Resonance sensitization structure of distributed optical fiber vibration measurement system

Abstract

The utility model provides a distributed optical fiber vibration measurement system's resonance sensitization structure, including arc base, W-shaped vibration transmission support and vibration amplification platform, the arc base is installed on the pipeline surface and is used for providing the stable installation platform, the vibration amplification platform is connected to the top of W-shaped vibration transmission support, and the vibration amplification platform is connected to the vibration transmission support. The bottom is rigidly connected with the arc-shaped base; the vibration amplification platform is composed of a plurality of mutually spaced platforms, and the plurality of mutually spaced platforms are provided with optical fiber fixing grooves used for clamping sensing optical fibers. A mechanical resonance effect is generated through the W-shaped vibration transmission support and the multiple spaced platforms of the vibration amplification platform, the sensitivity of the distributed optical fiber sensor to low-frequency signals is remarkably improved, and the distributed optical fiber sensor is suitable for safety early warning of oil and gas pipelines.

Description

Technical Field

[0001] This utility model relates to the field of pipeline safety monitoring technology, specifically to a resonance enhancement structure for a distributed optical fiber vibration measurement system, used to improve the detection sensitivity of low-frequency vibration signals in pipelines. Background Technology

[0002] With the continuous rise in global energy demand, many energy-deficient countries need to purchase large quantities of energy from abroad, making pipeline transportation the only viable option. As a major artery of energy transport, pipelines often traverse complex environments and face numerous safety threats during long-term operation. These threats include damage from third-party construction activities such as mechanical excavation and drilling, which are the primary causes of pipeline accidents, accounting for over 30% of all pipeline accidents globally. Natural disasters such as landslides, earthquakes, and geological subsidence can also cause pipeline deformation or even fracture, leading to accidents. Furthermore, fluctuations in internal fluid pressure, the opening and closing of valves, and mechanical factors such as equipment vibration can cause cumulative damage to the pipeline structure, known as fatigue damage. These external disturbances often propagate through the pipe wall in the form of vibration waves, primarily in the 5Hz-2kHz range, with mechanical impact signals (80-300Hz) and leakage acoustic emission signals (above 1kHz) exhibiting typical characteristic frequencies. Traditional pipeline monitoring methods, such as piezoelectric accelerometers, utilize the positive piezoelectric effect of piezoelectric materials to convert external mechanical vibrations of the pipeline into electrical signals for vibration measurement. However, this method is suitable for high-frequency vibration detection, is susceptible to electromagnetic interference, and can only detect single points, making it unsuitable for real-time monitoring of long-distance pipeline transportation. Fiber Bragg sensors infer pipeline vibration by measuring strain changes on the pipeline surface. These sensors are resistant to electromagnetic interference, but their deployment is complex, requiring densely arranged sensor arrays, resulting in high costs. Therefore, traditional pipeline vibration measurement methods suffer from insufficient spatial coverage, poor environmental adaptability, high maintenance costs, limited sensitivity, and difficulty in meeting real-time monitoring requirements.

[0003] Distributed fiber optic vibration measurement systems, as a new generation of pipeline vibration detection technology, have become an important technical means for safety monitoring of oil and gas pipelines due to their significant advantages such as resistance to electromagnetic interference, corrosion resistance, and long-distance real-time detection. Among them, monitoring systems based on phase-sensitive optical time-domain reflectometry (OTDR) technology accurately detect the phase change of backscattered Rayleigh light by injecting highly coherent optical pulses into the sensing fiber, achieving real-time monitoring and precise location of pipeline vibrations with meter-level spatial resolution. In recent years, φ-OTDR systems have made significant breakthroughs in sensing mechanism research, signal demodulation algorithm optimization, and system performance improvement, extending their detection frequency range to 0.1Hz-10kHz, effectively identifying various typical vibration characteristics such as pipeline leaks and mechanical excavation. However, the system still faces significant challenges in low-frequency vibration detection. This is mainly because low-frequency vibration signals such as slow pipeline deformation and minor leaks are easily drowned out by internal system noise (such as laser frequency drift and coherent fading effects) and environmental interference (such as wind load and temperature changes), making signal extraction difficult. This technological bottleneck, to some extent, limits the in-depth application of distributed fiber optic sensing technology in pipeline lifecycle health monitoring, especially in scenarios requiring early warning of subtle abnormal vibrations. Utility Model Content

