A safety monitoring device mounted on a large structure

Abstract

This utility model relates to the field of safety monitoring technology, specifically to a safety monitoring device installed on a large structure, comprising a distributed fiber Bragg grating string, an adhesive, and a multi-channel fiber demodulator. This device achieves distributed strain monitoring of large structures through the distributed fiber Bragg grating string, possessing advantages such as strong anti-interference capability, corrosion resistance, and long service life, making it particularly suitable for safety monitoring of large structures such as wind turbine blades. The fiber demodulator can identify wavelength changes caused by temperature variations, achieving temperature compensation and improving monitoring accuracy. Furthermore, when a circumferential crack appears in a structural component, the fiber Bragg grating string will break, causing some gratings to become undetectable, thereby enabling crack monitoring and location. The entire device is easy to install, has low maintenance costs, and can effectively ensure the safe operation of large structures. It also solves the problem of poor anti-interference capability in existing monitoring devices.

Description

Technical Field

[0001] This utility model relates to the field of safety monitoring technology, and in particular to a safety monitoring device installed on a large structure. Background Technology

[0002] During the operation of large structures (such as wind turbine blades), real-time monitoring of their strain status is crucial for ensuring the safety and reliability of the structure.

[0003] Traditional strain monitoring methods suffer from problems such as complex installation, poor anti-interference capability, and difficulty in achieving distributed measurement. Therefore, a new type of monitoring device is needed that can achieve distributed strain monitoring of large structures, while possessing advantages such as anti-interference, corrosion resistance, and long service life. Utility Model Content

[0004] The purpose of this invention is to provide a safety monitoring device that can be installed on large structures, aiming to solve the problem of poor anti-interference capability of existing monitoring devices.

[0005] To achieve the above objectives, this utility model provides a safety monitoring device installed on a large structure, comprising a distributed fiber Bragg grating string, an adhesive, and a multi-channel fiber demodulator. The distributed fiber Bragg grating string is formed by etching fiber Bragg gratings at equal intervals on a single optical fiber, with an interval length of approximately 0.5m to 1m. Each fiber Bragg grating can sense the strain on the surface of the structural component at its location. The distributed fiber Bragg grating string is adhered to the surface of the large structural component using adhesive, or pre-embedded in the surface of the structural component. The multi-channel fiber demodulator is used to receive and process the light signals reflected by the fiber Bragg gratings to monitor the strain of the structural component.

[0006] The reflectivity of each fiber grating in the distributed fiber grating string is less than 5%, preferably 3%; the equally spaced fiber gratings can be formed by cyclically etching the same fixed wavelength or multiple fixed wavelengths.

[0007] The optical fibers of the distributed fiber grating string are coated with a coating layer with high peel strength to prevent the optical fibers from falling off when the structural components deform.

[0008] The distributed fiber optic grating string has fiber optic connectors at its ends for connection to a multi-channel fiber optic demodulator.

[0009] The multi-channel fiber optic demodulator can determine the strain felt by the blade by the reverse change of positive and negative strain. It can also set the strain value limit for each region or position of the blade and output corresponding alarm information.

[0010] This invention relates to a safety monitoring device installed on a large structure. Distributed fiber Bragg grating strings are formed by etching fiber Bragg gratings at equal intervals on optical fibers, with an interval length of approximately 0.5m to 1m. Each fiber Bragg grating has a reflectivity of less than 5%, typically around 3%. The gratings can be etched with a single wavelength (e.g., 1550nm) or several fixed wavelengths in a cyclic pattern (e.g., 1530nm-1540nm-1550nm-1560nm). The surface of the fiber Bragg grating strings is coated with a polyimide layer to enhance tensile strength and corrosion resistance. The grating strings are adhered to the surface of the large structural component using adhesive, or pre-embedded during the component's manufacturing process, typically arranged axially. Each fiber Bragg grating string has an FC / APC or other fiber optic connector at its end, connected to a multi-channel fiber demodulator. The demodulator demodulates the wavelength change of each fiber Bragg grating by emitting narrowband pulsed light and capturing the reflected light signal, thereby calculating the strain value. The demodulator can identify wavelength changes caused by temperature variations, achieving temperature compensation. This device uses distributed fiber optic grating strings to achieve distributed strain monitoring of large structures, offering advantages such as strong anti-interference capabilities, corrosion resistance, and long service life. It is particularly suitable for safety monitoring of large structures such as wind turbine blades. The fiber optic demodulator can identify wavelength changes caused by temperature variations, achieving temperature compensation and improving monitoring accuracy. Furthermore, when a circumferential crack appears in a structural component, the fiber optic grating string will break, causing some gratings to become undetectable, thus enabling crack detection and location. The entire device is easy to install, has low maintenance costs, and can effectively ensure the safe operation of large structures. This also solves the problem of poor anti-interference capabilities in existing monitoring devices. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0012] Figure 1 This is a schematic diagram of a safety monitoring device for installation on a large structure according to the present invention.

