Active heating FBG optical fiber shield tail sealing detection composite sensor

Abstract

The invention belongs to the related technical field of temperature measurement optical fibers, and discloses an active heating FBG (Fiber Bragg Grating) optical fiber shield tail sealing detection composite sensor, which comprises a temperature measurement optical fiber, a reinforcing assembly, a heating assembly, a high-temperature-resistant silica gel filler and an external protection device, the temperature measuring optical fiber, the reinforcing assembly and the heating assembly are sequentially arranged in a row and closely adjacent to each other to jointly form a center assembly of the sensor. The external protection device comprises an inner layer and an outer layer, the inner layer is used for wrapping the high-temperature-resistant silica gel filler, and the outer layer is a high-thermal-conductivity sheath; and the high-temperature-resistant silica gel filler is filled between the inner layer and the central component. The self-insulation resistance wire is used for active heating, the temperature field of a medium around the sensor is actively changed, due to the fact that the heat absorption capacity of a leakage material is different from that of grease, the FBG optical fiber temperature sensor is used for collecting temperature data of all measuring points after heating, and the abnormal condition of local temperature can be shown at the leakage position; therefore, the sealing performance of the shield tail sealing grease cavity is judged.

Description

Technical Field

[0001] The present invention belongs to the technical field related to temperature - measuring optical fibers, and more specifically, relates to an actively - heated FBG optical - fiber shield - tail seal detection composite sensor. Background Art

[0002] Bragg fiber - grating sensors have many advantages such as small volume, easy integration and embedding, high resolution and sensitivity, anti - interference and corrosion resistance. Since they are made of optical fibers, they are easy to realize quasi - distributed sensing and measurement, and the measurement range meets the requirements of most engineering applications, so they are applied in many fields such as aerospace, engineering detection, and medical devices.

[0003] During shield tunneling construction, because the operation is in an underground environment, it often faces complex environments such as rivers, lakes, seas, groundwater, and soft geological strata, and the shield - tail seal system is prone to leakage. The existing technology has deficiencies in the research on the state monitoring of the shield - tail seal system. The commonly used grease - chamber pressure monitoring system can only realize the real - time monitoring of the oil pressure (medium pressure) in the seal chamber to achieve timely grease replenishment, and cannot accurately judge whether the tunnel - formation mud and water penetrate into the grease chamber. Currently, there is a lack of endoscopic sensors in this field to monitor the changes of the medium in the grease seal chamber, and it is impossible to monitor and give early warnings in advance whether the shield - tail seal is penetrated by underground soil and water and leaks, resulting in the inability to take effective remedial measures when the entire grease seal chamber of the shield - tail is penetrated and leaks.

[0004] Therefore, there is an urgent need to design an endoscopic fiber - grating sensor to solve the technical problem of real - time detection of the shield - tail seal state. Summary of the Invention

[0005] In view of the above - mentioned defects or improvement requirements of the existing technology, the present invention provides an actively - heated FBG optical - fiber shield - tail seal detection composite sensor, aiming to monitor and give early warnings whether the shield - tail seal is penetrated by underground soil and water and leaks through an endoscopic sensing method, thereby solving the technical problem of real - time detection of the shield - tail seal state.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided an actively - heated FBG optical - fiber shield - tail seal detection composite sensor, including a temperature - measuring optical fiber 6, a strengthening component 5, a heating component 4, a high - temperature - resistant silica - gel gel filler 3, and an external protection device; the temperature - measuring optical fiber 6, the strengthening component 5, and the heating component 4 are arranged in a row adjacent to each other in sequence to jointly form the central component of the sensor; the external protection device includes an inner layer 2 and an outer layer 1, the inner layer 2 is used to wrap the high - temperature - resistant silica - gel gel filler 3, and the outer layer 1 is a high - thermal - conductivity sheath; the high - temperature - resistant silica - gel gel filler 3 is filled between the inner layer 2 and the central component.

[0007] Preferably, the type of the temperature - measuring optical fiber 6 is FBG optical fiber, and a plurality of grating measuring points are uniformly inscribed on the temperature - measuring optical fiber 6 at equal intervals.

[0008] Preferably, the spacing of the grating measurement points is set as follows: one grating measurement point is arranged every 5° along the cross-section of the shield tail grease seal cavity; each grating measurement point can measure the surrounding ambient temperature and present it in the form of wavelength data on the FBG optical fiber demodulator. The FBG optical fiber has high sensitivity, and through multi-point detection, the changes in the surrounding temperature field can be accurately measured, which is convenient for determining whether external muddy water has penetrated into the shield tail grease seal cavity and the leakage point.

