A multi-channel laser hydrogen sensor system for hydrogen transmission pipelines

Abstract

The present invention relates to a multi-channel laser hydrogen sensor system for hydrogen pipelines, which includes a host, a micro-nano fiber sensing probe, and a connecting optical cable. The host includes a power conversion unit, a laser control and signal processing circuit, a distributed feedback (DFB) laser, an erbium-doped fiber amplifier module EDFA, an optical switch and data control circuit, an optical switch, a wavelength division multiplexer (WDM), and an optical fiber connector. Multiple micro-nano fiber sensing probes can be connected in the system of the present invention. The probes are respectively installed at the joints of the hydrogen pipelines and are connected to the host through the connecting optical cable. The micro-nano fiber sensing probe detects the hydrogen concentration based on the stimulated Raman scattering effect of light, and the system realizes time division multiplexing by switching different probes through the optical switch. The present invention will achieve multi-point remote leakage monitoring of hydrogen pipelines, with high sensitivity and fast response speed.

Description

Technical Field

[0001] The present invention relates to a hydrogen sensor system, and particularly to a multi-channel laser hydrogen sensor system for hydrogen transmission pipelines. Background Art

[0002] Regarding the industrial application of hydrogen energy, safety in the links of hydrogen production, storage, transportation, and hydrogen refueling stations has become increasingly important, especially in preventing the leakage risk of long-distance hydrogen transmission pipelines. In terms of hydrogen leakage detection, there are not many hydrogen sensors industrialized as mature products at home and abroad, and most of them cannot meet the actual use requirements in terms of indicators. Fundamentally, from the technical principle, they are basically divided into catalytic combustion type, electro-chemical type, metal oxide type, optical fiber type, etc. Among them, the optical fiber hydrogen sensor mainly coats a hydrogen-sensitive material (such as metal palladium or palladium alloy) thin film on various optical fiber sensing structures, and changes the properties of light through the physical and chemical reactions between the hydrogen-sensitive material and hydrogen to achieve hydrogen detection. The above-mentioned hydrogen sensors cannot simultaneously take into account the characteristics of intrinsic safety, gas selectivity, detection sensitivity, response speed, service life, etc., and face difficulties in practical applications. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art, provide a multi-channel laser hydrogen sensor system for hydrogen transmission pipelines, realize remote multi-point leakage detection at the joints of hydrogen transmission pipelines, and at the same time improve the detection sensitivity and response speed. Moreover, the sensing probe is passive, and the transmitted signal is light instead of electricity, ensuring the intrinsic safety of the device. In principle, it is determined that the sensing probe is only sensitive to hydrogen and can be used for a long time.

[0004] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0005] A multi-channel laser hydrogen sensor system for hydrogen transmission pipelines includes a host, N micro-nano optical fiber sensing probes, and a connecting optical cable. The host includes a laser control and signal processing circuit, a first distributed feedback laser, a second distributed feedback laser, an erbium-doped fiber amplifier module EDFA, an optical switch and data control circuit, a first optical switch, a second optical switch, a dense wavelength division multiplexer DWDM, a coarse wavelength division multiplexer CWDM, and an optical fiber connector; the first optical switch and the second optical switch are 1×N voltage-controlled optical switches;

[0006] The i-th branch end of the first optical switch is connected to the input end of the i-th micro-nano optical fiber sensing probe, and the output end of the i-th micro-nano optical fiber sensing probe is connected to the i-th branch end of the second optical switch, where i = 1, 2,..., N; the optical switch and data control circuit simultaneously control the i-th branch end of the first optical switch and the second optical switch to be connected to the current loop according to the channel switching instruction of the laser control and signal processing circuit;

[0007] The laser control and signal processing circuit controls the first distributed feedback laser to generate pump light, and controls the second distributed feedback laser to generate probe light. The pump light is amplified by the erbium-doped fiber amplifier module (EDFA) and then enters the dense wavelength division multiplexer (DWDM) together with the probe light. After the light is combined, it enters the common end of the first optical switch, and enters the i-th micro-nano fiber sensing probe through the i-th splitting end under the control of the optical switch and the data control circuit. The return light of the i-th micro-nano fiber sensing probe is connected to the i-th splitting end of the second optical switch, and is output from the common end of the second optical switch to the coarse wavelength division multiplexer (CWDM) under the control of the optical switch and the data control circuit. The CWDM filters out the return light and inputs it to the laser control and signal processing circuit. The laser control and signal processing circuit performs signal processing and demodulation on the return light, calculates the hydrogen concentration data at the position of the corresponding micro-nano fiber sensing probe according to the demodulation result, and sends it to the optical switch and the data control circuit. The optical switch and the data control circuit package the hydrogen concentration data into data packets and send them out according to the communication protocol.

