Wind speed sensor based on double gratings
By combining a dual-grating array with a high-temperature capillary tube and a metal tube, the problems of large size and susceptibility to interference of traditional fiber Bragg grating wind speed sensors are solved, realizing miniaturized, stable and interference-resistant wind speed measurement, which is suitable for industrial environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-06
- Publication Date
- 2026-03-17
AI Technical Summary
Existing fiber Bragg grating wind speed sensors are bulky, require additional compensation structures, are susceptible to interference, and lack stability and reusability.
A dual-grating array component is combined with a high-temperature capillary tube and a metal tube, which are fixed with sealant. The metal tube is made of nickel-chromium alloy and copper. The wind speed is measured by heating with a constant current source and calculated by combining the principles of heat transfer.
A wind speed sensor with small size, strong anti-interference ability, and high stability has been developed, which is suitable for industrial scenarios, has high measurement accuracy, and is easy to maintain.
Smart Images
Figure 1
Abstract
Description
Technical Field
[0001] This utility model relates to the field of fiber optic grating sensor technology, and in particular to a wind speed sensor based on dual gratings. Background Technology
[0002] A fiber grating is a structure that periodically changes the refractive index within the core of an optical fiber, enabling it to reflect light of a specific wavelength, known as the Bragg wavelength. When the fiber is subjected to external environmental influences (such as temperature changes or strain), the Bragg wavelength changes. This property makes fiber gratings highly effective sensing tools for detecting changes in various physical quantities.
[0003] Traditional fiber Bragg grating anemometers operate based on the mechanical response of fiber Bragg gratings to external environmental factors, such as wind speed. Typically, the fiber Bragg grating is fixed to a structure that responds to wind speed. For example, it can be fixed to a cantilever beam; when wind blows, the cantilever beam bends or vibrates, causing the fiber Bragg grating to undergo mechanical deformation, which results in a change in its Bragg wavelength. By monitoring the change in the Bragg wavelength, the magnitude of the wind speed acting on the sensor can be calculated. Alternatively, it can be designed as a vortex street, utilizing the relationship between vortex street frequency and wind speed to measure wind speed.
[0004] Sensors made using the above technologies generally suffer from large size or require additional compensation structures to correct the results. Utility Model Content
[0005] The technical problem to be solved by this utility model is how to provide a wind speed sensor based on dual gratings that is small in size, stable, reusable, drift-free, and has strong anti-interference ability.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a wind speed sensor based on a dual grating, including a dual grating array assembly, a high-temperature capillary tube sleeved on the outside of the dual grating array assembly, a sealant between the end of the dual grating array assembly and the high-temperature capillary tube, the sealant fixing the dual grating array assembly and the high-temperature capillary tube together, a metal circular tube on the outside of the high-temperature capillary tube, the metal circular tube including a heating alloy part and a conductive metal part, the two ends of a constant current source being connected to the heating alloy part and the conductive metal part of the metal circular tube respectively through electrode leads.
[0007] A further technical solution is that the high-temperature capillary also includes heat transfer fins, which are equally spaced on the outer periphery of the high-temperature capillary and arranged radially.
[0008] A further technical solution is that the length of the metal tube is less than the length of the high-temperature capillary, so that part of the high-temperature capillary is located on the outside of the metal tube.
[0009] A further technical solution is that the dual grating array assembly includes an optical fiber and two grating arrays with different Bragg wavelengths located within the optical fiber, wherein the grating array with the larger wavelength is located within the optical fiber in the area covered by the metal tube, and the grating array with the smaller wavelength is located within the optical fiber outside the metal tube.
[0010] A further technical solution is that the distance between the two grating arrays is not less than 20mm, and the wavelength interval between the two grating arrays is greater than 6nm, and the small wavelength grating array maintains a distance of at least 20mm from the end of the metal tube.
