Hydrogen sensor for monitoring hydrogen leakage

Abstract

The utility model relates to a hydrogen sensor for monitoring hydrogen leakage, which is applied to the technical field of hydrogen monitoring and comprises a laser light source, a first optical switch, N optical fibers, N sensing units, a second optical switch, a signal receiving unit and a signal processing unit, the first optical switch is used for transmitting the laser to the target optical fiber when the first optical switch is switched to the target optical fiber; the target optical fiber is used for transmitting the laser to the target sensing unit; the target sensing unit is used for irradiating laser onto leaked hydrogen to generate a Raman scattering signal; the second optical switch is used for transmitting a Raman scattering signal to the signal receiving unit when the second optical switch is switched to the target sensing unit; the signal receiving unit is used for dividing the Raman scattering signals into two beams, filtering out Raman scattering signals of hydrogen molecules and nitrogen molecules, and converting the Raman scattering signals into a first electric signal and a second electric signal; the signal processing unit is used for determining the hydrogen concentration according to the first electric signal and the second electric signal and judging whether hydrogen leakage exists or not. And multi-point monitoring of hydrogen leakage can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogen monitoring, and in particular to a hydrogen sensor for monitoring hydrogen leakage. Background Art

[0002] As a clean energy, hydrogen energy is known as the most promising secondary energy in the 21st century. Hydrogen energy has many excellent characteristics such as wide sources, non-toxicity and pollution-free, and countries around the world have begun to pay attention to the development of hydrogen energy. While the hydrogen energy industry chain is gradually improving and the market scale is growing rapidly, hydrogen is prone to leakage, fire, and explosion accidents due to its unstable nature during production, storage, transportation, and utilization, and the safety risks are prominent.

[0003] In related technologies, hydrogen leakage can be detected by electrochemical and electrical methods. However, these two methods are difficult to meet the requirements of non-contact, large-scale, long-distance, stable and reliable in detection scenarios such as hydrogen refueling stations, hydrogen storage tanks, and hydrogen pipelines. They require the deployment of a large number of sensors, which is costly. In addition, they use many active devices and are not suitable for flammable and explosive places, which can easily cause safety hazards. Utility Model Content

[0004] In order to solve the above technical problems, the present application provides a hydrogen sensor for monitoring hydrogen leakage.

[0005] According to one aspect of the present application, a hydrogen sensor for monitoring hydrogen leakage is provided, comprising: a laser light source, a first optical switch, N optical fibers, N sensing units arranged at different positions, a second optical switch, a signal receiving unit and a signal processing unit; N is a positive integer;

[0006] The N optical fibers are all connected to the first optical switch, each optical fiber is connected to a sensor unit, and the N sensor units are all connected to the second optical switch;

[0007] The laser light source is used to emit laser light;

[0008] The first optical switch is used to transmit the laser to the target optical fiber when switching to the target optical fiber among the N optical fibers; wherein the sensing unit connected to the target optical fiber is the target sensing unit located at the position to be measured;

[0009] The target optical fiber is used to transmit the laser to the target sensing unit;

[0010] The target sensing unit is used to irradiate the leaked hydrogen with laser light to generate a Raman scattering signal;

[0011] The second optical switch is used to transmit the Raman scattering signal to the signal receiving unit when switching to the target sensing unit;

[0012] The signal receiving unit is configured to split the Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal, filter out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal, and convert the Raman scattering signal of hydrogen molecules into a first electrical signal; filter out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal, and convert the Raman scattering signal of nitrogen molecules into a second electrical signal;

[0013] The signal processing unit is configured to determine the hydrogen concentration at the position to be measured according to the intensities of the first electrical signal and the second electrical signal, and determine whether there is a hydrogen leak at the position to be measured according to the hydrogen concentration.

[0014] Optionally, each sensing unit includes: a first coupler, a longitudinal focusing lens, a transverse focusing lens, a second coupler, and a laser collection cylinder;

[0015] Wherein, the first coupler, the longitudinal focusing lens, and the laser collection cylinder are sequentially distributed on the optical path of the laser, and the transverse focusing lens and the second coupler are distributed in the vertical direction of the laser optical path between the longitudinal focusing lens and the laser collection cylinder;

[0016] The longitudinal focusing lens is configured to focus the laser output by the first coupler so that the focused laser irradiates the leaked hydrogen to generate a Raman scattering signal;

[0017] The laser collection cylinder is configured to collect noise signals;

[0018] The transverse focusing lens is configured to focus the Raman scattering signal and transmit it to the second optical switch through the second coupler.

