A precision calibration method for blade vibration measurement system with traceable tip timing

Abstract

The present invention discloses a method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing, which relates to the field of non-contact tip timing vibration measurement, including: determining blade vibration signal parameters; obtaining a timing pulse signal based on the blade vibration signal parameters; performing pulse width modulation according to the tip timing pulse signal to obtain a vibration frequency true value and a vibration amplitude true value; inputting the timing pulse signal into a blade vibration measurement system to calculate a vibration frequency indication and a vibration amplitude indication; and comparing the vibration frequency true value and the vibration amplitude true value with the vibration frequency indication and the vibration amplitude indication to obtain a measurement accuracy index. The present invention can be traced back to national and international metrology standards, and can control the generation of high-precision blade vibration signals, with an amplitude accuracy of 1 μm, an amplitude range of 0-100 mm, and a frequency range of 0-10 kHz, thereby meeting the calibration index requirements within the full parameter range of the blade vibration measurement system, and has a wide range of applications.

Description

Technical Field

[0001] The invention belongs to the field of non-contact blade tip timing vibration measurement, and in particular relates to a precision calibration method for a blade vibration measurement system with traceable blade tip timing. Background Art

[0002] In large rotating machinery such as aircraft engines, gas turbines, steam turbines, and flue gas turbines, moving blades are the core working elements, and their operating status parameters directly affect the working performance and operating safety of the equipment. Online measurement of blade vibration parameters at high temperatures is the key to ensuring the working performance and operating safety of the equipment.

[0003] Tip timing vibration measurement technology is currently a hot topic in the research of online measurement of blade vibration parameters. At present, there is no universal third-party calibration method and corresponding equipment for non-contact blade vibration measurement technology and products based on the tip timing principle. In particular, it is impossible to calibrate or verify the blade vibration displacement and amplitude measurement accuracy. The existing idea is to verify the strain amplitude comparison of frequency and finite element transformation by comparing with strain gauges, but the strain gauge method is to measure by sticking strain gauges on the surface of the blade, which is a contact measurement and will change the vibration characteristics of the blade. In addition, the strain gauge measurement accuracy is low and there is an error of 5-10%. The strain gauge measurement results can only verify the correctness of the measurement results of the tip timing vibration measurement system, and its accuracy is difficult to meet the calibration requirements of the tip timing vibration measurement system. Therefore, there is currently no mature method for calibrating the tip timing vibration measurement system.

[0004] In addition, during the calibration or measurement process of the blade vibration measurement system, according to the actual blade monitoring needs of aircraft engines, gas turbines, etc., a blade amplitude signal for measurement must be generated, the amplitude accuracy must be controlled at the order of 1μm, the amplitude measurement range must be set within 0-100mm, and the frequency must be set within the range of 0-several thousand Hz. However, such indicators cannot be achieved on equipment such as rotating tables. Therefore, there is currently no calibration device that can produce high-precision and widely applicable blade tip timing vibration measurement systems.

[0005] Therefore, there is an urgent need for a precision calibration method for a blade vibration measurement system with traceable tip timing to address the deficiencies in the prior art. Summary of the invention

[0006] The purpose of the present invention is to propose a method for calibrating the accuracy of a blade tip timing blade vibration measurement system that can be traced back to the source, so as to realize the calibration of the blade tip timing vibration measurement system and verify the accuracy and reliability of the measurement results of the blade tip timing vibration measurement system.

[0007] To achieve the above object, the present invention provides a method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing, comprising the following steps:

[0008] determining blade vibration signal parameters;

[0009] Based on the blade vibration signal parameters, an OPR pulse signal and a blade tip timing pulse signal are obtained as timing pulse signals;

[0010] Performing pulse width modulation according to the blade tip timing pulse signal to obtain a vibration frequency true value and a vibration amplitude true value;

[0011] Inputting the timing pulse signal into the blade vibration measurement system calculates the vibration frequency indication and the vibration amplitude indication;

[0012] The vibration frequency true value and the vibration amplitude true value are respectively compared with the vibration frequency indication and the vibration amplitude indication to obtain a measurement accuracy index, thereby achieving accuracy calibration of the blade vibration measurement system.

