Force-temperature dual-channel flexible backboard device and superconducting coil quenching monitoring method

Abstract

The invention provides a force-temperature dual-channel flexible back plate device and a superconducting coil quenching monitoring method. The force-temperature dual-channel flexible back plate device comprises a back plate base material, optical fibers, strain gauges and optical fiber guide grooves, the backboard substrate is provided with an optical fiber guide groove, and the optical fiber is installed in the optical fiber guide groove. A strain gauge is installed on the backboard substrate. The distributed optical fibers and the resistance strain gauges are integrated in the sensing structure at the same time, a temperature-force dual-channel information acquisition path is constructed, the sensing structure can be used for detecting local temperature rise caused by quenching of the superconducting coil, the stress state of the surface of the coil can be synchronously obtained, and the accuracy and robustness of fault recognition are improved.

Description

Technical Field

[0001] The present invention relates to the fields of low-temperature sensor technology and high-temperature superconducting applications, specifically to a flexible backplane device with dual force and temperature channels and a method for monitoring superconducting coil quenches. In particular, the invention relates to a device that embeds distributed optical fiber sensors in a flexible structural backplane and integrates strain gauges for simultaneous force-temperature dual-parameter monitoring. The device is suitable for quench monitoring, temperature rise location, and stress analysis in high-temperature superconducting coils. Background Art

[0002] High-temperature superconducting (HTS) technology, due to its outstanding performance in high current carrying capacity, low energy loss, and compact magnetic field structure design, is being increasingly applied to cutting-edge engineering systems such as power systems, magnetic resonance imaging, particle accelerators, and controlled nuclear fusion. However, during operation, factors such as local thermal disturbances, process defects, or electromagnetic overload can trigger superconducting state instability, known as quenching. This can lead to increased local coil resistance, Joule heating accumulation, material degradation, and even complete system collapse. Therefore, the development of highly sensitive, high-resolution, and low-temperature adaptable quench monitoring technology is crucial for ensuring the safe operation of HTS systems.

[0003] Traditional quench monitoring methods, such as voltage detection, are unable to meet the requirements of HTS coils for continuous, full-field monitoring of rapid temperature changes and heat diffusion paths. In recent years, distributed fiber optic sensing technology, with its advantages in electromagnetic interference resistance, high spatial resolution, and flexible deployment, has gradually become an important means of quench monitoring in low-temperature environments.

[0004] However, existing embedded or adhesive-type fiber optic deployment methods have several limitations. On the one hand, optical fibers are susceptible to shear, compressive stress, or thermal expansion and contraction within the packaging or superconductor operating environment, leading to signal drift, microcracks, or failure, which in turn reduces monitoring stability. On the other hand, the system lacks real-time feedback on the actual stress state of the optical fiber, making it difficult to determine whether the optical fiber sensing signal truly reflects the state of the measured object. Therefore, there is an urgent need to develop a sensing device with a stable structure, convenient deployment, strong low-temperature reliability, and dual-channel force-temperature fusion sensing capability to enhance the integrity and reliability of superconducting system operating status perception.

[0005] After searching, patent CN115615347A proposed a superconducting coil strain monitoring device based on distributed optical fiber. This solution embeds optical fibers into the upper and lower edges of the superconducting coil and uses epoxy curing agent to encapsulate it, so that the optical fiber can sense the mechanical strain generated by the coil under the action of electromagnetic force, thereby realizing continuous monitoring of the overall strain state of the coil. However, the core of this patent focuses on the acquisition of strain information, and has not yet involved temperature monitoring and multi-parameter fusion. In addition, the rigid packaging structure between the optical fiber and the curing agent is susceptible to damage and loss in low-temperature environments, causing signal instability, and is easily affected by shear stress. In addition, this solution does not set up an auxiliary monitoring channel, making it difficult to perform real-time verification of the stress state of the optical fiber. Once the optical fiber fails due to debonding or damage, there will be a lack of a reliable signal validity judgment mechanism. Summary of the Invention

[0006] In view of the defects in the prior art, the purpose of the present invention is to provide a force-temperature dual-channel flexible backplane device and a superconducting coil quench monitoring method.

[0007] According to the present invention, a force-temperature dual-channel flexible backplane device includes: a backplane substrate, an optical fiber, a strain gauge, and an optical fiber guide groove;

[0008] The backplane substrate is provided with an optical fiber guide groove, and the optical fiber is installed in the optical fiber guide groove;

[0009] A strain gauge is installed on the back plate substrate.

[0010] Preferably, the backplane substrate is made of a flexible material.

[0011] Preferably, heat-conducting insulating silica gel is filled between the optical fiber and the optical fiber guide groove.