[0008] Preferably, it further includes a power conversion unit, which converts 220V alternating current into +12V, +5V and -5V direct current, and supplies power to the erbium-doped fiber amplifier module (EDFA), the laser control and signal processing circuit, and the optical switch and data control circuit respectively.

[0009] Preferably, the laser control and signal processing circuit uses a single-chip microcomputer and an FPGA as the control core, and communicates with the optical switch and data control circuit through the RS232 interface.

[0010] Preferably, the laser control and signal processing circuit outputs a control signal according to the set modulation parameters to drive the first distributed feedback laser to emit pump light and drive the second distributed feedback laser to emit probe light. The wavelength of the pump light is modulated by the superposition of a low-frequency sawtooth wave signal and a high-frequency sine wave signal, and the wavelength of the probe light is fixed and not dynamically modulated; at the end of the sawtooth wave period, the laser control and signal processing circuit sends a channel switching instruction to the optical switch and data control circuit.

[0011] Preferably, each sawtooth wave period corresponds to a channel, each channel is connected to a micro-nano fiber sensing probe, and switches to the next channel at the end of the sawtooth wave period. After the N-th channel ends, it switches to the first channel, and so on in a cycle.

[0012] Preferably, the laser control and signal processing circuit detects the return light signal, converts it into an electrical signal, obtains a digital signal after filtering and analog-to-digital conversion, calculates the hydrogen concentration data after demodulation, and sends it to the optical switch and data control circuit.

[0013] Preferably, the erbium-doped fiber amplifier module (EDFA) amplifies the input pump light power to 500mW and then outputs it.

[0014] Preferably, the optical switch and data control circuit use a single-chip microcomputer as the control core, communicate with the laser control and signal processing circuit through the RS232 interface, and communicate with the upper device through the RS485 interface.

[0015] Preferably, after receiving the hydrogen concentration data sent by the laser control and signal processing circuit, the optical switch and data control circuit extract the valid data therefrom, calculate the CRC check code, and package it into a data packet according to the communication protocol and send it to the upper device.

[0016] Preferably, the micro-nano fiber sensing probe is composed of a micro-nano fiber and a packaging structure. The micro-nano fiber is obtained by tapering an ordinary single-mode fiber. The packaging structure is made by 3D printing technology. The packaging structure is in the shape of a long box, which is divided into a bottom shell and a top cover. Three windows are respectively opened on the bottom surface and the top surface for air intake, and the outer surface is covered with a waterproof and breathable film to prevent dust and water vapor from entering.

[0017] Preferably, the connecting optical cable connects the host and the micro-nano fiber sensing probe. The form of the optical cable is a single multi-core optical cable or multiple double-core optical cables; the connecting optical cable is connected to the female head of the host optical fiber connector after fusing the male head of the optical fiber connector, and the female head of the optical fiber connector is installed on the side wall of the host and is fused to the splitting ends of the first optical switch and the second optical switch inside the host.

[0018] Preferably, the micro-nano fiber sensing probe is placed at the connection of the hydrogen transmission pipeline, and one micro-nano fiber sensing probe is placed at each connection.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] (1) The laser hydrogen sensor system of the present invention is based on the stimulated Raman scattering effect of light, without heating or chemical reaction, with high detection sensitivity and fast response speed.

[0021] (2) The multi-channel sensor system of the present invention can connect multiple sensing probes with a single host, which is beneficial to reducing costs in large-scale applications.

[0022] (3) The micro-nano fiber sensing probe of the present invention is passive, uses optical signals to sense and transmit information, and the intrinsically safe characteristic is beneficial to the monitoring of hydrogen, an inflammable and explosive gas.

[0023] (4) The present invention can place the host in the monitoring center computer room, connect the remote sensing probe through the optical cable, and the data processing and data transmission methods of the host are simple, which is convenient for communication with the upper device or debugging device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The multi-channel laser hydrogen sensor system for hydrogen transmission pipeline of the present invention;

[0025] Figure 2 This is the flowchart of the laser control and signal processing circuit of the present invention;

[0026] Figure 3 This is the flowchart of the optical switch and data control circuit of the present invention. Specific embodiments

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The following illustrative description of the present invention is for the convenience of those skilled in the art to understand the present invention, but it should be clear that the present invention is not limited to the scope of the specific embodiments.

