected by temperature and oil contamination. Fiber optic measurement methods: These methods use a fiber optic probe to emit a beam of light onto the blade and calculate the clearance based on the intensity of the reflected light or the flight time. However, the optical window is easily contaminated, and reliability is poor under high temperature, high speed, and vibration conditions. Microwave / millimeter-wave measurement methods: These methods utilize the principle of electromagnetic wave reflection to measure the clearance. These systems are complex, costly, and have low spatial resolution. Traditional eddy current measurement methods: These methods install eddy current sensors on the inner wall of the casing to directly measure the blade tip clearance. However, because the eddy current sensors are exposed to harsh environments with high temperature and high pressure, their lifespan is short and maintenance is difficult.

[0004] The common drawbacks of the aforementioned existing technologies are: they all require drilling holes or slots in the casing to install the sensor, which compromises the structural integrity and aerodynamic sealing of the casing; they increase installation difficulty and maintenance costs; and installing sensors inside the casing exposes them to extreme working environments such as high temperatures (600-1000℃), high pressure, high-speed airflow, and strong vibration, making it difficult to guarantee sensor reliability and lifespan. Therefore, there is an urgent need for a high-temperature resistant, through-shell eddy current blade tip clearance measurement device and method to solve the technical problems of requiring holes in the casing, harsh sensor working environments, and poor reliability. Summary of the Invention

[0005] The purpose of this invention is to provide a through-shell type eddy current blade tip clearance measuring device and method to solve the problems in the prior art, such as the need for opening holes in the casing, harsh working environment of the sensor, and poor reliability, so as to achieve non-contact, through-shell, high-precision, and high-reliability blade tip clearance measurement.

[0006] The purpose of this invention is to provide a high-temperature resistant through-shell eddy current blade tip clearance measuring device, comprising: a sensor probe module, a signal conditioning module, a data acquisition module, and a data processing module;

[0007] The sensor probe module is mounted on the outer wall of the casing; the casing is made of non-magnetic material; the sensor probe module includes: a permanent magnet excitation source, a soft magnet core, and a receiving coil; the permanent magnet excitation source generates a constant static magnetic field, and the magnetic lines of force pass through the casing wall to reach the rotating blade area; the soft magnet core is set in the direction of magnetic field radiation of the permanent magnet excitation source, and is set separately from the permanent magnet excitation source, used to guide the magnetic field and serve as the core of the receiving coil; the receiving coil is used to sense a secondary magnetic field and generate an induced voltage;

[0008] The signal conditioning module is electrically connected to the receiving coil to amplify, filter, and integrate weak induced signals; the data acquisition module is electrically connected to the signal conditioning module to convert analog signals into digital signals; and the data processing module processes the acquired digital signals to extract blade tip clearance information.

[0009] The permanent magnet excitation source adopts a samarium cobalt permanent magnet or a neodymium iron boron permanent magnet, which is cylindrical in shape and magnetized in the axial direction. The magnetic induction intensity of the permanent magnet excitation source is 200-500mT.

[0010] The soft magnetic core is made of permalloy or ferrite material, with a relative permeability of μr≥10,000 and a temperature resistance of ≥350℃.

[0011] The receiving coil is made of enameled copper wire wound on a soft magnetic core. The diameter of the enameled copper wire is 0.1-0.3mm, the number of turns is 500-3000, the inductance is 50-200mH, and the DC resistance is 200-800Ω.

[0012] The sensor probe module also includes: a cooling system and a shielding device;

[0013] The cooling system adopts an air cooling method, using compressed air to cool the soft magnetic core and the receiving coil; the shielding device includes: a stainless steel shell to encapsulate the sensor probe module and an electromagnetic shielding layer to reduce external electromagnetic interference; and signal output is achieved using twisted-pair or coaxial cable.

[0014] The signal conditioning module includes a preamplifier, a bandpass filter, and an integrator circuit. The signal conditioning module is electrically connected to the receiving coil and amplifies, filters, and integrates the weak induced signal.

[0015] The preamplifier uses a high-performance instrumentation amplifier chip to amplify the weak mV-level signal output from the receiving coil to the 0.1-5V range.

[0016] The bandpass filter is a second-order Butterworth active filter with a passband range of 100Hz-300kHz and a filter gain of 20dB.

[0017] The integrator circuit uses an RC active integrator.

[0018] The data acquisition module includes a high-speed analog-to-digital converter and a data buffer and communication interface. The data acquisition module is electrically connected to the signal conditioning module to convert analog signals into digital signals.

[0019] The high-speed analog-to-digital converter adopts a continuous sampling mode to continuously acquire the integrated Gaussian signal waveform data;

[0020] The data buffer and communication interface uses an FPGA or high-performance MCU for data buffering and preprocessing, and transmits digital signals to the host computer via an Ethernet interface;

[0021] The data acquisition module uses the UDP protocol for data packaging.

[0022] The data processing module includes:

[0023] Gaussian peak detection unit: performs threshold judgment on the acquired digital signal to identify the peak position of the Gaussian waveform, and each peak corresponds to a blade passage event;

[0024] Gaussian fitting unit: Extracts the waveform data segment around each detected peak, performs Gaussian function fitting, and extracts the amplitude parameter after fitting as the input for gap calculation;

[0025] Rotational speed calculation unit: Calculates rotational speed based on the time interval between two adjacent blades passing by and the number of blades;

[0026] Clearance calculation unit: Based on the amplitude obtained from Gaussian fitting and the rotational speed calculated from the rotational speed, the blade tip clearance is calculated through a pre-calibrated mapping relationship; the clearance calculation adopts the bilinear interpolation method to establish a three-dimensional calibration table of rotational speed-amplitude-clearance;

[0027] Data output and display unit: Outputs the clearance value, rotational speed, and timestamp of each blade in real time, displaying them in the form of numerical values, waveforms, and trend curves, and records and stores the data.

[0028] Another object of the present invention is to improve the high-temperature resistant through-shell eddy current blade tip clearance measurement method of the high-temperature resistant through-shell eddy current blade tip clearance measurement device according to the present invention, comprising the following steps:

[0029] A calibration system for the casing and rotating blades was built, and the amplitude of the Gaussian signal output by the sensor under different rotational speeds and clearances was collected. Based on the amplitude of the Gaussian signal, a mapping relationship between rotational speed, amplitude, and clearance was established.

[0030] The sensor probe module is installed on the outer wall of the casing. The signal conditioning module continuously acquires the Gaussian signal after amplification, filtering and integration. The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream.

[0031] The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and uses the rotational speed-amplitude-gap mapping relationship to solve the tip clearance and output the measurement results.

[0032] The casing and rotating blade calibration system includes: a high-speed rotary table, a precision displacement stage, and a simulated casing; the high-speed rotary table has a rotational speed range of 0-30,000 rpm and a rotational speed accuracy of ±0.1%; the precision displacement stage has a stroke ≥10 mm and a positioning accuracy ≤5 μm; the simulated casing is made of the same material as the actual casing, with a thickness of 3-8 mm.

[0033] The steps for assembling the casing and rotating blade calibration system include:

[0034] Select blade simulation components to be installed on a high-speed rotating table, with 6-12 blades, and the material is titanium alloy or stainless steel;

[0035] Multiple speed points can be set, covering the actual working range of 0-30,000 rpm;

[0036] Set multiple gap points, with the gap range covering the measurement range of 0.5-5mm;

[0037] The amplitude of the Gaussian signal output by the sensor under different rotational speeds and different gaps includes:

[0038] For each speed-clearance combination, perform the following operations:

[0039] Set the rotary table speed to ni and wait for the first preset time.

[0040] The precision displacement stage moves to the gap position dj and waits for the second preset time.