[0013] Optionally, determining the blade vibration signal parameter includes:

[0014] The blade vibration signal parameters are determined according to the target measurement standard, wherein the blade vibration parameters include rotational speed frequency, number of blades, blade length, standard vibration amplitude, standard vibration frequency, OPR sensor angle, number of blade tip timing sensors, and an angle between the blade tip timing sensor and the OPR sensor.

[0015] Optionally, acquiring an OPR pulse signal and a blade tip timing pulse signal as a timing pulse signal based on the blade vibration signal parameter includes:

[0016] According to the blade vibration signal parameters, the OPR sensor and the blade tip timing sensor are used to obtain the OPR pulse signal and a plurality of blade tip timing pulse signals as the timing pulse signal.

[0017] Optionally, the OPR pulse signal is a square wave pulse signal, and a duty cycle of the square wave pulse signal is <50%.

[0018] Optionally, performing pulse width modulation according to the blade tip timing pulse signal to obtain the vibration frequency true value and the vibration amplitude true value includes:

[0019] Performing pulse width modulation on the blade tip timing pulse signal, and calculating and obtaining the pulse width of the blade tip timing sensor by jittering the falling edge of the blade tip timing pulse signal;

[0020] Taking the falling edge as the actual arrival time to obtain the actual blade arrival time of the simulated timing pulse signal;

[0021] Setting a theoretical blade arrival time of the simulated timing pulse signal, and obtaining a standard arrival time difference according to the actual blade arrival time of the simulated timing pulse signal and in combination with the pulse width of the blade tip timing sensor;

[0022] Calculating a theoretical vibration displacement using the standard arrival time difference, and combining a plurality of the theoretical vibration displacements in chronological order to obtain a theoretical vibration displacement data set;

[0023] Performing a fast Fourier transform on the theoretical vibration displacement data set to obtain the true value of the vibration frequency and the true value of the vibration amplitude.

[0024] Optionally, the blade tip timing sensor pulse width is:

[0025]

[0026] in, For the Tip timing sensors Pulse width, To simulate the actual blade arrival time of the timing pulse signal, is the pulse width of the blade tip timing pulse signal, is the variation range of the modulation pulse width, is the frequency of the modulating signal.

[0027] Optionally, the standard arrival time difference is:

[0028]

[0029] in,

[0030]

[0031]

[0032] In the formula, is the standard arrival time difference, To simulate the theoretical blade arrival time of the timing pulse signal, For the The angle between the blade tip timing sensor and the OPR sensor, is the number of leaves, is the speed frequency.

[0033] Optionally, the theoretical vibration displacement is:

[0034]

[0035] in,

[0036]

[0037] In the formula, For the Circle The theoretical vibration displacement of each blade, is the blade tip rotation radius, is the standard arrival time difference.

[0038] Compared with the closest prior art, the present invention has the following beneficial effects:

[0039] The present invention is based on the basic principle of PWM modulation, and uses a high-precision function generator to generate a high-precision blade tip timing pulse signal carrying blade vibration, and calibrates the vibration measurement system or data acquisition system based on blade tip timing. At present, there is no other method for the rotating blade to generate a standard high-precision, controllable blade vibration pulse signal within the full parameter range. There is no national measurement and verification standard for the blade vibration measurement system. The present invention uses a high-precision function generator that has been traced and measured to generate a vibration signal simulating the blade, and realizes the calibration or measurement of the non-contact blade vibration measurement system. At the same time, the present invention can be traced back to national and international measurement standards, and can control the generation of high-precision blade vibration signals with an amplitude accuracy of 1μm, an amplitude range of 0-100mm, and a frequency range of 0-10kHz, thereby meeting the calibration index requirements within the full parameter range of the blade vibration measurement system, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A block diagram of blade vibration measurement based on blade tip timing and the accuracy of a blade vibration measurement system with traceable blade tip timing based on PWM proposed in an embodiment of the present invention, wherein: 1-casing, 2-blade, 3-speed synchronization sensor, 4-blade tip timing sensor, 5-sensor signal conditioning module, 6-high-precision function generator after traceability, 7-blade tip timing vibration measurement system;

[0042] Figure 2 This is a flow chart of a method for calibrating the accuracy of a blade vibration measurement system with traceable blade tip timing according to an embodiment of the present invention;

[0043] Figure 3 A schematic diagram of the actual process of the method for calibrating the accuracy of the blade vibration measurement system with traceable blade tip timing proposed in an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the blade tip timing signal generation principle based on PWM modulation proposed in an embodiment of the present invention;

[0045] Figure 5A schematic diagram of a detection data curve proposed in an embodiment of the present invention;

[0046] Figure 6 A schematic diagram of the amplitude-spectrum result proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0048] The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.

