High-temperature and high-pressure fiber bragg grating temperature sensor system for aerospace field and demodulation method

Abstract

The invention discloses a high-temperature and high-pressure fiber bragg grating temperature sensor system for the aerospace field, which comprises a sweep frequency light source, the sweep frequency light source is connected with a high-temperature and high-pressure fiber bragg grating temperature sensor through a circulator, the circulator is connected with a spectrum unit through an optical fiber coupler, and the spectrum unit is connected with a spectrum driving circuit through an optical fiber coupler. The spectrum driving circuit is connected with an AD conversion circuit through a PCI bus, the AD conversion circuit is connected with a control system through a PCI bus, and the control system is connected with an industrial control system through an RJ45 network cable. The invention further discloses a demodulation method of the high-temperature and high-pressure fiber bragg grating temperature sensor system for the aerospace field. The invention discloses a high-temperature and high-pressure fiber grating temperature sensor system for the aerospace field and a demodulation method, and solves the problem that the temperature field distribution of a storage tank cannot be measured in the pressurization process of a propellant in the storage tank of a spacecraft at present.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber grating sensors, and in particular relates to a high-temperature and high-pressure fiber grating temperature sensor system for aerospace applications, and also relates to a demodulation method for the high-temperature and high-pressure fiber grating temperature sensor system for aerospace applications. Background Art

[0002] Whether the pressurization capacity of rocket and other spacecraft tanks meets the flight requirements is a key parameter that affects the success or failure of rocket launches. At present, during the flight of HAN-based and other new propellant satellites, the temperature of the propellant will change with the pressure change during the pressurization process of the tank. Therefore, in order to obtain the temperature field distribution of the propellant in the spacecraft tank, a coupling relationship covering the fluid area and the solid wall area is established to realize the propellant temperature field distribution in the pre-pressurization process, which is of great significance to improving the propellant temperature quality and improving the thrust-to-weight ratio. At present, the temperature field measurement of the tank in the spacecraft requires accurate measurement of the temperature field of more than 800℃ at 8 temperature points within a short distance range of 200mm and a high pressure environment of 20MPa.

[0003] At present, temperature measurement generally adopts electrical temperature measurement methods such as thermocouples or platinum resistance. Thermocouples refer to armored filament thermocouples that are directly fixed to the measured surface by welding or bonding. However, traditional electrical temperature measurement methods have major problems when measuring temperature field distribution in spacecraft tanks. First, multiple sensors cannot be installed on the same cross-section, which will lead to large errors in measuring temperature field distribution. Second, the problem of a large number of leads due to difficulty in reuse still exists. A large number of leads leading from the inside of the tank can easily cause leaks in the high-pressure seal. Third, there will be synchronous measurement errors when multiple sensors are measured at the same time. Fourth, traditional electrical temperature measurement methods cannot achieve high-frequency rapid measurement of more than 5kHz during the pressurization process. Summary of the invention

[0004] The purpose of the present invention is to provide a high-temperature and high-pressure fiber Bragg grating temperature sensor system for the aerospace field, which solves the problem that the temperature field distribution of the propellant in the spacecraft tank cannot be measured during the pressurization process.

[0005] Another object of the present invention is to provide a demodulation method for a high-temperature and high-pressure fiber Bragg grating temperature sensor system used in the aerospace field.

[0006] The technical solution adopted by the present invention is a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace field, comprising a swept-frequency light source, the swept-frequency light source is connected to the high-temperature and high-pressure fiber Bragg grating temperature sensor through a circulator, the circulator is connected to a spectrum unit through a fiber coupler, the spectrum unit is connected to a spectrum driving circuit through a fiber coupler, the spectrum driving circuit is connected to an AD conversion circuit through a PCI bus, the AD conversion circuit is connected to a control system through a PCI bus, and the control system is connected to an industrial control system through an RJ45 network cable.

[0007] The present invention is also characterized in that: The high-temperature and high-pressure fiber Bragg grating temperature sensor is connected to the circulator through a fiber coupler.

