A differential pressure flow meter flow measurement system and method based on strain and temperature self-compensation

Abstract

The present application relates to the technical field of flow measurement system, especially relates to a kind of flow measurement system of strain and temperature self-compensated differential pressure flowmeter, the system includes differential pressure flowmeter table body, installation component, differential pressure piece, strain sensor, optical fiber, fiber grating demodulator, microprocessor and power supply device;Two ends of differential pressure flowmeter table body outside are equipped with installation component between measurement pipeline and are assembled, differential pressure piece is installed in the center position of a section of pipeline in the center of differential pressure flowmeter table body, and two groups of strain sensors symmetrically arranged on the two sides of differential pressure piece are pasted on differential pressure flowmeter table;The strain difference change of differential pressure flowmeter is measured by pasting strain sensor, it does not need to open hole, does not affect the internal flow field of differential pressure flowmeter, improves its flow measurement accuracy, when calculating strain difference, the change amount caused by temperature is offset, solve the problem of temperature and stress cross-sensitivity when strain sensor is measured.

Description

Technical Field

[0001] This invention relates to the field of flow measurement system technology, and in particular to a differential pressure flow meter flow measurement system and method based on strain and temperature self-compensation. Background Technology

[0002] In the development of key military models such as rocket engines and aero engines, the flow rates of propellant and oxidizer are critical parameters that have a significant impact on the test models during the testing process. Effectively mastering the flow rates during testing can provide reliable data support for engine performance verification, fault analysis, and design improvement.

[0003] Currently, over 40% of flow measurements in industry still use differential pressure flow meters. These flow meters require pressure taps on both sides of the differential pressure element to measure flow. A differential pressure transmitter is then connected to these taps to measure the differential pressure. However, during actual testing of rocket engines, the high pressure in the flow meter's measuring pipeline causes stress concentration at the taps, leading to material fatigue and propellant or oxidizer leaks. Furthermore, the testing environment inevitably presents harsh conditions such as high temperatures, strong vibrations, and water spray, making conventional differential pressure transmitters unsuitable for these environments. This significantly complicates flow measurement.

[0004] For the development or testing needs of engines, there is a need for a flow measurement method that can measure flow without damaging the pipeline of the flow measurement medium, and has high reliability and high measurement accuracy. Summary of the Invention

[0005] This invention provides a flow measurement system and method for differential pressure flowmeters based on strain and temperature self-compensation. It can avoid opening pressure taps on differential pressure flowmeters, solve the technical problems of low measurement accuracy, poor vibration resistance, and inability to achieve non-contact measurement in the prior art, and meet the requirements of differential pressure flowmeters for use in harsh working conditions at the commissioning site.

[0006] The technical solution of the present invention is as follows: a differential pressure flow meter flow measurement system based on strain and temperature self-compensation. The system includes a differential pressure flow meter body, an installation assembly, a differential pressure component, strain sensors, optical fibers, a fiber optic demodulator, a microprocessor, and a power supply device. The differential pressure flow meter body has installation assemblies at both ends of its outer side for assembly with the measuring pipeline. A differential pressure component is installed at the center of a section of pipeline inside the differential pressure flow meter body. Two sets of strain sensors are symmetrically arranged on both sides of the differential pressure component and attached to the flow meter. Optical fibers for transmitting optical signals are installed on the outer side of each set of strain sensors. The other end of the optical fiber is connected to a fiber optic demodulator. A microprocessor connected via an electrical interface is installed on the outer side of the fiber optic demodulator. A power supply device is installed on the outer side of the microprocessor.

[0007] The fiber Bragg grating demodulator includes a light source module that generates a stable optical signal, a demodulation module, a signal processing module, and a communication interface;

[0008] A microprocessor includes a central processing unit that controls the operation of the entire system, memory, input / output interfaces, and communication interfaces;

[0009] The power supply device includes a power conversion module that converts the input AC or DC power into DC power or AC power of a specific voltage required by the system, a protection module, and a monitoring module that monitors the output voltage and current of the power supply.