[0028] As Figure 1 shown, the present invention provides a multi-channel laser hydrogen sensor system for hydrogen transmission pipelines, including: a host 1, a micro-nano fiber sensing probe, and a connecting optical cable 3. The host mainly includes a power conversion unit, a laser control and signal processing circuit, a first distributed feedback (DFB) laser, a second distributed feedback (DFB) laser, an erbium-doped fiber amplifier (EDFA) module, an optical switch and data control circuit, a first optical switch, a second optical switch, a wavelength division multiplexer (DWDM, CWDM), and an optical fiber connector 2. The i-th branch end of the first optical switch is connected to the input end of the i-th micro-nano fiber sensing probe, and the output end of the i-th micro-nano fiber sensing probe is connected to the i-th branch end of the second optical switch, where i = 1, 2,..., N; the optical switch and data control circuit simultaneously controls the i-th branch ends of the first optical switch and the second optical switch to be connected to the current loop according to the channel switching instruction of the laser control and signal processing circuit. Figure 1 Among them, the thin dashed arrow line is for electrical connection to transmit electrical signals, the thin solid arrow line is for optical path connection to transmit optical signals, and the thick arrow line is for the power supply line. Under the control of the laser control and signal processing circuit, the two DFB lasers respectively emit pump light and probe light. The pump light passes through the EDFA and then enters the DWDM together with the probe light. After the light is combined, it is connected to the common end of the first optical switch. Under the control of the optical switch and data control circuit, it respectively enters N micro-nano fiber sensing probes through the branch ends. The return light is respectively connected to the branch ends of the second optical switch and is respectively output from the common end under the control of the optical switch and data control circuit. The probe light is filtered out by the CWDM and input to the laser control and signal processing circuit for signal demodulation. The final result is packaged into a data packet by the optical switch and data control circuit according to the communication protocol and sent out.

[0029] The power conversion unit converts 220V alternating current into +12V, +5V, and -5V direct current to supply power to the EDFA module, the laser control and signal processing circuit, and the optical switch and data control circuit respectively.

[0030] The laser control and signal processing circuit uses a single-chip microcomputer and an FPGA as the control core, and communicates with the optical switch and data control circuit through the RS232 interface. This circuit outputs control signals according to the set modulation parameters to drive two DFB lasers to emit pump light and probe light respectively. The wavelength of the pump light is modulated by the superposition of a low-frequency sawtooth wave signal and a high-frequency sine wave signal, while the wavelength of the probe light is fixed and not dynamically modulated. At the end of the sawtooth wave cycle, a channel switching instruction is sent to the optical switch and data control circuit. This circuit detects the returned optical signal, converts it into an electrical signal, and obtains a digital signal after filtering and analog-to-digital conversion. The signal is demodulated using a demodulation algorithm, and the hydrogen concentration data is inverted and sent to the optical switch and data control circuit.

[0031] The EDFA module inputs pump light, amplifies its power to 500 mW and then outputs it. The optical switch is a 1×N voltage-controlled optical switch, and the common end is connected to which branch end is determined by voltage setting. The two optical switches are located at the optical output end and the optical input end of the host respectively.

[0032] The optical switch and data control circuit uses a single-chip microcomputer as the control core, communicates with the laser control and signal processing circuit through the RS232 interface, and communicates with the upper-level device through the RS485 interface. The optical switch and data control circuit receives the channel switching instruction sent by the laser control and signal processing circuit and simultaneously controls the two optical switches to switch to the corresponding channels, so that the corresponding sensing probes are connected to the system loop. The optical switch and data control circuit receives the concentration data sent by the laser control and signal processing circuit, extracts the valid data, calculates the CRC check code, and packs it into a data packet according to the communication protocol and sends it to the upper-level device.

[0033] The channel switching method is that each sawtooth wave cycle of the modulation signal corresponds to a channel, each channel is connected to a sensing probe, and it switches to the next channel at the end of the sawtooth wave cycle. After the Nth channel ends, it switches to the first channel, and so on in a cycle.

[0034] The wavelength division multiplexer is divided into DWDM and CWDM. The DWDM input ends are respectively connected to the pump light and the probe light, and the output end is connected to the first optical switch and finally input to the sensing probe. The light output by the sensing probe is connected to the CWDM input end after passing through the second optical switch, and the probe light is output from the corresponding wavelength channel.

[0035] The micro-nano fiber sensing probe is composed of a micro-nano fiber and a packaging structure. The micro-nano fiber is obtained by tapering an ordinary single-mode fiber, and the packaging structure is made using 3D printing technology. The packaging structure is in the shape of a long box and is divided into a bottom shell and a top cover. Three large-area windows (with an area of 7.2 cm 2 ) are respectively opened on the bottom surface and the top surface for air intake, and the outer surface is covered with a waterproof and breathable film to prevent dust and moisture from entering.