[0008] The high-temperature and high-pressure fiber Bragg grating temperature sensor includes a sensor mounting outer tube, a sensor mounting inner tube is fixedly mounted inside the sensor mounting outer tube, a fiber Bragg grating temperature measuring point is fixedly mounted inside the sensor mounting inner tube, the lead end optical fiber of the fiber Bragg grating temperature measuring point is connected to an armored optical cable, the other end of the armored optical cable is connected to a circulator, a ball head plug is provided on the outer side of one end of the sensor mounting outer tube close to the armored optical cable, the end of the ball head plug close to the sensor mounting outer tube is fixedly connected to the sensor mounting outer tube through a sheath nut, and also includes a wire locking kit, the end of the ball head plug close to the sensor mounting outer tube is fixed to the armored optical cable through a wire locking kit.

[0009] The base of the fiber Bragg grating temperature measuring point is made of silica optical fiber. The temperature resistance of the fiber Bragg grating temperature measuring point is 1700°C. The fiber Bragg grating temperature measuring point generates short pulse laser through a femtosecond laser with a laser pulse energy of not less than 300μJ. The short pulse laser spot diameter is not greater than 1μm. The fiber Bragg grating temperature measuring point controls the movement of the femtosecond laser. The position platform motion error is less than 1mm. There are 8 grating areas evenly engraved on the fiber Bragg grating temperature measuring point, and the surfaces of the 8 grating areas are sprayed with gold coating.

[0010] The sensor installation inner tube is made of stainless steel capillary, and the length of the sensor installation inner tube is greater than the length of the fiber optic Bragg grating temperature measuring point; the sensor installation outer tube is made of stainless steel material.

[0011] The armored optical cable includes an armored stainless steel inner casing, an armored stainless steel outer casing and a rubber hose.

[0012] The ball plug and the outer sleeve nut are both 60° ball head type standard parts. The ball plug is made of steel. The ball plug and the sensor mounting outer tube are laser welded through laser welding points.

[0013] The inner diameter of one side of the wire locking kit is the same as the outer diameter of the armored optical cable, and the wire locking kit and the armored optical cable are sealed by high-temperature ceramic glue.

[0014] Another technical solution adopted by the present invention is a demodulation method for a high-temperature and high-pressure fiber Bragg grating temperature sensor system used in the aerospace field, comprising the following steps: S1, judging the wavelength calibration situation through the control system and calibrating by comparing the wavelength to obtain a fitting curve; S2. After wavelength calibration, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the rocket tank; S3, reading the wavelength change value of the high-temperature and high-pressure fiber Bragg grating temperature sensor in the rocket tank caused by temperature change; S4. After reading the wavelength change, the optimal temperature value is calculated according to the fitting curve, and the temperature value is displayed on the industrial control system.

[0015] Another technical solution of the present invention is also characterized in that: The specific process of S1 is: S1.1. The control system determines that the wavelength calibration has not been performed; S1.2. Set the calibration conditions of the temperature calibration device regarding wavelength and measured temperature value; the standard temperature bath provides a temperature range of 0℃~300℃, the standard temperature box provides a temperature range of 300℃~800℃, and 16 points are evenly set in the temperature range of 0℃~800℃ with a step length of 50℃; S1.3. After the calibration conditions are set, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the temperature calibration device. At the temperature measurement points of the 8 grating areas, the fiber Bragg grating temperature measurement points will meet the wavelength The pulsed laser reflection is sent back to the spectrum unit, and the test is repeated 10 times, and the temperature value and the corresponding wavelength value are recorded respectively; , is the effective refractive index of the optical fiber, is the grating grid period; S1.4. Calculate the optimal wavelength value according to the recorded temperature value and the corresponding wavelength value according to the self-learning optimization algorithm; the formula of the self-learning optimization algorithm is shown in equations (1), (2) and (3); (1); (2); (3); In the formula, is the optimal wavelength value calculated based on the coefficient for the jth time at the kth temperature point; The jth measured wavelength value at the kth temperature point; is the jth theoretical wavelength value at k temperature points; The wavelength of the measuring point deviates from the theoretical worst value at the jth measurement; is the best learning factor, is the worst learning factor; It is the average value of 10 wavelength measurements of a single sensor at the same temperature point; S1.5. Further optimize the optimal wavelength value according to the differential evolution algorithm to obtain the optimal wavelength value of a single high-temperature and high-pressure fiber Bragg grating temperature sensor at a single temperature point. The formula of the differential evolution algorithm is shown in formula (4); (4); Where F is the scaling factor, which is generally set to [0, 2]. They are the measured wavelength values ​​at three randomly selected current temperature points; S1.6. Set the number of iterations to 10. After the iterations are completed, all temperature points under a single high-temperature and high-pressure fiber Bragg grating temperature sensor are fitted with the corresponding optimal wavelength values ​​to obtain a fitting curve.