[0010] Preferably, the mounting assembly includes flanges that are fixedly connected to both sides of the differential pressure flow meter body. The flanges have fastening screw holes, and fastening bolts are detachably connected inside the fastening screw holes.

[0011] Preferably, the differential pressure component is any one of the following: standard orifice plate, conical flow cut-off component, wedge-shaped flow cut-off component, eccentric orifice plate, multi-hole orifice plate, bend, and averaging pitot tube.

[0012] Preferably, the two sets of strain sensors also employ FBG sensor a located upstream of the flow rate and FBG sensor b located downstream of the flow rate. The reflection wavelength range of FBG sensor a and FBG sensor b is between 1500nm and 1580nm. When light passes through FBG sensor a and FBG sensor b, the reflected wavelength of the light is:

[0013]

[0014] in For effective refractive index, This is the Bragg period of the fiber Bragg grating.

[0015] Preferably, bonding measuring points are provided on both sides of the differential pressure component. FBG sensor a and FBG sensor b are connected to the fiber optic demodulator via optical fiber. The strain values ​​of FBG sensor a and FBG sensor b are obtained by the fiber optic demodulator through acquisition and calculation.

[0016] Preferably, the demodulation module receives the optical signal and demodulates it into an electrical signal corresponding to the physical quantity. The signal processing module further processes the demodulated electrical signal, including filtering, amplification, and digital processing.

[0017] Preferably, the memory stores programs and data, including the operating system, applications, and measurement data, and the communication interface enables data communication with other systems, including remote monitoring and data uploading.

[0018] As a preferred option, the differential pressure flowmeter flow measurement system with strain and temperature self-compensation is calibrated before use, assuming the standard flow rate is... The fluid flows through the differential pressure flowmeter body, and the strain value collected by the fiber optic demodulator at FBG sensor a is... The strain value collected by the fiber optic demodulator at sensor b is Then the strain difference for:

[0019]

[0020] Multiple sets of standard flow values ​​were measured using a standard flow calibration device and a grating fiber optic demodulator. and the corresponding multiple sets of strain difference values ;

[0021] The formula for calculating flow rate is:

[0022] a+b

[0023] in This is the strain difference value, in units of ; This is the standard flow rate, expressed in L / min.

[0024] A flow measurement method for a differential pressure flow meter based on strain and temperature self-compensation, comprising a differential pressure flow meter flow measurement system based on strain and temperature self-compensation as described above, and the steps are as follows:

[0025] S1: Calibration Process

[0026] S11: Install the differential pressure flow meter body onto the measuring pipeline of the standard flow calibration device through the flange, ensuring a tight and leak-free connection;

[0027] S12: Connect the optical fiber to FBG sensor a and FBG sensor b, and then connect it to the fiber optic demodulator to transmit and receive optical signals. Start the motor through the controller, and then drive the ball screw and piston rod to make the piston reciprocate in the active volume tube to simulate different flow rates.

[0028] S13: Initialize the data acquisition unit and computer, set the data acquisition parameters, including sampling frequency and data storage path. The fiber optic demodulator receives the strain signals from FBG sensor a and FBG sensor b and converts them into digital signals for computer processing.

[0029] S14: Open the first, second, and third control valves to allow fluid to flow from the oil tank into the active volume tube. The piston movement generates different flow rates. At these different flow rates, the computer receives strain signals from FBG sensor a and FBG sensor b transmitted by the fiber optic grating demodulator via the data acquisition unit, and simultaneously records the corresponding flow rate values. Repeat the above steps to measure multiple sets of flow rates. and the corresponding strain difference value ;

[0030] S15: Measure the multiple sets of flow values ​​obtained. and the corresponding strain difference value Import the data into a computer for processing, and use the least squares method or other suitable fitting methods to analyze the flow rate values. and strain difference By fitting the data, the corresponding relationships between them are obtained. Based on the fitting results, a mathematical model of the flow meter is established for subsequent flow measurement and calibration.