[0041] Repeat the measurement a first preset number of times, and each time collect a first preset number of blade passage events and record the corresponding Gaussian signal amplitude;

[0042] The establishment of the rotational speed-amplitude-gap mapping relationship based on the Gaussian signal amplitude includes:

[0043] Establish a three-dimensional mapping table of rotational speed, amplitude, and clearance, and store all calibration data points;

[0044] Calibration and verification: Select 5-10 intermediate points that were not involved in the calibration, perform actual measurements and compare them with the theoretical values, and require the error to be correct;

[0045] Obtain the calculated mean amplitude and standard deviation.

[0046] The sensor probe module is mounted on the outer wall of the casing, and the signal conditioning module continuously acquires the amplified, filtered, and integrated Gaussian signal; the data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream, including:

[0047] Install the sensor probe module on the outer wall of the casing, ensuring that the front end of the probe is in close contact with the casing wall, the probe axis is perpendicular to the casing wall, and aligned with the area swept by the blade;

[0048] Start the signal conditioning module, set the ADC sampling rate to ≥1MSPS, and the sampling mode to continuous sampling;

[0049] The signal conditioning module continuously acquires the induced signal output by the receiving coil. The signal is processed by a preamplifier, a bandpass filter, and an integrator circuit to obtain a Gaussian signal. The gain of the preamplifier is 40-60dB. The frequency of the bandpass filter is 100Hz-300kHz. The time constant of the integrator circuit is 5-10μs.

[0050] The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream, which is then buffered by the FPGA / MCU and transmitted to the data processing module.

[0051] The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and calculates the tip clearance using the rotational speed-amplitude-clearance mapping relationship, outputting the measurement results including:

[0052] The data processing module receives real-time digital signal streams and processes them in real time; first, it performs digital filtering to remove high-frequency noise.

[0053] The acquired digital signals are thresholded to detect the Gaussian peak position. The threshold is set using the 3σ criterion. When the signal amplitude exceeds the threshold and meets the local maximum condition, it is determined to be a valid Gaussian peak, and the peak index and timestamp are recorded.

[0054] Extract a single Gaussian waveform data segment corresponding to each peak, and collect a preset second threshold of sampling points;

[0055] Gaussian function fitting for a single Gaussian waveform: nonlinear least squares method is used for fitting, and amplitude parameters, peak center, and width are extracted after fitting;

[0056] Calculate the goodness of fit R 2 ;

[0057] The rotational speed is calculated based on the time interval between two adjacent peak values ​​and the number of blades.

[0058] Substitute the amplitude and rotational speed into the calibration relationship to calculate the blade tip clearance: Use bilinear interpolation method, find four adjacent points according to the calibration table, and calculate the blade tip clearance according to the interpolation formula.

[0059] Output measurement results, including: blade number, tip clearance, rotational speed, timestamp, and goodness-of-fit R-value. 2 ;

[0060] Statistical analysis was performed on the gap values ​​of multiple blades in each revolution, and the mean and standard deviation were calculated. Outliers exceeding the range of ±3σ were removed.

[0061] Real-time display of measurement results, including: Numerical display: current rotational speed, clearance values ​​for each blade; Waveform display: original signal waveform, integrated Gaussian signal waveform, fitted curve; Trend curve: clearance variation trend over time or rotational speed; Alarms triggered according to preset alarm rules;

[0062] Record and store all measurement data for subsequent fault diagnosis, life prediction and performance evaluation.

[0063] The beneficial effects of this invention are as follows:

[0064] (1) Non-contact measurement through the casing, maintaining the structural integrity of the casing.

[0065] The sensor is mounted on the outer wall of the casing, eliminating the need for holes or slots in the casing. This maintains the structural integrity and aerodynamic sealing of the casing and avoids the weakening of strength and airflow leakage problems caused by openings.

[0066] (2) The sensor is environmentally friendly and has high reliability.

[0067] The sensor is located on the outer wall of the casing and is not directly exposed to the harsh environment of high temperature (600-1000℃), high pressure, and high-speed airflow. Its operating temperature is relatively low (<200℃, and can adapt to higher temperatures with the help of a cooling system), which greatly improves the reliability and service life of the sensor.

[0068] (3) Permanent magnet excitation source is used, eliminating the need for excitation circuit.

[0069] Using permanent magnet 1 as the static magnetic field source eliminates the need for AC excitation circuits, simplifying the system structure, reducing power consumption, and improving reliability. The permanent magnet's magnetic field is stable and unaffected by temperature and time (the temperature coefficient of samarium cobalt permanent magnets is <0.04% / ℃).

[0070] (4) Soft magnetic core focuses magnetic field to improve sensitivity

[0071] The use of a high-permeability soft magnetic core (μr≥10,000) effectively focuses the magnetic field, improves the magnetic flux density and signal induction intensity, compensates for the signal attenuation caused by through-shell measurement, and improves the measurement sensitivity and signal-to-noise ratio.

[0072] (5) Air cooling system, adapted to high temperature environment

[0073] An air-cooled system was designed to cool the soft magnetic core and receiving coil with compressed air, enabling the sensor to maintain a reasonable operating temperature even at 200°C on the outer wall of the casing. Under air-cooled conditions, it can adapt to high-temperature environments up to 650°C, thus expanding its application range.

[0074] (6) Gaussian fitting algorithm to improve measurement accuracy

[0075] A Gaussian curve fitting algorithm is used to extract signal amplitude. Compared with simple peak detection, the fitting algorithm has the advantages of strong noise resistance and high accuracy. Data quality is evaluated by goodness-of-fit (R²), and outliers are automatically removed, thus improving measurement reliability.

[0076] (7) Speed ​​decoupling calibration to achieve accurate measurement

[0077] By establishing a three-dimensional mapping relationship between rotational speed, amplitude, and clearance, the coupling problem of the inductive signal being simultaneously affected by rotational speed and clearance is solved. Real-time measurement of rotational speed combined with signal amplitude allows for accurate calculation of the blade tip clearance, avoiding the influence of rotational speed variations on the measurement results.

[0078] (8) High bandwidth, high precision, and wide measurement range

[0079] With a system bandwidth of >300kHz, it can adapt to the measurement needs of high-speed (0-30,000rpm) and multi-blade (60-100 blades); the measurement range is 0.5-5mm, and the accuracy is ±0.05mm or ±3%FS, meeting the actual needs of aero-engine blade tip clearance measurement.

[0080] (9) Real-time online monitoring, supporting full lifecycle management

[0081] The system can achieve real-time online continuous monitoring, acquire clearance data for each blade, support performance monitoring, fault diagnosis and life prediction throughout the engine's entire life cycle, and provide key data support for engine health management. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of the structure of a high-temperature resistant through-shell type eddy current blade tip clearance measuring device of the present invention;

[0083] Figure 2 This is a schematic diagram of the principle of the high-temperature resistant through-shell type eddy current blade tip clearance measuring device according to an embodiment of the present invention;

[0084] Figure 3 This is a cross-sectional view of the sensor probe module structure according to an embodiment of the present invention;

[0085] Figure 4 This is a schematic diagram of the casing and rotating blade calibration system according to an embodiment of the present invention;

[0086] Figure 5 This is a schematic diagram of the high-temperature resistant through-shell eddy current blade tip clearance measurement method according to an embodiment of the present invention, wherein (a) is the original signal of the receiving coil - Gaussian differential signal, (b) is the integrated signal - Gaussian signal, and (c) is the continuous measurement signal of multiple blades.