[0016] The beneficial effects of the present invention are: The high-temperature and high-pressure fiber Bragg grating temperature sensor system and demodulation method for the aerospace field provided by the present invention adopt femtosecond laser grating writing technology and gold-plated coating technology to achieve accurate temperature field measurement of more than 800°C at 8 temperature points within a short distance range of 200 mm and a high-pressure environment of 20 MPa; humidity control technology and inert reaction technology are adopted to solve the structural strength problem of the fiber Bragg grating sensor during long-term high-temperature measurement; ball head sealing and laser welding are adopted to achieve sealing in a high-pressure environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace field of the present invention; Figure 2 It is a schematic diagram of the structure of the high temperature and high pressure optical fiber sensor of the present invention.

[0018] In the figure, 1. sensor installation inner tube, 2. sensor installation outer tube, 3. fiber grating temperature measurement point, 4. ball head plug, 5. jacket nut, 6. wire locking kit, 7. armored optical cable, 8. laser welding point, 9. high temperature and high pressure fiber grating temperature sensor, 10. swept frequency light source, 11. circulator, 12. spectrum unit, 13. spectrum driving circuit, 14. AD conversion circuit, 15. industrial control system, 16. control system. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The present invention provides a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1As shown, it includes a swept-frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11. The central wavelength of the swept-frequency light source 10 is 1550nm, the laser power is not less than 10mW, and the bandwidth is 80nm. The circulator 11 is connected to a spectrum unit 12 through a fiber coupler. The spectrum unit 12 has a single-channel maximum measurement frequency of 20kHz, a 16-channel maximum measurement frequency of 5 kHz, a measurement range of 1500nm~1580nm, and a repeatability of less than 2pm. The spectrum unit 12 is connected to a spectrum driving circuit 13 through a fiber coupler. The spectrum driving circuit 13 is connected to an AD conversion circuit 14 through a PCI bus. The AD conversion circuit 14 is connected to a control system 16 through a PCI bus. The control system 16 adopts high-speed FPGA control, and the maximum operating frequency is not less than 500M. The control system 16 is connected to an industrial control system 15 through an RJ45 network cable; the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 is connected to the circulator 11 through a fiber coupler. As shown Figure 2As shown, the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 includes a sensor installation outer tube 2, a sensor installation inner tube 1 is fixedly installed in the sensor installation outer tube 2, a fiber Bragg grating temperature measuring point 3 is fixedly installed in the sensor installation inner tube 1, the lead end optical fiber of the fiber Bragg grating temperature measuring point 3 is connected to an armored optical cable 7, the other end of the armored optical cable 7 is connected to a circulator 11, a ball head plug 4 is provided on the outer side of the end of the sensor installation outer tube 2 close to the armored optical cable 7, the end of the ball head plug 4 close to the sensor installation outer tube 2 is fixedly connected to the sensor installation outer tube 2 through a jacket nut 5, and also includes a locking wire kit 6, the end of the ball head plug 4 close to the sensor installation outer tube 2 is fixedly connected to the armored optical cable 7 through a locking wire kit The fiber grating temperature measuring point 3 is fixed with a wire kit 6; the substrate of the fiber grating temperature measuring point 3 is made of silica optical fiber. Silica is the most stable optical fiber material and can work in high temperature and high pressure environment for a long time. The temperature resistance value of the fiber grating temperature measuring point 3 is 1700°C. The fiber grating temperature measuring point 3 generates a short pulse laser through a femtosecond laser with a laser pulse energy of not less than 300μJ. The short pulse laser spot diameter is not greater than 1μm. The fiber grating temperature measuring point 3 controls the movement