[0013] Figure 2 yes Figure 1 A sectional view.

[0014] Figure 3 This is a schematic diagram of the S-shaped layout of the distributed fiber optic grating string on the windward side.

[0015] In the figure: 1-wind turbine blade, 2-distributed fiber optic grating string, 3-multi-channel fiber optic demodulator, 4-wind turbine hub, 101-windward side of wind turbine blade, 102-leeward side of wind turbine blade. Detailed Implementation

[0016] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0017] Please see Figures 1-3 This invention provides a safety monitoring device installed on a large structure, comprising a distributed fiber Bragg grating string 2, an adhesive, and a multi-channel fiber demodulator 3. The distributed fiber Bragg grating string 2 is formed by etching fiber Bragg gratings at equal intervals on a single optical fiber, with an interval length of approximately 0.5m to 1m. Each fiber Bragg grating can sense the strain on the surface of the structural component at its location. The distributed fiber Bragg grating string 2 is adhered to the surface of the large structural component by adhesive or pre-embedded in the surface of the structural component. The multi-channel fiber demodulator 3 is used to receive and process the light signals reflected by the fiber Bragg gratings to monitor the strain of the structural component.

[0018] Furthermore, the reflectivity of each fiber grating in the distributed fiber grating string 2 is less than 5%, preferably 3%; the equally spaced fiber gratings can be formed by cyclically etching the same fixed wavelength or multiple fixed wavelengths.

[0019] Furthermore, the outer surface of the optical fiber of the distributed fiber grating string 2 is coated with a coating layer with high peel strength to prevent the optical fiber from falling off when the structural components deform.

[0020] Furthermore, the distributed fiber grating string 2 has fiber optic connectors at its ends for connection to the multi-channel fiber demodulator 3.

[0021] Furthermore, the multi-channel fiber optic demodulator 3 can determine the strain felt by the blade by the reverse change of positive and negative strain, and can set the strain value limit for each region or position of the blade and output corresponding alarm information.

[0022] In this embodiment, the distributed fiber Bragg grating string 2 is formed by etching fiber Bragg gratings at equal intervals on an optical fiber, with an interval length of approximately 0.5m to 1m. The reflectivity of each fiber Bragg grating is less than 5%, typically around 3%. The grating can be etched with a single wavelength (e.g., 1550nm) or several fixed wavelengths in a cycle (e.g., 1530nm-1540nm-1550nm-1560nm). The surface of the fiber Bragg grating string is coated with a polyimide layer to enhance tensile strength and corrosion resistance. The grating string is adhered to the surface of a large structural component using adhesive, or pre-embedded inside during the manufacturing process of the structural component, typically arranged axially. Each fiber Bragg grating string has an FC / APC or other fiber optic connector at its end, which is connected to a multi-channel fiber demodulator 3. The multi-channel fiber demodulator 3 demodulates the wavelength change of each fiber Bragg grating by emitting narrowband pulsed light and capturing the reflected light signal, thereby calculating the strain value. The multi-channel fiber optic demodulator 3 can identify wavelength changes caused by temperature variations and achieve temperature compensation. This device uses distributed fiber optic grating strings to achieve distributed strain monitoring of large structures, offering advantages such as strong anti-interference capabilities, corrosion resistance, and long service life. It is particularly suitable for safety monitoring of large structures such as wind turbine blades. The multi-channel fiber optic demodulator 3 can identify wavelength changes caused by temperature variations, achieving temperature compensation and improving monitoring accuracy. Furthermore, when a circumferential crack appears in a structural component, the fiber optic grating string will break, causing some gratings to become undetectable, thus enabling crack monitoring and location. The entire device is easy to install, has low maintenance costs, and can effectively ensure the safe operation of large structures. This also solves the problem of poor anti-interference capabilities in existing monitoring devices.

[0023] PS side: Windward side of the fan blade 101; SS side: Leeward side of the fan blade 102;

