An optical fiber sensor for monitoring the flow rate of pipeline fluid

Abstract

The present invention provides an optical fiber sensor for monitoring the flow rate of pipeline fluid, which belongs to the field of measurement technology. The optical fiber sensor for monitoring the flow rate of pipeline fluid includes an optical fiber, an optical fiber protective armor, an optical fiber fixing clamp, a metal pad, a ceramic rod, a ceramic sheet, a spring top seat, a spring, a spring base, a reflective mirror, a hollow cylinder, a ceramic shell, a ceramic ring, and a bearing. The device realizes real-time monitoring of the flow rate of the fluid in the pipeline by observing the changes in the spectrum in the spectrometer, using the Fabry-Perot optical fiber interference principle, the principle that the force generated by the fluid flowing through the sensor is equivalent to the internal force generated by the spring, and the relationship between the fluid resistance and the relative speed, thereby ensuring the safety and stability of pipeline transportation. The present invention has low labor cost, simple operation, wide coverage, and broad application prospects and promotion market.

Description

Technical Field

[0001] The invention relates to an optical fiber sensor for monitoring the flow velocity of pipeline fluid, belonging to the technical field of measurement. Background Art

[0002] Pipeline transportation is one of the five major transportation industries along with railways, highways, waterways and aviation, and plays an important role in my country's economic development. In an international environment of energy shortage, international oil and gas trade has effectively improved energy utilization. Pipeline flow measurement is the key to oil and gas trade, and accurate measurement can reduce trade disputes. Therefore, it is necessary to monitor pipeline fluid flow and velocity. The medium transported by pipelines is mainly kerosene, oil and natural gas. Fiber optic sensors have the advantages of corrosion resistance, high sensitivity, and real-time monitoring, and can be used to monitor pipeline fluid flow velocity.

[0003] At present, there are many methods for measuring the flow velocity of fluid in pipelines, including pitot tube velocity measurement technology, flow meter velocity measurement technology, hot wire velocity measurement technology, laser Doppler velocity measurement technology, etc. Among them, pitot tube velocity measurement technology measures the linear velocity at a certain point to obtain the fluid flow velocity of the pipeline cross section; hot wire velocity measurement technology measures the flow velocity based on the temperature difference; laser Doppler velocity measurement technology measures the Doppler signal of the laser probe tracer particles to obtain the fluid velocity; flow meter velocity measurement technology measures the flow velocity based on the pressure difference, and commonly used flow meters include differential pressure type, ultrasonic type and vortex type, among which differential pressure flow meter has high requirements for the measurement environment and low measurement accuracy; ultrasonic flow meter has the disadvantages of complex structure and high maintenance cost.

[0004] In recent years, with the increase in China's demand for energy, higher requirements have been placed on pipeline fluid flow rate monitoring technology. Fiber optic sensors have the advantages of small size, high sensitivity, anti-electromagnetic interference, compactness and lightness, and have attracted great attention in the field of measurement technology. Compared with traditional measurement methods, they have the advantages of low cost, convenient installation, high accuracy and real-time monitoring.

[0005] Therefore, for pipeline fluid flow rate monitoring, it is very necessary to provide a fiber optic sensor with high sensitivity, high accuracy and corrosion resistance to achieve control of pipeline flow rate uniformity, thereby ensuring the safety, reliability and stability of pipeline transportation. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an optical fiber sensor for monitoring the flow rate of a fluid in a pipeline, the purpose of which is to monitor the flow rate of the fluid in the pipeline in real time, thereby achieving control of the flow rate of the fluid in the pipeline.

[0007] The technical solution of the present invention:

[0008] A fiber optic sensor for monitoring the flow rate of a pipeline fluid comprises an optical fiber 1, an optical fiber protective armor 2, an optical fiber fixing clamp 3, a metal pad 4, a ceramic rod 5, a ceramic sheet 6, a spring top seat 7, a spring 8, a spring base 9, a reflective mirror 10, a hollow cylinder 11, a ceramic shell 12, a ceramic ring 13, and a bearing 14.

[0009] Design 1:

[0010] The optical fiber protection armor 2 is used to protect the optical fiber 1;

[0011] The optical fiber 1 is fixed to the top of the hollow cylinder 11 by the optical fiber fixing clamp 3. The optical fiber fixing clamp 3 is consistent with the axis angle of the hollow cylinder 11 and the inclination angle of the reflective mirror 10, so that the end of the optical fiber 1 is always perpendicular to the reflective mirror 10 on the metal pad 4 during the rotation of the hollow cylinder 11. The initial position of the optical fiber 1 is located outside the circumference of the reflective mirror 10 on the upper surface of the hollow cylinder 11, and maintains a certain distance from the hollow cylinder 11;

[0012] The optical fiber 1 and the reflective mirror 10 form a Fabry-Perot cavity, forming a Fabry-Perot optical fiber sensing unit. When the ceramic sheet 6 rotates along with the flow direction of the fluid, the hollow cylinder 11 is driven to rotate accordingly, further causing the distance between the end face of the optical fiber 1 and the reflective mirror 10, that is, the cavity length of the Fabry-Perot cavity to change accordingly.