[0087] Figure 6 This is a schematic diagram of the specific process of the high-temperature resistant through-shell eddy current blade tip clearance measurement method according to an embodiment of the present invention;

[0088] Figure 7 This is a schematic diagram of the signal processing flow of the data processing module in an embodiment of the present invention;

[0089] In the diagram, 1-permanent magnet, 2-soft magnetic core, 3-receiving coil, 4-spiral cooling air duct, 5-shielding shell, 6-signal output, 7-casing wall, 8-rotating blade. Detailed Implementation

[0090] This invention provides a high-temperature resistant through-shell type eddy current blade tip clearance measuring device and method. The invention will be further described in detail below with reference to the accompanying drawings.

[0091] Aero-engine casings are typically made of non-magnetic materials such as tungsten-nickel alloys and nickel-iron alloys, which allows electromagnetic fields to penetrate the casing. If through-shell measurement can be achieved, i.e., the sensor is mounted on the outer wall of the casing and the gap is measured through the casing wall 7, it is possible to avoid openings in the casing, maintain the structural integrity of the casing, and allow the sensor to operate in a relatively mild environment, significantly improving reliability and service life. This invention discloses a high-temperature resistant through-shell eddy current blade tip gap measuring device and method, particularly suitable for non-contact real-time measurement of the gap between the rotating blade 8 of an aero-engine turbine and the casing wall 7, especially suitable for high-temperature operating environments (-55℃ to +650℃). The following technical challenges are encountered in the specific implementation process:

[0092] 1) Sensor structure design: How to optimize the configuration of permanent magnets and receiving coils to achieve high-sensitivity signal reception while ensuring magnetic field strength;

[0093] 2) High temperature adaptability: How to ensure the sensor operates stably when the outer wall of the housing is exposed to temperatures above 200°C;

[0094] 3) Signal processing methods: Trans-shell measurement results in weak signals. How to extract effective information through signal conditioning and digital processing techniques?

[0095] 4) Rotational speed coupling problem: The amplitude of the inductive signal is affected by both the gap and the rotational speed. How to decouple these two parameters to achieve accurate measurement?

[0096] 5) Calibration method: How to establish an accurate mapping relationship between rotational speed, signal amplitude and clearance.

[0097] To address the aforementioned technical problems, this invention proposes a high-temperature resistant, through-shell type eddy current blade tip clearance measuring device and method. For example... Figure 1 The embodiment of the present invention disclosed herein provides a high-temperature resistant, through-shell type eddy current blade tip clearance measuring device, comprising: a sensor probe module, a signal conditioning module, a data acquisition module, and a data processing module; Figure 1 In the diagram, "first transparent shell sensor", "second transparent shell sensor", and "nth transparent shell sensor" indicate the installation positions of the n transparent shell sensors.

[0098] The sensor probe module is mounted on the outer wall of the casing; the casing is made of non-magnetic material; the sensor probe module includes: a permanent magnet excitation source, a soft magnet core, and a receiving coil; the permanent magnet excitation source generates a constant static magnetic field, and the magnetic lines of force pass through the casing wall 7 to reach the rotating blade area; the soft magnet core is set in the direction of magnetic field radiation of the permanent magnet excitation source, and is set separately from the permanent magnet excitation source, and is used to guide the magnetic field and serve as the core of the receiving coil; the receiving coil is used to sense a secondary magnetic field and generate an induced voltage;

[0099] The signal conditioning module is electrically connected to the receiving coil to amplify, filter, and integrate weak induced signals; the data acquisition module is electrically connected to the signal conditioning module to convert analog signals into digital signals; and the data processing module processes the acquired digital signals to extract blade tip clearance information.

[0100] The permanent magnet excitation source adopts a samarium cobalt permanent magnet or a neodymium iron boron permanent magnet, which is cylindrical in shape and magnetized in the axial direction. The magnetic induction intensity of the permanent magnet excitation source is 200-500mT.

[0101] The soft magnetic core is made of permalloy or ferrite material, with a relative permeability of μr≥10,000 and a temperature resistance of ≥350℃.

[0102] The receiving coil is made of enameled copper wire wound on a soft magnetic core. The diameter of the enameled copper wire is 0.1-0.3mm, the number of turns is 500-3000, the inductance is 50-200mH, and the DC resistance is 200-800Ω.

[0103] The principle of the high-temperature resistant through-shell type eddy current blade tip clearance measuring device of this invention is as follows: Figure 2 As shown, Figure 2 The image shows the spatial relationship between the sensor probe, the housing, and the rotating blade 8, as well as the path of the magnetic field penetrating the housing. Figure 2 The connection relationship between permanent magnet 1, soft magnetic core 2, and receiving coil 3 is shown in the figure; the signal from the sensor probe is transmitted outward through signal output 6; the static magnetic field passes through the casing wall 7 and reaches the rotating blade 8.

[0104] In one specific embodiment, the sensor probe module is mounted on the outer wall of the casing and adopts a separate structure for the permanent magnet excitation source and the soft magnet receiving coil, specifically including:

[0105] Permanent magnet excitation source: Samarium cobalt (SmCo) or neodymium iron boron (NdFeB) permanent magnets are used, with a magnetic induction intensity of 200-500mT (preferably 300mT), a cylindrical shape, and an axial magnetization direction. The permanent magnet 1 generates a constant static magnetic field, and the magnetic field lines pass through the casing wall 7 to reach the rotating blade area.

[0106] In a preferred embodiment, the magnetic induction intensity of the permanent magnet excitation source is 300 mT.

[0107] Soft magnetic core: Made of permalloy or ferrite material, wherein the permalloy is an iron-nickel alloy; the relative permeability μr of the soft magnetic core is ≥10,000, and the temperature resistance is ≥350℃. The soft magnetic core is positioned in the magnetic field radiation direction of the permanent magnet excitation source, separated from the permanent magnet excitation source (air gap 3-5mm), for focusing and guiding the magnetic field, and also serves as the core of the receiving coil.

[0108] The receiving coil is made of enameled copper wire (0.1-0.3mm in diameter) wound on a soft magnetic core, with 500-3000 turns, an inductance of 50-200mH, and a DC resistance of 200-800Ω. When the rotating blade 8 cuts the magnetic lines of force, eddy currents are formed on the blade surface. These eddy currents generate a secondary magnetic field, which passes through the casing and is induced by the receiving coil, producing an induced voltage.

[0109] In a preferred embodiment, the number of turns of the enameled copper wire is 1000-2000;

[0110] In an optional embodiment, the sensor probe module further includes a cooling system and a shielding device;

[0111] The cooling system adopts an air cooling method, using compressed air to cool the soft magnetic core and the receiving coil; the shielding device includes: a stainless steel shell to encapsulate the sensor probe module and an electromagnetic shielding layer to reduce external electromagnetic interference; and signal output is achieved using twisted-pair or coaxial cable.

[0112] In this optional embodiment, the cooling system adopts an air cooling method, which uses compressed air to cool the soft magnetic core and the receiving coil, so that it can maintain a reasonable operating temperature (<150°C) in an environment of 200°C on the outer wall of the casing, and can adapt to a high temperature environment of 650°C under air cooling conditions.

[0113] The shielding device achieves both shielding and encapsulation: the sensor probe is encapsulated in a stainless steel shell and equipped with an electromagnetic shielding layer to reduce external electromagnetic interference. Signal output uses shielded twisted-pair cable or coaxial cable to ensure signal transmission quality.

[0114] The cross-sectional view of the sensor probe module structure in this embodiment of the invention is shown below. Figure 3 As shown, in Figure 3 The detailed structure of the permanent magnet 1, air gap, soft magnetic core 2, receiving coil 3, spiral cooling air channel 4, and shielding shell 5 is shown in the figure.

[0115] The signal conditioning module includes a preamplifier, a bandpass filter, and an integrator circuit. The signal conditioning module is electrically connected to the receiving coil 3 and amplifies, filters, and integrates the weak induced signal.