[0011] A further technical solution is that the metal tube is made of sheet material formed by two materials, nickel-chromium alloy and copper, and the main body structure of the sensor is formed by friction welding with a diameter not exceeding 1mm, an inner diameter of at least 0.3mm, and a length of less than 100mm.
[0012] A further technical solution is that an electrode terminal is formed on the heating alloy part and the conductive metal part of the metal tube, respectively, for welding electrode leads.
[0013] The beneficial effects of adopting the above technical solution are as follows: the wind speed sensor manufactured using dual gratings described in this application is small in size, can fully resist electromagnetic interference, and minimizes its impact on the flow field, thus improving the sensor's practicality. At the same time, the sensor has a simple structure, reducing maintenance difficulty and making it more suitable for industrial scenarios.
[0014] This method of measuring wind speed utilizes convection cooling to infer wind speed by measuring the rate of cooling or the change in power required to maintain a constant temperature. Further calibration can refine the accuracy of the results. This method is suitable for various applications, including laboratory testing and industrial applications. Attached Figure Description
[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0016] Figure 1 This is a schematic diagram of the structure of the sensor described in an embodiment of this utility model;
[0017] Figure 2 This is a cross-sectional structural schematic diagram of the sensor described in an embodiment of this utility model;
[0018] Figure 3 This is a schematic diagram of the serial arrangement of the sensors described in an embodiment of the present invention;
[0019] Figure 4 This is a schematic diagram of the parallel arrangement of the sensors described in an embodiment of the present invention;
[0020] The components include: 1. Metal round tube; 1-1. Heating alloy part; 1-2. Conductive metal part; 2. High temperature capillary tube; 2-1. Heat transfer fins; 3. Dual grating array assembly; 3-1. Optical fiber; 3-2. Grating array; 4. Electrode leads; 5. Sealant. Detailed Implementation
[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present utility model, and not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0022] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0023] like Figures 1-2 As shown in the figure, this utility model discloses a wind speed sensor based on a dual-grating, including a dual-grating array assembly 3. A high-temperature capillary tube 2 is sleeved on the outside of the dual-grating array assembly 3. A sealant 5 is provided between the end of the dual-grating array assembly 3 and the high-temperature capillary tube 2, and the sealant 5 fixes the dual-grating array assembly 3 and the high-temperature capillary tube 2 together. A metal circular tube 1 is provided on the outside of the high-temperature capillary tube 2. The metal circular tube 1 includes a heating alloy part 1-1 and a conductive metal part 1-2. The two ends of a constant current source are respectively connected to the heating alloy part 1-1 and the conductive metal part 1-2 of the metal circular tube 1 through electrode leads 4. After the metal circular tube 1, the high-temperature capillary tube 2, and the dual-grating array assembly 3 are assembled, only one end is fixed with sealant 5, while the other end remains free.
[0024] like Figure 1As shown, the metal tube 1 is made of two materials. One material exhibits significant heating effect under current, while the other material possesses excellent electrical conductivity. Therefore, the heating alloy portion 1-1 can be made of materials such as nickel-chromium alloy or iron-chromium alloy, and the conductive metal portion 1-2 can be made of materials such as copper or platinum. Furthermore, the metal tube 1 is formed from sheets of nickel-chromium alloy and copper through friction welding to create the main structure of the sensor, with a diameter not exceeding 1 mm, an inner diameter of at least 0.3 mm, and a length within 100 mm. The length of the metal tube 1 is less than the length of the high-temperature capillary 2, such that a portion of the high-temperature capillary 2 is located on the outer side of the metal tube 1.
[0025] like Figure 2 As shown, the high-temperature capillary 2 further includes heat transfer fins 2-1, which are evenly spaced and radially arranged on the outer periphery of the high-temperature capillary 2. A fin structure is provided on the outer wall of the high-temperature capillary 2, the outer diameter of which perfectly matches the inner diameter of the metal tube, and its inner wall is smooth without protrusions, with a diameter of not less than 0.2 mm.