[0013] The metal pad 4 is fixed to the top of the hollow cylinder 11, and the arc length of the bottom surface of the metal pad 4 is 1 / 4 of the circumference of the hollow cylinder, and the width is 1 / 2 of the radius of the hollow cylinder 11;

[0014] The reflective mirror surface 10 can be formed by grinding and polishing the metal pad 4, or by ion sputtering metal coating on the surface of the metal pad 4;

[0015] The bearing 14 is used to support and drive the hollow cylinder 11;

[0016] The spring top seat 7 is fixed to the wall of the hollow cylinder 11, and the spring base 9 is fixed to the ceramic shell 12;

[0017] One end of the ceramic rod 5 is fixed to the hollow cylinder 11, and the other end is connected to the ceramic sheet 6;

[0018] The ceramic shell 12 has a cutout in the middle of the cylinder in the circumferential direction, the length of the cutout is 1 / 4 of the total circumference of the cross section of the ceramic shell 12, and the width of the cutout is equal to the diameter of the ceramic rod 5;

[0019] The ceramic ring 13 is located in the groove of the ceramic shell 12 and is connected to the ceramic rod 5 at the intersection. The groove surrounds the ceramic shell 12. The width of the ceramic ring 13 is greater than the width of the cutout.

[0020] The ceramic sheet 6, the ceramic rod 5 and the ceramic ring 13 are flow velocity sensing units. The flow velocity sensing unit and the ceramic housing 12 seal the entire monitoring device and protect the optical fiber Fabry-Perot interferometer.

[0021] The spring 8 is in a natural state when initially packaged, and the stiffness of the spring 8 can be adjusted according to the required sensitivity;

[0022] The ceramic ring 13 slides freely in the groove as the ceramic sheet 6 rotates, and the hollow cylinder 11 slides on the bearing 14 at the same time. The maximum rotation angle of the ceramic sheet 6 is 90°.

[0023] The hollow cylinder 11, the ceramic shell 12 and the ceramic ring 13 are concentric and coaxial;

[0024] The curvature of the metal pad 4 is consistent with the curvature of the cross-section of the hollow cylinder 11 .

[0025] Design 2 has the following differences from Design 1:

[0026] The optical fiber 1 and the optical fiber protective armor 2 pass through the hollow cylinder 11, the optical fiber 1 and the reflective mirror surface 10 of the metal spacer 4 form a Fabry-Perot cavity, and the optical fiber 1 is located below the outer side of the circumference of the metal spacer 4;

[0027] The metal pad 4 is located above the outer side of the circumference of the hollow cylinder 11 , and the base is fixed to the inner side of the top end of the ceramic shell 12 .

[0028] Working principle of the present invention:

[0029] The ceramic sheet 6, ceramic rod 5 and ceramic ring 13 of the present invention are the flow velocity sensing unit of the sensor. When the fluid flows through the sensor, the ceramic sheet 6 rotates along the cut direction, driving the ceramic ring 13 to slide in the groove, the bearing 14 drives the hollow cylinder 11 and the metal pad 4, and the length of the Fabry-Perot cavity formed between the reflective mirror 10 and the optical fiber 1 changes, and the process device remains sealed. By observing the changes in the spectrum in the spectrometer, the length of the Fabry-Perot cavity at a certain moment is determined, and the flow velocity of the fluid in the pipeline is monitored by using the geometric relationship, the balance relationship of forces, and the relationship between fluid resistance and relative velocity.

[0030] The core principle of the present invention is the working principle of the Fabry-Perot interferometer fiber optic sensor. The incident light is transmitted in the optical fiber 1, passes through the first reflection surface between the optical fiber 1 and the space and the second reflection surface between the space and the reflection surface, and then returns to the optical fiber 1. The interference signal I is expressed as:

[0031]

[0032] Where, I1 and I2 are the intensities of the reflected light input from the two reflection surfaces; n is the refractive index of the intermediate medium (air); δ is the length of the Fabry-Perot interferometer cavity; λ is the wavelength; is the phase difference between the two reflected lights.