[0012] Preferably, one or more optical fiber guide grooves are provided on the surface and / or inside of the backplane substrate, and the optical fiber guide grooves are arranged in a spiral shape, an annular shape, a linear array or a combination of shapes.

[0013] Preferably, the strain gauges are installed on both sides of the optical fiber guide groove or at the optical fiber turning point in the optical fiber guide groove.

[0014] Preferably, the strain gauge is a resistance strain gauge or a flexible metal foil strain gauge, and the strain gauge is connected to a micro-resistance bridge circuit via a flexible wire.

[0015] Preferably, the thermally conductive insulating silica gel is doped with nano thermally conductive fillers.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The application integrates distributed optical fiber and resistance strain gauge in the sensing structure, builds a temperature-force dual-channel information acquisition path, which can not only be used for detecting the local temperature rise caused by the quench of superconducting coils, but also can synchronously obtain the stress state of the coil surface, improving the accuracy and robustness of fault identification;

[0018] 2. The real-time stress signal fed back by the strain gauge can be used to verify whether the optical fiber sensing is in a stressed state, and then judge whether the optical fiber has debonding, damage or failure, significantly improving the signal reliability and operation safety of the sensing system;

[0019] 3. The application uses a flexible backboard as the integrated carrier of the sensing unit, which can be tailored and bent, suitable for the deployment of the outer surface of superconducting coils of various geometrical shapes, and has stronger adaptability and engineering application flexibility compared with rigid glue sealing structure;

[0020] 4. The application selects a flexible material (such as polyimide or copper-PI composite film) with a thermal expansion coefficient matching the REBCO tape, and uses a heat-conducting and insulating flexible silicone sealant to package the optical fiber, effectively relieving the stress concentration and structural degradation problems caused by thermal expansion and contraction, and improving the long-term reliability of the device in extremely low temperature environments such as liquid nitrogen;

[0021] 5. The sensing structure of the application adopts a patch-type modular design, which is easy to install and can be quickly replaced after damage, suitable for multi-point deployment and later maintenance requirements of large-scale superconducting systems, reducing the system integration and operation cost;

[0022] 6. The application can be modularly expanded and deployed in a distributed network, suitable for various complex cryogenic systems such as superconducting coils, low-temperature storage tanks, superconducting cables, etc., and has good engineering implementation and large-scale application promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0023] Other features, objects and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0024] Figure 1 Figure 1 is a schematic diagram of the overall structure of a force-temperature dual-channel flexible backboard device;

[0025] Figure 2 Figure 2 is a schematic diagram of the backboard substrate structure;

[0026] Figures shown in the drawings:

[0027] DETAILED DESCRIPTION

[0028] The application will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the application. These are within the scope of protection of the application.

[0029] Example 1

[0030] This embodiment aims to solve the problems of single temperature and stress monitoring dimension, poor fiber packaging stability and difficult signal reliability verification in existing superconducting coil optical fiber sensing system. By constructing a flexible backboard structure integrating distributed optical fiber and strain gauge, synchronous monitoring of temperature and stress in the area where the optical fiber is located is realized, and the stability, maintainability and multi-physical field fusion sensing ability of the sensing device in low temperature environment are improved.

[0031] The optical fiber 3 in this embodiment is laid in the optical fiber guide groove 5 in a pre-embedded manner and is packaged by heat-conducting insulating silicone 2. The uniform distribution of the glue is ensured by combining the uniform mixing and spin coating process, so as to realize good thermal coupling and mechanical protection in a low temperature environment. At the same time, strain gauges 4 are introduced in the corresponding area of the optical fiber 3 to realize real-time sensing of the local stress state, forming a temperature-stress dual-channel fusion sensing ability, which not only improves the accuracy and signal reliability of monitoring, but also significantly enhances the engineering adaptability and system reliability of the device under complex working conditions.

[0032] Specifically, as shown in Figures 1-2 This embodiment includes a backboard substrate 1, an optical fiber 3, a strain gauge 4 and an optical fiber guide groove 5. The optical fiber guide groove 5 is opened on the backboard substrate 1, and the optical fiber 3 is installed in the optical fiber guide groove 5. The strain gauge 4 is installed on the backboard substrate 1. The heat-conducting insulating silicone 2 is filled between the optical fiber 3 and the optical fiber guide groove 5.

