A fiber Bragg grating-based automatic flow measurement system for open channels

Abstract

The application discloses an open channel automatic flow measuring system based on fiber Bragg grating, which comprises an LD light source 1, a common optical fiber 3, an optical fiber coupler 5, a layer-twisted optical fiber box 2, a horizontal slide rail 8, a fiber Bragg grating 7, a flow measuring slide rail 9, a slide rail connecting block 10, a stepping motor 11, a level 12, a limit switch 4 and an optical fiber grating demodulator 14. The common optical fiber 3 is arranged in the layer-twisted optical fiber box 2 and can be telescopically adjusted in length. The optical fiber coupler 5 is arranged on the slide rail connecting block 10. The fiber Bragg grating 7 is fixed on the flow measuring slide rail 9 through a wire clamp 6. The horizontal slide rail 8 and the flow measuring slide rail 9 are connected through the slide rail connecting block 10. The foot base 15 is in a cylindrical shape, and the foot beam 17 is connected with the two ends of the horizontal slide rail 8 through angle codes 13. The application can comprehensively and accurately understand the flow velocity distribution of any cross section of the vertical water flow direction and accurately calculate the flow of the flow measuring cross section.

Description

Technical Field

[0001] This invention belongs to the field of flow velocity and flow rate measurement technology, and in particular relates to an automatic flow measurement system for open channels using fiber Bragg grating. Background Technology

[0002] In recent years, with the accelerated construction of irrigation projects and water-saving renovation projects, traditional water allocation and measurement technologies have become inadequate for the development requirements of agricultural production. Large and medium-sized irrigation districts now have standardized canals, providing a solid foundation and conditions for researching new open channel flow measurement methods. From the perspective of water resource management, accurate measurement of open channel flow can help us better understand the actual irrigation water volume in farmland, enabling more rational allocation and management of water resources to achieve water-saving irrigation goals. From the perspective of environmental protection and pollution control, flow measurement can be used to monitor wastewater discharge, thereby achieving scientific and effective environmental management.

[0003] Currently, many different flow measurement methods exist in the field of flow measurement, mainly including laser Doppler, radar bridge, remote sensing, and Pitot tube flow measurement. However, these methods all have some shortcomings. For example, the performance of the laser Doppler instrument may be affected in extreme weather conditions because water droplets or particles in the atmosphere can scatter the laser light in rain, snow, or fog, thus affecting the accuracy of flow measurement. The radar bridge method often cannot penetrate obstacles in the water body, such as floating objects and suspended particles, which may affect the accuracy of the measurement. Remote sensing has limited spatial resolution, which cannot meet the requirements for fine monitoring of the flow measurement process, and its low temporal resolution cannot meet the requirements for real-time monitoring of the flow measurement process. Furthermore, the quality of the measurement data is affected by various factors, such as meteorological conditions and topography.

[0004] Therefore, the ever-increasing demand for flow measurement necessitates a new flow measurement device to overcome the limitations of existing solutions and provide a more stable, accurate, and intelligent flow measurement technology. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an automatic flow measurement system for open channels using fiber Bragg gratings. This system can provide a more comprehensive and accurate understanding of the velocity distribution at any cross-section perpendicular to the flow direction and accurately calculate the flow rate at the measurement cross-section, offering a novel approach and method for future flow measurement research.

[0006] To achieve the above objectives, this invention provides a fiber Bragg grating-based automatic flow measurement system for open channels, comprising: an LD light source, a stranded fiber optic box, ordinary optical fiber, limit switches, fiber couplers, line clamps, a fiber Bragg grating, a horizontal slide rail, a flow measurement slide rail, a slide rail connecting block, a stepper motor, a level, angle brackets, a fiber Bragg grating demodulator, feet, feet, feet beams, screws, and nuts; the ordinary optical fiber is connected to the fiber coupler on the slide rail connecting block, a portion of the ordinary optical fiber is arranged in a groove above the horizontal slide rail, and the other portion of the ordinary optical fiber is connected to the LD light source and the fiber Bragg grating demodulator on both sides of the horizontal slide rail respectively through the stranded fiber optic box; the limit switches are installed on both horizontal sides of the horizontal slide rail at both ends of the horizontal slide rail; the horizontal slide rail is fixed to the feet beam by the angle brackets; and the bottom of the feet beam is connected to... The foot posts are connected by telescopic threads, and the foot base is connected to the foot posts by telescopic threads. The stranded fiber optic box is fixed to the foot beam by screws and nuts. The horizontal slide rail and the current measuring slide rail are connected by the slide rail connecting block. The fiber Bragg grating is fixed to the current measuring slide rail by the wire clamp. The current measuring slide rail is fixed to the slide rail connecting block by the screws and nuts. The current measuring slide rail can slide up and down by adjusting the screws and nuts. The stepper motor is fixed to the end of the horizontal slide rail near the fiber Bragg grating demodulator by screws. The stepper motor is connected to a conveyor belt device, which is set in the left and right grooves of the horizontal slide rail. The slide rail connecting block can be moved left and right by the drive of the conveyor belt device. The level is fixed to the end of the horizontal slide rail near the fiber Bragg grating demodulator.