of the femtosecond laser. The position platform motion error is less than 1mm. Eight grating areas are evenly engraved on the 200mm fiber grating temperature measuring point 3 at a spacing of 25mm, and each grating area corresponds to an independent central wavelength Different fiber Bragg grating temperature sensors can be distinguished according to different wavelengths. In this way, the fiber Bragg grating area is densely written by high-energy laser pulses. Through the side writing technology, the grating formed by permanent physical damage to the fiber core will not degrade at a temperature greater than 800°C. The surfaces of the 8 grating areas are sprayed with a gold-plated coating with a thickness controlled within 100um so that the grating area will not degrade at a temperature of 800°C; the sensor installation inner tube 1 is made of stainless steel capillary with a capillary diameter of 0.3mm and a length of 210mm. The length of the sensor installation inner tube 1 is greater than the length of the fiber Bragg grating temperature measurement point 3 to ensure that the bottom of the grating area will not touch the bottom of the steel pipe, with good Thermal expansion and contraction space; the sensor installation outer tube 2 is made of stainless steel to ensure that the external temperature changes can be transmitted to the fiber grating temperature measuring point 3 in time; the armored optical cable 7 includes an armored stainless steel tube inner sleeve, an armored stainless steel outer sleeve and a hose; the ball head plug 4 and the outer sleeve nut 5 are both 60° ball head type standard parts, the ball head plug 4 is made of steel and has a pressure resistance of up to 35MPa, the ball head plug 4 and the sensor installation outer tube 2 are laser welded by laser welding points 8 to ensure that the pressure resistance of the entire sensor can reach more than 15MPa; the inner diameter of one side of the locking wire kit 6 is the same as the outer diameter of the armored optical cable 7, and the locking wire kit 6 and the armored optical cable 7 are sealed by high-temperature ceramic glue.When the high-temperature and high-pressure fiber Bragg grating temperature sensor is placed in the rocket tank, when the external temperature changes are transmitted to the 8 temperature measuring points on the fiber Bragg grating temperature measuring point 3 through the sensor installation outer tube 2 and the sensor installation inner tube 1, the wavelength of the grating area of ​​the 8 temperature measuring points on the fiber Bragg grating temperature measuring point 3 will change. The external temperature change corresponds to the change in the central wavelength of the return light of the fiber Bragg grating temperature sensor. By measuring the reflected wavelength, the wavelength change can be obtained after demodulation, and then the temperature value can be obtained. The wavelength change of the fiber Bragg grating temperature measuring point 3 is transmitted to the high-temperature and high-pressure fiber Bragg grating temperature sensing system through the armored optical cable 7 through the transmitted light for demodulation.

[0021] The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use provided by the present invention has the following working principle: a frequency sweeping light source emits a pulsed laser and transmits it to the high-temperature and high-pressure fiber Bragg grating temperature sensor; after receiving the pulsed laser, the high-temperature and high-pressure fiber Bragg grating temperature sensor reflects the pulsed laser meeting the wavelength at the fiber Bragg grating temperature measuring point in 8 grating areas back to the spectral unit; the spectral unit transmits the reflected light to the spectral driving circuit; the spectral driving circuit converts the reflected light collected in the spectral unit into a photocurrent signal and transmits it to the AD conversion circuit; the AD conversion circuit converts the collected photocurrent signal into a digital signal and transmits it to the control system; the control system filters the received digital signal to obtain a wavelength digital signal, and converts the wavelength digital signal of each measuring point into temperature data according to an internal processing algorithm, and transmits it to the industrial control system; the industrial control system displays the received temperature data.