[0019] Optionally, the signal receiving unit includes: a coupler, a collimating lens, a beam splitter, a hydrogen narrowband filter, a first focusing lens, a first detector, a nitrogen narrowband filter, a second focusing lens, and a second detector;

[0020] Wherein, the coupler, the collimating lens, the beam splitter, the hydrogen narrowband filter, the first focusing lens, and the first detector are sequentially distributed on the optical path of the Raman scattering signal, and the nitrogen narrowband filter, the second focusing lens, and the second detector are sequentially distributed on the transverse optical path passing through the beam splitter;

[0021] The collimating lens is configured to collimate the Raman scattering signal output by the coupler;

[0022] The beam splitter is configured to split the collimated Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal;

[0023] A hydrogen narrowband filter for filtering out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal;

[0024] A first focusing lens for focusing the Raman scattering signal of hydrogen molecules;

[0025] A first detector for converting the collected Raman scattering signal of hydrogen molecules into a first electrical signal;

[0026] A nitrogen narrowband filter for filtering out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal;

[0027] A second focusing lens for focusing the Raman scattering signal of nitrogen molecules;

[0028] A second detector for converting the collected Raman scattering signal of nitrogen molecules into a second electrical signal.

[0029] Optionally, the central wavelength of the hydrogen narrowband filter is 416.06 nm, and the half bandwidth is less than 0.6 nm;

[0030] The central wavelength of the nitrogen narrowband filter is 386.85 nm, and the half bandwidth is less than 1.1 nm.

[0031] Optionally, both the first detector and the second detector are photomultiplier tubes.

[0032] The technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0033] By using Raman laser spectroscopy technology to measure the concentration of hydrogen, the monitoring site can work for a long time without power supply, realizing safe and reliable remote monitoring of gas concentration. The design of multiple sensing channels by combining two optical switches enables the sensing units in multiple channels to monitor hydrogen leakage, achieving the purpose of monitoring hydrogen leakage over a large range and at multiple points. Description of the Drawings

[0034] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0036] Figure 1This is a schematic structural diagram of a hydrogen sensor in an embodiment of the present application;

[0037] Figure 2 This is another schematic structural diagram of a hydrogen sensor in an embodiment of the present application. Detailed implementation manners

[0038] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present application, the solution of the present application will be further described below. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0039] Many specific details are set forth in the following description in order to fully understand the present application, but the present application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present application, rather than all the embodiments.

[0040] Hydrogen has no absorption band in the near-ultraviolet to near-infrared region, making it impossible to detect hydrogen by traditional optical methods such as absorption laser-induced fluorescence, differential absorption lidar, and Fourier transform infrared spectroscopy. However, hydrogen has a strong Raman effect. When a gas is irradiated by a laser, photons collide with gas molecules to produce elastic scattering (no energy change) and inelastic scattering (energy change). Most photons undergo elastic scattering (Rayleigh scattering, Mie scattering, etc.), and the scattered photons have the same frequency and wavelength as the incident light photons. A small portion of photons are scattered at a frequency different from the original frequency of the incident photons. The Raman-scattered photons have a frequency shift relative to the incident light photons. The energy absorption of the molecule causes Stokes scattering, and the energy loss of the molecule produces anti-Stokes scattering. Therefore, Raman scattering includes Stokes scattering and anti-Stokes scattering.

[0041] Under normal circumstances, the Stokes scattering effect is much stronger than the anti-Stokes scattering effect, so Stokes scattering is commonly used to represent Raman scattering. The difference Δv between the scattered spectral line generated by Raman scattering and the incident light frequency is called the Raman shift. For the same substance molecule, although the change in the incident light frequency will change the Raman scattering frequency, it will not change the Raman shift Δv. Different substance molecules have different vibration and rotation energy levels, and the Raman shift is only related to the vibration and rotation energy levels of the substance molecule, making each substance molecule have a specific Raman shift. Therefore, the displacement and intensity of the Raman signal can be used to qualitatively and quantitatively analyze gas molecules respectively.

[0042] Based on this, the embodiments of the present application provide a hydrogen sensor for monitoring hydrogen leakage. The Raman laser spectroscopy technology is used to measure the concentration of hydrogen, and the presence and intensity of the Raman scattering signal are used to qualitatively and quantitatively detect the concentration of hydrogen. The higher the hydrogen concentration, the stronger the Raman scattering signal. Compared with the electrochemical method and the electrical method, this method is safer, more stable and reliable. Moreover, a combined optical switch is used for the design of multiple sensing channels, realizing multi-point monitoring of hydrogen leakage in the optical method.

