Optical fiber temperature sensor for measuring curved surface temperature field

Abstract

The invention discloses an optical fiber temperature sensor for measuring a curved surface temperature field. The optical fiber temperature sensor comprises an optical fiber, a plurality of sections of sensitive structures engraved on the optical fiber, a plurality of sections of capillary glass tubes, a capillary metal tube and protective liquid, wherein each section of capillary glass tube wraps each section of sensitive structure and is ideally connected with the sensitive structure, the capillary metal tube wraps all the capillary glass tubes, the sensitive structures and the optical fibers among the capillary glass tubes and the sensitive structures, one end of the capillary metal tube is closed, and the other end of the capillary metal tube is rigidly connected with the optical fibers through adhesive, so that a closed space is formed. The sensitive structure can freely deform under the action of temperature in a closed space formed by the capillary metal tube; the closed space is filled with protective liquid, the protective liquid is a wide-temperature-range solution and does not chemically react with the optical fiber, the capillary glass tube, the capillary metal tube and the adhesive, the protective liquid wraps the capillary glass tube, and frictional contact between the capillary glass tube and the capillary metal tube is reduced. According to the invention, efficient and accurate continuous monitoring of the curved surface temperature field can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to an optical fiber temperature sensor for measuring a curved surface temperature field. Background Art

[0002] The fiber Bragg Grating (FBG) temperature sensor is a high-precision temperature measurement device based on fiber Bragg grating technology. Its sensing principle mainly relies on the wavelength-selective reflection characteristics of the fiber Bragg grating. When the light wave in the optical fiber propagates to the Bragg grating area, the light wave of a specific wavelength that meets the Bragg condition will be reflected back, and the light waves of the remaining wavelengths will continue to propagate. When the ambient temperature of the fiber Bragg grating changes, the thermo-optical effect and thermal expansion and contraction effect of the optical fiber material will cause the grating period and refractive index to change, thereby causing the drift of the reflected wavelength. By monitoring the change in the reflected wavelength and combining it with the known temperature-wavelength relationship curve, accurate temperature measurement can be achieved.

[0003] Fiber Bragg grating temperature sensors have been widely used in the field of temperature measurement due to their high precision, fast response, and anti-electromagnetic interference. As a sensing element, optical fiber is not only small in size and light in weight, but also has extremely high reliability, making it suitable for temperature measurement in various complex environments. In the industrial field, fiber optic temperature sensors are often used in environments such as high-temperature melting, heat treatment, and power equipment to monitor equipment temperature in real time to ensure work safety and stability. In the aerospace field, fiber optic temperature sensors are used to monitor the temperature of key equipment and systems in spacecraft and aircraft to ensure the performance and life of the equipment. In addition, in terms of environmental monitoring, fiber optic temperature sensors can monitor ocean water temperature, groundwater source temperature, and atmospheric environment, which is of great significance to ecological environmental protection and research.

[0004] Although fiber Bragg grating temperature sensors have shown many advantages in the field of temperature measurement, the measurement accuracy and stability of fiber Bragg grating temperature sensors are still facing challenges in the measurement of curved surface temperature fields. First, the complexity and irregularity of the curved surface structure make it difficult to install and position the fiber optic sensor, and it is difficult to ensure that the sensor can accurately cover the entire curved surface area. The bending of the sensor may cause the internal sensitive structure (such as the grating) to be affected by stress, reducing the measurement accuracy and stability. Secondly, the temperature distribution on the curved surface is often uneven, and there is a temperature gradient. Traditional fiber optic temperature sensors may find it difficult to capture such subtle temperature changes, resulting in a decrease in measurement accuracy. In addition, the optical fiber itself is susceptible to heat loss and mechanical damage, especially in a curved environment. These problems may be more prominent, increasing maintenance costs and difficulties. Therefore, it is of great practical significance and application value to develop a fiber optic temperature sensor specifically for curved surface temperature field measurement to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide an optical fiber temperature sensor for measuring curved surface temperature field, which can realize efficient and accurate continuous monitoring of the curved surface temperature field.

[0006] In order to achieve the above object, one aspect of the present invention provides an optical fiber temperature sensor for measuring a curved surface temperature field, the optical fiber temperature sensor comprising an optical fiber, a plurality of sensitive structures engraved on the optical fiber, a plurality of capillary glass tubes, a capillary metal tube, and a protective liquid;

[0007] Each section of the capillary glass tube wraps each section of the sensitive structure on the optical fiber and is ideally connected to the sensitive structure, the capillary metal tube wraps all the capillary glass tubes, the sensitive structure and the optical fiber connected between the capillary glass tubes and the sensitive structure, one end of the capillary metal tube is closed and the other end is rigidly connected to the optical fiber through an adhesive, thereby forming a closed space, and the sensitive structure can be freely deformed after being affected by temperature in the closed space formed by the capillary metal tube;