[0116] The preamplifier uses a high-performance instrumentation amplifier chip to amplify the weak mV-level signal output from the receiving coil 3 to the 0.1-5V range.

[0117] The bandpass filter is a second-order Butterworth active filter with a passband range of 100Hz-300kHz and a filter gain of 20dB.

[0118] The integrator circuit uses an RC active integrator.

[0119] In one specific embodiment, the signal conditioning module is electrically connected to the receiving coil 3, and performs amplification, filtering, and integration processing on the weak induced signal, specifically including:

[0120] 1) Preamplifier: Using a high-performance instrumentation amplifier chip, the preamplifier amplifies the weak millivolt-level signal output from receiving coil 3 to the range of 0.1-5V.

[0121] 2) Bandpass Filter: A second-order Butterworth active filter is used, with a passband range of 100Hz-300kHz. The lower cutoff frequency of 100Hz is used to remove DC drift and low-frequency noise, and the upper cutoff frequency of 300kHz is used for anti-aliasing filtering to meet the Nyquist criterion for subsequent ADC sampling. The filter gain is 20dB to further amplify the signal.

[0122] 3) Integrating Circuit: An RC active integrator is used, with a time constant τ = R × C, where R is the resistance and C is the capacitance. The integrating circuit restores the Gaussian differential signal (i.e., the derivative of the Gaussian function) output from receiving coil 3 to a Gaussian signal. The physical meaning of the Gaussian differential signal is the rate of change of magnetic flux dΦ / dt. After integration, the change of magnetic flux ΔΦ is obtained, corresponding to a Gaussian-shaped waveform.

[0123] The data acquisition module includes a high-speed analog-to-digital converter and a data buffer and communication interface. The data acquisition module is electrically connected to the signal conditioning module to convert analog signals into digital signals.

[0124] The high-speed analog-to-digital converter adopts a continuous sampling mode to continuously acquire the integrated Gaussian signal waveform data;

[0125] The data buffer and communication interface uses an FPGA or high-performance MCU for data buffering and preprocessing, and transmits digital signals to the host computer via an Ethernet interface;

[0126] The data acquisition module uses the UDP protocol for data packaging.

[0127] In one specific embodiment, the data acquisition module is electrically connected to the signal conditioning module, converting analog signals into digital signals. The data acquisition module specifically includes a high-speed analog-to-digital converter (ADC), which employs a continuous sampling mode to continuously acquire integrated Gaussian signal waveform data. A data buffer and communication interface are also included, using an FPGA or high-performance MCU for data buffering and preprocessing. The digital signals are transmitted to the host computer via an Ethernet interface (1Gbps). The Ethernet interface offers higher stability and interference resistance compared to USB, making it suitable for industrial applications. The data acquisition module uses the UDP protocol for data packetization, achieving low-latency real-time transmission.

[0128] The data processing module includes:

[0129] Gaussian peak detection unit: performs threshold judgment on the acquired digital signal to identify the peak position of the Gaussian waveform, and each peak corresponds to a blade passage event;

[0130] Gaussian fitting unit: Extracts the waveform data segment around each detected peak, performs Gaussian function fitting, and extracts the amplitude parameter after fitting as the input for gap calculation;

[0131] Rotational speed calculation unit: Calculates rotational speed based on the time interval between two adjacent blades passing by and the number of blades;

[0132] Clearance calculation unit: Based on the amplitude (A) obtained by Gaussian fitting and the speed (n) calculated, the tip clearance (delta) is calculated through a pre-calibrated mapping relationship; the clearance calculation adopts the bilinear interpolation method and establishes a three-dimensional calibration table of speed-amplitude-clearance;

[0133] Data output and display unit: Outputs the clearance value, rotational speed, and timestamp of each blade in real time, displaying them in the form of numerical values, waveforms, and trend curves, and records and stores the data.

[0134] In one specific embodiment, the data processing module is implemented through host computer software to process the collected digital signals and extract the blade tip gap information.

[0135] The data processing module includes: specifically, it includes:

[0136] Gaussian peak detection unit: performs threshold judgment on the acquired digital signal to identify the peak position of the Gaussian waveform. Each peak corresponds to a blade passage event.

[0137] Gaussian Fitting Unit: For each detected peak, extract the waveform data segments around it (e.g., 100 sampling points before and after the peak), perform Gaussian function fitting, and extract the amplitude parameters as input for gap calculation.

[0138] Rotational speed calculation unit: Calculates rotational speed based on the time interval between two adjacent blades passing by and the number of blades.

[0139] Clearance calculation unit: Based on the amplitude (A) obtained from Gaussian fitting and the speed (n) calculated, the tip clearance (delta) is calculated through a pre-calibrated mapping relationship. The clearance calculation adopts the bilinear interpolation method and establishes a three-dimensional calibration table of speed-amplitude-clearance.

[0140] Data output and display unit: Outputs the clearance value, rotational speed, and timestamp of each blade in real time, displaying them in the form of numerical values, waveforms, and trend curves, and records and stores the data.

[0141] Another embodiment of the present invention discloses a method for measuring the tip clearance of a high-temperature resistant through-shell eddy current blade, based on the high-temperature resistant through-shell eddy current blade tip clearance measuring device according to the present invention, comprising the following steps:

[0142] A calibration system for the casing and rotating blades was built, and the amplitude of the Gaussian signal output by the sensor under different rotational speeds and clearances was collected. Based on the amplitude of the Gaussian signal, a mapping relationship between rotational speed, amplitude, and clearance was established.

[0143] The sensor probe module is installed on the outer wall of the casing. The signal conditioning module continuously acquires the Gaussian signal after amplification, filtering and integration. The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream.

[0144] The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and uses the rotational speed-amplitude-gap mapping relationship to solve the tip clearance and output the measurement results.

[0145] The specific process of the high-temperature resistant through-shell eddy current blade tip clearance measurement method of this invention is as follows: Figure 6 As shown. The flow chart of the high-temperature resistant through-shell eddy current blade tip clearance measurement method of this invention is as follows: Figure 5 As shown, (a) is the original signal from the receiving coil – the Gaussian differential signal. Eddy currents on the blade surface generate a secondary magnetic field, which passes through the casing and is induced by the receiving coil 3, generating an induced Gaussian differential signal. (b) is the integrated signal – the Gaussian signal. After being pre-amplified, the Gaussian differential signal is restored to a Gaussian signal by the integrating circuit. (c) is the continuous measurement signal from multiple blades. Each blade generates a Gaussian signal, and the multiple blades output a continuous Gaussian measurement signal.

[0146] In one specific embodiment, the high-temperature resistant through-shell eddy current blade tip clearance measurement method is divided into: calibration stage, measurement stage, and signal processing stage.

[0147] I. Calibration Phase

[0148] The casing and rotating blade calibration system includes: a high-speed rotary table, a precision displacement stage, and a simulated casing; the high-speed rotary table has a rotational speed range of 0-30,000 rpm and a rotational speed accuracy of ±0.1%; the precision displacement stage has a stroke ≥10 mm and a positioning accuracy ≤5 μm; the simulated casing is made of the same material as the actual casing, with a thickness of 3-8 mm.

[0149] The structure of the casing and rotating blade calibration system in this embodiment of the invention is as follows: Figure 4 As shown, Figure 4 The exhibition showcases the layout of the high-speed rotary table, precision displacement stage, analog housing, sensor probe, and measurement system.

