A distributed hydrogen sensor based on hydrogen-sensitive optical fiber

Abstract

The application belongs to the field of optical devices and sensing technology, and specifically provides a distributed hydrogen sensor based on hydrogen-sensitive optical fiber. The application synthesizes tungsten trioxide cross-linked platinum gold nanoparticles by a mixed heating method, utilizes the reversible chemical reaction between the substance and hydrogen, releases heat in the chemical reaction process, utilizes a distributed fiber temperature demodulator to detect the chemical reaction intensity of hydrogen and tungsten trioxide cross-linked platinum gold nanoparticles; the cross-linked tungsten trioxide and platinum gold make the substances participating in the reaction and the catalyst closely combined, improve the catalytic efficiency; different concentrations of hydrogen react with tungsten trioxide cross-linked platinum gold nanoparticles to release different amounts of heat, the Raman backscattering light of the distributed fiber temperature demodulator also changes, and the intensity ratio of anti-Stokes light and Stokes light also changes, so that the distributed hydrogen sensing can be realized, low-concentration hydrogen can be quickly and effectively detected, and the safety of the hydrogen application scene is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical devices and sensing technology, and relates to optical fiber sensing technology, and specifically provides a distributed hydrogen sensor based on hydrogen-sensitive optical fiber. BACKGROUND

[0002] In recent years, with the increasing prominence of energy and environmental problems, the global energy is seeking a low-carbon and low-pollution transformation path; according to statistics, more than thirty countries have issued hydrogen energy roadmaps and announced more than two hundred hydrogen energy investment plans, and are actively developing the hydrogen energy and fuel cell industry; hydrogen energy can not only meet the requirements of sustainable development, but also bring huge economic benefits; therefore, the detection of hydrogen concentration has great application demand. In traditional hydrogen sensing, an electrochemical method is usually used to detect hydrogen, but due to the characteristics of hydrogen itself, the potential electric spark risk of the electrochemical method cannot be avoided; using hydrogen-sensitive optical fiber to make a distributed hydrogen sensing system can eliminate the risk of electric spark, and can realize distributed, large-scale, high-sensitivity, fast response speed, high precision, and strong electromagnetic interference capability sensing.

[0003] Tungsten trioxide (WO3) is a typical wide-bandgap semiconductor metal oxide, which has the property of hydrogen-induced discoloration, and when WO3 has ohmic contact with noble metals, it has an exothermic effect when reacting with hydrogen; compared with other metal oxides, WO3 has the characteristics of high sensitivity and stable chemical properties, and is an ideal material for hydrogen sensing. At the same time, nano-WO3 particles have the characteristics of large surface-to-volume ratio, and can be more uniformly mixed with the coating material to improve the bonding quality. In addition, platinum acetylacetone (C 10 H 14 04Pt) is a yellow powder that is insoluble in water, and is decomposed into platinum (Pt) and acetylacetone after high-temperature treatment; platinum has good optical constants in hydrogen and has a strong adsorption effect on hydrogen, and can also provide the initial activation energy for the reaction of tungsten trioxide and hydrogen, promoting the exothermic reaction of hydrogen and WO3; platinum acetylacetone can be uniformly mixed with tungsten trioxide by dissolving in ethanol first and then mixing and heating, thereby improving the catalytic efficiency.

[0004] At present, among many hydrogen sensors, the optical fiber hydrogen sensor has the advantages of good bendability, anti-electromagnetic interference, light weight, small volume, corrosion resistance, and can realize distributed sensing. In the existing optical fiber hydrogen sensor, the hydrogen sensitive materials mainly used are divided into two types: palladium alloy and tungsten trioxide. The combination form of hydrogen sensitive material and optical fiber is mainly divided into two types: one is to add hydrogen sensitive material into the cladding layer of optical fiber, which can improve the sensitivity, but will bring higher transmission loss, and it is difficult to realize long-distance distributed sensing; the second is to set the hydrogen sensitive material in the form of film or sleeve outside the cladding layer of optical fiber, which has the problems of poor mechanical strength, large consumption of hydrogen sensitive material and high cost, which greatly limits its distributed application. SUMMARY

[0005] In view of the problems existing in the prior art, the purpose of the present application is to provide a distributed optical fiber hydrogen sensor based on hydrogen sensitive optical fiber, tungsten trioxide cross-linked platinum gold nanoparticles are synthesized by a mixed heating method, a reversible chemical reaction occurs between the substance and hydrogen, heat is released during the chemical reaction process, and a distributed optical fiber temperature demodulator is used to detect the combination strength of hydrogen and tungsten trioxide cross-linked platinum gold nanoparticles; cross-linked tungsten trioxide and platinum gold make the reacting substances and catalysts closely combined, and the catalytic efficiency is improved; different concentrations of hydrogen react with tungsten trioxide cross-linked platinum gold nanoparticles to release different amounts of heat, and the Raman backscattered light of the distributed optical fiber temperature demodulator also changes, and the intensity ratio of anti-Stokes light to Stokes light also changes, so that the distributed hydrogen sensing can be realized, and low-concentration hydrogen can be quickly and effectively detected, and the safety of the hydrogen application scene is improved.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A distributed hydrogen sensor based on hydrogen sensitive optical fiber, which is composed of a distributed optical fiber temperature demodulator based on Raman-OTDR (1), a hydrogen sensitive optical fiber (2) and a computer (3); characterized in that:

[0008] The hydrogen sensitive optical fiber is composed of an optical fiber and a coating layer on the outer surface of the optical fiber, and the coating layer is composed of an acrylate polymer and tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt).

