A fiber grating target flowmeter based on a special-shaped isostatic beam and a use method thereof

Abstract

The application discloses a fiber grating target type flowmeter based on a special-shaped equal strength beam and a use method thereof, which is composed of a special-shaped equal strength beam, a first grating, a second grating, a sealing cover, a tank body, a pressing block, a water inlet joint and a water outlet joint, wherein the special-shaped equal strength beam is provided with a target disc at the end for sensing water flow, the special-shaped equal strength beam is preferably made of a metal with good elasticity, and the special-shaped equal strength beam is composed of two equal strength beams with different sizes which are connected in series, so that the strain on the two equal strength beams caused by the flow acting on the target disc has a large difference; the first grating and the second grating are connected in series and arranged on the surfaces of the two equal strength beams respectively, and the positions of the grating areas are respectively located at the uniform strain distribution positions of the two equal strength beams. The application has the advantages of simple structure, simple packaging, small volume, strong universality and temperature real-time compensation function.

Description

Technical field:

[0001] The present invention relates to the field of optical fiber sensing, and in particular to an optical fiber grating target flowmeter based on a special-shaped equal-strength beam and a use method thereof. Background technology:

[0002] Flow meters are widely used in industrial and agricultural production. Common flow meters include: mechanical rotor flow meters, differential pressure flow meters, vortex flow meters, electromagnetic flow meters, ultrasonic flow meters, etc. However, they all have their own shortcomings, such as the low accuracy of mechanical rotor flow meters, the large size of differential pressure flow meters, the complex structure of vortex flow meters, the susceptibility of electromagnetic flow meters to electromagnetic interference, and the high cost of ultrasonic flow meters. Summary of the invention:

[0003] The technical problem to be solved by the present invention is to provide a fiber Bragg grating target flowmeter based on a special-shaped equal-strength beam and a method of using the same to solve the above technical problems.

[0004] The technical solution of the present invention is to provide a fiber Bragg grating target flowmeter based on a special-shaped equal-strength beam, which is composed of a special-shaped equal-strength beam, a first grating, a second grating, a sealing cover, a tank body, a pressure block, a water inlet joint and a water outlet joint, wherein:

[0005] A target plate is provided at the end of the special-shaped constant strength beam for sensing water flow. The special-shaped constant strength beam is preferably made of metal with good elasticity. In addition, the special-shaped constant strength beam is composed of two constant strength beams of different sizes connected in series, so that the strain on the two constant strength beams caused by the flow acting on the target plate has a large difference.

[0006] The first grating and the second grating are connected in series up and down and are respectively arranged on the surfaces of two equal-strength beams, and the positions of the grating regions are respectively located at the places where the strain distribution of the two equal-strength beams is uniform;

[0007] The special-shaped equal-strength beam is fixed on the sealing cover, and the sealing cover and the tank body together form the liquid chamber of the target flowmeter;

[0008] The water inlet joint and the water outlet joint are connected to the lower end of the tank body, and are respectively connected to the water inlet and water outlet of the water pipe to be tested. The target plate of the special-shaped constant strength beam is concentric with the inner circle of the water inlet joint.

[0009] Preferably, the special-shaped constant strength beam is composed of two constant strength beams of different shapes, and the two constant strength beams and the target plate are integrally processed. The strains on the two constant strength beams caused by the flow acting on the target plate are greatly different.

[0010] Preferably, the first grating and the second grating are connected in series up and down and are respectively attached to one of the surfaces of the two equal-strength beams.

[0011] Preferably, the special-shaped constant-strength beam is fixed to the sealing cover by a pressing block, and the surface of the special-shaped constant-strength beam is perpendicular to the direction of water flow.

[0012] Preferably, the water inlet and outlet joints and the tank body are sealed by wrapping raw tape around standard threads. The seals of the sealing cap, water inlet and outlet joints, the fiber pigtail of the grating and the tank body should have a pressure resistance that can withstand no less than the pressure of the pipeline to be tested.

[0013] Preferably, in order to maximize the strain difference between the two beams in the special-shaped equal-strength beam, the ratio of the length to the width of the two equal-strength beams is not less than 2:1.

[0014] Preferably, to ensure that all water flows act on the target disk, the inner diameter of the water inlet joint should not be larger than the diameter of the target disk; to ensure smooth water outflow, the inner diameter of the water outlet joint should not be smaller than the inner diameter of the water inlet joint.

[0015] Furthermore, the present invention also provides a method for using a fiber Bragg grating target flowmeter based on a special-shaped equal-strength beam, comprising the following steps:

[0016] Step 1: The target flow meter is connected to the pipeline to be tested by connecting a hose with matching size;

[0017] Step 2: The hose and the water inlet and outlet joints can be sealed by locking them with a clamp;

[0018] Step 3: When the flow is generated, the liquid impacts the target plate of the special-shaped constant-strength beam, causing a certain degree of deflection change at the end of the special-shaped constant-strength beam, thereby driving the wavelength drift of the two gratings to different degrees;

[0019] Step 4: By detecting the wavelength shift difference between the two gratings, the flow rate can be inferred.