[0008] The enclosed space is filled with a protective liquid, which is a solution with a wide temperature range and does not chemically react with the optical fiber, the capillary glass tube, the capillary metal tube and the adhesive. The protective liquid wraps the capillary glass tube, which can reduce the friction contact between the capillary glass tube and the capillary metal tube;

[0009] The capillary metal tube is a flexible stainless steel capillary hollow tube. When the optical fiber temperature sensor is installed on the measured surface of the curved temperature field, the capillary metal tube and the protective liquid can effectively transfer the heat of the measured surface. The sensitive structure can change the central wavelength value of its output due to temperature changes, and the capillary glass tube has a sensitization effect on the sensitive structure.

[0010] Preferably, the sensitive structure comprises a plurality of periodic refractive index modulation regions.

[0011] Preferably, the sensitive structure is a fiber Bragg grating.

[0012] Preferably, the capillary glass tube and the capillary metal tube are both cylindrical tubes.

[0013] Preferably, the protective liquid is silicone oil.

[0014] The optical fiber temperature sensor for measuring the curved surface temperature field according to the above aspects of the present invention can realize efficient and accurate continuous monitoring of the curved surface temperature field. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0016] Figure 1 It is a schematic structural diagram of an optical fiber temperature sensor for measuring a curved surface temperature field according to an embodiment of the present invention;

[0017] Figure 2 for Figure 1 A schematic diagram of section A;

[0018] Figure 3 for Figure 1 A schematic diagram of section B;

[0019] Figure 4 This is an installation layout effect diagram of an optical fiber temperature sensor for measuring a curved surface temperature field according to an embodiment of the present invention;

[0020] Among them, 1-optical fiber; 2-sensitive structure; 3-capillary glass tube; 4-capillary metal tube; 5-protective liquid. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The embodiment of the present invention provides an optical fiber temperature sensor for measuring a curved surface temperature field, such as Figure 1-Figure 3 As shown, the optical fiber temperature sensor for measuring the temperature field of a curved surface according to the embodiment of the present invention comprises an optical fiber 1, a plurality of sensitive structures 2 engraved on the optical fiber 1, a plurality of capillary glass tubes 3, a capillary metal tube 4, and a protective liquid 5. The capillary glass tubes 3 respectively wrap each sensitive structure 2 on the optical fiber 1 and are ideally connected thereto; the capillary metal tube 4 wraps all the capillary glass tubes 3, the sensitive structures 2, and the connecting optical fibers 1 therebetween, with one end of the capillary metal tube 4 being closed and the other end being rigidly connected to the optical fiber 1 to form a closed space; the closed space is filled with the protective liquid 5.

[0023] The sensitive structure 2 includes a plurality of periodic refractive index modulation regions. The capillary glass tube 3 and the capillary metal tube 4 are both cylindrical tubes.

[0024] The protective liquid 5 is a solution with a wide temperature range and does not chemically react with the optical fiber 1, the capillary glass tube 3, the capillary metal tube 4 and the adhesive, such as silicone oil; the protective liquid 5 can protect the sensitive structure 2 wrapped around the capillary glass tube 3, and also reduce the frictional contact between the capillary glass tube 3 and the capillary metal tube 4, thereby avoiding stress transfer and improving the accuracy and durability of the sensor.

[0025] The other end (open end) of the capillary metal tube 4 is rigidly connected to the optical fiber through adhesive to form a closed space. The capillary metal tube 4 and the protective liquid 5 effectively transfer the heat of the measured surface, and the capillary glass tube 3 plays a sensitizing role on the sensitive structure 2, which significantly improves the sensitivity and accuracy of the sensor.

[0026] The sensitive structure 2 can be deformed freely after being affected by temperature in the closed space formed by the capillary metal tube 4. The capillary glass tube 3 is multi-section and is ideally connected to each section of the sensitive structure 2. The sensitive structure area of ​​the optical fiber temperature sensor is completely immersed in the protective liquid 5. Combined with the capillary metal tube 4 outside the sensitive structure area, the stress effect of the sensor bending on the sensitive structure area when installed on a curved surface is effectively avoided, and the measurement accuracy and stability when installed on a curved surface are improved.

[0027] In one embodiment, the sensitive structure 2 is a fiber Bragg grating with a length of 5 mm, and the capillary glass tube 3 respectively wraps each fiber Bragg grating on the optical fiber 1 and is ideally connected thereto. The capillary metal tube 4 is placed in the outermost layer and wraps all the capillary glass tubes 3, the fiber Bragg gratings and the connecting optical fibers therebetween. The inner diameter of the capillary metal tube 4 should be as small as possible on the basis of allowing the capillary glass tube 3 to pass through. The capillary glass tube 3 and the capillary metal tube 4 are both cylindrical tubes. The capillary metal tube 4 is a flexible stainless steel capillary hollow tube with one end closed and the other end open. The open end is rigidly connected to the optical fiber 1 through adhesive to form a closed space. The fiber Bragg grating can be deformed freely after being affected by temperature in the closed space. The closed space is filled with a protective liquid 5, which is silicone oil.