[0150] The steps for assembling the casing and rotating blade calibration system include:

[0151] Select blade simulation components to be installed on a high-speed rotating table, with 6-12 blades, and the material is titanium alloy or stainless steel;

[0152] Multiple speed points can be set, covering the actual working range of 0-30,000 rpm;

[0153] Set multiple gap points, with the gap range covering the measurement range of 0.5-5mm;

[0154] The amplitude of the Gaussian signal output by the sensor under different rotational speeds and different gaps includes:

[0155] For each speed-clearance combination, perform the following operations:

[0156] Set the rotary table speed to ni and wait for the first preset time.

[0157] The precision displacement stage moves to the gap position dj and waits for the second preset time.

[0158] Repeat the measurement a first preset number of times, and each time collect a first preset number of blade passage events and record the corresponding Gaussian signal amplitude;

[0159] The establishment of the rotational speed-amplitude-gap mapping relationship based on the Gaussian signal amplitude includes:

[0160] Establish a three-dimensional mapping table of rotational speed, amplitude, and clearance, and store all calibration data points;

[0161] Calibration and verification: Select 5-10 intermediate points that were not involved in the calibration, perform actual measurements and compare them with the theoretical values, and require the error to be correct;

[0162] Obtain the calculated mean amplitude and standard deviation.

[0163] In one specific embodiment, the calibration phase includes:

[0164] The calibration system consists of: a high-speed rotary table (speed range 0-30,000 rpm, speed accuracy ±0.1%), a precision displacement stage (stroke ≥10 mm, positioning accuracy ≤5 μm) and a simulated housing (material is the same as the actual housing, thickness 3-8 mm).

[0165] Install blade simulation components (6-12 blades, made of titanium alloy or stainless steel) on the rotating platform.

[0166] Multiple speed points can be set, covering the actual working range of 0-30,000 rpm.

[0167] Set multiple gap points, with the gap range covering the measurement range of 0.5-5mm.

[0168] For each speed-clearance combination, perform the following operations:

[0169] - Set the rotary table speed to ni and wait for the speed to stabilize (10 seconds);

[0170] - Move the precision displacement stage to the gap position dj and wait for the position to stabilize (5 seconds);

[0171] - Repeat the measurement 5-10 times, collecting 1000 blade passage events each time, and recording the corresponding Gaussian signal amplitude;

[0172] - Calculate the mean amplitude and standard deviation.

[0173] Establish a three-dimensional mapping table of rotational speed, amplitude, and clearance, and store all calibration data points.

[0174] Calibration and verification: Select 5-10 intermediate points that were not involved in the calibration, measure them, and compare them with the theoretical values, requiring the error to be correct.

[0175] In this embodiment, a casing and rotating blade calibration system is constructed: by obtaining reference data for blade tip clearance measurement under controllable and repeatable experimental conditions, and establishing a correspondence between "rotation speed - amplitude - clearance", the device can accurately calculate the blade tip clearance in actual measurement, especially to solve the measurement error problem caused by the coupling of rotation speed and clearance.

[0176] (1) Acquire standard Gaussian signal data under controllable speed and clearance conditions;

[0177] (2) Stable amplitude data are obtained by using Gaussian fitting and statistical processing;

[0178] (3) Establish a three-dimensional calibration relationship of rotational speed, amplitude and gap to solve the coupling problem of signal amplitude changing with rotational speed;

[0179] (4) Verify the reliability and accuracy of this calibration relationship;

[0180] (5) Provides the only available gap calculation basis for the actual measurement stage, and realizes high-precision measurement.

[0181] II. Measurement Phase

[0182] The sensor probe module is mounted on the outer wall of the casing, and the signal conditioning module continuously acquires the amplified, filtered, and integrated Gaussian signal; the data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream, including:

[0183] Install the sensor probe module on the outer wall of the casing, ensuring that the front end of the probe is in close contact with the casing wall 7, the probe axis is perpendicular to the casing wall 7, and the probe is aligned with the area swept by the blade.

[0184] Start the signal conditioning module, set the ADC sampling rate to ≥1MSPS, and the sampling mode to continuous sampling;

[0185] The signal conditioning module continuously acquires the induced signal output by the receiving coil 3. The signal is processed by a preamplifier, a bandpass filter, and an integrator circuit to obtain a Gaussian signal. The gain of the preamplifier is 40-60dB. The frequency of the bandpass filter is 100Hz-300kHz. The time constant of the integrator circuit is 5-10μs.

[0186] The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream, which is then buffered by the FPGA / MCU and transmitted to the data processing module.

[0187] In one specific embodiment, the measurement phase includes:

[0188] Install the sensor probe on the outer wall of the casing, ensuring that the front end of the probe is in close contact with the casing wall 7, the probe axis is perpendicular to the casing wall 7, and the probe is aligned with the area swept by the blade.

[0189] Start the cooling system, set the cooling airflow rate, monitor the sensor temperature, and ensure that the operating temperature is within the allowable range (<150℃ natural heat dissipation, <350℃ air path cooling).

[0190] Start the data acquisition system, set the ADC sampling rate to ≥1MSPS, and the sampling mode to continuous sampling.

[0191] The induced signal output by the receiving coil 3 is continuously acquired. The signal is processed by a preamplifier (gain 40-60dB), a bandpass filter (100Hz-300kHz), and an integrator circuit (time constant 5-10μs) to obtain a Gaussian signal.

[0192] The ADC collects the integrated Gaussian signal waveform data, which is then buffered by the FPGA / MCU and transmitted to the host computer.

[0193] III. Signal Processing Stage

[0194] The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and calculates the tip clearance using the rotational speed-amplitude-clearance mapping relationship, outputting the measurement results including:

[0195] The data processing module receives real-time digital signal streams and processes them in real time; first, it performs digital filtering to remove high-frequency noise.

[0196] The acquired digital signals are thresholded to detect the Gaussian peak position. The threshold is set using the 3σ criterion. When the signal amplitude exceeds the threshold and meets the local maximum condition, it is determined to be a valid Gaussian peak, and the peak index and timestamp are recorded.

[0197] Extract a single Gaussian waveform data segment corresponding to each peak, and collect a preset second threshold of sampling points;

[0198] Gaussian function fitting for a single Gaussian waveform: nonlinear least squares method is used for fitting, and the amplitude parameter (A), peak center (mu), and width (sigma) are extracted after fitting.

[0199] Calculate the goodness of fit R 2 ;

[0200] The rotational speed is calculated based on the time interval between two adjacent peak values ​​and the number of blades.

[0201] Substituting the amplitude (A) and rotational speed (n) into the calibration relationship, the tip clearance (d) is calculated: using the bilinear interpolation method, four adjacent points are found according to the calibration table, and (d) is calculated according to the interpolation formula;

[0202] Output measurement results, including: blade number, tip clearance (d), rotational speed (n), timestamp (t), and goodness of fit (R²). 2 );

[0203] Statistical analysis was performed on the gap values ​​of multiple blades in each revolution, and the mean and standard deviation were calculated. Outliers exceeding the range of ±3σ were removed.

[0204] Real-time display of measurement results, including: Numerical display: current rotational speed, clearance values ​​for each blade; Waveform display: original signal waveform, integrated Gaussian signal waveform, fitted curve; Trend curve: clearance variation trend over time or rotational speed; Alarms triggered according to preset alarm rules;

[0205] Record and store all measurement data for subsequent fault diagnosis, life prediction and performance evaluation.

[0206] In one specific embodiment, the signal processing stage includes:

[0207] The host computer software receives the digital signal data stream and processes it in real time. First, digital filtering (such as FIR low-pass filtering) is performed to remove high-frequency noise.

[0208] The acquired digital signals are subjected to threshold judgment to detect the location of Gaussian peaks. The threshold is set using the 3σ criterion. When the signal amplitude exceeds the threshold and meets the local maximum condition, it is determined to be a valid Gaussian peak, and the peak index and timestamp are recorded.