[0031] S16: Reinstall the calibrated flow meter onto the actual measuring pipeline, perform actual flow measurement, compare the measurement results with the standard flow value obtained by measuring other high-precision flow meters, and verify the accuracy of the calibration results;

[0032] S2: Attach FBG sensor a and FBG sensor b

[0033] After calibration, the differential pressure flow meter body is installed onto the pipeline to be tested via the flange. First, use sandpaper to clean the dirt, oxide layer, and rust covering the surface of the bonding test point. Then, use clean degreased cotton soaked in anhydrous ethanol to wipe the bonding test point until the cotton ball is completely clean. Finally, place FBG sensor a and FBG sensor b on the cleaned bonding test point, apply the adhesive evenly, and wait for it to cure before taking the measurement.

[0034] S3: When FBG sensors a and b are subjected to stress, they stretch or contract, causing changes in the effective refractive index and grating period of the fiber optic grating. This results in a corresponding change in the reflected spectral wavelength. The change is then measured by examining the spectral wavelength. The change in temperature indirectly measures the strain value change on both sides of the differential pressure component being measured. When the temperature of FBG sensor a and FBG sensor b changes, FBG sensor a and FBG sensor b undergo thermal expansion and contraction deformation, which changes the period length of the fiber optic grating sensor, and thus causes the center wavelength of the reflection spectrum to shift. A specific wavelength corresponds to a specific temperature. Therefore, by measuring the center wavelength of the reflection spectrum, the temperature of the fiber optic grating region can be measured.

[0035] As a preferred method, during flow measurement, the strain sensors attached to both sides of the differential pressure component are simultaneously affected by temperature and stress. Since the pipeline medium is in a state of long-term flow during measurement, the temperature change dynamics of the strain sensors on both sides of the differential pressure component are the same, and the amount of influence of temperature on the strain sensors is also equal. Therefore, when calculating the strain difference, the influence of temperature is eliminated to achieve the purpose of temperature self-compensation. Taking FBG sensor a and FBG sensor b as examples, the change in the center wavelength of the reflection spectrum caused by temperature is basically equal, and the change in resistance caused by temperature is also basically equal for strain gauges.

[0036] The beneficial effects of this invention are as follows: Currently used differential pressure flow meters require openings on both sides of the differential pressure component to measure the pressure difference. However, this invention measures the change in strain difference value of the differential pressure flow meter by attaching a strain sensor. This does not require openings and does not affect the internal flow field of the differential pressure flow meter, thereby improving the accuracy of flow measurement. When calculating the strain difference value, the change caused by temperature is offset, which solves the problem of cross-sensitivity of strain sensor to temperature and stress during measurement. Attached Figure Description

[0037] Figure 1 The diagram shows a three-dimensional structural schematic of the differential pressure flowmeter body of a differential pressure flowmeter flow measurement system based on strain and temperature self-compensation according to the present invention.

[0038] Figure 2 The diagram shows a three-dimensional structure of FBG sensor a and FBG sensor b in a differential pressure flow meter flow measurement system based on strain and temperature self-compensation according to the present invention.

[0039] Figure 3 The diagram shown is a schematic diagram of the calibration principle of a differential pressure flowmeter flow measurement system based on strain and temperature self-compensation according to the present invention.

[0040] Explanation of reference numerals in the attached drawings: 1. Differential pressure flow meter body; 3. Differential pressure component; 4. Strain sensor; 5. Optical fiber; 6. Fiber optic demodulator; 7. Microprocessor; 8. Power supply device; 9. Motor; 10. Ball screw; 11. Piston rod; 12. Piston; 13. Active volume tube; 14. First control valve; 15. Second control valve; 16. Third control valve; 17. Oil tank; 101. Adhesive measuring point; 201. Flange; 202. Fastening screw hole; 203. Fastening bolt; 401. FBG sensor a; 402. FBG sensor b. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Please see Figure 1-3This invention provides an embodiment: the system comprises a differential pressure flow meter body 1, an installation assembly, a differential pressure component 3, a strain sensor 4, an optical fiber 5, a fiber optic demodulator 6, a microprocessor 7, and a power supply device 8; the differential pressure flow meter body 1 has installation assemblies installed at both ends of its outer side for assembly with the measuring pipeline; a differential pressure component 3 is installed at the center of a section of pipeline inside the differential pressure flow meter body 1; two sets of strain sensors 4 are symmetrically arranged on both sides of the differential pressure component 3 and attached to the differential pressure flow meter body 1; optical fibers 5 for transmitting optical signals are installed on the outer side of both sets of strain sensors 4; the other end of the optical fiber 5 is connected to the fiber optic demodulator 6; a microprocessor 7 connected via an electrical interface is installed on the outer side of the fiber optic demodulator 6; and a power supply device 8 is installed on the outer side of the microprocessor 7.