[0004] To address the aforementioned issues, this invention proposes a resonance-enhancing structure for a distributed fiber optic vibration measurement system. By generating a mechanical resonance effect through a W-shaped vibration transmission support and several mutually spaced platforms of the vibration amplification platform, the sensitivity of the distributed fiber optic sensor to low-frequency signals is significantly improved, making it suitable for safety early warning of oil and gas pipelines.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0006] A resonance-enhancing structure for a distributed optical fiber vibration measurement system includes an arc-shaped base, a W-shaped vibration transmission bracket, and a vibration amplification platform. The arc-shaped base is installed on the surface of a pipe to provide a stable mounting platform. The top of the W-shaped vibration transmission bracket is connected to the vibration amplification platform, and the bottom is rigidly connected to the arc-shaped base. The vibration amplification platform is composed of several mutually spaced platforms, and optical fiber fixing slots are provided on the mutually spaced platforms for clamping sensing optical fibers.

[0007] Furthermore, the arc-shaped base has an inner arc surface that fits against the outer wall of the pipe and is fixed with bolts or clips.

[0008] Furthermore, the W-shaped vibration transmission bracket is a bracket made of titanium alloy or carbon fiber composite material with high elastic modulus.

[0009] Furthermore, the optical fiber fixing groove is an S-shaped groove with a width matching the sensing optical fiber and includes a flexible silicone pad and a pressure plate for flexibly clamping the sensing optical fiber.

[0010] Furthermore, all of the spaced-apart platforms are square platforms.

[0011] Beneficial effects: This utility model uses a W-shaped vibration transmission bracket and several mutually spaced platforms of the vibration amplification platform to generate a mechanical resonance effect, which significantly improves the sensitivity of the distributed fiber optic sensor to low-frequency signals and is suitable for safety early warning of oil and gas pipelines. Attached Figure Description

[0012] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0013] Figure 1 This is a three-dimensional structural diagram of the resonance sensitization structure of the distributed optical fiber vibration measurement system described in this embodiment of the utility model;

[0014] Figure 2 This is a side view of the resonance sensitization structure of the distributed optical fiber vibration measurement system according to an embodiment of the present invention;

[0015] Figure 3 This is a top view of the resonance sensitization structure of the distributed optical fiber vibration measurement system described in this embodiment of the present invention;

[0016] Figure 4 The modal analysis results of the resonant sensitization enhancement structure of the distributed optical fiber vibration measurement system described in this embodiment of the present invention are shown in the figure.

[0017] Figure 5 This is a harmonic response analysis diagram of the resonant sensitization structure of the distributed optical fiber vibration measurement system described in this embodiment of the present invention. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] Example 1

[0021] See Figure 1-3A resonance-enhancing structure for a distributed optical fiber vibration measurement system includes an arc-shaped base 1, a W-shaped vibration transmission bracket 2, and a vibration amplification platform 3. The arc-shaped base 1 is installed on the surface of a pipe to provide a stable installation platform. The top of the W-shaped vibration transmission bracket 2 is connected to the vibration amplification platform 3, and the bottom is rigidly connected to the arc-shaped base 1. The vibration amplification platform 3 is composed of several mutually spaced platforms 301, and each of the mutually spaced platforms 301 is provided with an optical fiber fixing groove 302 for clamping the sensing optical fiber.

[0022] This embodiment utilizes a W-shaped vibration transmission support and several mutually spaced platforms of the vibration amplification platform to generate a mechanical resonance effect, significantly improving the sensitivity of the distributed fiber optic sensor to low-frequency signals, making it suitable for safety early warning of oil and gas pipelines.