[0209] Extract a single Gaussian waveform data segment corresponding to each peak, for example, 100 sampling points before and after the peak, for a total of 200 points.

[0210] Gaussian function fitting is performed on a single Gaussian waveform: nonlinear least squares method (Levenberg-Marquardt algorithm) is used for fitting, and the amplitude parameter (A), peak center (mu), and width (sigma) are extracted after fitting.

[0211] Calculate the goodness of fit (R) 2 ).

[0212] The rotational speed is calculated based on the time interval between two adjacent peak values ​​and the number of blades.

[0213] Substituting the amplitude (A) and rotational speed (n) into the calibration relationship, the tip clearance (d) is calculated: using the bilinear interpolation method, four adjacent points are found according to the calibration table, and (d) is calculated according to the interpolation formula.

[0214] Output measurement results, including: blade number (obtained by taking the modulus of the peak number on the blade count), tip clearance (d), rotational speed (n), timestamp (t), and goodness of fit (R²). 2 )wait.

[0215] Statistical analysis was performed on the gap values ​​of multiple blades in each revolution, and the mean and standard deviation were calculated. Outliers exceeding the ±3σ range were removed.

[0216] Real-time display of measurement results, including: Numerical display: current speed, clearance value of each blade; Waveform display: original signal waveform, integrated Gaussian signal waveform, fitting curve; Trend curve: clearance change trend with time or speed; Alarm function: when the clearance is <0.3mm, a rubbing warning is issued, and when the clearance is >5.5mm, an efficiency reduction warning is issued.

[0217] Record and store all measurement data for subsequent fault diagnosis, life prediction and performance evaluation.

[0218] The signal processing flow of the data processing module in the embodiment of the invention is as follows: Figure 7 As shown.

[0219] By applying the high-temperature resistant through-shell type eddy current blade tip clearance measuring device and method disclosed in this invention, the following technical effects can be achieved:

[0220] I. Realizing through-shell non-contact measurement technology

[0221] Traditional eddy current / capacitive / fiber optic sensors all require openings in the housing. This invention achieves true through-housing measurement for the first time, eliminating the need for housing openings. The sensor is mounted on the outer wall of the housing, eliminating the need for openings or slots in the housing; the magnetic field penetrates the non-magnetic housing wall (tungsten-nickel alloy / nickel-iron based alloy, 3-8mm thick) for measurement; maintaining the structural integrity and aerodynamic sealing of the housing. This avoids the strength reduction caused by housing openings, eliminates the need to damage the housing's aerodynamic seal, simplifies installation and maintenance, allows for online sensor replacement, and enables the sensor to operate in a low-temperature environment (outer wall vs. inner wall of the housing).

[0222] II. Realizing a discrete structure of permanent magnet excitation source + soft magnet core receiver

[0223] Traditional eddy current sensors use AC excitation coils (high frequency 10-50MHz); permanent magnet solutions eliminate the need for high-frequency excitation circuits, simplifying the system and reducing power consumption; existing technologies do not disclose the focusing technology related to soft magnetic cores. This invention uses a permanent magnet 1 (300mT samarium cobalt) as the static magnetic field excitation source, eliminating the need for AC excitation circuits; the soft magnetic core (permalloy, μr≥10,000) is separately set from the permanent magnet 1 (air gap 3-5mm); the receiving coil 3 is wound on the soft magnetic core to focus the induced magnetic field and improve sensitivity. Permanent magnet excitation source: zero power consumption, high stability, long lifespan; Soft magnetic core focusing: increases magnetic flux density and compensates for through-shell losses; Discrete structure allows for optimized magnetic field configuration and improved signal-to-noise ratio.

[0224] III. Design an air-cooling system to improve high-temperature adaptability.

[0225] Existing through-shell sensors lack high-temperature adaptability design. This invention achieves 650℃ temperature resistance through material selection and active cooling, creatively applying air-path cooling in the field of blade tip clearance measurement. Permalloy is selected to achieve a soft magnetic core temperature resistance of 350℃; an integrated air-path cooling system (compressed air 0.5MPa, 10L / min) is used; a spiral air passage design uniformly cools the coil; combined with cooling, it can adapt to high-temperature environments up to 650℃. It also adapts to the high-temperature environment (200-300℃) of the casing outer wall; ensures the operating temperature of the soft magnetic core and coil is <150℃; and expands the application range to high-temperature regions (turbine section).

[0226] IV. System Integration Innovation

[0227] Design a complete system integrating sensor probe, signal conditioning, data acquisition, and host computer processing; design a targeted analog front-end (preamplifier, bandpass filter, and integrator); directly acquire the integrated signal using a high-speed ADC (≥5MSPS, 16bit); and implement real-time Gaussian fitting and gap calculation using host computer software. Systematic design achieves synergistic optimization of each module; achieves high bandwidth (>300kHz) to adapt to high-speed multi-blade operation; and enables real-time processing with a processing time of <1ms per blade.

[0228] To verify the effectiveness of the high-temperature resistant through-shell eddy current blade tip clearance measuring device and method disclosed in this invention, the following verification embodiments are disclosed to describe the implementation process of a complete through-shell eddy current blade tip clearance measuring system, including sensor fabrication, signal processing, calibration, and practical application.

[0229] (1) Sensor probe fabrication

[0230] The sensor probe employs a discrete structure consisting of a permanent magnet excitation source and a soft magnet receiving coil. A samarium cobalt (SmCo) permanent magnet is selected as the excitation source; it is cylindrical and axially magnetized. The soft magnet core is made of permalloy and is cylindrical. The receiving coil is made of high-temperature resistant enameled copper wire wound on the soft magnet core.

[0231] During sensor assembly, the permanent magnet 1 is fixed to the bottom of the stainless steel casing, and the soft magnet core and receiving coil assembly are installed 3-5mm above it, maintaining a uniform air gap. A spiral air cooling channel is set around the soft magnet core, and the coil is cooled by compressed air. The receiving coil 3 is wrapped with an electromagnetic shielding layer to reduce external interference. The leads are made of shielded twisted-pair cable, and a temperature sensor is installed inside to monitor the operating temperature. The entire unit is potted with high-temperature resistant epoxy resin to form an integrated probe.

[0232] Sensor testing included room temperature performance testing, high temperature performance testing, and long-term stability testing. Testing was conducted on the outer wall of a simulated housing (5mm thick) to verify the sensor's output characteristics under different gaps (0.5-5mm) and rotational speeds. High-temperature testing verified the sensor's stable operation at 200℃ with an air-cooled system. Long-term stability testing showed that after 100 hours of continuous operation, the zero-point drift was less than 1%FS, and the sensitivity drift was less than 2%.

[0233] (2) Implementation of signal conditioning circuit

[0234] The signal conditioning circuit consists of three cascaded modules: a preamplifier, a bandpass filter, and an integrator.

[0235] The preamplifier uses an instrumentation amplifier chip to amplify the weak millivolt-level signal output from receiving coil 3 to a range of 0.1-5V. A protection circuit is incorporated at the input, including a series resistor, a parallel capacitor, and a TVS diode, to prevent damage from overvoltage.

[0236] The bandpass filter employs a second-order active filter based on a Sallen-Key topology. The lower cutoff frequency is 100Hz to remove DC drift and low-frequency noise; the upper cutoff frequency is 300kHz to achieve anti-aliasing filtering. The filter gain is 10 times (20dB) for further signal amplification. It utilizes a Butterworth response design, resulting in a flat passband and linear phase.

[0237] The integrating circuit employs an RC active integrator with a time constant of approximately 5μs, restoring the Gaussian differential signal output from receiving coil 3 back to a Gaussian signal. To prevent integrator saturation, a large resistor is connected in parallel to achieve long-term constant reset. High-precision thin-film capacitors are used for the integrating capacitors, and metal film resistors are used for the resistors to ensure circuit stability.