[0009] Further, the mass percentage of tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt) in the coating layer is 10% to 90%.

[0010] Further, the thickness of the coating layer is 10nm to 200μm.

[0011] Further, the tungsten trioxide cross-linked platinum gold nanoparticles have a size of 100 nm to 1 micron, and the molar ratio of tungsten trioxide to platinum gold is 100:1 to 100:20.

[0012] Further, the hydrogen-sensitive optical fiber has a length of at least 1 m.

[0013] Further, the distributed optical fiber temperature demodulator injects narrow-band light pulses into the hydrogen-sensitive optical fiber, the hydrogen-sensitive optical fiber generates backscattering signals, which are received by the distributed optical fiber temperature demodulator and connected to a computer for data processing to obtain measurement results.

[0014] The working principle of the present application is that the distributed optical fiber temperature demodulator (1) emits probe light through the hydrogen-sensitive optical fiber (2), and the intensity ratio of backscattering anti-Stokes signals and Stokes signals at different position points on the hydrogen-sensitive optical fiber (2) changes with the temperature of the position points, so that the concentration of hydrogen can be sensed by the intensity ratio change of the anti-Stokes signals and the Stokes signals; the tungsten trioxide cross-linked platinum gold nanoparticles in the coating layer of the hydrogen-sensitive optical fiber (2) have a reversible chemical reaction with hydrogen, releasing a large amount of heat, and the platinum gold acts as a positive catalyst for the reversible reaction.

[0015] The present application has the following advantages: a distributed hydrogen sensor based on a hydrogen-sensitive optical fiber is proposed, which uses tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt) as a hydrogen-sensitive material, and innovatively proposes a new loading form of the hydrogen-sensitive material on the optical fiber, which is a coating layer composed of an acrylate polymer and tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt). The selection of nanoparticles as the loading form of the sensitive material can ensure the flexibility of the sensor and reduce the cost of the sensor. At the same time, the mixing of the sensitive material nanoparticles and the coating material for protecting the grating and the solidification on the grating not only ensure good adhesion and improve mechanical strength, but also ensure low cost and flexibility, and avoid large transmission loss. The mass percentage of tungsten trioxide cross-linked platinum gold nanoparticles mixed with the coating material changes with the change of the application scenario. When the demand for sensing sensitivity is high, the mass ratio of tungsten trioxide cross-linked platinum gold nanoparticles can reach 90%, which is attached to the grating in the form of a solid sleeve. When the requirement for sensing sensitivity is low and the requirement for flexibility is high, the mass percentage of tungsten trioxide cross-linked platinum gold nanoparticles can be reduced to 10%, and the influence of the small amount of hydrogen-sensitive material on the flexibility of the grating itself is relatively small.

[0016] In summary, the distributed hydrogen sensor based on the hydrogen-sensitive optical fiber provided by the application can realize distributed high-sensitivity hydrogen detection while ensuring mechanical strength and flexibility; and the distributed hydrogen sensor can be wrapped around by bending and be suitable for complex environments, thereby improving the usability of the distributed hydrogen sensor and providing a simple, reliable and practical method for distributed hydrogen detection. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A test system diagram of the distributed hydrogen sensor based on the hydrogen-sensitive optical fiber in the application.

[0018] Figure 2 An end face structure diagram of the hydrogen-sensitive optical fiber in the application. DETAILED DESCRIPTION

[0019] To make the purpose, technical scheme and beneficial effects of the application clearer, further detailed description of the application is made below in combination with the drawings and examples.

[0020] The embodiment provides a test system of a distributed optical fiber hydrogen sensor based on a hydrogen-sensitive optical fiber, which has the structure as shown in the figure. Figure 1 The test system specifically comprises a distributed optical fiber temperature demodulator based on Raman-OTDR (1), a hydrogen-sensitive optical fiber (2), a computer (3), a mixed gas chamber (4), a reaction gas chamber (5), a gas pump (6) and a hydrogen cylinder (7); the mixed gas chamber (4) is provided with a mixed gas inlet hole (8) and a mixed gas outlet hole (9), the reaction gas chamber (5) is provided with a reaction gas inlet hole (10), a reaction gas outlet hole (11), an optical fiber outlet (12) and an optical fiber inlet (13), the reaction gas inlet hole (10) of the reaction gas chamber (5) is connected with the mixed gas outlet hole (9) of the mixed gas chamber (4), the reaction gas outlet hole (11) is placed in air, and the mixed gas inlet hole (8) of the mixed gas chamber (4) is connected with the hydrogen cylinder (7) and the gas pump (6); one end of the hydrogen-sensitive optical fiber (2) is connected with the distributed optical fiber temperature demodulator based on Raman-OTDR (1), and the other end enters the reaction gas chamber (5) from the optical fiber outlet (12) and then leaves from the optical fiber inlet (13), that is, the optical fiber passes through the reaction gas chamber (5); the distributed optical fiber temperature demodulator based on Raman-OTDR (1) is used for receiving and processing optical signals and is connected with the computer (3) for further data processing.