[0026] Furthermore, such as Figure 1 As shown, the dual grating array assembly 3 includes an optical fiber 3-1 and two grating arrays 3-2 with different Bragg wavelengths located within the optical fiber 3-1. The grating array 3-2 with the larger wavelength is located within the optical fiber 3-1 covering the area of the metal tube 1, while the grating array 3-2 with the smaller wavelength is located within the optical fiber 3-1 outside the metal tube 1. Preferably, the spacing between the two grating arrays 3-2 is not less than 20 mm, and the wavelength interval between the two grating arrays 3-2 is greater than 6 nm. The smaller wavelength grating array 3-2 maintains a distance of at least 20 mm from the end of the metal tube 1.
[0027] In addition, an electrode terminal is formed on the heating alloy part 1-1 and the conductive metal part 1-2 of the metal tube 1, respectively, for welding the electrode lead 4.
[0028] The production process includes the following steps:
[0029] 1) Assemble the sensor: First, insert the high-temperature capillary tube 2 into the metal tube 1. With proper diameter matching, the two should maintain good contact and not slip. The length of the high-temperature capillary tube 2 should be greater than that of the metal tube 1.
[0030] 2) Install the dual grating array: Insert the dual grating array assembly 3 into the high-temperature capillary tube 2, ensuring a gap between them that allows for free movement; ensure one grating array 3-2 is within the coverage area of the metal tube 1, and the other grating array 3-2 is outside the area of the metal tube 1. Then, use sealant 5 to fix the grating array assembly 3 and the high-temperature capillary tube 2 at one end of the metal tube 1. The distance between the two grating arrays should be no less than 20mm, and ensure that the difference in their Bragg wavelengths is greater than 6nm.
[0031] 3) Connect the circuit: Connect the positive and negative terminals of the constant current source to the electrode terminals on the metal tube 1 through the electrode lead 4 to ensure that the circuit is connected correctly.
[0032] 4) Sensor installation: When installing the sensor, ensure that the sensor axis is perpendicular to the expected wind direction to obtain the best test results.
[0033] The test steps of the sensor
[0034] 1) Start the constant current source: Turn on the constant current source to provide a stable current for heating the metal tube 1.
[0035] 2) Data acquisition: Use a fiber optic sensor demodulator or other suitable equipment to monitor the Bragg wavelength changes of the two grating arrays.
[0036] 3) Calculate the temperature difference: Calculate the temperature difference based on the airflow temperature measured by the external fiber optic grating sensor and the temperature measured by the internal fiber optic grating.
[0037] 4) Calculate wind speed:
[0038] Based on the above structural design, the wind speed sensor, according to heat transfer principles, for an infinite cylinder in a crossflow, has an average Nusselt number N based on existing datasets. u The correlations are as follows:
[0039]
[0040] d represents the diameter of the cylinder / tube in the transverse flow field; here, it refers to the capillary diameter.
[0041] h convective heat transfer coefficient
[0042] k air Thermal conductivity coefficient of flowing air
[0043] Re is the Reynolds number of the capillary diameter.
[0044] Pr is Prandtl's constant.
[0045] The relationship between Reynolds number and wind speed is as follows:
[0046]
[0047] Where U is the wind speed, d is the capillary diameter, and v is the kinematic viscosity of the substance.
[0048] By heating the capillary tube, convective heat transfer and Joule heating reach equilibrium at different wind speeds, with the following relationship:
[0049] q j =h(πd)(TT) f (3)
[0050] Where, q j T is the Joule heat per unit length, and T is the grating test temperature inside the capillary. f It is the airflow temperature, obtained by measuring the external grating of the capillary tube. The Joule heat per unit length can be written as...
[0051]
[0052] Where I is the constant current source applied to the capillary tube, ρ is the resistivity (ohms), and A is the cross-sectional area of the heated wire (approximately A = πdt due to the use of capillary tubes in current sensor designs). wall , where t wall (This refers to the capillary wall thickness). Lumped analysis yields the following results.