[0049] The blade tip timing vibration measurement technology is currently a hot topic in the research of online measurement of blade vibration parameters. Figure 1 As shown, the tip timing sensor 4 is installed on the casing 1, and the speed synchronization sensor 3, namely the OPR sensor, is installed on the stator. When the blade 2 passes the tip timing sensor 4, a pulse signal is generated through the sensor signal conditioning module 5, and the arrival time of the pulse signal relative to the speed synchronization sensor 3 is extracted through the tip timing measurement system 7; the vibration displacement of the blade can be obtained by comparing the measured blade arrival time with the theoretical arrival time of the blade in the absence of vibration, combined with the current speed; then the vibration parameters such as the blade vibration frequency and amplitude can be calculated through the host computer program and related identification algorithms.

[0050] The blade tip timing vibration measurement system based on blade tip timing mainly consists of four parts: sensor, sensor drive and signal conditioning module, data acquisition system and host computer software. The blade tip timing vibration measurement system has been successfully applied in engine blade vibration measurement for nearly 10 years. After continuous improvement, the main technologies in productization, engineering, function, algorithm and software have been proven to meet the testing needs of aircraft engines. The sensor mainly senses the physical quantity changes when the blade and shaft benchmark arrive. At present, a variety of sensors of different types and parameters have been developed at home and abroad, mainly optical fiber, eddy current and microwave types; the sensor drive and signal conditioning module mainly drives the sensor, reduces noise and amplifies the sensor signal; the multi-channel parallel pulse signal output by the front circuit module of the data acquisition system is digitally processed by identification, counting, filtering, etc., and then the digital blade tip timing signal is transmitted to the host computer according to the communication protocol; the host computer software uses a variety of algorithms to extract blade vibration information from the blade tip timing signal uploaded by the data acquisition module, identify vibration parameters such as displacement, amplitude, frequency, phase, and provide real-time acquisition, data playback, offline analysis and other functions.

[0051] like Figure 2-3 As shown, an embodiment of the present invention provides a method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing, which uses a high-precision function generator to generate a timing pulse signal with preset blade vibration information based on the PWM principle. The above pulse signal is input into the blade vibration measurement system, that is, the calibrated system. The system processes the pulse signal and measures the blade vibration amplitude and frequency, which can be compared with the theoretical actual amplitude and frequency to achieve calibration or measurement. The specific steps are as follows:

[0052] Step 1: Determine the blade vibration signal parameters, specifically:

[0053] The blade vibration signal parameters are determined according to the target measurement standard, that is, the blade vibration signal parameters are determined by tracing back to the national standard or international standard, including setting the rotation speed frequency to , that is, the rotor frequency (how many revolutions per second); set the number of blades to , leaf length , the standard vibration amplitude is , the standard vibration frequency is ; Set the OPR sensor to 0°, that is, the speed synchronization sensor angle is 0°; Set the number of blade tip timing sensors to Only, numbered in order , where the blade tip timing sensor The angles with the OPR sensor are .

[0054] Step 2: Obtain the OPR pulse signal and blade tip timing pulse signal based on the blade vibration signal parameters, and use a high-precision function generator to obtain the timing pulse signal with blade vibration information based on the PWM principle, that is, obtain the true value of the vibration frequency and the true value of the vibration amplitude. Specifically:

[0055] According to the blade tip timing principle, the timing pulse signals that need to be generated have a total of Therefore, this implementation is based on the blade vibration signal parameters and the blade tip timing principle to obtain the timing pulse signal through the sensor, wherein one path is the timing pulse signal of the OPR sensor installed on the shaft, that is, the OPR pulse signal, and the rest Road The timing pulse signal of a blade tip timing sensor is called the blade tip timing pulse signal.

[0056] The OPR pulse signal has a frequency of The square wave pulse signal can be set to any value less than 50% of the duty cycle, with the first pulse rising edge of the OPR pulse signal as the 0 moment. For the blade tip timing pulse signal, it is necessary to use the modulated PWM signal. The specific principle is as follows: Figure 4 shown.