[0238] During circuit debugging, a function generator is used to input a standard signal to test the frequency response and noise performance. After connecting the sensor probe, the blade passage event is simulated, and the gain and time constant are adjusted to make the output waveform clear and distortion-free.

[0239] (3) Data acquisition and processing system

[0240] The data acquisition system employs a 16-bit high-speed ADC with a sampling rate of 5 MSPS, connecting to the main control chip via SPI or a parallel interface. The main control chip is configured with DMA operating in circular buffer mode to achieve continuous sampling and data transmission. Acquired data is transmitted to the host computer via an Ethernet interface (100Mbps), packaged using the UDP protocol to ensure real-time performance.

[0241] The host computer software is developed in C++ and based on the Qt5 graphical interface library. The software includes five main modules: data reception, signal processing, calibration management, display, and data logging.

[0242] Signal processing algorithms consist of four core steps:

[0243] Step 1) Gaussian Peak Detection: An adaptive thresholding method (3σ criterion) is used to detect Gaussian peaks. The mean and standard deviation of the signal are calculated, and the threshold is set to the mean plus three times the standard deviation. The signal data is iterated; when the amplitude at a certain point exceeds the threshold and is a local maximum, it is determined to be a valid peak.

[0244] Step 2) Gaussian curve fitting: Use the nonlinear least squares method (Levenberg-Marquardt algorithm) to fit the Gaussian function and extract the amplitude parameter A. Calculate the goodness of fit R², requiring R² > 0.95; otherwise, discard the data point.

[0245] Step 3) Rotational speed calculation: Calculate the rotational speed based on the time interval between two adjacent peak values ​​and the number of blades. A multi-cycle averaging method is used to improve accuracy, and a threshold for the rate of change of rotational speed is set to remove outlier data.

[0246] Step 4) Gap calculation: Based on the pre-established three-dimensional calibration table of speed-amplitude-gap, the gap value is calculated using bilinear interpolation or empirical formula.

[0247] The graphical interface includes a main window (real-time numerical display), a waveform window (raw signal and fitted curve), a trend window (gap changes over time), a calibration window (calibration data management), and a settings window (parameter configuration).

[0248] (4) Calibration experiment

[0249] The calibration system includes a high-speed rotary table (speed range 0-30,000 rpm, accuracy ±0.1%), a precision displacement stage (positioning accuracy ±1μm), a simulated casing (GH4169 alloy, thickness 5mm) and blade simulation components (TC4 titanium alloy, 8 pieces).

[0250] The calibration employed a grid method, setting 9 speed points (1000 to 30000 rpm) and 10 clearance points (0.5 to 5.0 mm), for a total of 90 calibration points. The procedure for each calibration point was as follows: set the speed and wait for it to stabilize; move the displacement stage to the target clearance; collect 1000 blade passage events; perform Gaussian fitting to extract the amplitude; calculate the mean and standard deviation; repeat 5 times and take the average.

[0251] The calibration results show that the signal amplitude A is directly proportional to the rotational speed n and inversely proportional to the clearance δ.

[0252] The above verification examples fully demonstrate the entire process of the through-shell eddy current blade tip clearance measurement system, from design, fabrication, calibration to simulation application. The examples verified the following key technical effects:

[0253] (1) Sensor structure design: The permanent magnet excitation source and the soft magnet receiving coil are separate structures. With the help of the air cooling system, it can work stably in the high temperature environment (650℃) on the outer wall of the casing, and the temperature of the sensor body is controlled below 350℃.

[0254] (2) Signal processing technology: The three-stage signal conditioning circuit (preamplifier, bandpass filter, and integral processing) effectively extracts the weak signal through the shell and restores the Gaussian differential signal into a clear Gaussian waveform, providing a high-quality signal source for subsequent digital processing.

[0255] (3) Application of intelligent algorithms: Gaussian fitting algorithm combined with rotational speed decoupling technology accurately calculates blade tip clearance through calibration mapping relationship, and the measurement accuracy reaches ±1%FS.

[0256] (4) System reliability verification: The simulated bench test shows that the error between the system measurement results and the laser measurement is less than ±0.03mm, and the deviation of the long-term stability test (200 hours) is within ±0.02mm, which meets the monitoring requirements of the entire life cycle of the aero-engine.

[0257] This invention achieves true through-shell non-contact measurement, eliminating the need for openings in the housing, maintaining the structural integrity and aerodynamic sealing of the housing, providing a user-friendly working environment for the sensor, high reliability, and significant engineering application value and broad market prospects. Specifically, this invention can be applied to the following fields:

[0258] Aero engines: Measurement of turbine and compressor blade tip clearance for performance optimization, condition monitoring, and fault diagnosis.

[0259] Gas turbines: Blade tip clearance monitoring for gas turbines used in power generation and marine gas turbines.

[0260] Steam turbine: Measuring the blade tip clearance of steam turbines in thermal power plants to improve efficiency.

[0261] Turbochargers: Online monitoring of blade tip clearance in automotive and marine turbochargers.

[0262] Compressor: Measurement of tip clearance of centrifugal compressors and axial compressors.

[0263] The through-shell measurement technology disclosed in this invention has significant advantages over traditional methods and is of great importance to the safety and economy of aero engines: Improved safety: Real-time monitoring of blade tip clearance allows for timely detection of rubbing risks, preventing blade damage and engine failure; Improved efficiency: Optimized blade tip clearance design reduces airflow leakage, improves engine efficiency, and saves fuel; Extended lifespan: Accurately grasping the trend of blade tip clearance changes enables predictive maintenance and extends engine overhaul intervals.

[0264] Another embodiment of the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes a high-temperature resistant through-shell eddy current blade tip clearance measurement method according to the present invention.

[0265] Another embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the processor performs a high-temperature resistant through-shell eddy current blade tip clearance measurement method according to the present invention.

Claims

1. A high-temperature resistant through-shell type eddy current blade tip clearance measuring device, characterized in that, include: Sensor probe module, signal conditioning module, data acquisition module, and data processing module; The sensor probe module is mounted on the outer wall of the casing; The casing is made of a non-magnetic material; the sensor probe module includes: a permanent magnet excitation source, a soft magnet core, and a receiving coil; the permanent magnet excitation source generates a constant static magnetic field, and the magnetic lines of force pass through the casing wall to reach the rotating blade area; the soft magnet core is set in the direction of magnetic field radiation of the permanent magnet excitation source, and is set separately from the permanent magnet excitation source, used to guide the magnetic field and serve as the core of the receiving coil; the receiving coil is used to sense a secondary magnetic field and generate an induced voltage; the receiving coil is wound on the soft magnet core to focus the induced magnetic field; The signal conditioning module is electrically connected to the receiving coil and amplifies, filters, and integrates the weak induced signal; the data acquisition module is electrically connected to the signal conditioning module and converts the analog signal into a digital signal; the data processing module processes the acquired digital signal and extracts the blade tip clearance information. The signal conditioning module includes a preamplifier, a bandpass filter, and an integrator circuit. The signal conditioning module is electrically connected to the receiving coil and amplifies, filters, and integrates the weak induced signal. The preamplifier uses a high-performance instrumentation amplifier chip to amplify the weak mV-level signal output from the receiving coil to the 0.1-5V range. The bandpass filter is a second-order Butterworth active filter with a passband range of 100Hz-300kHz and a filter gain of 20dB. The integrating circuit uses an RC active integrator; The data processing module includes: Gaussian peak detection unit: performs threshold judgment on the acquired digital signal to identify the peak position of the Gaussian waveform, and each peak corresponds to a blade passage event; Gaussian fitting unit: Extracts the waveform data segment around each detected peak, performs Gaussian function fitting, and extracts the amplitude parameter after fitting as the input for gap calculation; Rotational speed calculation unit: Calculates rotational speed based on the time interval between two adjacent blade passes and the number of blades; Clearance calculation unit: Based on the amplitude obtained from Gaussian fitting and the rotational speed calculated from the rotational speed, the blade tip clearance is calculated through a pre-calibrated mapping relationship; the clearance calculation adopts the bilinear interpolation method and establishes a three-dimensional calibration table of rotational speed-amplitude-clearance; Data output and display unit: Outputs the clearance value, rotational speed, and timestamp of each blade in real time, displaying them in the form of numerical values, waveforms, and trend curves, and records and stores the data.

