Optical fiber liquid level sensor, system and method used in irradiation environment

Abstract

The invention relates to an optical fiber liquid level sensor, system and method used in an irradiation environment. A shell is provided with a pressure guiding hole; the pressure sensing diaphragm is installed in the shell and divides the inner space of the shell into a first cavity and a second cavity, and the first cavity is communicated with the pressure guiding hole. The optical fiber assembly comprises an optical fiber, a pressure measurement grating and a temperature compensation grating, the pressure measurement grating and the temperature compensation grating are inscribed on the optical fiber, the temperature compensation grating is located in the second cavity, the pressure measurement grating is bonded to the pressure sensing diaphragm, and one end of the optical fiber penetrates out of the shell from the shell; a fiber core of the optical fiber is a pure silicon fiber core, and an anti-radiation sheath is arranged on the outer surface of the optical fiber. The problem that the monitoring precision is affected due to the fact that a liquid level sensor is prone to radiation damage in the prior art can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of fiber Bragg grating sensors, and particularly to an optical fiber liquid level sensor, system and method for an irradiation environment. Background Art

[0002] All along, nuclear power technology is of great significance for ensuring a country's energy security. As a stable and reliable energy source, nuclear power can provide long-term and continuous power supply for the country. As a high-quality and clean energy, nuclear power itself has important strategic significance for improving the country's energy industry supply structure, reducing dependence on traditional energy, and realizing the diversification of energy supply.

[0003] In nuclear reactor control technology, it is usually necessary to add boric acid to the reactor cooling system to control and adjust the number of neutrons in the reactor, thereby controlling the reaction rate of nuclear fission and ensuring the stable operation of the nuclear power plant. However, in order to avoid environmental pollution caused by boron-containing wastewater, it needs to be placed in a storage pit for temporary storage and separation and precipitation. Therefore, it is crucial to monitor the liquid level change of boron wastewater in the storage pit with high precision.

[0004] However, traditional liquid level monitoring methods have some drawbacks in the face of extreme working conditions such as high irradiation environments. For example, in an actual irradiation environment, traditional liquid level sensors are easily damaged by radiation, which greatly affects the sensing accuracy and thus the performance of liquid level monitoring. Another example is that conventional fiber Bragg grating sensors are prone to problems such as damaged grating structures due to thermal radiation effects in an irradiation environment, affecting the monitoring accuracy. Summary of the Invention

[0005] Embodiments of the present application provide an optical fiber liquid level sensor, system and method for an irradiation environment to solve the problem in related technologies that the liquid level sensor is easily damaged by radiation and affects the monitoring accuracy.

[0006] In a first aspect, an optical fiber liquid level sensor for an irradiation environment is provided, which includes:

[0007] A housing with a pressure guiding hole opened thereon;

[0008] A pressure sensing diaphragm installed inside the housing, which divides the internal space of the housing into a first chamber and a second chamber, and the first chamber is communicated with the pressure guiding hole;

[0009] An optical fiber assembly, which includes an optical fiber and a pressure measurement grating and a temperature compensation grating inscribed on the optical fiber. The temperature compensation grating is located in the second chamber, the pressure measurement grating is bonded to the pressure sensing diaphragm, and one end of the optical fiber passes through the housing. The core of the optical fiber is a pure silica core, and an anti-irradiation sheath is provided on the outer surface of the optical fiber.

[0010] In some embodiments, the anti-irradiation sheath is made of polyimide;

[0011] and / or, an optical fiber connector is connected to the end of the optical fiber;

[0012] and / or, the pressure measurement grating is bonded to the middle of the pressure-sensitive diaphragm;

[0013] and / or, the temperature compensation grating is located at the edge of the pressure-sensitive diaphragm.

[0014] In some embodiments, the pressure measurement grating and the temperature compensation grating are inscribed on the same optical fiber;

[0015] Alternatively, the pressure measurement grating and the temperature compensation grating are respectively inscribed on two optical fibers.

[0016] In some embodiments, the pressure measurement grating is located in the first chamber or the second chamber;

[0017] and / or, a liquid guiding column is provided on the housing, and the liquid guiding channel in the liquid guiding column is communicated with the pressure guiding hole;

[0018] and / or, the housing includes a first housing, a pressing ring and a second housing which are arranged in sequence, the first housing, the pressing ring and the second housing are fastened by bolts, and the edge of the pressure-sensitive diaphragm is located between the first housing and the pressing ring.