[0043] The fiber optic grating demodulator 6 includes a light source module for generating stable optical signals, a demodulation module, a signal processing module, and a communication interface;

[0044] The microprocessor 7 includes a central processing unit that controls the operation of the entire system, memory, input / output interfaces, and communication interfaces;

[0045] The power supply device 8 includes a power conversion module that converts the input AC or DC power into DC power or AC power of a specific voltage required by the system, a protection module, and a monitoring module that monitors the output voltage and current of the power supply.

[0046] Example 1

[0047] This invention provides an embodiment: the system includes a differential pressure flow meter body 1, mounting components, a differential pressure element 3, strain sensors 4, optical fibers 5, a fiber optic demodulator 6, a microprocessor 7, and a power supply device 8; mounting components for assembly with the measuring pipeline are installed at both ends of the differential pressure flow meter body 1; a differential pressure element 3 is installed at the center of a section of pipeline inside the differential pressure flow meter body 1; two sets of strain sensors 4 are symmetrically arranged on both sides of the differential pressure element 3 and attached to the differential pressure flow meter body 1; optical fibers 5 for transmitting optical signals are installed on the outside of both sets of strain sensors 4; the other end of the optical fiber 5 is connected to the fiber optic demodulator 6; a microprocessor 7 connected via an electrical interface is installed on the outside of the fiber optic demodulator 6; and a power supply device 8 is installed on the outside of the microprocessor 7. The power supply device 8 includes flanges 201 fixedly connected to both sides of the differential pressure flowmeter body 1. Fastening screw holes 202 are provided inside the flanges 201, and fastening bolts 203 are detachably connected inside the fastening screw holes 202. The differential pressure component 3 specifically adopts any one of the following: standard orifice plate, conical flow cut-off component, wedge-shaped flow cut-off component, eccentric orifice plate, multi-hole orifice plate, bend, and averaging pitot tube. The two sets of strain sensors 4 also employ FBG sensor a401 located upstream of the flow meter and FBG sensor b402 located downstream of the flow meter. The reflection wavelength range of FBG sensor a401 and FBG sensor b402 is between 1500nm and 1580nm. When light passes through FBG sensor a401 and FBG sensor b402, the reflected wavelength is:

[0048]

[0049] in For effective refractive index, This is the Bragg period of the fiber Bragg grating.

[0050] As a preferred embodiment, the differential pressure component 3 is provided with adhesive measuring points 101 on both sides. FBG sensor a401 and FBG sensor b402 are connected to fiber optic demodulator 6 through fiber optic cable 2. The strain values ​​of FBG sensor a401 and FBG sensor b402 are collected and calculated by fiber optic demodulator 6.

[0051] The fiber optic grating demodulator 6 includes a light source module that generates a stable optical signal, a demodulation module, a signal processing module, and a communication interface. The demodulation module receives the optical signal and demodulates it into an electrical signal corresponding to the physical quantity. The signal processing module further processes the demodulated electrical signal, including filtering, amplification, and digital processing.

[0052] The microprocessor 7 includes a central processing unit that controls the operation of the entire system, a memory, an input / output interface, and a communication interface. The memory stores programs and data, including the operating system, application programs, and measurement data. The communication interface enables data communication with other systems, including remote monitoring and data uploading.

[0053] The power supply device 8 includes a power conversion module that converts the input AC or DC power into DC power or AC power of a specific voltage required by the system, a protection module, and a monitoring module that monitors the output voltage and current of the power supply.