[0023] In a specific example, the arc-shaped base 1 has an inner arc surface that fits against the outer wall of the pipe and is fixed by bolts or clips.

[0024] The arc-shaped base in this embodiment is the primary structure for installing the distributed fiber optic vibration measurement system. Its main function is to fix the entire system onto the pipeline requiring real-time monitoring. It provides a stable mounting platform, ensuring that the system's position does not change due to external vibration or impact during the monitoring process, thus ensuring the accuracy of the monitoring data. The fixing device for the arc-shaped base can be selected using bolts or clips depending on the characteristics of different pipelines. The material of the base is reasonably selected based on the pipeline installation environment and the frequency range of vibration to be measured; for example, stainless steel (corrosion resistant) or aluminum alloy (lightweight).

[0025] In a specific example, the W-shaped vibration transmission bracket 2 is a bracket made of titanium alloy or carbon fiber composite material with high elastic modulus.

[0026] The W-shaped vibration transmission bracket in this embodiment efficiently transmits the vibration generated by the pipeline to the optical fiber, reducing energy loss. When the pipeline under test vibrates due to internal or external factors, this W-shaped bracket effectively transmits the vibration to the sensing optical fiber, enabling the fiber to detect the vibration more effectively. Furthermore, the W-shaped design increases the rigidity of the structure while reducing vibration loss during transmission. The structure is typically made of elastic materials, such as high-elastic-modulus titanium alloys or carbon fiber composites, to enhance rigidity, thus ensuring effective vibration transmission to the optical fiber.

[0027] In a specific example, the optical fiber fixing groove 302 is an S-shaped groove with a width matching the sensing optical fiber and a built-in flexible silicone pad and pressure plate for flexibly clamping the sensing optical fiber.

[0028] The S-groove in this embodiment can extend the effective sensing length of the optical fiber, enhance the continuity and coverage density of long-distance monitoring, and prevent damage. Fixing the sensing optical fiber through the S-groove ensures its fixed position within the distributed optical fiber vibration measurement system. It allows the optical fiber to generate corresponding strain when subjected to vibration, thereby altering the characteristics of the light waves within the fiber. The structure incorporates a flexible silicone pad and a clamping plate to provide sufficient clamping force, preventing the optical fiber from slipping or loosening during vibration. It also provides protection against mechanical damage. The appropriate groove width should be selected based on the chosen optical fiber to prevent excessive clamping force from causing the optical fiber to become insensitive to vibrations in the pipeline, resulting in unnecessary losses.

[0029] In a specific example, the plurality of spaced-apart platforms 301 are all square platforms.

[0030] The main function of the square platform in this embodiment is to amplify vibrations. When vibrations are transmitted to the optical fiber through the W-shaped vibration transmission bracket, the platform can further amplify these vibrations, enabling the optical fiber to be more sensitive to changes in the external environment. At the same time, it also has a vibration damping function to reduce unnecessary vibration interference and improve the signal-to-noise ratio of the system.

[0031] Vibration amplification: 1. Form of steady-state solution:

[0032] Displacement response: X(t)=X0×sin(ωt-φ)

[0033] Amplitude formula:

[0034] Phase difference formula:

[0035] 2. Resonance condition: The total impedance Z of the system is determined by the inertial impedance (j ωm ), elastic resistance (k / j) ω It consists of (c) and damping impedance. When the vibration frequency ω of the pipe is equal to the natural frequency of the structure... At that time, the inertial term and the elastic term cancel each other out (j ωm +k / j ω =0), the system only exhibits damping impedance (Z) min =c), which causes the vibration velocity amplitude X0 = F0 / c to reach its peak value.

[0036] 3. Energy perspective: The work done by the external force W = πF0X0·sinφ. At resonance, φ = 90°, maximizing energy input. When the vibration effect occurs, the input energy is the maximum, the impedance is the minimum, and the vibration is amplified.