[0043] See Figure 1 , Figure 1 which is a schematic structural diagram of the hydrogen sensor in the embodiments of the present application, including: a laser light source 101, a first optical switch 102, N optical fibers 103, N sensing units 104 arranged at different positions, a second optical switch 105, a signal receiving unit 106 and a signal processing unit 107; N is a positive integer; wherein, the N optical fibers are all connected to the first optical switch 102, each optical fiber is connected to a sensing unit, and the N sensing units are all connected to the second optical switch 105.

[0044] Assume that the sensing unit at the position to be measured is the target sensing unit, and the optical fiber connected to the target sensing unit is the target optical fiber. By switching the first optical switch 102 to the target optical fiber and the second optical switch 105 to the target sensing unit, the measurement of the hydrogen concentration at the position to be measured can be realized.

[0045] Specifically as follows:

[0046] The laser light source 101 is used to emit laser light. For example, the laser light source 101 can be a Nd:YAG laser, emitting pulsed laser light with a wavelength of 354.7 nm.

[0047] The first optical switch 102 is used to transmit the laser to the target optical fiber when switched to the target optical fiber among the N optical fibers; wherein, the sensing unit connected to the target optical fiber is the target sensing unit located at the position to be measured.

[0048] The target optical fiber 103 is used to transmit the laser to the target sensing unit 104.

[0049] The target sensing unit 104 is used to irradiate the leaked hydrogen with the laser to generate a Raman scattering signal.

[0050] In the case of hydrogen leakage at the position to be measured, hydrogen diffuses into the target sensing unit. The laser irradiates the leaked hydrogen and collides with hydrogen molecules to generate a Raman scattering signal.

[0051] The second optical switch 105 is used to transmit the Raman scattering signal to the signal receiving unit when switched to the target sensing unit.

[0052] The signal receiving unit 106 is configured to split the Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal, filter out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal, and convert the Raman scattering signal of hydrogen molecules into a first electrical signal; filter out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal, and convert the Raman scattering signal of nitrogen molecules into a second electrical signal.

[0053] In the embodiments of the present application, the concentration of hydrogen is qualitatively and quantitatively detected by the presence and intensity of the Raman scattering signal. The higher the hydrogen concentration, the stronger its Raman scattering signal. Therefore, the Raman scattering signal can be split into a first Raman scattering signal and a second Raman scattering signal, and the intensity of the Raman scattering signal of nitrogen, which is relatively stable in the atmosphere, is used as a reference value. The Raman scattering signal intensities of hydrogen and nitrogen at the position to be measured are obtained through the following lidar equation (1).

[0054]

[0055] Wherein, S(r) refers to the intensity of the Raman scattering signal of the gas detected by the detector; η is the photon efficiency of the detector; P0 is the power of the laser light source; K is the optical efficiency of the Raman scattering signal receiving device; N is the loss of the Raman scattering signal in the light beam transmission (including connection loss, microbend loss, etc.); Y(r) is the overlap function of the laser emitted by the light source and the light signal receiving field of view; A is the area of the Raman scattering signal receiving surface; r is the distance from the beam focus point to the focusing lens in the sensing unit; D is the density of the gas to be measured; σ is the Raman scattering cross section; c is the speed of light; τ is the pulse width of the laser; α L is the extinction coefficient of the laser; α R is the extinction coefficient of the Raman scattered light.

[0056] The signal processing unit 107 is configured to determine the hydrogen concentration at the position to be measured according to the intensities of the first electrical signal and the second electrical signal, and determine whether there is a hydrogen leak at the position to be measured according to the hydrogen concentration.

[0057] In the case of the near field, the product of the extinction coefficient of the Raman scattered light of hydrogen and nitrogen and r is almost equal to 0. Therefore, the transmittance T(r) can be set to 1. Based on formula (1), the ratio S H (r) / S N (r) is:

[0058]

[0059] Where C is a constant. When the concentration of the leaked hydrogen is relatively low (for example, the concentration of hydrogen is lower than 80% of the nitrogen concentration), the nitrogen concentration N N in the air can be regarded as a fixed value of 78%. When the concentration of the leaked hydrogen is relatively high, the nitrogen concentration NN will be diluted and will no longer be 78%. Therefore, when the concentration of hydrogen is less than 80% of the concentration of nitrogen, the concentration N of hydrogen H can be determined according to S H (r) / S N (r).