[0022] Example 1 This embodiment proposes a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1 As shown, it includes a swept frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11, the circulator 11 is connected to a spectrum unit 12 through a fiber coupler, the spectrum unit 12 is connected to a spectrum driving circuit 13 through a fiber coupler, the spectrum driving circuit 13 is connected to an AD conversion circuit 14 through a PCI bus, the AD conversion circuit 14 is connected to a control system 16 through a PCI bus, and the control system 16 is connected to an industrial control system 15 through an RJ45 network cable.

[0023] Example 2 This embodiment proposes a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1As shown, it includes a swept-frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11, the circulator 11 is connected to a spectrum unit 12 through a fiber optic coupler, the spectrum unit 12 is connected to a spectrum driving circuit 13 through a fiber optic coupler, the spectrum driving circuit 13 is connected to an AD conversion circuit 14 through a PCI bus, the AD conversion circuit 14 is connected to a control system 16 through a PCI bus, and the control system 16 is connected to an industrial control system 15 through an RJ45 network cable; the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 is connected to the circulator 11 through a fiber optic coupler.

[0024] Example 3 This embodiment proposes a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1 As shown, it includes a swept frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11, which is connected to a spectrum unit 12 through a fiber coupler, which is connected to a spectrum driving circuit 13 through a fiber coupler, which is connected to an AD conversion circuit 14 through a PCI bus, which is connected to a control system 16 through a PCI bus, which is connected to an industrial control system 15 through an RJ45 network cable; the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 is connected to the circulator 11 through a fiber coupler. Figure 2 As shown, the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 includes a sensor mounting outer tube 2, a sensor mounting inner tube 1 is fixedly mounted inside the sensor mounting outer tube 2, a fiber Bragg grating temperature measuring point 3 is fixedly mounted inside the sensor mounting inner tube 1, the lead end optical fiber of the fiber Bragg grating temperature measuring point 3 is connected to an armored optical cable 7, the other end of the armored optical cable 7 is connected to a circulator 11, a ball head plug 4 is provided on the outer side of one end of the sensor mounting outer tube 2 close to the armored optical cable 7, the end of the ball head plug 4 close to the sensor mounting outer tube 2 is fixedly connected to the sensor mounting outer tube 2 through a sleeve nut 5, and also includes a locking wire kit 6, the end of the ball head plug 4 close to the sensor mounting outer tube 2 is fixed to the armored optical cable 7 through the locking wire kit 6.

[0025] Example 4 This embodiment proposes a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1As shown, it includes a swept frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11, which is connected to a spectrum unit 12 through a fiber coupler, which is connected to a spectrum driving circuit 13 through a fiber coupler, which is connected to an AD conversion circuit 14 through a PCI bus, which is connected to a control system 16 through a PCI bus, which is connected to an industrial control system 15 through an RJ45 network cable; the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 is connected to the circulator 11 through a fiber coupler. Figure 2 As shown, the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 includes a sensor installation outer tube 2, a sensor installation inner tube 1 is fixedly installed in the sensor installation outer tube 2, a fiber Bragg grating temperature measuring point 3 is fixedly installed in the sensor installation inner tube 1, the lead end optical fiber of the fiber Bragg grating temperature measuring point 3 is connected to an armored optical cable 7, and the other end of the armored optical cable 7 is connected to a circulator 11, and a ball head plug 4 is provided on the outer side of the end of the sensor installation outer tube 2 close to the armored optical cable 7, and the end of the ball head plug 4 close to the sensor installation outer tube 2 is fixedly connected to the sensor installation outer tube 2 through a jacket nut 5, and also includes a locking wire kit 6, and the ball head plug 4 is close to the outer tube 2 of the sensor installation. One end of the proximity sensor installation outer tube 2 is fixed to the armored optical cable 7 through a locking wire kit 6; the base of the fiber grating temperature measuring point 3 is made of silica optical fiber, the temperature resistance of the fiber grating temperature measuring point 3 is 1700°C, the fiber grating temperature measuring point 3 generates a short pulse laser through a femtosecond laser with a laser pulse energy of not less than 300μJ, the short pulse laser spot diameter is not greater than 1μm, the fiber grating temperature measuring point 3 controls the movement of the femtosecond laser position platform The motion error is less than 1mm, and 8 grating areas are evenly engraved on the fiber grating temperature measuring point 3, and the surfaces of the 8 grating areas are sprayed with a gold-plated coating.