[0007] Furthermore, there are two fiber optic couplers, both with FC / APC interface models.

[0008] Furthermore, the fiber Bragg grating type is single-mode, PM, double-clad, or LMA.

[0009] Furthermore, both the horizontal slide rail and the flow measuring slide rail are I-shaped and made of aluminum alloy, and can be disassembled.

[0010] Furthermore, the base is made of lightweight aluminum alloy.

[0011] Furthermore, the horizontal slide rail has grooves on its upper, left, and right sides. The ordinary optical fiber is arranged in the upper groove, and the conveyor belts in the left and right grooves are connected to the stepper motor at one end of the horizontal slide rail. The slide rail connecting block can move left and right on the horizontal slide rail through the conveyor device.

[0012] Furthermore, the flow measuring slide rail has grooves on both its left and right sides, and the fiber Bragg grating is arranged vertically on the side facing the water flow direction. After reaching the required flow measuring depth, the fiber Bragg grating continues to extend into the groove on the right side of the flow measuring slide rail until it connects to the fiber coupler above.

[0013] Furthermore, the stranded fiber optic box is fixed to both ends of the horizontal slide rail by the screw and the nut.

[0014] Technical effects of the invention:

[0015] (1) High measurement efficiency and wide applicability: When measuring flow rate, the flow velocity at various points on any vertical line of the flow measurement section can be obtained by using fiber Bragg gratings. Furthermore, the number of fiber Bragg grating grids can be increased or decreased as needed; the more grids, the clearer the underwater velocity distribution and the more accurate the flow rate measurement. Simultaneously, by adjusting the position of the fiber Bragg gratings, the grid's position in the water flow can be changed to achieve multi-directional measurement, which can effectively reflect the flow rate and velocity distribution of the cross-section. In addition, diverse grid arrangements can be made according to the characteristics of different channels to achieve accurate measurement. The device can also adapt to different channel cross-sectional coefficients, making it very convenient and practical.

[0016] (2) When measuring flow rate, the fiber Bragg grating flow measurement device is highly sensitive and can accurately reflect the pressure value at each grid, thereby accurately deriving the flow velocity corresponding to each grid and further accurately calculating the flow rate value to achieve precise measurement.

[0017] (3) Simple structure and easy maintenance: The fiber Bragg grating current measurement device has a simple structure, consisting of a light source, optical fiber, and slide rail, and is easy to manufacture. At the same time, the device adopts a quick-release structure design, which is convenient to carry. The current measurement slide rail is made of aluminum alloy, which is not easily deformed and is corrosion resistant. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of a fiber Bragg grating-based automatic flow measurement system for open channels according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the three-dimensional structure of an embodiment of the present invention;

[0021] Figure 3This is a three-dimensional structural diagram of the actual object of the present invention without external devices such as optical fibers, light sources, and fiber optic demodulators.

[0022] Figure 4 This is a three-dimensional structural diagram of the horizontal slide rail, the flow measuring slide rail, and related supporting devices according to an embodiment of the present invention;

[0023] Figure 5 This is a front view schematic diagram of the actual structure of an embodiment of the present invention;

[0024] Figure 6 This is a top view schematic diagram of the actual structure of an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the right-side structure of the flow measuring slide rail according to an embodiment of the present invention;

[0026] Figure 8 This is a perspective view of a fiber Bragg grating according to an embodiment of the present invention;