[0060] And so on. When the two optical switches are simultaneously switched to channel 2, the sensing unit in channel 2 starts to work. The Raman scattering signal is collected by the signal receiving unit and divided into two paths, and finally sent to detector 1 and detector 2 respectively to be converted into electrical signals. By analyzing the intensity of the signals, the concentration of hydrogen in channel 2 can be obtained, and then it can be determined whether there is a hydrogen leak.

[0061] See Figure 2 , Figure 2 which is another schematic structural diagram of the hydrogen sensor for monitoring hydrogen leakage in the embodiment of the present application. Among them, each sensing unit includes: a first coupler, a longitudinal focusing lens, a transverse focusing lens, a second coupler, and a laser collection cylinder. Among them, the first coupler, the longitudinal focusing lens, and the laser collection cylinder are distributed in sequence on the optical path of the laser. The Raman scattering signal of gas molecules is collected at 90° relative to the laser direction. Therefore, the transverse focusing lens and the second coupler are distributed in the vertical direction of the laser optical path between the longitudinal focusing lens and the laser collection cylinder.

[0062] The longitudinal focusing lens is used to focus the laser output by the first coupler so that the focused laser irradiates the leaked hydrogen to generate a Raman scattering signal;

[0063] The laser collection cylinder is used to collect noise signals to prevent the laser from being reflected multiple times on the optical path.

[0064] The transverse focusing lens is used to focus the Raman scattering signal and transmit it to the second optical switch through the second coupler. The Raman scattering signal forms a laser focus at the second coupler through the transverse focusing lens, which is convenient for collecting the Raman scattering signal.

[0065] The signal receiving unit includes: a coupler, a collimating lens, a wavelength division plate, a hydrogen narrowband filter, a first focusing lens, a first detector, a nitrogen narrowband filter, a second focusing lens, and a second detector. Among them, the coupler, the collimating lens, the wavelength division plate, the hydrogen narrowband filter, the first focusing lens, and the first detector are distributed in sequence on the optical path of the Raman scattering signal, and the nitrogen narrowband filter, the second focusing lens, and the second detector are distributed in sequence on the transverse optical path passing through the wavelength division plate.

[0066] The collimating lens is used to collimate the Raman scattering signal output by the coupler;

[0067] A wavelength division multiplexer is used to split the collimated Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal. One path is used to measure the concentration of hydrogen, and the other path is used to measure the concentration of nitrogen. Each path passes through a narrowband filter and a focusing lens, which are used to filter out the Raman scattering signals of hydrogen and nitrogen gas molecules and form a laser focus at the coupler for easy collection.

[0068] A hydrogen narrowband filter is used to filter out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal. The hydrogen narrowband filter filters out the direct reflection light signal of the laser light source, the Rayleigh scattering light signal, and the Raman scattering light signals of irrelevant gas molecules to the greatest extent, and only allows the Raman scattering signal of a specific wavelength to pass through, thereby filtering out the Raman scattering signal of hydrogen molecules. The Raman scattering wavelength of hydrogen molecules is 416.1 nm. Optionally, the central wavelength of the hydrogen narrowband filter is 416.06 nm, and the half bandwidth is less than 0.6 nm.

[0069] A first focusing lens is used to focus the Raman scattering signal of hydrogen molecules;

[0070] A first detector is used to convert the collected Raman scattering signal of hydrogen molecules into a first electrical signal;

[0071] A nitrogen narrowband filter is used to filter out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal. The nitrogen narrowband filter filters out the direct reflection light signal of the laser light source, the Rayleigh scattering light signal, and the Raman scattering light signals of irrelevant gas molecules to the greatest extent, and only allows the Raman scattering signal of a specific wavelength to pass through, thereby filtering out the Raman scattering signal of nitrogen molecules. The Raman scattering wavelength of nitrogen molecules is 386.7 nm. Optionally, the central wavelength of the nitrogen narrowband filter is 386.85 nm, and the half bandwidth is less than 1.1 nm.

[0072] A second focusing lens is used to focus the Raman scattering signal of nitrogen molecules;

[0073] A second detector is used to convert the collected Raman scattering signal of nitrogen molecules into a second electrical signal.

[0074] After the Raman scattering signal of gas molecules passes through the filtering device, although its signal-to-noise ratio has been greatly improved, since the Raman scattering signal itself is still very weak, it is still difficult to effectively collect the signal with ordinary signal acquisition devices. The photomultiplier tube has higher sensitivity and can collect the weak Raman scattering signal, convert it into an electrical signal and amplify it. Optionally, a high-gain photomultiplier tube can be used for detection, that is, both the first detector and the second detector are photomultiplier tubes to improve the detection accuracy.