[0026] Example 5 This embodiment proposes a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications. Figure 1 As shown, it includes a swept frequency light source 10, which is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor 9 through a circulator 11, which is connected to a spectrum unit 12 through a fiber coupler, which is connected to a spectrum driving circuit 13 through a fiber coupler, which is connected to an AD conversion circuit 14 through a PCI bus, which is connected to a control system 16 through a PCI bus, which is connected to an industrial control system 15 through an RJ45 network cable; the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 is connected to the circulator 11 through a fiber coupler. Figure 2As shown, the high-temperature and high-pressure fiber Bragg grating temperature sensor 9 includes a sensor installation outer tube 2, a sensor installation inner tube 1 is fixedly installed in the sensor installation outer tube 2, a fiber Bragg grating temperature measuring point 3 is fixedly installed in the sensor installation inner tube 1, the lead end optical fiber of the fiber Bragg grating temperature measuring point 3 is connected to the armored optical cable 7, the other end of the armored optical cable 7 is connected to the circulator 11, a ball head plug 4 is provided on the outer side of the end of the sensor installation outer tube 2 close to the armored optical cable 7, the end of the ball head plug 4 close to the sensor installation outer tube 2 is fixedly connected to the sensor installation outer tube 2 through a jacket nut 5, and also includes a locking wire kit 6, the end of the ball head plug 4 close to the sensor installation outer tube 2 is fixed to the armored optical cable 7 through the locking wire kit 6; the substrate of the fiber Bragg grating temperature measuring point 3 is made of silica optical fiber, the temperature resistance value of the fiber Bragg grating temperature measuring point 3 is 1700°C, and the fiber Bragg grating temperature measuring point 3 is fixed by a laser pulse energy of not less than 300μJ The femtosecond laser generates short pulse laser, and the diameter of the short pulse laser spot is not more than 1μm. The motion error of the position platform of the fiber Bragg grating temperature measuring point 3 controlling the movement of the femtosecond laser is less than 1mm. Eight grating areas are evenly engraved on the fiber Bragg grating temperature measuring point 3, and the surfaces of the eight grating areas are sprayed with gold-plated coatings. The sensor installation inner tube 1 is made of stainless steel capillary, and the length of the sensor installation inner tube 1 is greater than the length of the fiber Bragg grating temperature measuring point 3. The sensor installation outer tube 2 is made of stainless steel material. The armored optical cable 7 includes an armored stainless steel inner sleeve, an armored stainless steel outer sleeve and a rubber hose. The ball head plug 4 and the outer sleeve nut 5 are both 60° ball head type standard parts, the ball head plug 4 is made of steel, and the ball head plug 4 and the sensor installation outer tube 2 are laser welded by laser welding points 8. The inner diameter of one side of the locking wire kit 6 is the same as the outer diameter of the armored optical cable 7, and the locking wire kit 6 and the armored optical cable 7 are sealed by high-temperature ceramic glue.