[0024] The main large structural component is currently the wind turbine blade 1 of the wind turbine. This blade is primarily made of composite fiberglass and, relative to its external dimensions, can be considered a thin-walled and hollow structure. An entire fiber optic cable with a grating string can be bonded to the structural component using adhesive, and then adhered to the inner surface of the blade. Alternatively, the fiber optic cable with a grating string can be pre-embedded into the inner surface of the blade during production, primarily distributed axially from the blade root to the blade tip. Fiber optic cables with grating strings are laid on the inner surfaces of all three blades of the wind turbine. Multiple fiber optic cables with grating strings can be laid on the inner surface of each blade. Each fiber optic cable has an FC / APC or other fiber optic connector at its end, which connects to a multi-channel fiber optic demodulator 3 located within the hub at the center of the wind turbine blade 1's rotation. The device includes a distributed fiber optic grating multi-channel fiber optic demodulator 3, which can achieve multi-channel measurement through optical switching. Each channel can carry a grating string of hundreds or thousands of meters with gratings spaced 0.5 meters apart. The distributed fiber optic grating multi-channel fiber demodulator 3 can modulate and demodulate the wavelength of each fiber grating on a string of optical fibers by emitting narrowband pulses and capturing the reflected light signals at equal intervals. When the blade is under zero external force (i.e., micro-strain) (the blade can be in a vertically downward position), the multi-channel fiber demodulator 3 records the wavelength value of each fiber grating in all channels and records it as the zero micro-strain wavelength value. When the blade state changes, the wavelength value of each fiber grating is recorded again and compared with the zero micro-strain wavelength value to measure the wavelength difference. The strain value at each fiber grating can be demodulated by the correlation coefficient between the wavelength difference and the strain value. Furthermore, the strain values ​​at different locations along the circumference of the entire blade will vary significantly, and the wavelength will also change with temperature. However, since the bonded blade is made of the same material from the root to the tip, the increase in wavelength is equal with temperature rise. The algorithm inside the multi-channel fiber demodulator 3 can identify the way the wavelength changes, thus ignoring the strain caused by temperature. In the wind turbine blade 1, grating strings are bonded to both the windward side 101 and the leeward side 102. During the wind turbine's operation and blade rotation, the strain changes in opposite directions: the strain on the PS side is tensile (positive strain), and the strain on the SS side is compressive (negative strain). The multi-channel fiber optic demodulator 3 can determine the strain felt by the blade by observing the inverse changes in positive and negative strain. The strain caused by temperature increases or decreases, resulting in thermal expansion and contraction of the material, is unidirectional and can be distinguished within the algorithm. This monitors the strain state of the blade, allows setting strain limits for each region or location of the blade, and can also output corresponding alarm information.After the grating string is installed on the wind turbine blade 1, it can not only monitor the strain of the wind turbine blade 1 online, but also, in extreme cases, when the wind turbine blade 1 has been running for a long time or when a large circumferential crack occurs under extreme weather conditions, the optical fiber arranged at the crack on the inner surface of the blade will be pulled apart along with it. As a result, the grating string at the rear end of the optical fiber that is far away from the multi-channel fiber demodulator 3 cannot be detected, thereby locating the breakage location and realizing the monitoring and location of the circumferential crack of the blade.

[0025] Beneficial effects:

[0026] 1) By laying distributed fiber optic strain gauges on the surface of large structural components, strain changes of structural components, especially composite material surfaces, can be monitored, which can effectively monitor the health status of structural components in real time. At the same time, the use of optical fibers in large and tall buildings has the advantages of intrinsic safety, immunity to electromagnetic interference, lightning strike resistance, corrosion resistance, and long service life.

[0027] 2) Distributed fiber optic strain gauges are laid on the windward PS side and the leeward SS side of the wind turbine blades. The strain can be accurately calculated by the inverse changes of the strain on the two sides, and the strain is determined to be temperature-induced strain by the positive changes of the strain.

[0028] 3) When a circumferential crack appears on the wind turbine blade, it will pull the optical fiber arranged at the crack on the inner surface of the blade to break. As a result, the grating string at the back end of the optical fiber that is far away from the demodulator cannot be detected. It can also be used to monitor and locate the circumferential crack of the blade.

[0029] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A safety monitoring device installed on a large structure, characterized in that, The system includes a distributed fiber Bragg grating string, an adhesive, and a multi-channel fiber demodulator. The distributed fiber Bragg grating string is formed by etching fiber Bragg gratings at equal intervals on a single optical fiber, with an interval length of 0.5m to 1m. Each fiber Bragg grating can sense the strain on the surface of a structural component at its location. The distributed fiber Bragg grating string is adhered to the surface of a large structural component using adhesive, or pre-embedded in the surface of the structural component. The multi-channel fiber demodulator is used to receive and process the optical signals reflected by the fiber Bragg gratings to monitor the strain of the structural component.

2. The safety monitoring device installed on a large structure as described in claim 1, characterized in that, The reflectivity of each fiber grating in the distributed fiber grating string is less than 5%; the equally spaced fiber gratings are etched by the same fixed wavelength or multiple fixed wavelengths in a cyclic pattern.

3. The safety monitoring device installed on a large structure as described in claim 1, characterized in that, The optical fibers of the distributed fiber grating string are coated with a coating layer with high peel strength to prevent the optical fibers from falling off when the structural components deform.

4. The safety monitoring device installed on a large structure as described in claim 1, characterized in that, The distributed fiber optic grating string has fiber optic connectors at its ends for connection to a multi-channel fiber optic demodulator.

5. The safety monitoring device installed on a large structure as described in claim 1, characterized in that, The multi-channel fiber optic demodulator can determine the strain felt by the blade by the reverse change of positive and negative strain. At the same time, it can set the strain value limit for each region or position of the blade and output corresponding alarm information.

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