[0033] The optical fiber 3 uses a distributed optical fiber sensing technology, uses a standard single-mode optical fiber or a polarization maintaining optical fiber, and is connected to an external optical fiber demodulator through a standard optical fiber interface (such as an FC / PC, an FC / APC, and an SC port), thereby ensuring good optical path compatibility and low insertion loss characteristics with commercial optical fiber demodulation equipment (an optical frequency domain reflectometer OFDR, a phase-sensitive Φ-OTDR, or a Brillouin scattering BOTDR, etc.). In actual work, when the backboard substrate 1 is attached to the surface of the superconducting coil, the local temperature change along the embedded path of the optical fiber 3 will cause a slight drift of the Rayleigh scattering spectrum of the optical fiber. The demodulator captures the backscattering signals at different positions along the optical fiber 3 by scanning the laser source or the coherent detection module, and reconstructs the scattering spectrum in the spatial and frequency domains with high resolution. Combined with the OFDR technology (optical frequency domain reflectometry), a spatial resolution of sub-millimeter to centimeter can be achieved, which is suitable for capturing the instantaneous slight temperature rise caused by local quenching. Combined with the Φ-OTDR technology (optical time domain reflectometer), the dynamic monitoring of the rapid mutation of the hot spot diffusion process can be realized, which is suitable for the space-time characteristics of the coil under different working conditions.

[0034] The strain gauge 4 preferably uses a resistance strain gauge or a flexible metal foil strain gauge, which is connected to a micro-resistance bridge circuit through a low-temperature-resistant flexible wire to amplify and filter the slight resistance change, and is connected to the temperature signal output by the optical fiber demodulator after analog-to-digital conversion, and is connected to the edge computing processing unit. Through time sequence synchronization and multi-source data coupling algorithm, the temperature-force channel signals are compared and analyzed in real time to monitor the stress state of the optical fiber 3. At the same time, when the optical fiber 3 signal drifts and the strain gauge 4 has no corresponding response, a redundant check is triggered to form a physical self-diagnosis mechanism; the calculation result can output the temperature-force coupling coefficient and abnormal trend based on the built-in algorithm and transmit to the upper computer or remote terminal. (The calculation method described above is realized by means known in the art, which is not described here.)

[0035] In an embodiment, the backboard substrate 1 is made of flexible material. One or more optical fiber guide grooves 5 are formed on the surface and / or inside of the backboard substrate 1, which are arranged in the form of a spiral, a ring, a linear array or a combination. In turn, the optical fibers 3 are arranged in the form of a spiral or a straight line in the optical fiber guide grooves 5 of the backboard substrate 1. In order to realize global coverage and continuous monitoring of the surface temperature field of the superconducting coil, the backboard substrate 1 can be provided with multiple optical fiber guide grooves 5 on its surface or inside along a preset path. The optical fiber guide grooves 5 can be flexibly designed in the form of a spiral, a ring, a linear array or a combination according to the geometric shape of the target coil and the distribution position of the key hot spots. For example, for a cylindrical or double-pie superconducting winding, a ring or spiral arrangement can be adopted to ensure high-resolution tracking capability for local thermal disturbance; for a complex segmented or irregular geometric coil, a linear array or an adaptive branch guide groove can be adopted to form a multi-channel parallel sensing network. The guide groove structure of the optical fiber guide groove 5 can be adjusted in density according to the sensitivity of hot spots in different regions to construct a distributed sensing topology of “dense sensing area + sparse coverage area”, which significantly improves the early detection sensitivity and position recognition resolution of local quench.

[0036] In an embodiment, the strain gauges 4 are installed on both sides of the optical fiber guide grooves 5 or at the turning points of the optical fibers 3 in the optical fiber guide grooves 5. The strain gauges 4 are made of a resistance strain gauge or a flexible metal foil strain gauge, and are connected to a micro-resistance bridge circuit through flexible wires. In order to improve the authenticity and anti-interference of the temperature signal, the strain gauges 4 are arranged on both sides of each optical fiber guide groove 5 or at the turning points with large curvature changes, so as to realize real-time sensing of the local stress state of the region. In particular, when the optical fibers 3 pass through corners, bends or high stress points, the optical fibers 3 are prone to micro-shift, loosening or breakage due to stress concentration, thermal expansion and contraction or aging of adhesion. Therefore, the present embodiment realizes physical redundancy verification through multiple distributed strain gauges 4. The strain gauges 4 are made of a micro-resistance strain gauge or a metal foil strain gauge, which can accurately respond to local surface micro-deformation, and the signal can be coupled with the output of the optical fibers 3 to form a verification mechanism. When the temperature data of the same region abnormally jumps, but the output of the strain gauges 4 does not appear corresponding stress fluctuation, it can be judged that the optical fibers 3 in this section may be invalid or detached, and the maintenance or alarm logic is triggered in time.