[0019] In a second aspect, a liquid level monitoring system is provided, which includes:

[0020] a mounting bracket having a mounting space therein;

[0021] The optical fiber liquid level sensor for an irradiation environment as described in any one of the above, there are several optical fiber liquid level sensors, and they are fixedly arranged in the mounting space of the mounting bracket at intervals along the length direction of the mounting bracket, and the pressure guiding hole extends out of the mounting space;

[0022] a coupler connected to the optical fibers of each optical fiber liquid level sensor;

[0023] an optical circulator connected to the coupler, and the optical circulator is also connected to a light source;

[0024] a diffraction grating connected to the optical circulator;

[0025] a photodetector connected to the diffraction grating;

[0026] a host computer connected to the photodetector.

[0027] In a third aspect, a monitoring method for the liquid level monitoring system as described above is provided, which includes:

[0028] Vertically place the mounting bracket in the storage pit, and sequentially number each of the fiber optic liquid level sensors from bottom to top, and determine the height of each fiber optic liquid level sensor in the storage pit;

[0029] Use the host computer to receive the monitoring data, and based on the monitoring data, calculate the liquid level height Y in the storage pit;

[0030]

[0031] where n is the total number of fiber optic liquid level sensors on the mounting bracket; j is the number of fiber optic liquid level sensors that send monitoring data among all the fiber optic liquid level sensors; H i，储坑 is the height of the i-th fiber optic liquid level sensor in the storage pit, and H i，监测 is the liquid level height calculated based on the monitoring data of the i-th fiber optic liquid level sensor.

[0032] In some embodiments, it further includes:

[0033] Perform temperature sensitivity calibration on the fiber optic liquid level sensor;

[0034] Perform pressure sensitivity calibration on the fiber optic liquid level sensor.

[0035] In some embodiments, performing pressure sensitivity calibration on the fiber optic liquid level sensor specifically includes:

[0036] Under a constant temperature environment, apply different pressures to the fiber optic liquid level sensor, and monitor the central wavelength corresponding to the pressure measurement grating at each pressure and calculate the wavelength drift amount;

[0037] Based on each pressure and the corresponding wavelength drift amount, obtain the mapping relationship between the pressure value and the wavelength drift amount of the pressure measurement grating.

[0038] In some embodiments, performing temperature sensitivity calibration on the fiber optic liquid level sensor specifically includes:

[0039] Heat the fiber optic liquid level sensor to different temperature measurement points, keep it at a constant temperature for a period of time at each temperature measurement point, and monitor the central wavelength corresponding to the temperature compensation grating at each temperature measurement point and calculate the wavelength drift amount, as well as the central wavelength corresponding to the pressure measurement grating and calculate the wavelength drift amount;

[0040] Based on each temperature measurement point and the corresponding wavelength drift amount of the temperature compensation grating, obtain the mapping relationship between the temperature value and the wavelength drift amount of the temperature compensation grating;

[0041] Based on the difference in wavelength drift between each temperature measurement point and the corresponding temperature compensation grating and pressure measurement grating, a mapping relationship of the temperature value with respect to the wavelength drift of the pressure measurement grating is obtained.

[0042] In some embodiments, the liquid level height H is calculated i，监测 , including the following steps:

[0043] Collect the monitoring data of the i-th fiber optic liquid level sensor to obtain the wavelength drift of the temperature compensation grating and the wavelength drift of the pressure measurement grating;

[0044] Based on the obtained wavelength drift of the temperature compensation grating and the mapping relationship of the temperature value with respect to the wavelength drift of the temperature compensation grating, calculate the current temperature value;

[0045] Based on the current temperature value and the mapping relationship of the temperature value with respect to the wavelength drift of the pressure measurement grating, calculate the wavelength drift of the pressure measurement grating caused by temperature;

[0046] Subtract the wavelength drift of the pressure measurement grating caused by temperature from the wavelength drift of the pressure measurement grating to obtain the wavelength drift of the pressure measurement grating caused by the liquid level;

[0047] Based on the wavelength drift of the pressure measurement grating caused by the liquid level and the mapping relationship of the pressure value with respect to the wavelength drift of the pressure measurement grating, obtain the current pressure value;

[0048] Based on the current pressure value and the mapping relationship of the liquid level height with respect to the pressure value, obtain the liquid level height H i，监测 .

[0049] The beneficial effects brought by the technical solution provided by this application include:

[0050] The fiber optic liquid level sensor provided by this application uses a femtosecond laser to write an extremely stable and non-erasable femtosecond grating FsFBG for its grating, and uses a pure silica fiber core and an anti-radiation sheath, which can reduce the influence of radiation on liquid level measurement, thereby improving the monitoring accuracy.