[0036] The connecting optical cable connects the system host and the micro-nano fiber sensing probe. The form of the optical cable can be a single multi-core optical cable or multiple dual-core optical cables. The male fiber optic connector of the connecting optical cable is fused to the host connection end, and the female fiber optic connector is installed on the side wall of the host and fused to the splitting ends of the first optical switch and the second optical switch inside the host.

[0037] Specifically, the detection light wavelength is set to 1620.86 nm, and the pump light wavelength performs wavelength scanning centered on 1532.82 nm under the action of the modulation signal, so that the frequency difference between the two beams of light sweeps across the S0(0) hydrogen rotational Raman transition line. The two optical switches are respectively installed on the front and back of the optical switch and data control circuit, and the optical switch and data control circuit are connected to the laser control and signal processing circuit using signal lines. The diameter of the waist region of the micro-nano fiber in the micro-nano fiber sensing probe is controlled within 750 nm ± 10 nm.

[0038] As Figure 2 shown, the laser control and signal processing circuit of the present invention includes a single-chip microcomputer, an FPGA, and an optical detection module. The working process steps are as follows:

[0039] (1) Read the system parameter information stored in the single-chip microcomputer, including the temperature control parameters, modulation parameters, and demodulation parameters of the first distributed feedback laser and the second distributed feedback laser. The modulation parameters and some demodulation parameters need to be sent to the FPGA;

[0040] (2) The FPGA generates a modulation signal, which is converted into a control signal through DAC digital-to-analog conversion to drive the first distributed feedback laser and the second distributed feedback laser. The FPGA also generates a reference signal at the same time;

[0041] (3) The optical detection module converts the optical signal from the second optical switch into an electrical signal, which is converted into a digital signal through ADC and input into the FPGA for signal processing and demodulation;

[0042] (4) The FPGA sends the demodulation result to the single-chip microcomputer. The single-chip microcomputer judges whether the sawtooth wave period ends. If so, it sends a channel switching instruction to the optical switch and data control circuit, otherwise it returns to step (3);

[0043] (5) After sending the channel switching instruction, the single-chip microcomputer performs concentration data inversion on the demodulation result, and after completion, sends the concentration data to the optical switch and data control circuit;

[0044] (6) Repeat steps (2)-(5).

[0045] As Figure 3 shown, the working process steps of the optical switch and data control circuit of the present invention are as follows:

[0046] (1) System initialization, waiting for the end of the current channel cycle;

[0047] (2) If a channel switching instruction and concentration data are received, set the channel flag to 1 and the data number to 01, align the channel and data and enter the control loop; otherwise, continue to wait.

[0048] (3) If a reset instruction is received in the control loop, return to step (1).

[0049] (4) When a channel switching instruction is received, increment the channel flag by 1 and increment the data number by 1.

[0050] (5) If the channel flag is equal to N + 1, reset the channel flag and the data number and then execute step (6); otherwise, directly execute step (6).

[0051] (6) When concentration data is received, extract the valid data, calculate the CRC check code, and pack and send the data to the upper-layer device according to the communication protocol.

[0052] (7) Repeat steps (3)-(6).

[0053] Specifically, N = 4, the optical switch is a 1×4 voltage-controlled optical switch, and the connection of the common end to which branch end is determined by voltage setting. The two optical switches are respectively located at the optical output end and the optical input end of the host.

[0054] Multiple micro-nano fiber sensing probes can be connected in the system of the present invention. The probes are respectively installed at the joints of the hydrogen transmission pipeline and are connected to the host through connecting optical cables. The micro-nano fiber sensing probe detects the hydrogen concentration based on the stimulated Raman scattering effect of light. The system realizes time-division multiplexing by switching different probes through the optical switch. The present invention will realize multi-point remote leakage monitoring of the hydrogen transmission pipeline, with high sensitivity and fast response speed.