[0037] In an embodiment, the nano-thermal conductive filler is doped in the thermal conductive insulating silica gel 2. To improve the thermal coupling efficiency between the optical fiber 3 and the measured target, while preventing the optical fiber 3 from breaking or signal drift due to thermal expansion and contraction or local stress concentration in a low-temperature environment, the thermal conductive insulating silica gel 2 is filled in the optical fiber guide groove 5 as a packaging and buffering medium. The selected thermal conductive insulating silica gel 2 has high thermal conductivity (>1 W / m·K), low-temperature flexibility, and electrical insulation, and can be uniformly filled into the optical fiber guide groove 5 by spin coating or dispensing, ensuring uniform bubble-free coating around the optical fiber 3. After curing, a continuous thermal coupling path is formed, and flexible support is provided between the optical fiber 3 and the backboard substrate 1, absorbing micro-movement caused by external load or internal stress during low-temperature operation. If necessary, nano-thermal conductive fillers can be doped in the thermal conductive insulating silica gel 2 to further improve the thermal conductivity, or low-temperature expansion matching agents can be introduced to reduce the difference in thermal expansion coefficient between the packaging layer and the optical fiber 3 coating layer.

[0038] Working principle:

[0039] The present embodiment mainly realizes synchronous sensing and dynamic analysis of the temperature field and stress field of the local area on the surface of the superconducting coil through the cooperative work of the distributed optical fiber 3 and the strain gauge 4. The core physical mechanism relies on the optical scattering spectrum drift response characteristics of the optical fiber 3 to temperature changes, and the resistance change sensitivity of the strain gauge 4 to small structural deformation.

[0040] In the system working state, the superconducting coil is in a deep low-temperature operating environment, and the flexible sensing device of the present embodiment is tightly attached to the outer wall of the coil through a thermal conductive bonding structure. When the superconducting coil loses superconductivity due to local overcurrent, interface defects or environmental disturbance, a slight temperature rise occurs inside the coil, accompanied by non-uniform thermal expansion and redistribution of local electromagnetic forces, resulting in local stress and micro-deformation of the coil structure.

[0041] The distributed optical fiber sensing unit (optical fiber 3) is arranged in the optical fiber guide groove 5 of the backboard substrate 1 in a spiral or straight line path, forming a continuous sensing network. Under the action of temperature change, the refractive index and optical path length inside the optical fiber 3 change slightly, causing the Rayleigh scattering spectrum along the transmission path of the optical fiber 3 to produce a position-dependent drift. With the help of optical frequency domain reflection (OFDR) or existing coherent detection technology, the change can be demodulated, thereby realizing temperature distribution reconstruction with high spatial resolution.

[0042] Meanwhile, the strain gauges 4 in the backboard substrate 1 directly perceive the slight deformation of the superconducting coil surface caused by the thermal-mechanical disturbance coupling, output voltage signals through the strain gauge bridge, and reflect the stress level of the local area of the device in real time. The response results of the strain gauges 4 can not only be used to assist in determining the mechanical behavior corresponding to the quench position, but also can be used as an effectiveness criterion for the optical fiber data, especially in the case of possible debonding, breaking or decoupling of the optical fiber 3 to provide physical redundancy support.

[0043] By integrating the above two sensing mechanisms in the same backboard substrate 1, the embodiment can realize the cooperative monitoring of temperature change and stress evolution, and through time-synchronous sampling and data comparison, multi-dimensional identification of the starting point, evolution path and coupling characteristics of the quench event can be realized. The design has accuracy, reliability and engineering practicability for monitoring the running state of the superconducting system.

[0044] The embodiment is not only suitable for quench monitoring of high-temperature superconducting coils, but also has good scalability and multi-scenario adaptability. It can be flexibly applied to structural health monitoring and abnormal early warning of various cryogenic electrical equipment, liquid hydrogen or liquid helium storage tanks, superconducting cables, superconducting motor rotors, and high-end equipment such as magnetic resonance imaging (MRI) and particle accelerators according to different low-temperature or extreme operating environment requirements. Through the proposed multi-guide groove embedded optical fiber network, local multi-point strain gauge layout and edge computing integrated processing, the device can be customized and cut according to the curvature, material and working conditions of the measured object, quickly attached, support multi-module series or distributed networking deployment, and effectively improve the multi-physical field coupling monitoring capability on large area and complex structure.

[0045] Embodiment 2

[0046] Embodiment 2 is a preferred example of Embodiment 1.