[0057] Tip timing sensor As an example, a high-precision function generator with a frequency of , the pulse width is , the phase is The blade tip timing pulse signal is PWM modulated, and the modulation signal is ,in, is the variation range of the modulation pulse width, is the frequency of the modulation signal. At this time, the falling edge of the blade tip timing pulse signal caused by PWM modulation has regular jitter. Tip timing sensors Pulse width for:

[0058]

[0059] in, The tip timing sensor measures Tip timing pulses.

[0060] Taking the falling edge as the actual arrival time, the actual blade arrival time of the simulated timing pulse signal can be obtained for:

[0061]

[0062] in, To simulate the actual blade arrival time of the timing pulse signal, For the The angle between the blade tip timing sensor and the OPR sensor;

[0063] The theoretical blade arrival time of the simulated timing pulse signal is It can be set as:

[0064]

[0065] At this time, the standard arrival time difference for:

[0066]

[0067] According to the blade tip timing principle formula, the standard arrival time difference is matched with the sequence in the blade tip timing principle, that is, , so , For the The standard arrival time difference of the blades is measured by the blade tip timing sensor, where is the number of circles, is the blade number.

[0068] Can get the first Circle Theoretical vibration displacement of each blade for:

[0069]

[0070] in, is the blade tip rotation radius;

[0071] like Figure 5 As shown, the calibrated system arranges and combines the vibration displacement data of all blades in the order of their arrival time, i.e. the theoretical vibration displacement data set. ,in , , The pulses come in sequence, which is a non-negative integer. The data is equivalent to Frequency to Frequency The sine wave is sampled, so Perform a fast Fourier transform, such as Figure 6 As shown, the spectral line frequency is , the amplitude is .

[0072] In summary, the standard vibration amplitude of the blade set in step 1 can be and frequency Calculate the amplitude and frequency of the function generator, that is, the standard function generator is set to , set the frequency to .

[0073] In the process of generating the calibration signal, the stability accuracy of the frequency signal of the existing function generator can reach 1.0×10 -9 The above, that is The accuracy can also be as high as 1.0×10 -9 The blade tip rotation diameter is not greater than 10m. The accuracy is much less than 1μm.

[0074] By setting different and Value, the amplitude calibration range can be set from 0 to 100 mm.

[0075] By setting If the value changes between 0-10kHz, the blade vibration measurement system calibration is realized within the range of 0-10kHz.

[0076] Therefore, the present invention can generate a high-precision blade vibration measurement system calibration signal, and the parameter range of the signal can be set to be wide.

[0077] Step 3: Input the timing pulse signals of the blade tip timing sensor and the OPR sensor into the blade vibration measurement system, i.e., the calibrated blade vibration test equipment, obtain the vibration frequency indication and the vibration amplitude indication, and compare them with the vibration frequency true value and the vibration amplitude true value respectively to obtain the measurement accuracy index;

[0078] The OPR pulse signal generated by the high-precision function generator in step 2 and The blade tip timing pulse signal is input into the blade vibration test equipment to be calibrated. After the system collects the signal, based on the blade tip timing vibration measurement principle, the blade vibration parameter identification algorithm in the system to be calibrated is used to calculate the output measurement frequency and amplitude indication; by changing the amplitude and frequency, the performance indicators of the blade vibration measurement system can be calibrated or measured within the full parameter range;

[0079] The amplitude display value and the set amplitude Subtract the output frequency from the set frequency to obtain the system amplitude measurement error. By making a difference, the system frequency measurement error is obtained, and then the measurement accuracy index is obtained, thereby realizing the measurement or calibration of the blade vibration measurement system. Example

[0080] A pulse signal from a function generator, such as , as the OPR signal, the speed is 12000rpm; the other pulse signal frequency is =OPR signal frequency*number of blades N (e.g. number of blades 50), then the signal frequency is 10kHz, and PWM modulation is performed on the signal. , then the edge of each pulse signal will change back and forth at the standard position according to the modulation frequency over time, simulating the vibration of the blades. PWM modulation makes the edges of all blades change at the modulation frequency. and modulation amplitude By changing , compared with the blade amplitude displayed by the system monitoring With input signal The difference, comparing the vibration frequency and difference to verify the measurement performance.