[0027] Among them, 1-LD light source, 2-stranded fiber optic box, 3-ordinary fiber optic, 4-limit switch, 5-fiber optic coupler, 6-line clamp, 7-fiber Bragg grating, 8-horizontal slide rail, 9-flow measurement slide rail, 10-slide rail connecting block, 11-stepper motor, 12-level, 13-angle code, 14-fiber Bragg grating demodulator, 15-foot, 16-foot column, 17-foot beam, 18-screw, 19-nut, 20-fiber Bragg grating grid, 21-fiber core, 22-cladding, 23-fiber protective layer. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0030] like Figure 1-7As shown, this embodiment provides a fiber Bragg grating-based automatic flow measurement system for open channels, including: an LD light source 1, a stranded fiber optic box 2, a common fiber optic cable 3, a limit switch 4, a fiber optic coupler 5, a line clamp 6, a fiber Bragg grating 7, a horizontal slide rail 8, a flow measurement slide rail 9, a slide rail connecting block 10, a stepper motor 11, a level 12, a corner bracket 13, a fiber Bragg grating demodulator 14, a base 15, a foot post 16, a foot beam 17, a screw 18, and a nut 19. The common fiber optic cable 3 is connected to the fiber optic coupler 5 on the slide rail connecting block 10. One part of the common fiber optic cable 3 is arranged in a groove above the horizontal slide rail 8, and the other part of the common fiber optic cable 3 is connected to the LD light source 1 on both sides of the horizontal slide rail 8 and the fiber Bragg grating demodulator 14 through the stranded fiber optic box 2. The limit switch 4 is installed on both horizontal sides of the horizontal slide rail 8 at both ends of the horizontal slide rail 8. The horizontal slide rail 8 is fixed by the corner bracket 13. The foot beam 17 is connected to the foot column 16 via a telescopic thread. The foot seat 15 is connected to the foot column 16 via a telescopic thread. The stranded fiber optic box 2 is fixed to the foot beam 17 by screws and nuts. The horizontal slide rail 8 and the current measuring slide rail 9 are connected by a slide rail connecting block 10. The fiber Bragg grating 7 is fixed to the current measuring slide rail 9 by a wire clip 6. The current measuring slide rail 9 is fixed to the slide rail connecting block 10 by screws 18 and nuts 19. At the same time, the current measuring slide rail 9 can slide up and down by adjusting the screws 18 and nuts 19. The stepper motor 11 is fixed to the end of the horizontal slide rail 8 near the fiber Bragg grating demodulator 14 by screws. The stepper motor is connected to a conveyor belt device, which is set in the left and right grooves of the horizontal slide rail. The slide rail connecting block 10 can be moved left and right by the drive of the conveyor belt device. The level 12 is fixed to the end of the horizontal slide rail 8 near the fiber Bragg grating demodulator 14.

[0031] The horizontal slide rail 8 has an I-shaped structure with grooves on its three upper sides. Ordinary optical fibers 3 are installed in the upper groove, and conveyor belts connected to stepper motors 11 at one end of the horizontal slide rail 8 are located in the left and right grooves. The conveyor belts allow the slide rail connecting block 10 to move left and right on the horizontal slide rail 8. The flow measuring slide rail 9 also has an I-shaped structure with grooves on its left and right sides. A fiber Bragg grating 7 is installed vertically on the side facing the water flow direction. After reaching the required flow measurement depth, the fiber Bragg grating 7 extends into the groove on the right side of the flow measuring slide rail 9 until it connects to the upper fiber coupler 5. The flow measuring slide rail 9 is fixed to the slide rail connecting block 10 by screws 18 and nuts 19. Adjusting the screws 18 and nuts 19 allows the flow measuring slide rail 9 to slide up and down to accommodate various water depths. The slide rail connecting block 10 is equipped with a wire clip for fixing the fiber Bragg grating 7, and the slide rail connecting block 10 is equipped with a fiber coupler for connecting the ordinary fiber 3 and the fiber Bragg grating 7.

[0032] When the ordinary optical fiber 3 is connected to the optical fiber coupler 5 on the slide rail connecting block 10, one section is positioned in the groove above the horizontal slide rail 8, while the other section is connected to the LD light source 1 on both sides of the horizontal slide rail 8 and the fiber optic demodulator 14 via the stranded fiber optic box 2. When the device is started via the fiber optic demodulator 14, the current measuring slide rail 9 moves on the horizontal slide rail 8 along with the slide rail connecting block 10. The extra length required for the ordinary optical fiber 3 on the left side extends out through the stranded fiber optic box 2, while the ordinary optical fiber 3 on the other side retracts through the stranded fiber optic box 2. The stranded fiber optic box 2 is fixed to both ends of the horizontal slide rail 8 by screws 18 and nuts 19.