[0051] The fiber optic liquid level sensor provided by this application adopts a dual-grating design scheme. By bonding one grating on the pressure-sensitive diaphragm as the liquid level height measurement grating and placing one on the pressure-sensitive diaphragm as the temperature compensation grating, the wavelength changes caused by temperature and liquid level are separated, effectively eliminating the interference of temperature on the measurement, thereby improving the accuracy of liquid level measurement. Description of the Drawings

[0052] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0053] Figure 1 Schematic diagram of the fiber optic liquid level sensor provided by the embodiment of the present application;

[0054] Figure 2 Installation schematic diagram of the fiber optic liquid level sensor provided by the embodiment of the present application;

[0055] Figure 3 Block diagram of the liquid level monitoring system provided by the embodiment of the present application.

[0056] In the figure: 1. Outer shell; 10. Pressure guiding hole; 11. First chamber; 12. Second chamber; 13. First housing; 14. Pressure ring; 15. Liquid guiding column; 2. Pressure sensing diaphragm; 3. Optical fiber; 30. Pressure measurement grating; 31. Temperature compensation grating; 32. Optical fiber connector; 4. Installation bracket; 5. Coupler; 6. Optical circulator; 60. Light source; 7. Diffraction grating; 8. Photoelectric detector; 9. Host computer. Detailed implementation manners

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0058] Refer to Figure 1 As shown, the embodiment of the present application provides a fiber optic liquid level sensor for an irradiated environment, which includes an outer shell 1, a pressure sensing diaphragm 2, and an optical fiber assembly. A pressure guiding hole 10 is opened on the outer shell 1; the pressure sensing diaphragm 2 is installed inside the outer shell 1 and divides the internal space of the outer shell 1 into a first chamber 11 and a second chamber 12, and the first chamber 11 is communicated with the pressure guiding hole 10, and the liquid level is introduced through the pressure guiding hole 10 to cause deformation of the pressure sensing diaphragm 2; the optical fiber assembly includes an optical fiber 3 and a pressure measurement grating 30 and a temperature compensation grating 31 inscribed on the optical fiber 3. The temperature compensation grating 31 is located in the second chamber 12, the pressure measurement grating 30 is bonded to the pressure sensing diaphragm 2, and one end of the optical fiber 3 passes through the outer shell 1 out of the outer shell 1; the core of the optical fiber 3 is a pure silicon core, and an anti-irradiation sheath is provided on the outer surface of the optical fiber 3.

[0059] The fiber optic liquid level sensor provided by this application uses a femtosecond laser to write an extremely stable and non-erasable femtosecond grating FsFBG for the grating, and uses a pure silica core and an anti-irradiation sheath, which can reduce the influence of irradiation on liquid level measurement, thereby improving the monitoring accuracy.

[0060] The fiber optic liquid level sensor provided by this application adopts a dual-grating design scheme. By bonding one grating on the pressure-sensitive diaphragm as the liquid level height measurement grating and placing one on the pressure-sensitive diaphragm as the temperature compensation grating, the wavelength changes caused by temperature and liquid level are separated, effectively eliminating the interference of temperature on the measurement, thereby improving the accuracy of liquid level measurement.

[0061] It should be noted that when the liquid level height changes, the hydraulic pressure will cause the deformation of the pressure-sensitive diaphragm, change the grating period, and thus change the central wavelength of the pressure measurement grating. At the same time, the temperature compensation grating collects the temperature information of the liquid level.

[0062] In this application, the grating can be written on the core of the optical fiber 3.

[0063] As a preferred example, in this application, the anti-irradiation sheath is made of polyimide or other materials that can resist irradiation;

[0064] As a preferred example, in this application, refer to Figure 1 As shown, the end of the optical fiber 3 is connected with an optical fiber connector 32, and the optical fiber connector 32 can adopt an optical fiber connector for easy plugging.

[0065] As a preferred example, in this application, the pressure measurement grating 30 is bonded to the middle of the pressure-sensitive diaphragm 2; since the edge of the pressure-sensitive diaphragm 2 is fixed, the deformation at the edge is too small under the action of hydraulic pressure and the sensitivity is low, while the deformation in the middle area is large and more sensitive. Therefore, bonding the pressure measurement grating 30 in the middle will be more sensitive and the measurement accuracy will be higher. At the same time, being glued ensures that it can deform synchronously with the pressure-sensitive diaphragm 2 and the sensitivity is higher.