[0020] Specifically, during operation, the target flowmeter is connected to the water pipe under test via the inlet and outlet connectors. The grating pigtail is connected to a fiber Bragg grating (FBG) demodulator for signal demodulation. When water flows through the pipe, it impacts the target disc, causing it to deflect. Due to the structural differences between the two equal-strength beams on the special-shaped equal-strength beam, the strain caused by the deflection of the target disc at the end differs, resulting in different wavelength shifts for the two gratings due to this strain. However, the two gratings operate in essentially the same environment, meaning their wavelength shifts due to temperature changes are essentially the same. Therefore, subtracting their wavelength shifts eliminates the effects of temperature changes, resolving the issue of temperature cross-sensitivity. As the water flow increases, the wavelength shift of the first grating becomes significantly greater than that of the second grating. This difference in wavelength shifts exhibits a specific relationship with the flow rate. Therefore, by measuring the difference in wavelength shifts between the two gratings, the flow rate can be inferred. It should be noted that the surface of the target flowmeter that contacts the liquid to be measured should be treated with rust and corrosion prevention during operation.

[0021] Compared with the prior art, the present invention has the following advantages after adopting the above scheme:

[0022] (1) Real-time temperature compensation: The environments of the two gratings are basically the same, but their strain sensitivities differ greatly. By subtracting the wavelength drift of the two, we can obtain a parameter that is independent of temperature and only related to the flow rate, thereby achieving real-time temperature compensation.

[0023] (2) Simple structure and easy packaging: The core component of this solution is a special-shaped equal-strength beam with two gratings attached. The special-shaped equal-strength beam can be machined from existing stainless steel plates; the grating packaging process only requires applying a certain amount of pre-tension and then attaching it with adhesive. The overall structure is simple, the packaging is simple, and the yield rate is high.

[0024] (3) Small size and strong universality: The flow meter is small in size. When in use, it only needs to adapt the corresponding water inlet and outlet connectors according to the size of the water pipe, and it can be easily connected to the water pipe for flow monitoring. It is not picky about the type of liquid being measured. It only needs to provide corresponding protection for special-shaped strength beams, tank structures, etc. according to the corrosiveness and temperature characteristics of the liquid. Description of the drawings:

[0025] Figure 1 It is a structural schematic diagram of the fiber Bragg grating target flowmeter based on the special-shaped equal-strength beam of the present invention.

[0026] Figure 2 It is a schematic diagram of the special-shaped equal-strength beam and grating pasting structure of the present invention.

[0027] Figure 3 The figure is a schematic diagram of the working principle of the fiber Bragg grating target flowmeter based on the special-shaped equal-strength beam of the present invention.

[0028] Figure 4 The figure shows the strain distribution simulation result of the special-shaped constant-strength beam after deflection is applied to the end of the present invention. Specific implementation method:

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] like Figure 1-3 As shown, a fiber grating target flowmeter based on a special-shaped constant strength beam is composed of a special-shaped constant strength beam 1, a first grating 2, a second grating 3, a sealing cover 4, a tank body 5, a pressing block 6, a water inlet joint 7 and a water outlet joint 8.

[0031] The special-shaped constant-strength beam 1 is composed of two constant-strength beams of different sizes, and their structures can be the same or different. In this embodiment, the upper constant-strength beam of the two constant-strength beams arranged above and below is larger than the lower constant-strength beam. A target plate 9 for sensing water flow is provided at the end of the special-shaped constant-strength beam 1. The two constant-strength beams and the target plate 9 are integrally processed.

[0032] The first grating 2 and the second grating 3 are connected in series up and down and are respectively attached to one of the surfaces of the two equal-strength beams of the special-shaped equal-strength beam 1, and the positions of the grating areas are respectively located at the places where the strain distribution of the two equal-strength beams is uniform;

[0033] The special-shaped constant-strength beam 1 is fixed to the sealing cover 4 by a pressing block 6. The sealing cover 4 and the tank body 5 together constitute the liquid chamber of the target flowmeter. That is, the sealing cover 4 seals the opening at the upper end of the tank body 5. One end of the water inlet joint 7 and the water outlet joint 8 are respectively connected to the water inlet and water outlet of the water pipe to be measured, and the other ends are sealed and connected to both sides of the lower end of the tank body 5. The target plate 9 of the special-shaped constant-strength beam 1 is concentric with the inner circle of the water inlet joint 7.

[0034] According to the theory of equal strength beams:

[0035]

[0036] Where ε is the strain on the beam, F is the force applied at the beam end, L is the beam length, E is the beam elastic modulus, B is the beam width, and h is the beam thickness. It can be seen that the strain on the beam is directly proportional to the beam length and inversely proportional to the beam width and thickness. To maximize the strain difference between the two uniform-strength beams in irregular uniform-strength beam 1, the ratio of their lengths and widths should be no less than 2:1, given the same beam thickness and a constant end force.