[0054] Before use, the differential pressure flow meter flow measurement system with strain and temperature self-compensation should be calibrated, assuming the standard flow rate is... The fluid flows through the differential pressure flowmeter body 1, and the strain value collected by the fiber optic demodulator 6 at the FBG sensor a401 is... The strain value acquired by the fiber optic demodulator 6 at sensor b402 is... Then the strain difference for:

[0055]

[0056] Multiple sets of standard flow values ​​were measured using a standard flow calibration device and a grating fiber optic demodulator. and the corresponding multiple sets of strain difference values As shown in the table below:

[0057]

[0058] Table 1. Correspondence between standard flow rate values ​​and strain difference values

[0059] The formula for calculating flow rate is:

[0060] a+b

[0061] in This is the strain difference value, in units of ; This is the standard flow rate, expressed in L / min.

[0062] Using the least squares method on the data in Table 1, we obtain: intercept a: -0.512352, unit L / min; slope b: 0.986362, unit L / (min* );

[0063] Substituting into the above formula yields the flow rate value. =-0.512352+0.986362 .

[0064] A flow measurement method for a differential pressure flow meter based on strain and temperature self-compensation, comprising a differential pressure flow meter flow measurement system based on strain and temperature self-compensation as described above, and the steps are as follows:

[0065] S1: Calibration Process

[0066] S11: Install the differential pressure flow meter body 1 onto the measuring pipeline of the standard flow calibration device through flange 201, ensuring a tight connection without leakage;

[0067] S12: Connect the optical fiber 5 to the FBG sensor a401 and FBG sensor b402, and then connect it to the fiber grating demodulator 6 to transmit and receive optical signals. Start the motor 9 through the controller, and then drive the ball screw 10 and piston rod 11 to make the piston 12 reciprocate in the active volume tube 13 to simulate different flow rates.

[0068] S13: Initialize the data acquisition unit and computer, set the data acquisition parameters, including sampling frequency and data storage path. The fiber optic demodulator 6 receives the strain signals from FBG sensor a401 and FBG sensor b402 and converts them into digital signals for computer processing.

[0069] S14: Open the first control valve 14, the second control valve 15, and the third control valve 16 to allow fluid to flow from the oil tank 17 into the active volume pipe 13. The movement of the piston 12 generates different flow rates. At different flow rates, the computer receives the strain signals from the FBG sensor a401 and FBG sensor b402 transmitted by the fiber optic demodulator 6 via the data acquisition unit, and simultaneously records the corresponding flow rate values. Repeat the above steps to measure multiple sets of flow rates. and the corresponding strain difference value ;

[0070] S15: Measure the multiple sets of flow values ​​obtained. and the corresponding strain difference value Import the data into a computer for processing, and use the least squares method or other suitable fitting methods to analyze the flow rate values. and strain difference By fitting the data, the corresponding relationships between them are obtained. Based on the fitting results, a mathematical model of the flow meter is established for subsequent flow measurement and calibration.

[0071] S16: Reinstall the calibrated flow meter onto the actual measuring pipeline, perform actual flow measurement, compare the measurement results with the standard flow value obtained by measuring other high-precision flow meters, and verify the accuracy of the calibration results;

[0072] S2: Attach FBG sensor a401 and FBG sensor b402

[0073] After calibration, the differential pressure flow meter body 1 is installed onto the pipeline to be tested via flange 201. First, use sandpaper to clean the stains, oxide layer, and rust covering the surface of the adhesive measuring point 101. Then, use clean degreased cotton soaked in anhydrous ethanol to wipe the adhesive measuring point 101 until the cotton ball is completely clean. Finally, place the FBG sensor a401 and FBG sensor b402 on the cleaned adhesive measuring point 101, apply the adhesive evenly, and wait for it to cure before taking the measurement.