[0075] Finally, by monitoring the intensity changes of two electrical signals, the change in the hydrogen concentration in the air can be obtained, achieving the purpose of monitoring hydrogen leakage.

[0076] The hydrogen sensor according to the embodiment of the present application uses Raman laser spectroscopy technology to measure the hydrogen concentration, enabling long-term operation without power supply at the monitoring site and realizing safe and reliable remote monitoring of gas concentration. The design of multiple sensing channels using a combined optical switch enables the sensing units in multiple channels to monitor hydrogen leakage, achieving the purpose of large-scale multi-point monitoring of hydrogen leakage.

[0077] It should be noted that in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0078] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments described herein, but rather will conform to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hydrogen sensor for monitoring hydrogen leakage, characterized in that, Including: A laser light source, a first optical switch, N optical fibers, N sensing units arranged at different positions, a second optical switch, a signal receiving unit, and a signal processing unit; N is a positive integer; Wherein, the N optical fibers are all connected to the first optical switch, each optical fiber is connected to a sensing unit, and the N sensing units are all connected to the second optical switch; The laser light source is used to emit laser light; The first optical switch is used to transmit the laser light to the target optical fiber when switching to the target optical fiber among the N optical fibers; wherein, the sensing unit connected to the target optical fiber is the target sensing unit located at the position to be measured; The target optical fiber is used to transmit the laser light to the target sensing unit; The target sensing unit is used to irradiate the leaked hydrogen with the laser light to generate a Raman scattering signal; The second optical switch is used to transmit the Raman scattering signal to the signal receiving unit when switching to the target sensing unit; The signal receiving unit is used to split the Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal, filter out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal, and convert the Raman scattering signal of hydrogen molecules into a first electrical signal; filter out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal, and convert the Raman scattering signal of nitrogen molecules into a second electrical signal; The signal processing unit is used to determine the hydrogen concentration at the position to be measured according to the intensities of the first electrical signal and the second electrical signal, and judge whether there is hydrogen leakage at the position to be measured according to the hydrogen concentration.

2. The hydrogen sensor according to claim 1, wherein Each sensing unit includes: a first coupler, a longitudinal focusing lens, a transverse focusing lens, a second coupler, and a laser collection cylinder; Wherein, the first coupler, the longitudinal focusing lens, and the laser collection cylinder are sequentially distributed on the optical path of the laser light, and the transverse focusing lens and the second coupler are distributed in the vertical direction of the laser optical path between the longitudinal focusing lens and the laser collection cylinder; The longitudinal focusing lens is used to focus the laser light output by the first coupler so that the focused laser light irradiates the leaked hydrogen to generate a Raman scattering signal; The laser collection cylinder is used to collect noise signals; The transverse focusing lens is used to focus the Raman scattering signal and transmit it to the second optical switch through the second coupler.

3. The hydrogen sensor according to claim 1, characterized in that, The signal receiving unit includes: a coupler, a collimating lens, a beam splitter, a hydrogen narrowband filter, a first focusing lens, a first detector, a nitrogen narrowband filter, a second focusing lens, and a second detector; Wherein, the coupler, the collimating lens, the beam splitter, the hydrogen narrowband filter, the first focusing lens, and the first detector are sequentially distributed on the optical path of the Raman scattering signal, and the nitrogen narrowband filter, the second focusing lens, and the second detector are sequentially distributed on the transverse optical path passing through the beam splitter; The collimating lens is used to collimate the Raman scattering signal output by the coupler; The beam splitter is configured to split the collimated Raman scattering signal into a first Raman scattering signal and a second Raman scattering signal; The hydrogen narrowband filter is configured to filter out the Raman scattering signal of hydrogen molecules from the first Raman scattering signal; The first focusing lens is configured to focus the Raman scattering signal of hydrogen molecules; The first detector is configured to convert the collected Raman scattering signal of hydrogen molecules into a first electrical signal; The nitrogen narrowband filter is configured to filter out the Raman scattering signal of nitrogen molecules from the second Raman scattering signal; The second focusing lens is configured to focus the Raman scattering signal of nitrogen molecules; The second detector is configured to convert the collected Raman scattering signal of nitrogen molecules into a second electrical signal.

4. The hydrogen sensor according to claim 3, characterized in that, The central wavelength of the hydrogen narrowband filter is 416.06 nm, and the half bandwidth is less than 0.6 nm; The central wavelength of the nitrogen narrowband filter is 386.85 nm, and the half bandwidth is less than 1.1 nm.

5. The hydrogen sensor according to claim 3, wherein Both the first detector and the second detector are photomultiplier tubes.

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