[0037] In the specific implementation and verification, it is necessary to calculate the natural frequencies of the resonant sensitizing structure used for distributed fiber optic vibration measurement: The model of the resonant sensitizing structure is imported into ANSYS, the material settings are selected as CR-PLA during simulation, the arc-shaped base is selected as fixed contact, modal analysis is performed after mesh generation, and the results are as follows: Figure 4 As shown:

[0038] Harmonic response analysis: The relationship between the vibration behavior of a vibrating system and the frequency of the external force when subjected to a periodic external force. If the frequency of the external force matches the natural frequency of the designed structure, the system will experience resonance. A fixed constraint is applied to the curved base of the structure. Simulating the vibration of a pipe, a force is generated on the curved base. Therefore, a force of 4 m / s² is applied to the fixed base. 2 The acceleration is obtained by frequency sweeping to get the vibration amplitude at the fiber fixation point, and then the amplitude is obtained by formula a. max =4π 2 f 2 A calculates the vibration amplitude of the base and obtains the amplification factor of the vibration at the optical fiber after the resonance effect occurs, as follows: Figure 5 As shown:

[0039] As can be seen from the natural frequency and the amplification factor of the vibration at the optical fiber obtained above, when the external vibration frequency matches the natural frequency of the designed structure, a resonance effect occurs, the vibration is significantly amplified, and the sensitivity of the distributed optical fiber vibration measurement system is improved, thus enabling more accurate detection and quantification of vibration events.

[0040] In practice, the size and dimensions of the resonant structure can be adjusted to match the frequency range of the pipe vibration we want to measure. The natural frequency can be estimated using the following formula: Where f is the natural frequency of the structure, k is the stiffness, and m is the mass. The formula shows that the natural frequency of a structure is directly proportional to its stiffness and inversely proportional to its mass. Therefore, we can increase stiffness by increasing stiffness or decreasing mass, and vice versa, to meet our needs for pipe vibration measurement. The stiffness of an object is proportional to the cube of its dimensions, while mass is usually proportional to its volume; for most materials, volume is proportional to the cube of its dimensions. Therefore, we can adjust the natural frequency by adjusting the dimensions of the structure. Increasing dimensions: Increasing the dimensions of a structure usually increases its mass and stiffness, but the increase in stiffness is usually more significant than the increase in mass, which may lead to a decrease in the natural frequency. Decreasing dimensions: Decreasing the dimensions usually decreases mass and stiffness, but the decrease in mass is usually more significant than the decrease in stiffness, which may lead to an increase in the natural frequency. Thus, by reasonably adjusting the structure, its dimensions, and materials, we can achieve our requirements.

[0041] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A resonance-enhanced structure for a distributed fiber-optic vibration measurement system, characterized by, The device includes an arc-shaped base (1), a W-shaped vibration transmission bracket (2), and a vibration amplification platform (3). The arc-shaped base (1) is installed on the surface of the pipe to provide a stable installation platform. The top of the W-shaped vibration transmission bracket (2) is connected to the vibration amplification platform (3), and the bottom is rigidly connected to the arc-shaped base (1). The vibration amplification platform (3) is composed of several mutually spaced platforms (301). The several mutually spaced platforms (301) are provided with fiber optic fixing slots (302) for clamping sensing fibers.

2. The resonance-enhanced structure of a distributed fiber vibration measurement system according to claim 1, characterized in that, The arc-shaped base (1) has an inner arc surface, which is in contact with the outer wall of the pipe and is fixed by bolts or clips.

3. The resonance-enhanced structure of a distributed fiber vibration measurement system according to claim 1, wherein, The W-shaped vibration transmission bracket (2) is a bracket made of titanium alloy or carbon fiber composite material with high elastic modulus.

4. The resonance-enhanced structure of a distributed fiber vibration measurement system according to claim 1, wherein, The fiber fixing groove (302) is an S-shaped groove. The width of the S-shaped groove matches the sensing fiber and has a built-in flexible silicone pad and a pressure plate for flexibly clamping the sensing fiber.

5. The resonance-enhanced structure of a distributed fiber vibration measurement system according to claim 1, wherein, The plurality of mutually spaced platforms (301) are all square platforms.

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