2. The high-temperature resistant through-shell type eddy current blade tip clearance measuring device according to claim 1, characterized in that, The permanent magnet excitation source adopts a samarium cobalt permanent magnet or a neodymium iron boron permanent magnet, which is cylindrical in shape and magnetized in the axial direction. The magnetic induction intensity of the permanent magnet excitation source is 200-500mT. The soft magnetic core is made of permalloy or ferrite material, with a relative permeability of μr≥10,000 and a temperature resistance of ≥350℃. The receiving coil is made of enameled copper wire wound on a soft magnetic core. The diameter of the enameled copper wire is 0.1-0.3mm, the number of turns is 500-3000, the inductance is 50-200mH, and the DC resistance is 200-800Ω.

3. The high-temperature resistant through-shell type eddy current blade tip clearance measuring device according to claim 1, characterized in that, The sensor probe module also includes: a cooling system and a shielding device; The cooling system adopts an air cooling method, using compressed air to cool the soft magnetic core and the receiving coil; the shielding device includes: a stainless steel shell to encapsulate the sensor probe module and an electromagnetic shielding layer to reduce external electromagnetic interference; and signal output is achieved using twisted-pair or coaxial cable.

4. The high-temperature resistant through-shell type eddy current blade tip clearance measuring device according to claim 1, characterized in that, The data acquisition module includes a high-speed analog-to-digital converter and a data buffer and communication interface. The data acquisition module is electrically connected to the signal conditioning module to convert analog signals into digital signals. The high-speed analog-to-digital converter adopts a continuous sampling mode to continuously acquire the integrated Gaussian signal waveform data; The data buffer and communication interface uses an FPGA or high-performance MCU for data buffering and preprocessing, and transmits digital signals to the host computer via an Ethernet interface; The data acquisition module uses the UDP protocol for data packaging.

5. A method for measuring the tip clearance of a high-temperature resistant through-shell eddy current blade, as described in any one of claims 1-4, characterized in that... Includes the following steps: A calibration system for the casing and rotating blades was built, and the amplitude of the Gaussian signal output by the sensor under different rotational speeds and clearances was collected. Based on the amplitude of the Gaussian signal, a mapping relationship between rotational speed, amplitude, and clearance was established. The sensor probe module is installed on the outer wall of the casing. The signal conditioning module continuously acquires the Gaussian signal after amplification, filtering and integration. The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream. The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and uses the rotational speed-amplitude-gap mapping relationship to solve the tip clearance and output the measurement results; The sensor probe module is installed on the outer wall of the casing, and the signal conditioning module continuously acquires the Gaussian signal after amplification, filtering and integration. The data acquisition module acquires the integrated Gaussian signal waveform data to obtain the real-time digital signal stream, including: Install the sensor probe module on the outer wall of the casing, ensuring that the front end of the probe is in close contact with the casing wall, the probe axis is perpendicular to the casing wall, and aligned with the area swept by the blade; Start the signal conditioning module, set the ADC sampling rate to ≥1MSPS, and the sampling mode to continuous sampling; The signal conditioning module continuously acquires the induced signal output by the receiving coil. The signal is processed by a preamplifier, a bandpass filter, and an integrator circuit to obtain a Gaussian signal. The gain of the preamplifier is 40-60dB. The frequency of the bandpass filter is 100Hz-300kHz. The time constant of the integrator circuit is 5-10μs. The data acquisition module acquires the integrated Gaussian signal waveform data to obtain a real-time digital signal stream, which is then buffered by the FPGA / MCU and transmitted to the data processing module. The data processing module performs peak detection, Gaussian fitting, and rotational speed calculation on the real-time digital signal stream, and calculates the tip clearance using the rotational speed-amplitude-clearance mapping relationship, outputting the measurement results including: The data processing module receives real-time digital signal streams and processes them in real time; first, it performs digital filtering to remove high-frequency noise. The acquired digital signals are thresholded to detect the Gaussian peak position. The threshold is set using the 3σ criterion. When the signal amplitude exceeds the threshold and meets the local maximum condition, it is determined to be a valid Gaussian peak, and the peak index and timestamp are recorded. Extract a single Gaussian waveform data segment corresponding to each peak, and collect a preset second threshold of sampling points; Gaussian function fitting for a single Gaussian waveform: nonlinear least squares method is used for fitting, and amplitude parameters, peak center, and width are extracted after fitting; Calculate the goodness of fit R 2 ; The rotational speed is calculated based on the time interval between two adjacent peak values ​​and the number of blades. Substitute the amplitude and rotational speed into the calibration relationship to calculate the blade tip clearance: Use bilinear interpolation method, find four adjacent points according to the calibration table, and calculate the blade tip clearance according to the interpolation formula. Output measurement results, including: blade number, tip clearance, rotational speed, timestamp, and goodness-of-fit R-value. 2 ; Statistical analysis was performed on the gap values ​​of multiple blades in each revolution, and the mean and standard deviation were calculated. Outliers exceeding the range of ±3σ were removed. Real-time display of measurement results, including: Numerical display: current rotational speed, clearance values ​​for each blade; Waveform display: original signal waveform, integrated Gaussian signal waveform, fitted curve; Trend curve: clearance variation trend over time or rotational speed; Alarms triggered according to preset alarm rules; Record and store all measurement data for subsequent fault diagnosis, life prediction and performance evaluation.

6. The high-temperature resistant through-shell eddy current blade tip clearance measurement method according to claim 5, characterized in that, The casing and rotating blade calibration system includes: a high-speed rotary table, a precision displacement stage, and a simulated casing; the high-speed rotary table has a rotational speed range of 0-30,000 rpm and a rotational speed accuracy of ±0.1%; the precision displacement stage has a stroke ≥10 mm and a positioning accuracy ≤5 μm; the simulated casing is made of the same material as the actual casing, with a thickness of 3-8 mm. The steps for assembling the casing and rotating blade calibration system include: Select blade simulation components to be installed on a high-speed rotating table, with 6-12 blades, and the material is titanium alloy or stainless steel; Multiple speed points can be set, covering the actual working range of 0-30,000 rpm; Set multiple gap points, with the gap range covering the measurement range of 0.5-5mm; The amplitude of the Gaussian signal output by the sensor under different rotational speeds and different gaps includes: For each speed-clearance combination, perform the following operations: Set the rotary table speed to ni and wait for the first preset time. The precision displacement stage moves to the gap position dj and waits for the second preset time. Repeat the measurement a first preset number of times, and each time collect a first preset number of blade passage events and record the corresponding Gaussian signal amplitude; The establishment of the rotational speed-amplitude-gap mapping relationship based on the Gaussian signal amplitude includes: Establish a three-dimensional mapping table of rotational speed, amplitude, and clearance, and store all calibration data points; Calibration and verification: Select 5-10 intermediate points that were not involved in the calibration, perform actual measurements and compare them with the theoretical values, and require the error to be correct; Obtain the calculated mean amplitude and standard deviation.

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