[0037] like Figure 4As shown in the figure, when a certain force is applied to the ends of the beams, the strains at the uniform strain distribution of the two beams of equal strength are approximately 98με and 35με, respectively. The corresponding grating wavelength drifts are approximately 118pm and 42pm, respectively. When the two wavelength drifts are subtracted to achieve real-time temperature compensation, the wavelength drift still reaches 76pm. This shows that the flowmeter has high sensitivity and lays the foundation for high-precision flow measurement.

[0038] Before attaching the first and second gratings 2 and 3, the surfaces of the shaped constant-strength beam 1 should be degreased, cleaned, and polished to maximize adhesion reliability. A certain amount of pre-tension should be applied to both the first and second gratings 2 and 3 so that their post-attachment stretching or contraction remains within a linear range.

[0039] The special-shaped uniform-strength beam 1 is pre-clamped and fixed on both sides with two clamps 6, which are then assembled and fixed to the sealing cover 4. After the grating's pigtail is ejected through the small hole in the sealing cover 4, the hole is sealed with sealant. A sealing ring is used to radially seal the sealing cover 4 and the tank body 5. The water inlet joint 7, the water outlet joint 8, and the tank body 5 are tightened and sealed using standard threaded raw tape. To ensure that the entire water flow acts on the target disk 9, the inner diameter of the water inlet joint 7 should not be larger than the diameter of the target disk 9; to ensure smooth water discharge, the inner diameter of the water outlet joint 8 should not be smaller than the inner diameter of the water inlet joint 7.

[0040] During use, the fiber grating target flowmeter based on the shaped constant-strength beam is connected to the pipeline to be measured by connecting a matching hose. The hose is sealed to the water inlet connector 7 and the water outlet connector 8 by means of a clamp. When flow is generated, the liquid impacts the target plate 9 of the shaped constant-strength beam 1, causing a certain degree of deflection at the end of the beam, which in turn causes the two gratings to shift in wavelength to varying degrees. By measuring the difference in wavelength shift between the two gratings, the flow rate can be inferred.

[0041] The above description is only for the preferred embodiment of the present invention, which should not be understood as limiting the claims. Any equivalent structure or equivalent process transformation made by using the description of the present invention is included in the patent protection scope of the present invention.

Claims

1. A fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam, characterized by: It is composed of a special-shaped equal-strength beam (1), a first grating (2), a second grating (3), a sealing cover (4), a tank body (5), a pressing block (6), a water inlet joint (7) and a water outlet joint (8), wherein: A target plate (9) for sensing water flow is provided at the end of the special-shaped equal-strength beam (1). The special-shaped equal-strength beam (1) is composed of two equal-strength beams of different sizes connected in series up and down, so that the strains on the two equal-strength beams caused by the flow acting on the target plate (9) are different. The first grating (2) and the second grating (3) are connected in series up and down and are respectively arranged on the surfaces of two equal-strength beams, and the positions of the grating regions are respectively located at the locations where the strain distribution of the two equal-strength beams is uniform; The special-shaped equal-strength beam (1) is fixed on the sealing cover (4), and the sealing cover (4) and the tank body (5) together form a liquid chamber of the target flowmeter; The water inlet joint (7) and the water outlet joint (8) are connected to the lower end of the tank body, and the target plate (9) of the special-shaped constant strength beam (1) is concentric with the inner circle of the water inlet joint (7).

2. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 1, characterized in that: The two equal-strength beams and the target plate (9) are integrally machined.

3. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 2, characterized in that: The first grating (2) and the second grating (3) are connected in series up and down and are respectively adhered to one of the surfaces of the two equal-strength beams (1).

4. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 1, characterized in that: The special-shaped equal-strength beam (1) is fixed on the sealing cover (4) through a pressing block (6), and the surface of the special-shaped equal-strength beam (1) is perpendicular to the direction of water flow.

5. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 1, characterized in that: The water inlet joint (7), the water outlet joint (8) and the tank body (5) are sealed by wrapping a raw tape around a standard thread.

6. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 2, characterized in that: The ratio of the length and width of two equal strength beams shall not be less than 2:

1.

7. The fiber Bragg grating target flowmeter based on a special-shaped constant-strength beam according to claim 1, characterized in that: The inner diameter of the water inlet joint (7) is not greater than the diameter of the target plate (9); and the inner diameter of the water outlet joint (8) is not less than the inner diameter of the water inlet joint (7).

8. A method for using the fiber Bragg grating target flowmeter based on a special-shaped constant strength beam according to claim 1, characterized in that: The following steps are included: Step 1: The target flow meter is connected to the pipeline to be tested by connecting a hose with matching size; Step 2: sealing the hose with the water inlet connector (7) and the water outlet connector (8); Step 3, when the flow is generated, the liquid impacts the target plate (9) of the special-shaped equal strength beam (1), and the impact force causes the target plate (9) to be deflected. The two equal strength beams of the special-shaped equal strength beam (1) have different strain amounts caused by the deflection of the end target plate, so that the wavelength drift amounts of the two gratings caused by the strain change are different, thereby driving the two gratings to have different degrees of wavelength drift; Step 4: By detecting the wavelength shift difference between the two gratings, the flow rate can be inferred.

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