[0066] As a preferred example, in the present application, the temperature compensation grating 31 is located at the edge of the pressure-sensitive diaphragm 2. The edge of the pressure-sensitive diaphragm 2 is fixed. Under the action of hydraulic pressure, the deformation at the edge is too small and the sensitivity is low, while the deformation in the middle region is large and more sensitive. Since the temperature compensation grating 31 is used to accurately measure temperature and needs to avoid being affected by hydraulic pressure as much as possible, the temperature compensation grating 31 is placed at the edge of the pressure-sensitive diaphragm 2 as much as possible, which can reduce the influence of hydraulic pressure as much as possible and improve the temperature measurement accuracy. At the same time, the temperature compensation grating 31 can just be placed on the surface of the pressure-sensitive diaphragm 2 without sticking, which can also avoid the influence of deformation on the temperature compensation grating 31. In addition, since the first chamber 11 is communicated with the pressure-introducing hole 10, the hydraulic pressure will directly enter the first chamber 11. Therefore, placing the temperature compensation grating 31 in the second chamber 12 can avoid directly sensing the hydraulic pressure and also reduce the influence of the hydraulic pressure, thereby improving the temperature measurement accuracy.

[0067] As a preferred example, in the present application, the pressure measurement grating 30 and the temperature compensation grating 31 can be inscribed on the same optical fiber 3. At this time, both the pressure measurement grating 30 and the temperature compensation grating 31 are located in the second chamber 12.

[0068] Alternatively, the pressure measurement grating 30 and the temperature compensation grating 31 are respectively inscribed on two optical fibers 3. At this time, both the pressure measurement grating 30 and the temperature compensation grating 31 can be located in the second chamber 12, or the pressure measurement grating 30 is located in the first chamber 11. It can be understood that it is optimal for the pressure measurement grating 30 to be located in the first chamber 11.

[0069] To facilitate the introduction of the liquid level, refer to Figure 1 As shown, a liquid-introducing column 15 is provided on the housing 1, and the liquid-introducing channel in the liquid-introducing column 15 is communicated with the pressure-introducing hole 10.

[0070] As a preferred example, in the present application, refer to Figure 1 As shown, the housing 1 includes a first housing 13, a compression ring 14 and a second housing arranged in sequence. The first housing 13, the compression ring 14 and the second housing are fastened by bolts, and the edge of the pressure-sensitive diaphragm 2 is located between the first housing 13 and the compression ring 14.

[0071] Refer to Figure 2 and Figure 3 As shown, the embodiment of the present application further provides a liquid level monitoring system, which includes a mounting bracket 4, an optical fiber liquid level sensor, a coupler 5, an optical circulator 6, a diffraction grating 7, a photodetector 8 and a host computer 9. The mounting bracket 4 has a mounting space inside; there are several optical fiber liquid level sensors, which are fixedly arranged in the mounting space of the mounting bracket 4 at intervals along the length direction of the mounting bracket 4, and the pressure-introducing hole 10 extends out of the mounting space, for example Figure 2Among them, the liquid guiding column 15 extends outwards, so that the liquid level enters the first chamber. At the same time, it is necessary to ensure the sealing between the installation space and the outside world. During installation, the fiber optic liquid level sensors can be arranged at equal intervals, so that they can be evenly distributed at different heights of the liquid level to be measured.

[0072] The coupler 5 is connected to the optical fibers 3 of each of the fiber optic liquid level sensors; the first output end and the second input end of the optical circulator 6 are connected to the coupler 5, and the first input end of the optical circulator 6 is connected to a light source 60; the diffraction grating 7 is connected to the second output end of the optical circulator 6 and can distinguish the signals of each fiber optic liquid level sensor; the photodetector 8 is connected to the diffraction grating 7 and can perform optoelectronic signal conversion; the host computer 9 is connected to the photodetector 8 to process the received monitoring data.

[0073] Furthermore, it is necessary to calibrate the temperature sensitivity and pressure sensitivity of the fiber optic liquid level sensor.

[0074] The calibration of the pressure sensitivity is carried out in a constant temperature environment. The pressure sensitivity of the pressure measurement grating 30 is calibrated by a pressure device (such as a pneumatic pump), and the specific steps are as follows:

[0075] 101: Build a pressure sensitivity calibration system, which includes a light source, a demodulator, a fiber optic liquid level sensor, and a pressure device.

[0076] 102: In a constant temperature environment, use the pressure device to apply different pressures to the fiber optic liquid level sensor, and monitor the center wavelength corresponding to the pressure measurement grating 30 at each pressure and calculate the wavelength drift amount;

[0077] Among them, when applying different pressures, a certain pre-pressure can be applied to the fiber optic liquid level sensor first, and then the remaining part after removing the pre-pressure from each pressure can be applied.

[0078] 103: Based on each pressure and the corresponding wavelength drift amount, obtain the mapping relationship between the pressure value and the wavelength drift amount of the pressure measurement grating 30.

[0079] Perform curve fitting on each pressure and the corresponding wavelength drift amount, and then the mapping relationship between the pressure value and the wavelength drift amount of the pressure measurement grating 30 can be obtained. Furthermore, the pressure coefficient of the pressure measurement grating 30 can be obtained, and this pressure coefficient reflects the pressure sensitivity.