[0028] Figure 4 This is an installation layout effect diagram of an optical fiber temperature sensor for measuring a curved surface temperature field according to an embodiment of the present invention. Multiple optical fiber temperature sensors are used, and each optical fiber temperature sensor contains multiple sensitive structures. Multi-point temperature measurement can be performed to achieve curved surface temperature field measurement.

[0029] When the optical fiber temperature sensor of the embodiment of the present invention is installed on a curved surface structure, the sensor is bent. Through the protection of the capillary glass tube, silicone oil and stainless steel capillary hollow tube, the stress effect caused by the bending is reduced, especially the friction contact between the capillary glass tube and the flexible stainless steel capillary hollow tube is reduced to avoid stress transmission, thereby improving the measurement accuracy and stability of the curved surface installation, and also improving the durability of the optical fiber temperature sensor. When subjected to temperature changes, the flexible stainless steel capillary hollow tube and silicone oil sense the temperature change of the curved surface structure and effectively transfer the heat of the measured surface. Therefore, the sensitive structure is affected by the temperature change so that the central wavelength value of its output changes. It is necessary to obtain the central wavelength of each grating of the optical fiber temperature sensor through the acquisition processor, and then by establishing the relationship between the output central wavelength value of each fiber Bragg grating with no temperature change and temperature change and the temperature change, the temperature working curve of each temperature measuring point of the optical fiber temperature sensor can be obtained, so as to establish the temperature field of the measured curved surface according to the measured temperature of each temperature measuring point of the optical fiber temperature sensor.

[0030] The optical fiber temperature sensor for measuring curved surface temperature field according to the embodiment of the present invention has the following beneficial effects:

[0031] Realize curved surface installation: By designing the structure of the optical fiber temperature sensor, the problem that the complexity and irregularity of the curved surface structure make the installation and positioning of the optical fiber Bragg grating sensor difficult is solved, ensuring that the sensor can accurately cover the entire curved surface area;

[0032] Improve measurement accuracy: The innovative design of the fiber optic temperature sensor structure reduces the stress effect when installed on a curved surface, enables the fiber optic temperature sensor to measure the temperature field on the curved surface, and improves the measurement accuracy;

[0033] Enhanced durability: The capillary metal tube and the injected protective fluid on the outside of the sensitive structure of the fiber grating sensor provide good protection for the sensitive structure, reduce friction contact with the external environment, and thus extend the service life of the sensor.

[0034] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An optical fiber temperature sensor for measuring curved surface temperature field, characterized in that: The optical fiber temperature sensor comprises an optical fiber, a plurality of sensitive structures engraved on the optical fiber, a plurality of capillary glass tubes, a capillary metal tube, and a protective liquid; Each section of the capillary glass tube wraps each section of the sensitive structure on the optical fiber and is ideally connected to the sensitive structure, the capillary metal tube wraps all the capillary glass tubes, the sensitive structure and the optical fiber connected between the capillary glass tubes and the sensitive structure, one end of the capillary metal tube is closed and the other end is rigidly connected to the optical fiber through an adhesive, thereby forming a closed space, and the sensitive structure can be freely deformed after being affected by temperature in the closed space formed by the capillary metal tube; The enclosed space is filled with a protective liquid, which is a solution with a wide temperature range and does not chemically react with the optical fiber, the capillary glass tube, the capillary metal tube and the adhesive. The protective liquid wraps the capillary glass tube, which can reduce the friction contact between the capillary glass tube and the capillary metal tube; The capillary metal tube is a flexible stainless steel capillary hollow tube. When the optical fiber temperature sensor is installed on the measured surface of the curved temperature field, the capillary metal tube and the protective liquid can effectively transfer the heat of the measured surface. The sensitive structure can change the central wavelength value of its output due to temperature changes, and the capillary glass tube has a sensitization effect on the sensitive structure.

2. The optical fiber temperature sensor according to claim 1, characterized in that: The sensitive structure includes a plurality of periodic refractive index modulation regions.

3. The optical fiber temperature sensor according to claim 2, characterized in that: The sensitive structure is a fiber Bragg grating.

4. The optical fiber temperature sensor according to any one of claims 1 to 3, characterized in that: The capillary glass tube and the capillary metal tube are both cylindrical tubes.

5. The optical fiber temperature sensor according to any one of claims 1 to 3, characterized in that: The protective liquid is silicone oil.

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