[0009] Preferably, the reinforcing component 5 is set as a high-strength metal reinforcing wire with a diameter of 1 mm. The high-strength metal reinforcing wire can enhance the overall structural stiffness of the composite sensor, prevent the FBG optical fiber from breaking due to bending and vibration, and facilitate the mutual fixation of the central components; the thickness is set to 1 mm, which is beneficial to the control of the overall diameter of the composite sensor and is convenient for the composite sensor to be bent and arranged in the grease cavity to be detected.

[0010] Preferably, the heating component 4 is set as a self-insulating resistance wire heating tape with a circular cross-section and a diameter of 1 mm.

[0011] Preferably, the heating component is heated by connecting to an external power supply, and a self-heating temperature control switch is provided at the external power supply to adjust the heating power and heating temperature. The heating power is set to 25W - 40W per meter, and the heating temperature is set not to exceed 40°C to avoid grease melting. By connecting to an external power supply for heating, the temperature field of the composite sensor and the surrounding environment can be actively changed.

[0012] Preferably, the high-temperature resistant silica gel gel filler 3 uniformly wraps the temperature measurement optical fiber 6, the reinforcing component 5, and the heating component 4, and is used to separate and fix the temperature measurement optical fiber 6, the reinforcing component 5, and the heating component 4 from each other. The high-temperature resistant property can ensure that the filler does not easily melt during the active heating process, maintain the structural stability, and achieve the functions of waterproofing and shock absorption.

[0013] Preferably, the inner layer 2 is set as an aluminum-plastic armored layer, which is made of aluminum alloy material with a thickness of 1 mm. The aluminum-plastic armored layer is used to wrap the central components and plays a supporting role to reduce the influence of external environmental stress on the temperature measurement optical fiber. The aluminum-plastic armored layer has excellent heat conduction ability and can quickly achieve the temperature field balance between the internal central components and the external environment.

[0014] Preferably, the outer layer 1 is set as a high thermal conductivity XLPE sheath with a thickness of 1 mm, and its material is cross-linked polyethylene, which can be used to protect the central components. Cross-linked polyethylene is a polymer material that changes the linear structure of polyethylene molecules into a network structure through chemical or physical methods. By doping metal oxide nanoparticles in the material, the thermal conductivity of the sheath can be significantly improved, and it has the characteristics of high temperature and high pressure resistance, wear resistance, high insulation resistance, lightweight, and excellent mechanical properties.

[0015] Preferably, the composite sensor 7 is annularly arranged in the shield tail grease sealing cavity 11, closely attached to the inner surface of the shield shell 8, and fixed on the shield tail brush pressure plate 10.

[0016] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, a kind of actively heated FBG optical fiber shield tail seal detection composite sensor provided by the present invention mainly has the following

[0017] Advantages:

[0018] 1. Based on the FBG optical fiber grating, the present invention innovatively adopts the temperature measurement method to design a composite sensor for the penetration detection of the shield tail grease sealing cavity. The quasi-distributed FBG optical fiber is used to measure the temperature of the grease sealing cavity. Multiple grating measuring points are flexibly inscribed on the optical fiber structure according to the requirements of the shield diameter. By using its advantages of high resolution, high sensitivity and strong anti-interference, it can quickly detect whether the medium in the sealing cavity changes to determine whether there is leakage and the location of the leakage point. The detection is selected to be carried out during the pause of the shield tunneling construction, reducing the influence of the vibration generated by the shield construction and the change of the grease oil pressure in the sealing cavity on the wavelength data, and improving the accuracy of the detection.

[0019] 2. The central component of the composite sensor is internally provided with a self-insulated resistance wire heating belt, which actively changes the temperature field around the sensor in a self-heating form, and then judges the abnormal medium in the sealing system. The composite sensor can accurately control the heating power to ensure that the temperature field around it is changed without affecting the working performance of the grease.

[0020] 3. Using aluminum alloy material as the main material of the aluminum-plastic armored layer, taking advantage of the excellent thermal conductivity and ductility of aluminum alloy, it can not only quickly achieve the balance of the temperature field inside and outside the sensor, but also facilitate the composite sensor to be bent and arranged in the grease sealing cavity. Moreover, the aluminum-plastic armored layer has certain strength and toughness, playing a necessary protective role for the internal structure. Description of the Drawings

[0021] Figure 1 is a schematic structural diagram of an actively heated FBG optical fiber shield tail seal detection composite sensor of the present invention;

[0022] Figure 2 is a schematic diagram of the composite sensor of the present invention working in the shield tail grease sealing cavity;