[0033] When the fluid in the pipeline flows through the sensor, it generates thrust on the ceramic sheet 6, causing the ceramic sheet 6 to rotate by an angle of θ. The chord length b of the reflective mirror 10 relative to the optical fiber 1 is:

[0034]

[0035] Where R is the distance from the end of the optical fiber 1 to the axis of the hollow cylinder 11. Assuming that the initial position of the optical fiber 1 and the initial spacing (initial cavity length) of the reflector 10 are δ0, the relationship between the Fabry-Perot cavity length Δδ and the rotation angle θ is:

[0036]

[0037] Wherein, α is the angle between the reflective mirror surface 10 and the horizontal direction, that is, the inclination angle of the metal pad 4. The internal force F generated by the spring when the hollow cylinder 11 rotates is:

[0038] F=k·Δ (4)

[0039]

[0040] Wherein, k is the spring stiffness coefficient, Δ is the change in spring length, r2 is the radius of the cross section of the ceramic shell 12, and r1 is the radius of the cross section of the hollow cylinder 11. According to the moment balance condition of the spring internal force and the fluid resistance f acting on the ceramic sheet 6:

[0041] Rf=r1F (6)

[0042] Wherein, R is the distance from the centroid of the ceramic sheet 6 to the axis of the hollow cylinder 11 (i.e., the rotation radius of the ceramic sheet 6), and f is the fluid resistance received by the ceramic sheet 6. When the ceramic sheet 6 and the fluid move relative to each other, the relationship between the fluid resistance f received by the ceramic sheet 6 and the relative velocity V is:

[0043]

[0044] Wherein, A is the area of ​​the ceramic sheet 6, ρ is the density of the fluid; and C is the resistance coefficient.

[0045] By monitoring the change of the Fabry-Perot cavity length Δδ, the angle θ of the ceramic sheet 6 is obtained. Since the rotation radius R of the reflector 10 relative to the optical fiber 1, the radius r1 of the cross section of the hollow cylinder 11, and the radius r2 of the cross section of the ceramic shell 12 are known, the chord length b of the reflector 10 relative to the optical fiber 1 and the change in the spring length Δ can be calculated. According to the balance of forces and the relationship between the fluid resistance f and the relative velocity V, the fluid resistance f on the ceramic sheet 6 and the corresponding fluid linear velocity are calculated, thereby achieving real-time monitoring of the fluid flow rate in the pipeline.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The present invention realizes real-time monitoring of the flow rate of the fluid in the pipeline by monitoring the change in the cavity length of the Fabry-Perot optical fiber sensor;

[0048] (2) The present invention adopts optical fiber sensing technology, which has high sensitivity and accuracy and can achieve more accurate measurement;

[0049] (3) The present invention is suitable for monitoring the flow rate of fluids in long-distance pipelines, has the advantages of anti-electromagnetic interference, corrosion resistance, long service life, and saves maintenance costs;

[0050] (4) The present invention can meet the sensitivity required by actual engineering by changing the torsional stiffness of the spring, the rotation radius of the ceramic sheet and the angle between the rigid pad and the horizontal direction;

[0051] (5) The present invention has a simple structure, is easy to install, has strong applicability, and has broad application prospects and promotion markets. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Two structural schematic diagrams of optical fiber sensors for monitoring the flow velocity of fluid inside a pipeline according to the present invention;

[0053] Figure 2 AA cross-sectional views of two types of optical fiber sensors used to monitor the flow velocity of fluid inside a pipeline;

[0054] Figure 3 BB cross-sectional views of two types of optical fiber sensors used to monitor the flow rate of fluid inside a pipeline;

[0055] Figure 4 Two optical fiber sensing units for monitoring the flow rate of fluid inside a pipeline;

[0056] Figure 5 It is a schematic diagram of the placement of the present invention applied to monitoring the flow rate of fluid inside an actual pipeline.

[0057] In the figure: optical fiber 1, optical fiber protection armor 2, optical fiber fixing clamp 3, metal spacer 4, ceramic rod 5, ceramic sheet 6, spring top seat 7, spring 8, spring base 9, reflecting mirror 10, hollow cylinder 11, ceramic shell 12, ceramic ring 13, bearing 14. DETAILED DESCRIPTION

[0058] The following will describe a specific implementation of an optical fiber sensor device for monitoring the flow rate of a pipeline fluid in conjunction with the accompanying drawings.

[0059] like Figures 1 to 5 As shown, the present invention provides an optical fiber sensor for monitoring the flow rate of pipeline fluid, including an optical fiber 1, an optical fiber protective armor 2, an optical fiber fixing clamp 3, a metal pad 4, a ceramic rod 5, a ceramic sheet 6, a spring top seat 7, a spring 8, a spring base 9, a reflective mirror 10, a hollow cylinder 11, a ceramic shell 12, a ceramic ring 13, and a bearing 14.