[0055] The above is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

[0056] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline, characterized in that: It includes a host, N micro-nano fiber sensing probes, and connecting optical cables. The host includes a laser control and signal processing circuit, a first distributed feedback laser, a second distributed feedback laser, an erbium-doped fiber amplifier module EDFA, an optical switch and data control circuit, a first optical switch, a second optical switch, a dense wavelength division multiplexer DWDM, a coarse wavelength division multiplexer CWDM, and an optical fiber connector. The first optical switch and the second optical switch are 1×N voltage-controlled optical switches. The i-th branching end of the first optical switch is connected to the input end of the i-th micro-nano fiber sensing probe, and the output end of the i-th micro-nano fiber sensing probe is connected to the i-th branching end of the second optical switch, where i = 1, 2,..., N. The optical switch and data control circuit simultaneously control the i-th branching ends of the first optical switch and the second optical switch to be connected to the current loop according to the channel switching instruction of the laser control and signal processing circuit. The laser control and signal processing circuit controls the first distributed feedback laser to generate pump light and controls the second distributed feedback laser to generate probe light. The pump light is amplified by the erbium-doped fiber amplifier module EDFA and then enters the dense wavelength division multiplexer DWDM together with the probe light. After optical beam combination, it enters the common end of the first optical switch and enters the i-th micro-nano fiber sensing probe through the i-th branching end under the control of the optical switch and data control circuit. The return light of the i-th micro-nano fiber sensing probe is connected to the i-th branching end of the second optical switch and is output from the common end of the second optical switch to the coarse wavelength division multiplexer CWDM under the control of the optical switch and data control circuit. The coarse wavelength division multiplexer CWDM filters out the return light and inputs it to the laser control and signal processing circuit. The laser control and signal processing circuit performs signal processing and demodulation on the return light, calculates the hydrogen concentration data at the position of the corresponding micro-nano fiber sensing probe according to the demodulation result, and sends it to the optical switch and data control circuit. The optical switch and data control circuit packs the hydrogen concentration data into a data packet according to the communication protocol and sends it out. The wavelength of the pump light is modulated by the superposition of a low-frequency sawtooth signal and a high-frequency sine wave signal, and the wavelength of the probe light is fixed without dynamic modulation. At the end of the sawtooth wave period, the laser control and signal processing circuit sends a channel switching instruction to the optical switch and data control circuit. Each sawtooth wave period corresponds to a channel, and each channel is connected to a micro-nano fiber sensing probe. At the end of the sawtooth wave period, it switches to the next channel. After the N-th channel ends, it switches to the first channel, and so on in a cycle. The micro-nano fiber sensing probe is composed of a micro-nano fiber and a packaging structure. The micro-nano fiber is obtained by tapering a common single-mode fiber, and the packaging structure is made by 3D printing technology. The packaging structure is in the shape of a long box, divided into a bottom shell and a top cover. Three windows are respectively opened on the bottom surface and the top surface for air intake, and the outer surface is covered with a waterproof and breathable film to prevent dust and moisture from entering.

2. The multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: It also includes a power conversion unit, which converts 220V alternating current into +12V, +5V, and -5V direct current to supply power to the erbium-doped fiber amplifier module EDFA, the laser control and signal processing circuit, and the optical switch and data control circuit respectively.

3. The multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: The laser control and signal processing circuit uses a single-chip microcomputer and an FPGA as the control core, and communicates with the optical switch and data control circuit through the RS232 interface.

4. A multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: The laser control and signal processing circuit outputs control signals according to the set modulation parameters to drive the first distributed feedback laser to emit pump light and drive the second distributed feedback laser to emit probe light.

5. The multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: The laser control and signal processing circuit detects the returned optical signal, converts it into an electrical signal, obtains a digital signal after filtering and analog-to-digital conversion, calculates the hydrogen concentration data after demodulation, and sends it to the optical switch and data control circuit.

6. The multi-channel laser hydrogen gas sensor system for a hydrogen pipeline according to claim 1, characterized in that: The erbium-doped fiber amplifier module EDFA amplifies the input pump optical power to 500 mW and then outputs it.

7. A multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: The optical switch and data control circuit uses a single-chip microcomputer as the control core, communicates with the laser control and signal processing circuit through the RS232 interface, and communicates with the upper-level device through the RS485 interface.

8. A multi-channel laser hydrogen sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: After receiving the hydrogen concentration data sent by the laser control and signal processing circuit, the optical switch and data control circuit extracts the valid data therefrom, calculates the CRC check code, and packs it into a data packet according to the communication protocol and sends it to the upper-level device.

9. The multi-channel laser hydrogen sensor system for a hydrogen pipeline according to claim 1, characterized in that: The connecting optical cable connects the host and the micro-nano fiber sensing probe. The form of the optical cable is a single multi-core optical cable or multiple double-core optical cables; the connecting optical cable is fused with the male head of the fiber optic connector and then connected to the female head of the host fiber optic connector. The female head of the fiber optic connector is installed on the side wall of the host and is fused with the splitting ends of the first optical switch and the second optical switch inside the host.

10. A multi-channel laser hydrogen gas sensor system for a hydrogen transmission pipeline according to claim 1, characterized in that: The micro-nano fiber sensing probe is placed at the hydrogen pipeline connection, and one micro-nano fiber sensing probe is placed at each connection.

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