[0021] Further, in the above test system, the Raman-OTDR based distributed optical fiber temperature demodulator (1), the hydrogen sensitive optical fiber (2) and the computer (3) constitute a distributed optical fiber hydrogen sensor based on the hydrogen sensitive optical fiber; in the test process, a predetermined flow of gas is introduced into the mixed gas chamber (4) through the hydrogen cylinder (7) and the air pump (6), the predetermined hydrogen concentration of the measured gas in the mixed gas chamber (4) is input into the reaction gas chamber (5), and the hydrogen concentration measurement is completed by the distributed optical fiber hydrogen sensor.

[0022] Further, the structure of the hydrogen sensitive optical fiber is as shown in Figure 2 The hydrogen sensitive optical fiber is composed of an optical fiber and a coating layer on the outer surface of the optical fiber, and the coating layer is composed of an acrylate polymer and tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt). The mass percentage of tungsten trioxide cross-linked platinum gold nanoparticles (WO3+Pt) in the coating layer is 10% to 90%. The tungsten trioxide cross-linked platinum gold nanoparticles are prepared by mixing and heating tungsten trioxide nanoparticles and platinum acetylacetone.

[0023] In terms of working principle: the ultra-narrow linewidth laser inside the Raman-OTDR based distributed optical fiber temperature demodulator injects narrow-band optical pulses into the hydrogen sensitive optical fiber with a length of L, at this time the backward scattering signals of the Stokes signal φ s and the anti-Stokes signal φ a are respectively:

[0024]

[0025]

[0026] Wherein, l represents the position variable with the light source as the starting point, K s and K s respectively represent the cross-section coefficients of the Stokes signal and the anti-Stokes signal, Δv, κ, T respectively represent the Raman shift, the Boltzmann constant and the absolute temperature, α s , α a , α respectively represent the attenuation coefficients of the Stokes signal, the anti-Stokes signal and the incident signal, υ s represents the frequency of the Raman Stokes signal, h represents the Planck constant, and Φ0 represents the intensity of the incident signal.

[0027] When hydrogen sensitive optical fiber appears hydrogen along the line at any position, the tungsten trioxide crosslinked platinum gold nanoparticles in the coating layer reacts with hydrogen, releases a large amount of heat, makes the temperature of the hydrogen sensitive optical fiber at the position change, the corresponding relative position of the anti-stokes signal and the stokes signal intensity ratio will change, the intensity ratio change information demodulated by the distributed optical fiber temperature demodulator of Raman-OTDR quantitatively reflects the temperature change of the measured environment, realizes the hydrogen concentration sensing; at the same time, the Raman-OTDR itself can detect the temperature distribution of all positions along the optical fiber line, can expand the local hydrogen sensing to distributed hydrogen sensing, and can measure the corresponding hydrogen concentration at any position of the hydrogen sensitive optical fiber.

[0028] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A distributed hydrogen sensor based on a hydrogen-sensitive optical fiber, comprising a Raman-OTDR-based distributed optical fiber temperature demodulator (1), a hydrogen-sensitive optical fiber (2), and a computer (3); characterized in that: The hydrogen-sensitive optical fiber consists of an optical fiber and a coating on its outer surface. The coating is composed of an acrylate polymer and tungsten trioxide crosslinked platinum nanoparticles.

2. The distributed hydrogen sensor based on hydrogen-sensitive optical fiber as described in claim 1, characterized in that, The tungsten trioxide cross-linked platinum nanoparticles account for 10% to 90% of the mass of the coating.

3. The distributed hydrogen sensor based on hydrogen-sensitive optical fiber as described in claim 1, characterized in that, The thickness of the coating is 10nm~200μm.

4. The distributed hydrogen sensor based on hydrogen-sensitive optical fiber as described in claim 1, characterized in that, The size of the tungsten trioxide crosslinked platinum nanoparticles ranges from 100 nm to 1 μm, with the molar ratio of tungsten trioxide to platinum being 100:1 to 100:

20.

5. The distributed hydrogen sensor based on hydrogen-sensitive optical fiber as described in claim 1, characterized in that, The length of the hydrogen-sensitive optical fiber is at least 1m.

6. The distributed hydrogen sensor based on hydrogen-sensitive optical fiber as described in claim 1, characterized in that, The distributed fiber optic temperature demodulator injects narrowband optical pulses into the hydrogen-sensitive fiber. The hydrogen-sensitive fiber generates backscattered signals, which are received by the distributed fiber optic temperature demodulator and connected to a computer for data processing to obtain measurement results.

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