[0060] For design plan 1:

[0061] The optical fiber protection armor 2 is used to protect the optical fiber 1;

[0062] The optical fiber 1 is fixed to the top of the hollow cylinder 11 by the optical fiber fixing clamp 3. The optical fiber fixing clamp 3 is consistent with the axis angle of the hollow cylinder 11 and the inclination angle of the reflective mirror 10, so that the end of the optical fiber 1 is always perpendicular to the reflective mirror 10 on the metal pad 4 during the rotation of the hollow cylinder 11. The initial position of the optical fiber 1 is located outside the circumference of the reflective mirror 10 on the upper surface of the hollow cylinder 11, and maintains a certain distance from the hollow cylinder 11;

[0063] The optical fiber 1 and the reflective mirror 10 form a Fabry-Perot cavity, forming a Fabry-Perot optical fiber sensing unit. When the ceramic sheet 6 rotates along with the flow direction of the fluid, the hollow cylinder 11 is driven to rotate accordingly, further causing the distance between the end face of the optical fiber 1 and the reflective mirror 10, that is, the cavity length of the Fabry-Perot cavity to change accordingly.

[0064] The metal pad 4 is fixed to the top of the hollow cylinder 11, and the arc length of the bottom surface of the metal pad 4 is 1 / 4 of the circumference of the hollow cylinder, and the width is 1 / 2 of the radius of the hollow cylinder 11;

[0065] The reflective mirror surface 10 can be formed by grinding and polishing the metal pad 4, or by ion sputtering metal coating on the surface of the metal pad 4;

[0066] The bearing 14 is used to support and drive the hollow cylinder 11;

[0067] The spring top seat 7 is fixed to the wall of the hollow cylinder 11, and the spring base 9 is fixed to the ceramic shell 12;

[0068] One end of the ceramic rod 5 is fixed to the hollow cylinder 11, and the other end is connected to the ceramic sheet 6;

[0069] The ceramic shell 12 has a cutout in the middle of the cylinder in the circumferential direction, the length of the cutout is 1 / 4 of the total circumference of the cross section of the ceramic shell 12, and the width of the cutout is equal to the diameter of the ceramic rod 5;

[0070] The ceramic ring 13 is located in the groove of the ceramic shell 12 and is connected to the ceramic rod 5 at the intersection. The groove surrounds the ceramic shell 12. The width of the ceramic ring 13 is greater than the width of the cutout.

[0071] The ceramic sheet 6, the ceramic rod 5 and the ceramic ring 13 are flow velocity sensing units. The flow velocity sensing unit and the ceramic housing 12 seal the entire monitoring device and protect the optical fiber Fabry-Perot interferometer.

[0072] The spring 8 is in a natural state when initially packaged, and the stiffness of the spring 8 can be adjusted according to the required sensitivity;

[0073] The ceramic ring 13 slides freely in the groove as the ceramic sheet 6 rotates, and the hollow cylinder 11 slides on the bearing 14 at the same time. The maximum rotation angle of the ceramic sheet 6 is 90°.

[0074] The hollow cylinder 11, the ceramic shell 12 and the ceramic ring 13 are concentric and coaxial;

[0075] The curvature of the metal pad 4 is consistent with the curvature of the cross-section of the hollow cylinder 11 .

[0076] Design 2 has the following differences from Design 1:

[0077] The optical fiber 1 and the optical fiber protective armor 2 pass through the hollow cylinder 11, the optical fiber 1 and the reflective mirror surface 10 of the metal spacer 4 form a Fabry-Perot cavity, and the optical fiber 1 is located below the outer side of the circumference of the metal spacer 4;

[0078] The metal pad 4 is located above the outer side of the circumference of the hollow cylinder 11 , and the base is fixed to the inner side of the top end of the ceramic shell 12 .