[0081] Take 10 points and compare the measured blade tip amplitude values. Theoretical amplitude value The difference between the amplitude measurement accuracy and vibration displacement resolution can be used to verify whether they meet the requirements; the actual measurement can be compared in a table. and theory The difference is used to verify whether the vibration frequency measurement accuracy meets the requirements, as shown in Table 1, a measurement calibration data record table.

[0082] Table 1

[0083]

[0084] The above records show that the vibration displacement resolution is better than 2um and the frequency recognition error is less than 1Hz.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing, characterized in that: The specific steps include: determining blade vibration signal parameters; Determining the blade vibration signal parameters includes: Determine the blade vibration signal parameters according to the target measurement standard, wherein the blade vibration signal parameters include rotational speed frequency, number of blades, blade length, standard vibration amplitude, standard vibration frequency, OPR sensor angle, number of blade tip timing sensors, and an angle between the blade tip timing sensor and the OPR sensor; Based on the blade vibration signal parameters, an OPR pulse signal and a blade tip timing pulse signal are obtained as timing pulse signals; Performing pulse width modulation according to the blade tip timing pulse signal to obtain a vibration frequency true value and a vibration amplitude true value; Performing pulse width modulation according to the blade tip timing pulse signal to obtain the vibration frequency true value and the vibration amplitude true value includes: Performing pulse width modulation on the blade tip timing pulse signal, and calculating and obtaining the pulse width of the blade tip timing sensor by jittering the falling edge of the blade tip timing pulse signal; Taking the falling edge as the actual arrival time to obtain the actual blade arrival time of the simulated timing pulse signal; Setting a theoretical blade arrival time of the simulated timing pulse signal, and obtaining a standard arrival time difference according to the actual blade arrival time of the simulated timing pulse signal and in combination with the pulse width of the blade tip timing sensor; Calculating a theoretical vibration displacement using the standard arrival time difference, and combining a plurality of the theoretical vibration displacements in chronological order to obtain a theoretical vibration displacement data set; Performing a fast Fourier transform on the theoretical vibration displacement data set to obtain the vibration frequency true value and the vibration amplitude true value; Inputting the timing pulse signal into the blade vibration measurement system calculates the vibration frequency indication and the vibration amplitude indication; The vibration frequency true value and the vibration amplitude true value are respectively compared with the vibration frequency indication and the vibration amplitude indication to obtain a measurement accuracy index, thereby achieving accuracy calibration of the blade vibration measurement system.

2. The method for calibrating the accuracy of the traceable tip timing blade vibration measurement system according to claim 1, characterized in that: Acquiring an OPR pulse signal and a blade tip timing pulse signal as a timing pulse signal based on the blade vibration signal parameter includes: According to the blade vibration signal parameters, the OPR sensor and the blade tip timing sensor are used to obtain the OPR pulse signal and a plurality of blade tip timing pulse signals as the timing pulse signal.

3. The method for calibrating the accuracy of the traceable tip timing blade vibration measurement system according to claim 2, characterized in that: The OPR pulse signal is a square wave pulse signal, and the duty cycle of the square wave pulse signal is less than 50%.

4. The method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing according to claim 1, characterized in that: The pulse width of the blade tip timing sensor is: Among them, dt jm is the pulse width of the jth blade tip timing sensor m, t jm is the actual blade arrival time of the simulated timing pulse signal, d t0 is the pulse width of the blade tip timing pulse signal, A0 is the variation range of the modulation pulse width, f c is the frequency of the modulating signal.

5. The method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing according to claim 4, characterized in that: The standard arrival time difference is: in, In the formula, Δt jm is the standard arrival time difference, is the theoretical blade arrival time of the simulated timing pulse signal, β j is the angle between the jth blade tip timing sensor and the OPR sensor, N is the number of blades, and f r is the speed frequency.

6. The method for calibrating the accuracy of a blade vibration measurement system with traceable tip timing according to claim 5, characterized in that: The theoretical vibration displacement is: in, m%k=i In the formula, y jki is the theoretical vibration displacement of the i-th blade in the k-th circle, R is the tip rotation radius, Δt jki is the standard arrival time difference.

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