[0033] Limit switches 4 are installed on both sides of the horizontal slide rail 8 at both ends, ensuring that the flow measuring slide rail 9 can measure the required channel width and flow information. When the device is started via the fiber optic demodulator 14, the conveyor belt begins to move the slide rail connecting block 10 connected to the flow measuring slide rail 9, thereby measuring the stress information on the vertical lines perpendicular to the flow direction. When the slide rail connecting block 10 connected to the flow measuring slide rail 9 touches the limit switch 4 on either side, the movement stops, completing the hydraulic information measurement of the entire channel cross-section.

[0034] A level 12, positioned at one end of the horizontal slide rail 8, can be used to check the balance of the entire device in both horizontal and vertical directions. The connection between the foot 15 and the foot column 16 has a telescopic thread; when the device is unbalanced, this thread can be adjusted to level it. The horizontal slide rail 8 is fixed to the foot beam 17 via angle brackets 13.

[0035] There are two fiber optic couplers (5), both with FC / APC interface types. The fiber Bragg grating (7) is of single-mode, PM, double-clad, LMA type. Both the horizontal slide rail (8) and the current measuring slide rail (9) are I-shaped and made of aluminum alloy, and are detachable. The feet (15) are made of lightweight aluminum alloy.

[0036] like Figure 8As shown, a fiber Bragg grating typically consists of an optical fiber core 21, a cladding 22, and a protective layer 23. The fiber Bragg grating grid 20 is a periodic structure introduced into the fiber core. The core 21 is the core of the optical fiber, used to transmit optical signals. The cladding 22 is a glass or plastic layer wrapped around the core, protecting it and providing light reflection. The core 21 and cladding 22 transmit optical signals through total internal reflection, ensuring no signal leakage. The protective layer 23 is a protective material covering the cladding 22, typically a polymer or metal. Its main function is to protect the optical fiber from external environmental influences, preventing mechanical damage and chemical corrosion. The fiber Bragg grating is formed by introducing a periodic refractive index modulation structure into the fiber core 21. This is typically achieved using techniques such as photolithography or laser exposure to create periodic refractive index changes within the core 21, thus realizing the grating's function. The connections between these components are achieved through the fiber manufacturing process and are tightly linked together, collectively forming the structure of the fiber Bragg grating device. Fiber Bragg gratings are only connected to ordinary optical fibers through fiber couplers and are not connected to other devices.

[0037] Working Principle: A fiber Bragg grating (FBG) is a grating structure that utilizes the periodic refractive index variation within an optical fiber. It typically involves introducing periodic refractive index modulation into a section of the fiber core, ranging from a few millimeters to a few centimeters in length. This refractive index modulation causes the fiber to reflect light of a specific wavelength, a phenomenon known as Bragg reflection. This is because the periodic change in the fiber's refractive index causes light of that specific wavelength to be reflected back, while other wavelengths continue to propagate. FBGs have many applications, the most common being in fiber optic sensing. By monitoring changes in the reflected wavelength of the FBG, physical quantities such as temperature, pressure, and stress can be measured.

[0038] When using this fiber Bragg grating-based automatic flow measurement system for open channels, firstly, adjust the fiber Bragg grating perpendicular to the water flow direction and the fiber Bragg grating located in the groove on the side of the flow measurement rail so that corresponding grids in these two sections are at the same height. Next, place the flow measurement rail into the water flow, positioning it on either side of the horizontal rail. Turn on the LD light source and the fiber Bragg grating demodulator. Once the device is activated via the fiber Bragg grating demodulator, the flow measurement rail begins to move. The fiber Bragg grating perpendicular to the water flow direction measures the total pressure at different depths in the water flow; this can be called the first pressure sensor. The fiber Bragg grating located in the groove on the side of the flow measurement rail measures the static pressure at corresponding depths in the water flow; this can be called the second pressure sensor. The pressure values ​​measured by each grid are uploaded to a computer cloud platform via the fiber Bragg grating demodulator. Using algorithms and formulas designed on the computer cloud platform, the total pressure and static pressure values ​​are calculated and analyzed to obtain the specific flow velocity value. Next, the velocity-area method is used, combined with the calculated velocity value, to calculate the channel flow rate.