[0027] Example 6 The demodulation method of the high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace field proposed in this embodiment specifically includes the following steps: S1, judging the wavelength calibration situation through the control system and calibrating by comparing the wavelength to obtain a fitting curve; The specific process is: S1.1. The control system determines that the wavelength calibration has not been performed; S1.2. Set the calibration conditions of the temperature calibration device regarding wavelength and measured temperature value; the standard temperature bath provides a temperature range of 0℃~300℃, the standard temperature box provides a temperature range of 300℃~800℃, and 16 points are evenly set in the temperature range of 0℃~800℃ with a step length of 50℃; S1.3. After the calibration conditions are set, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the temperature calibration device. At the temperature measurement points of the 8 grating areas, the fiber Bragg grating temperature measurement points will meet the wavelength The pulsed laser reflection is sent back to the spectrum unit, and the test is repeated 10 times, and the temperature value and the corresponding wavelength value are recorded respectively; , is the effective refractive index of the optical fiber, is the grating grid period; S1.4. Calculate the optimal wavelength value according to the recorded temperature value and the corresponding wavelength value according to the self-learning optimization algorithm; the formula of the self-learning optimization algorithm is shown in equations (1), (2) and (3); (1); (2); (3); In the formula, is the optimal wavelength value calculated based on the coefficient for the jth time at the kth temperature point; The jth measured wavelength value at the kth temperature point; is the jth theoretical wavelength value at k temperature points; The wavelength of the measuring point deviates from the theoretical worst value at the jth measurement; is the best learning factor, is the worst learning factor; It is the average value of 10 wavelength measurements of a single sensor at the same temperature point; S1.5. Further optimize the optimal wavelength value according to the differential evolution algorithm to obtain the optimal wavelength value of a single high-temperature and high-pressure fiber Bragg grating temperature sensor at a single temperature point. The formula of the differential evolution algorithm is shown in formula (4); (4); Where F is the scaling factor, which is generally set to [0, 2]. They are the measured wavelength values ​​at three randomly selected current temperature points; S1.6. Set the number of iterations to 10. After the iterations are completed, all temperature points under a single high-temperature and high-pressure fiber Bragg grating temperature sensor are fitted with the corresponding optimal wavelength value to obtain a fitting curve; S2. After wavelength calibration, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the rocket tank; S3, reading the wavelength change value of the high-temperature and high-pressure fiber Bragg grating temperature sensor in the rocket tank caused by temperature change; S4. After reading the wavelength change, the optimal temperature value is calculated according to the fitting curve, and the temperature value is displayed on the industrial control system.

Claims

1. A high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications, characterized in that: The invention comprises a swept-frequency light source (10), wherein the swept-frequency light source (10) is connected to a high-temperature and high-pressure fiber Bragg grating temperature sensor (9) via a circulator (11), wherein the circulator (11) is connected to a spectrum unit (12) via a fiber coupler, wherein the spectrum unit (12) is connected to a spectrum driving circuit (13) via a fiber coupler, wherein the spectrum driving circuit (13) is connected to an AD conversion circuit (14) via a PCI bus, wherein the AD conversion circuit (14) is connected to a control system (16) via a PCI bus, and wherein the control system (16) is connected to an industrial control system (15) via an RJ45 network cable.

2. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace application according to claim 1, characterized in that: The high-temperature and high-pressure fiber Bragg grating temperature sensor (9) is connected to the circulator (11) via a fiber coupler.

3. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 2, characterized in that: The high-temperature and high-pressure fiber Bragg grating temperature sensor (9) comprises a sensor mounting outer tube (2), a sensor mounting inner tube (1) being fixedly mounted inside the sensor mounting outer tube (2), a fiber Bragg grating temperature measuring point (3) being fixedly mounted inside the sensor mounting inner tube (1), the lead end optical fiber of the fiber Bragg grating temperature measuring point (3) being connected to an armored optical cable (7), the other end of the armored optical cable (7) being connected to the circulator (11), a ball head plug (4) being provided on the outer side of one end of the sensor mounting outer tube (2) close to the armored optical cable (7), the end of the ball head plug (4) close to the sensor mounting outer tube (2) being fixedly connected to the sensor mounting outer tube (2) via an outer sleeve nut (5), and also comprises a locking wire set (6), the end of the ball head plug (4) close to the sensor mounting outer tube (2) being fixed to the armored optical cable (7) via the locking wire set (6).

4. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 3, characterized in that: The base of the fiber Bragg grating temperature measuring point (3) is made of silica optical fiber. The temperature resistance value of the fiber Bragg grating temperature measuring point (3) is 1700°C. The fiber Bragg grating temperature measuring point (3) generates short pulse laser through a femtosecond laser with a laser pulse energy of not less than 300 μJ. The short pulse laser spot diameter is not greater than 1 μm. The fiber Bragg grating temperature measuring point (3) controls the movement of the femtosecond laser. The position platform motion error is less than 1 mm. Eight grating areas are evenly engraved on the fiber Bragg grating temperature measuring point (3). The surfaces of the eight grating areas are sprayed with a gold coating.

5. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 4, characterized in that: The sensor installation inner tube (1) is made of a stainless steel capillary tube, and the length of the sensor installation inner tube (1) is greater than the length of the fiber optic grating temperature measurement point (3); the sensor installation outer tube (2) is made of stainless steel.

6. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 5, characterized in that: The armored optical cable (7) comprises an armored stainless steel inner sleeve, an armored stainless steel outer sleeve and a rubber hose.

7. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 6, characterized in that: The ball head plug (4) and the outer sleeve nut (5) are both 60° ball head type standard parts, the ball head plug (4) is made of steel, and the ball head plug (4) and the sensor mounting outer tube (2) are laser welded via laser welding points (8).

8. The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 7, characterized in that: The inner diameter of one side of the wire locking kit (6) is the same as the outer diameter of the armored optical cable (7), and the wire locking kit (6) and the armored optical cable (7) are sealed by high-temperature ceramic glue.

9. A demodulation method for a high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace applications, characterized in that: The high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace use according to claim 8 specifically comprises the following steps: S1, judging the wavelength calibration situation through the control system and calibrating by comparing the wavelength to obtain a fitting curve; S2. After wavelength calibration, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the rocket tank; S3, reading the wavelength change value of the high-temperature and high-pressure fiber Bragg grating temperature sensor in the rocket tank caused by temperature change; S4. After reading the wavelength change, the optimal temperature value is calculated according to the fitting curve, and the temperature value is displayed on the industrial control system.

10. The demodulation method of the high-temperature and high-pressure fiber Bragg grating temperature sensor system for aerospace field according to claim 9, characterized in that: The specific process of S1 is as follows: S1.

1. The control system determines that the wavelength calibration has not been performed; S1.

2. Setting the calibration conditions of the temperature calibration device regarding wavelength and measured temperature value; The standard temperature bath provides a temperature range of 0℃~300℃, and the standard temperature box provides a temperature range of 300℃~800℃. 16 points are evenly set in the temperature range of 0℃~800℃ with a step length of 50℃; S1.

3. After the calibration conditions are set, place the high-temperature and high-pressure fiber Bragg grating temperature sensor into the temperature calibration device. At the temperature measurement points of the 8 grating areas, the fiber Bragg grating temperature measurement points will meet the wavelength The pulsed laser reflection is sent back to the spectrum unit, and the test is repeated 10 times, and the temperature value and the corresponding wavelength value are recorded respectively; The wavelength , is the effective refractive index of the optical fiber, is the grating grid period; S1.

4. Calculate the optimal wavelength value according to the recorded temperature value and the corresponding wavelength value according to the self-learning optimization algorithm; the formula of the self-learning optimization algorithm is shown in formulas (1), (2) and (3); （1）； （2）； （3）； In the formula, is the optimal wavelength value calculated based on the coefficient for the jth time at the kth temperature point; The jth measured wavelength value at the kth temperature point; is the jth theoretical wavelength value at k temperature points; The wavelength of the measuring point deviates from the theoretical worst value at the jth measurement; is the best learning factor, is the worst learning factor; It is the average value of 10 wavelength measurements of a single sensor at the same temperature point; S1.

5. Further optimize the optimal wavelength value according to the differential evolution algorithm to obtain the optimal wavelength value of a single high-temperature and high-pressure fiber Bragg grating temperature sensor at a single temperature point; the formula of the differential evolution algorithm is shown in formula (4); （4）； Where F is the scaling factor, which is generally set to [0, 2]. They are the measured wavelength values ​​at three randomly selected current temperature points; S1.

6. Set the number of iterations to 10. After the iterations are completed, all temperature points under a single high-temperature and high-pressure fiber Bragg grating temperature sensor are fitted with the corresponding optimal wavelength values ​​to obtain a fitting curve.

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