[0080] Furthermore, when calibrating the temperature sensitivity, it should be noted that the thermal expansion coefficient of the pressure sensing diaphragm is different from that of the fiber grating. The wavelength drift amount of the pressure measurement grating 30 on the pressure sensing diaphragm satisfies the following formula (1):

[0081] λ 30，波长漂移量= λ 30,T + λ 30,M (1)

[0082] where λ 30，波长漂移量 is the wavelength drift of the pressure measurement grating 30, λ 30,T is the wavelength drift of the pressure measurement grating 30 itself caused by temperature, and λ 30,M is the wavelength drift of the pressure measurement grating 30 caused by the deformation of the pressure-sensitive diaphragm 2.

[0083] And the above λ 30,M also satisfies the following formula (2):

[0084] λ 30,M = λ 30,M,T + λ 30,M,ε (2)

[0085] where λ 30,M,T is the wavelength drift of the pressure measurement grating 30 caused by the deformation of the pressure-sensitive diaphragm 2 itself due to temperature, and λ 30,M,ε is the wavelength drift of the pressure measurement grating 30 caused by the deformation of the pressure-sensitive diaphragm 2 itself due to the influence of liquid level pressure.

[0086] Therefore, in fact, the wavelength drift of the pressure measurement grating 30 caused by temperature should include, in addition to λ 30,T , also λ 30,M,T . So the wavelength drift of the pressure measurement grating 30 caused by temperature satisfies the following formula (3):

[0087]

[0088] Furthermore, for the packaged fiber optic liquid level sensor, an overall calibration scheme is adopted to obtain the temperature sensitivity of the temperature compensation grating 31 and the comprehensive temperature sensitivity of the pressure-sensitive diaphragm and the pressure measurement grating 30. The specific steps are as follows:

[0089] 201: Build a temperature sensitivity calibration system, which includes a light source, a demodulator, a fiber optic liquid level sensor, and a heating platform.

[0090] Set the temperature of the heating platform, with a step of 10°C, and heat it from room temperature 25°C to 65°C. For example, use 25°C, 35°C, 45°C, 55°C, 65°C as the temperature measurement points.

[0091] 202: Under the condition of no external force interference, heat the fiber optic liquid level sensor to different temperature measurement points, and keep it at a constant temperature for a certain period of time, such as 30 min, at each temperature measurement point to stabilize the heating platform, ensure data reliability and stability, and monitor the central wavelength corresponding to the temperature compensation grating 31 and calculate the wavelength drift amount at each temperature measurement point, as well as the central wavelength corresponding to the pressure measurement grating 30 and calculate the wavelength drift amount.

[0092] 203: Based on each temperature measurement point and the corresponding wavelength drift amount of the temperature compensation grating 31, obtain the mapping relationship between the temperature value and the wavelength drift amount of the temperature compensation grating 31.

[0093] It can be understood that since step 202 is tested under the condition of no external force interference, the wavelength drift amount corresponding to the temperature compensation grating 31 in step 202 is basically caused by temperature.

[0094] Therefore, by performing curve fitting on each temperature value and the corresponding wavelength drift amount, the mapping relationship between the temperature value and the wavelength drift amount of the temperature compensation grating 31 can be obtained, and then the temperature coefficient k of the temperature compensation grating 31 can be obtained. 31,T This temperature coefficient reflects the temperature sensitivity of the temperature compensation grating 31.

[0095] 204: Based on each temperature measurement point and the corresponding wavelength drift amount difference between the temperature compensation grating 31 and the pressure measurement grating 30, obtain the mapping relationship between the temperature value and the wavelength drift amount of the pressure measurement grating 30.

[0096] It can be understood that since step 202 is tested under the condition of no external force interference, the wavelength drift amount corresponding to the pressure measurement grating 30 in step 202 is basically caused by temperature. That is, this wavelength drift amount is the

[0097] By performing curve fitting on each temperature value and the corresponding wavelength drift amount, the mapping relationship between the temperature value and the wavelength drift amount of the pressure measurement grating 30 can be obtained, and then the temperature coefficient k of the pressure measurement grating 30 can be obtained. 30,T This temperature coefficient reflects the temperature sensitivity of the pressure measurement grating 30.

[0098] Thus, the liquid level height monitored by the fiber optic liquid level sensor can be calculated.

[0099] For the above liquid level monitoring system, the mounting bracket 4 is usually placed vertically in the storage pit, and the fiber optic liquid level sensors are sorted in sequence from bottom to top.