[0039] This invention boasts high measurement efficiency and a wide range of applications. When measuring flow rate, the fiber Bragg grating allows for the measurement of flow velocities at various points along any vertical line on the flow measurement cross-section. Furthermore, the number of fiber Bragg grating grids can be increased or decreased as needed; a larger number of grids provides a clearer underwater velocity distribution and more accurate flow rate measurement. Simultaneously, adjusting the position of the fiber Bragg gratings changes the grid's position in the water flow, enabling multi-directional measurement and effectively reflecting the flow rate and velocity distribution across the cross-section. In addition, diverse grid arrangements can be implemented based on the characteristics of different channels to achieve precise measurement. The device can also adapt to different channel cross-sectional coefficients, making it highly convenient and practical. During flow rate measurement, the fiber Bragg grating flow measurement device exhibits high sensitivity, accurately reflecting the pressure values ​​at each grid, thereby precisely deducing the flow velocity corresponding to each grid and further accurately calculating the flow rate, achieving precise measurement. This invention is simple in structure and easy to maintain: the fiber Bragg grating flow measurement device has a simple structure, consisting of a light source, optical fiber, and slide rail, making it easy to manufacture. Meanwhile, the device adopts a quick-release structure design, making it easy to carry. The flow measurement slide rail is made of aluminum alloy, which is not easily deformed and is corrosion resistant.

[0040] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An open channel automatic flow measurement system using fiber Bragg grating, characterized in that, It includes: LD light source (1), layer twisted optical fiber box (2), ordinary optical fiber (3), limit switch (4), optical fiber coupler (5), line card (6), fiber Bragg grating (7), horizontal slide rail (8), flow slide rail (9), slide rail connecting block (10), stepper motor (11), level (12), angle code (13), fiber grating demodulator (14), foot base (15), foot column (16), foot beam (17), screw rod (18) and nut (19); The ordinary optical fiber (3) is connected with the optical fiber coupler (5) on the slide rail connecting block (10), one part of the ordinary optical fiber (3) is arranged in the groove above the horizontal slide rail (8), the other part of the ordinary optical fiber (3) is connected with the LD light source (1) and the fiber grating demodulator (14) on both sides of the horizontal slide rail (8) through the layer twisted optical fiber box (2), the limit switch (4) is installed on both sides of the horizontal slide rail (8) at both ends of the horizontal slide rail (8), the horizontal slide rail (8) is fixed on the foot beam (17) through the angle code (13), the foot beam (17) is connected with the foot column (16) through the telescopic screw thread below, the foot base (15) is connected with the foot column (16) through the telescopic screw thread, the layer twisted optical fiber box (2) is fixed on the foot beam (17) through the screw rod and the nut, the horizontal slide rail (8) is connected with the flow slide rail (9) through the slide rail connecting block (10), the fiber Bragg grating (7) is fixed on the flow slide rail (9) through the line card (6), the flow slide rail (9) is fixed on the slide rail connecting block (10) through the screw rod (18) and the nut (19), and the flow slide rail (9) is adjusted up and down by adjusting the screw rod (18) and the nut (19), the stepper motor (11) is fixed on one end of the horizontal slide rail (8) close to the fiber grating demodulator (14) through the screw, the stepper motor is connected with the conveyor belt device, the conveyor belt device is arranged in the left and right grooves of the horizontal slide rail (8), and the slide rail connecting block (10) moves left and right under the drive of the conveyor belt device, and the level (12) is fixed on one end of the horizontal slide rail (8) close to the fiber grating demodulator (14).

2. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The optical fiber coupler (5) has two interfaces, and the interface type is FC / APC.

3. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The fiber Bragg grating (7) is single mode, PM, double clad and LMA.

4. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The horizontal slide rail (8) and the flow slide rail (9) are both I-shaped and made of aluminum alloy, and can be disassembled.

5. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The foot base (15) is made of light aluminum alloy.

6. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The left and right three faces of the horizontal slide rail (8) are designed with grooves, the ordinary optical fiber (3) is arranged in the upper groove, the conveyor belt device is arranged in the left and right grooves and connected with the stepper motor (11) at one end of the horizontal slide rail (8), and the slide rail connecting block (10) moves left and right on the horizontal slide rail (8) under the drive of the conveyor belt device.

7. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The left and right sides of the flow measuring slide rail (9) have grooves, and the fiber Bragg grating (7) is arranged in the vertical direction on the side of the flow measuring slide rail (9) facing the water flow direction, and the fiber Bragg grating (7) continues to extend into the right side groove of the flow measuring slide rail (9) until it is connected to the fiber coupler (5) above.

8. The open channel automatic flow measurement system using fiber Bragg grating as claimed in claim 1, wherein, The layer-stranded optical fiber box (2) is fixed to the two ends of the horizontal slide rail (8) through the screw rod (18) and the nut (19).

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