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical fiber sensor for monitoring the flow rate of a pipeline fluid, characterized in that: The optical fiber sensor for monitoring the flow rate of a pipeline fluid comprises an optical fiber (1), an optical fiber protective armor (2), an optical fiber fixing clamp (3), a metal pad (4), a ceramic rod (5), a ceramic sheet (6), a spring top seat (7), a spring (8), a spring base (9), a reflective mirror (10), a hollow cylinder (11), a ceramic housing (12), a ceramic ring (13), and a bearing (14); The optical fiber protection armor (2) is used to protect the optical fiber (1); The spring top seat (7) is fixed to the wall of the hollow cylinder (11), the spring base (9) is fixed to the ceramic shell (12), and the hollow cylinder (11), the ceramic shell (12) and the ceramic ring (13) are coaxial and concentric. One end of the ceramic rod (5) is fixed to the hollow cylinder (11), and the other end is connected to the ceramic sheet (6); The bearing (14) is used to support and drive the hollow cylinder (11); The arc of the metal pad (4) is consistent with the arc of the cross-section of the hollow cylinder (11); The spring (8) is in a natural state when initially packaged; The end of the optical fiber (1) always remains perpendicular to the reflective mirror surface (10) during the rotation of the hollow cylinder (11); the reflective mirror surface (10) is formed by grinding and polishing the metal pad (4), or by ion sputtering metal coating on the surface of the metal pad (4); The ceramic shell (12) has a cutout in the middle of the cylinder in a circumferential direction; The ceramic ring (13) is located in the groove of the ceramic shell (12) and is connected to the ceramic rod (5) at the intersection, and the groove surrounds the ceramic shell (12). The metal pad (4) is fixed to the top of the hollow cylinder (11), or the metal pad (4) is located above the outer side of the circumference of the hollow cylinder (11), and the base of the metal pad (4) is welded to the top of the ceramic shell (12); The optical fiber (1) and the reflective mirror (10) form a Fabry-Perot cavity, forming a Fabry-Perot optical fiber sensing unit. When the ceramic sheet (6) rotates along with the flow direction of the fluid, the hollow cylinder (11) is driven to rotate accordingly, further causing the distance between the end face of the optical fiber (1) and the reflective mirror (10), i.e., the cavity length of the Fabry-Perot cavity, to change accordingly.

2. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1, characterized in that: The optical fiber (1) is fixed to the top of the hollow cylinder (11) by means of an optical fiber fixing clamp (3); the angle between the optical fiber fixing clamp (3) and the axis of the hollow cylinder (11) and the inclination angle of the reflective mirror surface (10) are consistent, so that the end of the optical fiber (1) always remains perpendicular to the reflective mirror surface (10) during the rotation of the hollow cylinder (11); the initial position of the optical fiber (1) is located outside the circumference of the reflective mirror surface (10) on the upper surface of the hollow cylinder (11) and maintains a certain distance from the hollow cylinder (11).

3. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1 or 2, characterized in that: The optical fiber (1) and the reflective mirror (10) form a Fabry-Perot cavity, forming a Fabry-Perot optical fiber sensing unit. When the ceramic sheet (6) rotates along with the flow direction of the fluid, the hollow cylinder (11) is driven to rotate accordingly, further causing the distance between the end face of the optical fiber (1) and the reflective mirror (10), that is, the cavity length of the Fabry-Perot cavity, to change accordingly. The metal pad (4) is ion sputtered to form a metal film to form the reflective mirror (10).

4. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1 or 2, characterized in that: The metal pad (4) is fixed to the top of the hollow cylinder (11); the arc-shaped side length of the bottom surface of the metal pad (4) is 1 / 4 of the circumference of the hollow cylinder (11), and the width is 1 / 2 of the circumference of the hollow cylinder (11).

5. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1, characterized in that: The ceramic shell (12) has a cutout in the middle of the cylinder in the circumferential direction, the length of the cutout is 1 / 4 of the total circumference of the cross section of the ceramic shell (12), and the width of the cutout is equal to the diameter of the ceramic rod (5).

6. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1 or 5, characterized in that: The ceramic ring (13) is located in the groove of the ceramic shell (12) and is connected to the ceramic rod (5) at the intersection. The groove surrounds the ceramic shell (12) and the width of the ceramic ring (13) is greater than the width of the cutout.

7. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1, characterized in that: The ceramic sheet (6), the ceramic rod (5) and the ceramic ring (13) are a flow velocity sensing unit. The flow velocity sensing unit and the ceramic housing (12) seal the entire monitoring device, thereby protecting the optical fiber Fabry-Perot interferometer.

8. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1 or 2, characterized in that: The ceramic ring (13) slides freely in the groove as the ceramic sheet (6) rotates, and at the same time the hollow cylinder (11) slides on the bearing (14). The maximum rotation angle of the ceramic sheet (6) is 90°.

9. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1, characterized in that: The stiffness of the spring (8), the rotation radius of the ceramic sheet (6) and the angle between the metal pad (4) and the horizontal direction can be adjusted according to the required sensitivity.

10. The optical fiber sensor for monitoring the flow rate of pipeline fluid according to claim 1, characterized in that: The base of the metal pad (4) is welded to the top of the ceramic housing (12).

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