[0100] For example, as an example, calculate the liquid level height H monitored by the i-th fiber liquid level sensor i，监测 , which specifically includes the following steps:

[0101] 301: Collect the monitoring data of the i-th fiber liquid level sensor to obtain the wavelength drift of the temperature compensation grating 31 and the wavelength drift of the pressure measurement grating 30.

[0102] 303: Based on the obtained wavelength drift of the temperature compensation grating 31 and the mapping relationship between the temperature value and the wavelength drift of the temperature compensation grating 31, calculate the current temperature value.

[0103] Substitute the obtained wavelength drift of the temperature compensation grating 31 into the mapping relationship between the temperature value and the wavelength drift of the temperature compensation grating 31 in step 203 to calculate the current temperature value.

[0104] 303: Based on the current temperature value and the mapping relationship between the temperature value and the wavelength drift of the pressure measurement grating 30, calculate the wavelength drift of the pressure measurement grating 30 caused by temperature.

[0105] Substitute the current temperature value into the mapping relationship between the temperature value and the wavelength drift of the pressure measurement grating 30 in step 204 to calculate the wavelength drift of the pressure measurement grating 30 caused by temperature

[0106] 304: Subtract the wavelength drift of the pressure measurement grating 30 caused by temperature from the wavelength drift of the pressure measurement grating 30 to obtain the wavelength drift of the pressure measurement grating 30 caused by the liquid level.

[0107] The wavelength drift of the pressure measurement grating 30 is λ in Equation (1) 30，波长漂移量 , combined with Equation (1), Equation (2) and Equation (3), it can be seen that λ 30，波长漂移量 Subtract to obtain the wavelength drift λ of the pressure measurement grating 30 caused by the deformation of the pressure-sensitive diaphragm 2 itself due to the influence of the liquid level pressure 30,M,ε , this wavelength drift λ 30,M,ε is the wavelength drift of the pressure measurement grating 30 caused by the liquid level.

[0108] 305: Based on the wavelength drift of the pressure measurement grating 30 caused by the liquid level and the mapping relationship between the pressure value and the wavelength drift of the pressure measurement grating 30, obtain the current pressure value.

[0109] Substitute λ calculated in step 304 30,M,εSubstitute it into the mapping relationship between the pressure value in step 103 and the wavelength drift amount of the pressure measurement grating 30, and calculate the current pressure value.

[0110] 306: Based on the current pressure value and the mapping relationship between the liquid level height and the pressure value, obtain the liquid level height H i，监测 。

[0111] Since the mapping relationship between the liquid level height and the pressure value is a known quantity, substituting the current pressure value into the mapping relationship between the liquid level height and the pressure value can obtain the liquid level height H i，监测 。

[0112] It should be noted that the above liquid level height H i，监测 takes the elevation where the fiber optic liquid level sensor is located as the reference plane, and calculates the liquid level height above this reference plane.

[0113] The embodiment of the present application also provides a monitoring method for a liquid level monitoring system, which includes the following steps:

[0114] 401: Vertically place the mounting bracket 4 in the storage pit, and sequentially sort each of the fiber optic liquid level sensors from bottom to top, and determine the height of each fiber optic liquid level sensor in the storage pit.

[0115] 402: Use the upper computer 9 to receive the monitoring data, and based on the monitoring data, calculate the liquid level height Y in the storage pit as follows in formula (4):

[0116]

[0117] where n is the total number of fiber optic liquid level sensors on the mounting bracket 4; j is the number of fiber optic liquid level sensors that send monitoring data among all the fiber optic liquid level sensors; H i，储坑 is the height of the i-th fiber optic liquid level sensor in the storage pit, and H i，监测 is the liquid level height calculated based on the monitoring data of the i-th fiber optic liquid level sensor.

[0118] As an example, assume that the height of the storage pit is 2m, and the three fiber optic liquid level sensors are the first sensor, the second sensor, and the third sensor in sequence from bottom to top. The height H of the first sensor placed in the storage pit 1，储坑 is 0.1m, the height H of the second sensor placed in the storage pit 2，储坑 is 0.9m, and the height H of the third sensor placed in the storage pit 3，储坑 is 1.7m.

[0119] Since the three sensors are placed at heights of 0.1m, 0.9m, and 1.7m, using the first sensor for judgment, if the first sensor does not detect monitoring data and there is no indication at this time, it indicates that the liquid level height is lower than 0.1m. At this time, the liquid level height is not output and the liquid level height status is determined to be empty.