[0023] Figure 3 is a cross-sectional view of the shield tail grease sealing cavity where the composite sensor of the present invention is arranged;

[0024] Figure 4 is a working data diagram of the composite sensor of the present invention in different media;

[0025] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, where:

[0026] 1 - outer shell; 2 - inner shell; 3 - high - temperature resistant silica gel gel filler; 4 - heating component; 5 - strengthening component; 6 - temperature - measuring optical fiber; 7 - composite sensor; 8 - shield shell; 9 - shield tail brush; 10 - shield tail brush pressure plate; 11 - shield tail grease seal cavity; 12 - segment; 13 - inner channel of shield shell. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The present invention discloses an actively heated FBG optical fiber shield tail seal detection composite sensor. Please refer to Figure 1 , which includes a temperature - measuring optical fiber 6, a strengthening component 5, a heating component 4, a high - temperature resistant silica gel gel filler 3 and an external protection device; the temperature - measuring optical fiber 6, the strengthening component 5 and the heating component 4 are arranged in a row adjacent to each other in sequence to jointly form the central component of the sensor; the external protection device includes an inner layer 2 and an outer layer 1. The inner layer 2 is used to wrap the high - temperature resistant silica gel gel filler 3, and the outer layer 1 is a high - thermal - conductivity sheath; the high - temperature resistant silica gel gel filler 3 is filled between the inner layer and the central component.

[0029] The type of the temperature - measuring optical fiber 6 is FBG optical fiber, and a plurality of grating measurement points are equally and uniformly inscribed on the optical fiber structure. One of the grating measurement points is arranged every 5° on the cross - section of the shield tail grease seal cavity. Each grating measurement point can measure the surrounding environmental temperature and present it in the form of wavelength data on the FBG demodulator. The FBG optical fiber has high sensitivity, and through multi - point detection, the change of the surrounding temperature field can be accurately measured, which is convenient for determining whether external muddy water has penetrated into the shield tail grease seal cavity and the leakage point.

[0030] The strengthening component 5 is set as a high - strength metal strengthening wire with a diameter of 1 mm. The high - strength metal strengthening wire can enhance the overall structural stiffness of the composite sensor, prevent the FBG optical fiber from generating breakpoints due to bending and vibration, and facilitate the mutual fixation of the central components; the thickness is set to 1 mm, which is beneficial to controlling the overall diameter of the composite sensor and facilitating the bending of the composite sensor to be arranged in the grease cavity to be detected.

[0031] The heating component 4 is set as a self-insulating resistance wire heating tape with a circular cross-section and a diameter of 1 mm. The heating component is heated by connecting to an external power supply. At the external power supply, a self-heating temperature control switch is provided to adjust the heating power and heating temperature. The heating power is set to 25W - 40W per meter, and the heating temperature is set not to exceed 40°C to avoid the melting of grease. By connecting to the external power supply for heating, the temperature field of the composite sensor and the surrounding environment can be actively changed.

[0032] The high-temperature resistant silicone gel filler 3 evenly wraps the temperature measuring optical fiber 6, the strengthening component 5, and the heating component 4, and is used to separate and fix the temperature measuring optical fiber 6, the strengthening component 5, and the heating component 4 from each other. The high-temperature resistant property can ensure that the filler does not easily melt during the active heating process, maintain the structural stability, and achieve the functions of waterproofing and shock absorption; at the same time, the filler reduces the friction between the central component and the external protection device and reduces the wear risk of the composite sensor.

[0033] The inner layer 2 is set as an aluminum-plastic armored layer, which is made of aluminum alloy material with a thickness of 1 mm. The aluminum-plastic armored layer is used to wrap the central component and plays a supporting role to reduce the influence of external environmental stress on the temperature measuring optical fiber. The thermal conductivity of solid metal aluminum is 237 W / (m·K), and the thermal conductivity of aluminum alloy is 121 - 151 W / (m·K), which is much higher than that of common iron-based metal materials. Therefore, the aluminum-plastic armored layer has excellent thermal conductivity and can quickly achieve the temperature field balance between the internal central component and the external environment.

[0034] The outer layer 1 is set as a high thermal conductivity XLPE sheath with a thickness of 1 mm. Its material is cross-linked polyethylene, which plays a protective role for the internal central component and prevents external grease and liquid from penetrating into the composite sensor, improving the safety of the composite sensor. Cross-linked polyethylene is a polymer material that transforms the polyethylene molecules from a linear structure to a network structure by chemical or physical methods. By doping metal oxide nanoparticles in the material, the thermal conductivity of the sheath can be significantly improved, and it has the characteristics of high temperature and high pressure resistance, wear resistance, high insulation resistance, lightweight, and excellent mechanical properties.