[0047] As shown in Figure 1 and Figure 2 , the embodiment designs an embeddable flexible backboard device integrating distributed optical fiber 3 and strain gauge 4, which is suitable for real-time monitoring of the quench state of superconducting coils. The embodiment includes: backboard substrate 1, optical fiber guide groove 5, embedded optical fiber 3, and strain gauge 4. The distributed optical fiber 3 is laid along the preset optical fiber guide groove 5 and encapsulated with heat-conducting insulating silicone 2. The encapsulation process is carried out by spin coating operation through a mixing device to ensure that the heat-conducting insulating silicone 2 is evenly distributed around the optical fiber 3, forming a stable and reliable temperature sensing path. The strain gauge 4 is attached to the backboard substrate 1 for monitoring stress changes and assisting in calibrating the response of the optical fiber 3. The flexible backboard device is attached to the coil surface or side through flexible glue, and the shape can be freely designed to realize temperature-stress dual-parameter fusion detection, improving the monitoring accuracy and structural reliability. The device has the characteristics of modularity, easy deployment and strong adaptability, and is suitable for temperature rise positioning, stress and running state monitoring of high-temperature superconducting coils.

[0048] To verify the performance of the flexible backplane device with integrated distributed optical fiber 3 and strain gauge 4 in the quench monitoring of high temperature superconducting coils, a set of double pancake type planar coils wound with REBCO high temperature superconducting tapes was selected as the experimental object, and a low temperature charging and discharging test platform based on liquid nitrogen cooling environment was constructed.

[0049] The flexible backplane device uses flexible material as the backplane substrate 1, and laser cutting is performed on the surface to form a spiral optical fiber guide groove 5 for optical fiber 3 layout. The groove depth and width of the optical fiber guide groove 5 is 250μm. A φ200μm distributed optical fiber 3 is selected and embedded in the optical fiber guide groove 5 according to a straight line path, and is packaged by heat-conducting insulating silicone 2. The heat-conducting insulating silicone 2 is fully premixed by a high-speed mixing machine before use, and is uniformly coated around the optical fiber 3 by spin coating process. After the heat-conducting insulating silicone 2 is cured, polishing is performed to ensure a dense, continuous and uniform thermal coupling interface.

[0050] The backplane substrate 1 has good flexibility and processability, and can be designed as a strip structure attached to the radial side of the coil, or made into a circular structure attached to the surface of the coil to respond to temperature and stress changes in different geometric areas. The whole device is attached to the superconducting coil by high-performance thermal conductive adhesive to ensure the stability of thermal coupling and mechanical adhesion.

[0051] After the coil system is immersed in liquid nitrogen and cooled to 77K, when the current gradually increases to the critical level, the middle region of the coil shows a local temperature rise trend, and the Rayleigh spectrum shift mutation is detected in this region by the optical fiber 3 demodulation signal; at the same time, the strain gauge 4 output stress signal also synchronously changes, indicating that there is a local thermal-mechanical coupling response induced by quench in this region. Further analysis of the signal matching relationship between the optical fiber 3 and the strain gauge 4 can accurately locate the initial position of the quench, with an error of less than 1cm and a signal response time of less than 150ms.

[0052] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0053] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other at will without conflict.

Claims

1. A force-temperature dual-channel flexible backplane apparatus, characterized by, Comprise: A backboard substrate (1), an optical fiber (3), a strain gauge (4) and an optical fiber guide groove (5); The backboard substrate (1) is provided with an optical fiber guide groove (5), and the optical fiber (3) is installed in the optical fiber guide groove (5); The backboard substrate (1) is provided with a strain gauge (4).

2. The flexible backplane device of claim 1, wherein: The backboard substrate (1) is made of flexible material.

3. The flexible backplane device of claim 1, wherein: The optical fiber (3) and the optical fiber guide groove (5) are filled with heat-conducting insulating silica gel (2).

4. The flexible backplane device of claim 1, wherein: The surface and / or interior of the backboard substrate (1) is provided with one or more optical fiber guide grooves (5), which are arranged in spiral, ring, linear array or combined form.

5. The flexible backplane device of claim 1, wherein: The strain gauge (4) is installed on both sides of the optical fiber guide groove (5) or at the turning position of the optical fiber (3) in the optical fiber guide groove (5).

6. The flexible backplane device of claim 1, wherein: The strain gauge (4) is made of resistance strain gauge or flexible metal foil strain gauge.

7. The flexible backplane device of claim 3, wherein: The heat-conducting insulating silica gel (2) is doped with nano heat-conducting filler.

8. A method of quench monitoring of a superconducting coil, characterized by: The force-temperature dual-channel flexible backboard device according to any one of claims 1-7.

9. The superconducting coil quench monitoring method of claim 8, wherein: The temperature dual-channel flexible backboard device is attached to a superconducting coil.

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