[0120] If the first sensor detects monitoring data and the calculated liquid level height is H 1,监测 , but the second sensor has no indication, then the liquid level height is greater than 0.1m and less than 0.9m, and the liquid level height status is determined to be low. The output liquid level height is:

[0121] Y = H 1,监测 + 0.1

[0122] If the first and second sensors have indications and the third sensor has no indication, it means that the liquid level height is greater than 0.9m and less than 1.7m. At this time, the liquid level height status is determined to be medium, and the output liquid level height is:

[0123]

[0124] If the first, second, and third sensors all have indications, it means that the liquid level height is higher than 1.7m. At this time, the liquid level height status is determined to be high, and the output liquid level height is:

[0125]

[0126] In this application, by using multiple sensors of the liquid level monitoring system and combining the above formula (4), a comprehensive judgment is made on the liquid level height Y in the storage pit, which has the following advantages:

[0127] First, it simplifies the warning judgment of the liquid level height. For example, by placing three fiber optic liquid level sensors at the high, medium, and low positions of the storage pit through fixed brackets, it is possible to roughly determine the liquid level height range by whether the sensors sense pressure, without specifically calculating the liquid level height, so as to simplify the warning judgment of the liquid level height.

[0128] Example: For a 2m storage pit, three fiber optic liquid level sensors are placed at 0.1m, 0.9m, and 1.7m of the storage pit through fixed brackets. When the liquid level sensor at 0.1m does not sense water pressure, the warning for the liquid level height of the storage pit is "empty"; if the fiber optic liquid level sensor at 0.1m senses water pressure and the fiber optic liquid level sensor at 0.9m does not sense water pressure, the warning for the liquid level height of the storage pit is "low"; if the fiber optic liquid level sensor at 0.9m senses water pressure but the fiber optic liquid level sensor at 1.7m does not sense water pressure, the warning for the liquid level height of the storage pit is "medium"; if the fiber optic liquid level sensor at 1.7m senses water pressure, the warning for the liquid level height of the storage pit is "high".

[0129] Second, improve the fault tolerance. Through redundant design, if a certain fiber optic liquid level sensor fails, other fiber optic liquid level sensors can still work normally, avoiding monitoring interruption caused by single-point failure. And by cross-verifying the data of multiple sensors, the system can automatically identify and mark abnormal sensors, reducing maintenance costs and avoiding accident losses.

[0130] Third, increase the liquid level monitoring range. Through segmented measurement and relay-type data integration, the local ranges of multiple sensors are superimposed to cover a larger total measurement range.

[0131] Example: If the height of the storage pit is 2m and the range of a single fiber optic liquid level sensor is 1m, and three sensors are installed at heights of 0.1m, 0.9m, and 1.7m respectively, then each sensor covers a liquid level range of 0.1 - 0.9m, 0.9 - 1.7m, and 1.7m - 2m respectively. The total measurement range can be extended from 1m of a single sensor to 2m or even higher of multiple sensors.

[0132] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0133] It should be noted that in the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0134] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An optical fiber liquid level sensor for use in an irradiated environment, characterized in that: It includes: A housing (1) having a pressure-inducing hole (10) formed therein; A pressure-sensitive diaphragm (2) is installed in the housing (1) and divides the internal space of the housing (1) into a first chamber (11) and a second chamber (12), and the first chamber (11) is connected to the pressure-inducing hole (10); An optical fiber assembly comprises an optical fiber (3) and a pressure measurement grating (30) and a temperature compensation grating (31) inscribed on the optical fiber (3); the temperature compensation grating (31) is located in the second chamber (12); the pressure measurement grating (30) is bonded to the pressure-sensitive diaphragm (2); one end of the optical fiber (3) passes through the outer shell (1); the core of the optical fiber (3) is a pure silica core, and the outer surface of the optical fiber (3) is provided with an anti-radiation sheath.

2. The optical fiber liquid level sensor for use in an irradiated environment according to claim 1, characterized in that: The radiation-resistant sheath is made of polyimide; and / or, the end of the optical fiber (3) is connected to an optical fiber connector (32); And / or, the pressure measuring grating (30) is bonded to the middle part of the pressure-sensitive diaphragm (2); And / or, the temperature compensation grating (31) is located at the edge of the pressure-sensitive diaphragm (2).

3. The optical fiber liquid level sensor for use in an irradiated environment according to claim 1, characterized in that: The pressure measurement grating (30) and the temperature compensation grating (31) are inscribed on the same optical fiber (3); Alternatively, the pressure measurement grating (30) and the temperature compensation grating (31) are respectively inscribed on the two optical fibers (3).

4. The optical fiber liquid level sensor for use in an irradiated environment according to claim 1, characterized in that: The pressure measurement grating (30) is located in the first chamber (11) or the second chamber (12); And / or, a liquid introduction column (15) is provided on the housing (1), and a liquid introduction channel in the liquid introduction column (15) is connected to the pressure introduction hole (10); And / or, the housing (1) comprises a first shell (13), a pressure ring (14) and a second shell which are arranged in sequence, the first shell (13), the pressure ring (14) and the second shell are fastened by bolts, and the edge of the pressure-sensitive diaphragm (2) is located between the first shell (13) and the pressure ring (14).