[0035] During the use of the composite sensor in this embodiment, please refer to Figure 2, after the tail shield brush is welded and before the sealing grease is injected, the composite sensors are arranged in a ring in each grease sealing cavity. One composite sensor is arranged in each grease cavity, and is connected to a portable FBG optical fiber demodulator and a self-heating temperature control switch through the internal channel of the shield shell. After the composite sensors are arranged in the grease cavities, the FBG optical fiber demodulator is debugged and heat treatment is carried out to ensure the normal operation of each grating measuring point. After the sealing grease is injected, the shield machine starts to advance. After the shield advances 30 - 50 rings, select the pause interval of the shield machine to advance, turn on the self-heating temperature control switch of the sensor to start heating. After a period of time, cut off the power to stop heating and wait for the sensor to cool naturally. During the heating and cooling processes, collect the wavelength change data of each grating measuring point, and judge the leakage situation in the grease cavity according to the data anomalies.

[0036] For the layout position of the composite sensor in the shield in this embodiment, please refer to Figure 3 , the tail shield grease sealing cavity 11 is located between the shield shell 8 and the segment 12. The composite sensor 7 is independently arranged in a ring in each tail shield grease sealing cavity 11, close to the inner surface of the shield shell 8, and fixed on the tail shield brush pressure plate 10, and is connected to an external power supply and an FBG optical fiber demodulator through the internal channel 13 of the shield shell.

[0037] For the working data obtained by the composite sensor in this embodiment in different medium environments, please refer to Figure 4 , respectively in air, pure grease, slurry water and pure water environments, heat the sensor from room temperature to 40 °C, and record the wavelength data during the heating and cooling processes. There are obvious differences in the wavelength change values of the gratings due to different environmental media. In this embodiment, the wavelength data of the optical fiber during the detection process is analyzed, and compared with the wavelength data of the control group to judge the temperature abnormal points during the heating and cooling processes of the sensor, so as to determine the change of the medium in the grease sealing cavity and the position of the leakage point.

[0038] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An actively heated FBG optical fiber shield tail seal detection composite sensor, characterized in that: The invention comprises a temperature measuring optical fiber (6), a reinforcing component (5), a heating component (4), a high temperature resistant silicone gel filler (3) and an external protection device; the temperature measuring optical fiber (6), the reinforcing component (5) and the heating component (4) are arranged in a row and closely together to form a central component of the sensor; the external protection device comprises an inner layer (2) and an outer layer (1), the inner layer (2) is used to wrap the high temperature resistant silicone gel filler (3), and the outer layer (1) is a high thermal conductivity sheath; the high temperature resistant silicone gel filler (3) is filled between the inner layer (2) and the central component.

2. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The temperature measuring optical fiber (6) is of the type of FBG optical fiber, and a plurality of grating measuring points are evenly inscribed at equal intervals on the temperature measuring optical fiber (6).

3. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 2, characterized in that: The spacing of the grating measuring points is set as follows: a grating measuring point is arranged every 5° along the cross section of the shield tail grease sealing cavity; each grating measuring point can measure the ambient temperature and present it on the FBG optical fiber demodulator in the form of wavelength data.

4. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The reinforcing component (5) is configured as a high-strength metal reinforcing wire with a diameter of 1 mm.

5. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The heating component (4) is configured as a self-insulating resistance wire heating belt, the cross section of which is circular and the diameter is 1 mm.

6. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The heating component is heated by connecting to an external power supply. A self-heating temperature control switch is provided at the external power supply to adjust the heating power and heating temperature. The heating power is set to 25W-40W per meter, and the heating temperature is set to not exceed 40°C to avoid melting of the grease.

7. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The high temperature resistant silicone gel filler (3) uniformly wraps the temperature measuring optical fiber (6), the reinforcing component (5), and the heating component (4), and is used to separate and fix the temperature measuring optical fiber (6), the reinforcing component (5), and the heating component (4) from each other.

8. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The inner layer (2) is configured as an aluminum-plastic armor layer, made of an aluminum alloy material, and having a thickness of 1 mm.

9. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The outer layer (1) is configured as a high thermal conductivity XLPE sheath having a thickness of 1 mm and made of cross-linked polyethylene, and can be used to protect the core components.

10. The active heating FBG optical fiber shield tail seal detection composite sensor as claimed in claim 1, characterized in that: The composite sensor (7) is arranged in a ring shape in the shield tail grease sealing cavity (11), closely attached to the inner surface of the shield shell (8), and fixed on the shield tail brush pressure plate (10).

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