[0074] S3: When FBG sensors a401 and b402 are subjected to stress, they stretch or contract, causing changes in the effective refractive index and grating period of the fiber optic grating. This results in a corresponding change in the reflected spectral wavelength. The change is then measured by examining the spectral wavelength. The strain sensor 4 attached to both sides of the differential pressure component 3 is subjected to both temperature and stress during flow measurement. Since the pipeline medium is in a state of long-term flow during measurement, the temperature changes dynamically at both sides of the strain sensor 4, and the amount of temperature affecting the strain sensor 4 is also equal. Therefore, the effect of temperature on the strain sensor 4 is eliminated when calculating the strain difference, achieving temperature self-compensation. For example, the temperature-induced change in the center wavelength of the reflection spectrum is basically equal for FBG sensor a401 and FBG sensor b402, and the temperature-induced change in resistance value is also basically equal for strain gauges.

Claims

1. A differential pressure flowmeter flow measurement system based on strain and temperature self-compensation, the system comprising a differential pressure flowmeter body (1); characterized in that, It also includes an installation component, a differential pressure component (3), a strain sensor (4), an optical fiber (5), a fiber optic demodulator (6), a microprocessor (7), and a power supply device (8); the differential pressure flow meter body (1) is equipped with an installation component for assembly with the measuring pipeline at both ends of the outer side, the differential pressure component (3) is installed at the center of the outer surface of the inner side of the differential pressure flow meter body (1), two sets of strain sensors (4) are symmetrically arranged on both sides of the differential pressure component (3) and the outer side of the two sets of strain sensors (4) are equipped with optical fibers (5) for transmitting optical signals. The other end of the optical fiber (5) is connected to the fiber optic demodulator (6), the outer side of the fiber optic demodulator (6) is equipped with a microprocessor (7) connected through an electrical interface, and the outer side of the microprocessor (7) is equipped with a power supply device (8); The fiber optic grating demodulator (6) includes a light source module that generates a stable optical signal, a demodulation module, a signal processing module, and a communication interface; The microprocessor (7) includes a central processing unit that controls the operation of the entire system, a memory, an input / output interface, and a communication interface; The power supply device (8) includes a power conversion module that converts the input AC or DC power into DC power or AC power with a specific voltage required by the system, a protection module, and a monitoring module that monitors the output voltage and current of the power supply. The mounting assembly includes flanges (201) fixedly connected to both sides of the differential pressure flow meter body (1). Fastening screw holes (202) are provided inside the flanges (201), and fastening bolts (203) are detachably connected inside the fastening screw holes (202). The differential pressure component (3) is specifically adopted as any one of the following: standard orifice plate, conical cut-off component, wedge-shaped cut-off component, eccentric orifice plate, multi-hole orifice plate, bend and averaging pipe; The two sets of strain sensors (4) also employ an FBG sensor a (401) located upstream of the flow rate and an FBG sensor b (402) located downstream of the flow rate. The reflection wavelength range of FBG sensor a (401) and FBG sensor b (402) is between 1500nm and 1580nm. When light passes through FBG sensor a (401) and FBG sensor b (402), the reflection wavelength of the light is: in For effective refractive index, The Bragg period of the fiber Bragg grating; Before use, the differential pressure flow meter flow measurement system with strain and temperature self-compensation should be calibrated, assuming the standard flow rate is... The fluid flows through the differential pressure flowmeter body (1), and the strain value collected by the fiber optic demodulator (6) at the FBG sensor a (401) is... The strain value acquired by the fiber optic demodulator (6) at sensor b (402) is Then the strain difference for: Multiple sets of standard flow values ​​were measured using a standard flow calibration device and a grating fiber optic demodulator. and the corresponding multiple sets of strain difference values ; The formula for calculating flow rate is: a+b in This is the strain difference value, in units of ; 1 is the standard flow rate, in L / min; 'a' is the intercept calculated using the least squares method, in L / min; 'b' is the slope calculated using the least squares method, in L / (min) ).

2. The differential pressure flowmeter flow measurement system based on strain and temperature self-compensation according to claim 1, characterized in that: The differential pressure component (3) has adhesive measuring points (101) on both sides. FBG sensor a (401) and FBG sensor b (402) are connected to fiber optic demodulator (6) through fiber optic cable (2). The strain values ​​of FBG sensor a (401) and FBG sensor b (402) are collected and calculated by fiber optic demodulator (6).