5. A liquid level monitoring system, characterized in that: It includes: The mounting bracket (4) has a mounting space therein ； The optical fiber liquid level sensor for use in an irradiated environment according to any one of claims 1 to 4, wherein there are a plurality of optical fiber liquid level sensors, which are fixed in the installation space of the installation bracket (4) at intervals along the length direction of the installation bracket (4), and the pressure-inducing hole (10) extends out of the installation space; A coupler (5) connected to the optical fiber (3) of each of the optical fiber liquid level sensors; An optical circulator (6), which is connected to the coupler (5), and the optical circulator (6) is also connected to a light source (60); A diffraction grating (7) connected to the optical circulator (6); A photodetector (8) connected to the diffraction grating (7); A host computer (9) is connected to the photoelectric detector (8).

6. A monitoring method of a liquid level monitoring system as claimed in claim 5, characterized in that: It includes: The mounting bracket (4) is vertically placed in the storage pit, and each of the optical fiber liquid level sensors is arranged in order from bottom to top, and the height of each of the optical fiber liquid level sensors in the storage pit is determined; Using a host computer (9) to receive monitoring data, and based on the monitoring data, calculating the liquid level height Y in the storage pit; Wherein, n is the total number of optical fiber liquid level sensors on the mounting bracket (4); j is the number of optical fiber liquid level sensors that send monitoring data among all optical fiber liquid level sensors; H i，储坑 is the height of the ith fiber liquid level sensor in the storage pit, H i，监测 is the liquid level height calculated based on the monitoring data of the i-th fiber liquid level sensor.

7. The monitoring method of the liquid level monitoring system according to claim 6, characterized in that: It also includes: Calibrate the temperature sensitivity of the optical fiber liquid level sensor; The pressure sensitivity of the optical fiber liquid level sensor is calibrated.

8. The monitoring method of the liquid level monitoring system according to claim 7, characterized in that: Calibrate the pressure sensitivity of the optical fiber liquid level sensor, specifically including: Under a constant temperature environment, applying different pressures to the optical fiber liquid level sensor, monitoring the central wavelength corresponding to the pressure measurement grating (30) under each pressure, and calculating the wavelength drift; Based on each pressure and the corresponding wavelength drift, a mapping relationship between the pressure value and the wavelength drift of the pressure measurement grating (30) is obtained.

9. The monitoring method of the liquid level monitoring system according to claim 7, characterized in that: Calibrate the temperature sensitivity of the optical fiber liquid level sensor, specifically including: The optical fiber liquid level sensor is heated to different temperature measurement points, and each temperature measurement point is kept constant for a period of time, and the central wavelength corresponding to the temperature compensation grating (31) and the wavelength drift amount are monitored at each temperature measurement point, and the central wavelength corresponding to the pressure measurement grating (30) and the wavelength drift amount are calculated; Based on each temperature measurement point and the corresponding wavelength drift of the temperature compensation grating (31), a mapping relationship between the temperature value and the wavelength drift of the temperature compensation grating (31) is obtained; Based on each temperature measurement point and the wavelength drift difference between the corresponding temperature compensation grating (31) and the pressure measurement grating (30), a mapping relationship between the temperature value and the wavelength drift of the pressure measurement grating (30) is obtained.

10. The monitoring method of the liquid level monitoring system according to claim 9, characterized in that: Calculate the liquid level H i，监测 , including the following steps: Collecting monitoring data of the i-th fiber liquid level sensor to obtain the wavelength drift of the temperature compensation grating (31) and the wavelength drift of the pressure measurement grating (30); Calculating a current temperature value based on the obtained wavelength drift of the temperature compensation grating (31) and a mapping relationship between the temperature value and the wavelength drift of the temperature compensation grating (31); Based on the current temperature value and the mapping relationship between the temperature value and the wavelength drift of the pressure measurement grating (30), calculating the wavelength drift of the pressure measurement grating (30) caused by temperature; Subtracting the wavelength drift of the pressure measuring grating (30) caused by temperature from the wavelength drift of the pressure measuring grating (30) to obtain the wavelength drift of the pressure measuring grating (30) caused by the liquid level; Based on the wavelength drift of the pressure measuring grating (30) caused by the liquid level and the mapping relationship between the pressure value and the wavelength drift of the pressure measuring grating (30), a current pressure value is obtained; Based on the current pressure value and the mapping relationship between the liquid level and the pressure value, the liquid level height H is obtained. i，监测 .

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