[0053]
[0054] π is the mathematical constant of a circle. Nu can be calculated using the above formula. Combining (1) and (2), the wind speed U can be directly calculated.
[0055] The Nusselt coefficient is calculated using formulas (3) to (5), and the wind speed is then calculated using formulas (1) and (2).
[0056] Precautions:
[0057] During manufacturing, ensure all connections are secure to prevent loosening that could affect measurement accuracy. During use, pay attention to changes in the ambient temperature around the sensor and ensure temperature compensation measures are in place. During installation, ensure the sensor is perpendicular to the wind direction to avoid errors. Adjust the constant current source intensity according to actual conditions to ensure Joule heating and convective heat transfer are balanced. The calibration process in this patent implementation is not detailed here, as it is consistent with conventional sensor calibration methods.
[0058] like Figures 3-4 As shown, there can be two or more wind speed sensors, which can be connected in series or in parallel.
[0059] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A dual-grating based wind speed sensor, characterized by: The application relates to a wind speed sensor, which comprises a double-grating array component (3), the outer side of the double-grating array component (3) is sleeved with a high-temperature capillary tube (2), a sealant (5) is arranged between the end of the double-grating array component (3) and the high-temperature capillary tube (2), the double-grating array component (3) and the high-temperature capillary tube (2) are fixed together through the sealant (5), the outer side of the high-temperature capillary tube (2) is provided with a metal round tube (1), the metal round tube (1) comprises a heating alloy part (1-1) and a conductive metal part (1-2), and the two ends of a constant current source are connected with the heating alloy part (1-1) and the conductive metal part (1-2) of the metal round tube (1) through electrode lead wires (4) respectively.
2. The dual-grating based wind speed sensor of claim 1, wherein: The high-temperature capillary tube (2) further comprises heat transfer fins (2-1) which are arranged at the outer periphery of the high-temperature capillary tube (2) at equal intervals and in a radiating shape.
3. The dual-grating based wind speed sensor of claim 1, wherein: The length of the metal round tube (1) is smaller than the length of the high-temperature capillary tube (2), so that part of the high-temperature capillary tube (2) is located outside the metal round tube (1).
4. The dual-grating based wind speed sensor of claim 3, wherein: The double-grating array component (3) comprises an optical fiber (3-1) and two grating arrays (3-2) with different Bragg wavelengths which are located in the optical fiber (3-1), wherein the grating array (3-2) with a larger wavelength is located in the optical fiber (3-1) covered by the metal round tube (1), and the grating array (3-2) with a smaller wavelength is located in the optical fiber (3-1) outside the metal round tube (1).
5. The dual-grating based wind speed sensor of claim 4, wherein: The distance between the two grating arrays (3-2) is not less than 20 mm, and the wavelength interval of the two grating arrays (3-2) is greater than 6 nm; the grating array (3-2) with a smaller wavelength is kept at least 20 mm away from the end of the metal round tube (1).
6. The dual-grating based wind speed sensor of claim 1, wherein: The heating alloy part (1-1) is made of nickel-chromium alloy or iron-chromium alloy, and the conductive metal part (1-2) is made of copper material.
7. The dual-grating based wind speed sensor of claim 6, wherein: The metal round tube (1) is formed by friction welding of a sheet made of nickel-chromium alloy and copper, and has a diameter not more than 1 mm, an inner diameter at least 0.3 mm and a length within 100 mm.
8. The dual-grating based wind speed sensor of claim 1, wherein: The sealant (5) is a good conductor of heat.
9. The dual-grating based wind speed sensor of claim 1, wherein: An electrode terminal is formed on the heating alloy part (1-1) and the conductive metal part (1-2) of the metal round tube (1) respectively, and is used for welding the electrode lead wire (4).
10. The dual-grating based wind speed sensor of claim 1, wherein: The wind speed sensor can be combined for use, and two or more wind speed sensors can be connected in series or in parallel.