3. The differential pressure flowmeter flow measurement system based on strain and temperature self-compensation according to claim 1, characterized in that: The demodulation module receives the optical signal and demodulates it into an electrical signal corresponding to the physical quantity. The signal processing module further processes the demodulated electrical signal, including filtering, amplification, and digitization.

4. The differential pressure flowmeter flow measurement system based on strain and temperature self-compensation according to claim 1, characterized in that: The memory stores programs and data, including the operating system, applications, and measurement data, while the communication interface enables data communication with other systems, including remote monitoring and data uploading.

5. A flow measurement method for a differential pressure flowmeter based on strain and temperature self-compensation, characterized in that... The flow measurement system of a differential pressure flow meter based on strain and temperature self-compensation, as described in claim 2, comprises the following steps: S1: Calibration Process S11: Install the differential pressure flow meter body (1) onto the measuring pipeline of the standard flow calibration device through the flange (201) to ensure a tight connection without leakage; S12: Connect the optical fiber (5) to FBG sensor a (401) and FBG sensor b (402), and then connect it to the fiber grating demodulator (6) to transmit and receive optical signals. Start the motor (9) through the controller, and then drive the ball screw (10) and piston rod (11) to make the piston (12) reciprocate in the active volume tube (13) to simulate different flow rates; S13: Initialize the data acquisition unit and computer, set the data acquisition parameters, including sampling frequency and data storage path. The fiber optic demodulator (6) receives the strain signals from FBG sensor a (401) and FBG sensor b (402) and converts them into digital signals for computer processing. S14: Open the first control valve (14), the second control valve (15), and the third control valve (16) to allow fluid to flow from the oil tank (17) into the active volume tube (13). Different flow rates are generated by the movement of the piston (12). Under different flow rates, the computer receives the strain signals of FBG sensor a (401) and FBG sensor b (402) transmitted by the fiber optic grating demodulator (6) through the data acquisition unit, and records the corresponding flow rate values ​​at the same time. Repeat the above steps to measure multiple sets of flow rates. and the corresponding strain difference value ; S15: Measure the multiple sets of flow values ​​obtained. and the corresponding strain difference value Import the data into a computer for processing, using the least squares method to analyze the flow rate values. and strain difference By fitting the data, the corresponding relationships between them are obtained. Based on the fitting results, a mathematical model of the flow meter is established for subsequent flow measurement and calibration. S16: Reinstall the calibrated flow meter onto the actual measuring pipeline, perform actual flow measurement, compare the measurement results with the standard flow value obtained by measuring other high-precision flow meters, and verify the accuracy of the calibration results; S2: Attach FBG sensor a (401) and FBG sensor b (402). After calibration, the differential pressure flow meter body (1) is installed onto the pipeline to be tested via flange (201). First, use sandpaper to clean the stains, oxide layer and rust covering layer on the surface of the adhesive measuring point (101). Then, use clean degreased cotton soaked in anhydrous ethanol to wipe the adhesive measuring point (101) until the degreased cotton ball is completely clean. Finally, place FBG sensor a (401) and FBG sensor b (402) on the polished adhesive measuring point (101), apply the adhesive evenly, and wait for it to cure before measuring. S3: When FBG sensor a (401) and FBG sensor b (402) are subjected to stress, they are stretched or contracted, causing changes in the effective refractive index and grating period of the fiber optic grating, resulting in a corresponding change in the reflected spectral wavelength. This is achieved by measuring the spectral wavelength. The change in temperature indirectly measures the strain value change on both sides of the differential pressure component being measured. When the temperature of FBG sensor a (401) and FBG sensor b (402) changes, FBG sensor a (401) and FBG sensor b (402) undergo thermal expansion and contraction deformation, which changes the period length of the fiber optic grating sensor, thereby causing the center wavelength of the reflection spectrum to shift. A specific wavelength corresponds to a specific temperature. Therefore, by measuring the center wavelength of the reflection spectrum, the temperature of the fiber optic grating region can be measured.

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