Double-parameter synchronous detection system and method for temperature and hydrogen concentration

Abstract

The invention discloses a temperature and hydrogen concentration dual-parameter synchronous detection system and method, and the system comprises an ASE broadband light source, the output of the ASE broadband light source is divided into two paths through a coupler, one path enters a first circulator, the other path enters a second circulator, the output of the first circulator enters a first FBG sensor, the output of the second circulator enters a second FBG sensor, and the output of the first FBG sensor enters a second FBG sensor. The two FBG sensors are arranged in the gas chamber, the first FBG sensor and the second FBG sensor are provided with FBG topological optical fiber structures with different working wavelengths and have temperature sensitivity and gas selective response, and reflected signals of the two FBG sensors are coupled to one path through the dual-channel wavelength division multiplexer and are sent to the spectrum analyzer for wavelength demodulation. The temperature sensitivity and the gas selective response are integrated in the same sensing unit by utilizing the wavelength coding characteristic of the fiber bragg grating, so that precise decoupling and real-time output of double parameters are realized, and the detection efficiency and the data consistency are improved.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensor technology, and relates to a dual-parameter synchronous detection system and method for temperature and hydrogen concentration. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, energy storage power stations, and consumer electronics due to their advantages such as high energy density, high voltage platform, and low environmental pollution. However, the presence of flammable electrolytes and electrode materials inside lithium-ion batteries makes them prone to fires under abusive conditions. These accidents are mainly caused by thermal runaway, a violent electrochemical heat-generating reaction typically accompanied by significant heat generation, gas production, combustion, and even explosion. Therefore, monitoring thermal runaway phenomena such as heat and gas production can provide early warning of battery safety conditions, preventing serious accidents.

[0003] Battery thermal runaway is typically triggered by exothermic reactions within the battery, leading to a rapid rise in temperature. Therefore, temperature is a key indicator of battery thermal runaway. Among the gaseous products of battery thermal runaway, hydrogen is a hallmark gas in the early stages of thermal runaway. Its formation is closely related to electrolyte decomposition and SEI film rupture, and it can directly reflect the severity of internal side reactions. Therefore, dual-parameter detection of temperature and hydrogen is beneficial for early warning of battery thermal runaway and for a more comprehensive and accurate understanding of the specific stages of battery thermal runaway.

[0004] Patent CN 115377540 A discloses a multi-feature detection device for thermal runaway of lithium batteries based on fiber Bragg gratings. The device includes a miniature Bragg grating fiber assembly, a laser beam splitter, a multifunctional fiber, a laser emitter, and a fiber optic signal processor. The miniature Bragg grating fiber assembly is spirally arranged between the positive electrode and the separator or between the negative electrode and the separator, with the modulation beam splitting glass layer at a 45° angle to the fiber core. While this multi-feature detection device can detect multiple features, it cannot simultaneously measure multiple parameters, resulting in low detection efficiency and poor data consistency. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-parameter synchronous detection system and method for temperature and hydrogen concentration. It constructs an FBG topology fiber structure with different operating wavelengths and employs a space-division multiplexing method to achieve synchronous detection of temperature and hydrogen concentration during the thermal runaway of lithium-ion batteries. Utilizing the wavelength encoding characteristics of fiber optic gratings, temperature sensitivity and gas selectivity response are integrated into the same sensing unit. High-speed demodulation technology achieves precise decoupling and real-time output of the two parameters, significantly improving detection efficiency and data consistency.

[0006] The technical solution to achieve the purpose of this invention is as follows: A dual-parameter synchronous detection system for temperature and hydrogen concentration includes an ASE broadband light source. The output of the ASE broadband light source is split into two paths via a coupler: one path enters a first circulator, and the other path enters a second circulator. The first and second circulators are three-port circulators. The output of the first circulator enters a first FBG sensor, and the output of the second circulator enters a second FBG sensor. The first and second FBG sensors are disposed in a gas chamber. The first and second FBG sensors are configured with FBG topology fiber structures with different operating wavelengths, exhibiting temperature sensitivity and gas selectivity. The reflected signals from the first and second FBG sensors are coupled to one path via a dual-channel wavelength division multiplexer and sent to a spectrometer for wavelength demodulation.

[0007] In a preferred embodiment, the second FBG sensor is surrounded by a porous stainless steel protective sleeve with a pore size of 1-3 μm.

[0008] In a preferred embodiment, the stainless steel protective sleeve is treated with PTFE for hydrophobicity.

[0009] In a preferred embodiment, the gas chamber is an aluminum alloy gas chamber, the gas chamber is provided with a gas path, and the gas path is equipped with a three-way solenoid valve to realize the switching of measurement, calibration, and nitrogen purging modes.

[0010] In a preferred embodiment, the grating structure parameters of the first FBG sensor and the second FBG sensor are obtained through simulation, including: A three-dimensional simulation model with dual FBG was established based on multiphysics simulation software. The parameters of the first FBG sensor of standard single-mode fiber were optimized by changing the grating period and refractive index modulation depth, and the effect on the reflection spectrum of 1550nm band was analyzed to finally determine its temperature sensitivity. For the second FBG sensor, based on the 1530nm band design, an additional multiphysics coupling model of the palladium film layer was established to analyze the strain transfer efficiency of palladium films of different thicknesses during hydrogen adsorption and calculate its impact on grating wavelength drift.

[0011] In a preferred embodiment, the method for fabricating the grating structure of the first FBG sensor and the second FBG sensor includes: A KrF excimer laser is used to write gratings on hydrogen-loaded optical fibers using a phase mask; the first FBG sensor is first written at a predetermined position using a precision displacement stage, and then the second FBG sensor is written after moving a certain distance. After the inscription is completed, the sample is placed in a programmable annealing furnace to eliminate residual stress; To enable hydrogen-sensitive functionalization of the second FBG sensor, a high-vacuum magnetron sputtering system was used to deposit a palladium film on its surface. During the sputtering process, substrate rotation and low-temperature cooling were used to ensure the uniformity of the film layer. Finally, a porous stainless steel protective sleeve was fabricated in the area of ​​the second FBG sensor using laser micromachining.

[0012] This invention also discloses a method for constructing a dual-parameter simultaneous detection system for temperature and hydrogen concentration, comprising the following steps: Simulation of FBG grating structure parameters; FBG grating fabrication and functionalization; A detection system is constructed, comprising an ASE broadband light source. The output of the ASE broadband light source is split into two paths via a coupler: one path enters a first circulator, and the other path enters a second circulator. The first and second circulators are three-port circulators. The output of the first circulator enters a first FBG sensor, and the output of the second circulator enters a second FBG sensor. The first and second FBG sensors are disposed in a gas chamber and are configured with FBG topology fiber structures with different operating wavelengths, exhibiting temperature sensitivity and gas selectivity. The reflected signals from the first and second FBG sensors are coupled to one path via a dual-channel wavelength division multiplexer and sent to a spectrometer for wavelength demodulation.

[0013] This invention further discloses a method for simultaneous detection of two parameters, temperature and hydrogen concentration, applied to the aforementioned simultaneous detection system for two parameters, comprising the following steps: The spectrometer demodulates the wavelength of the obtained reflection signal and extracts the wavelength of the first FBG sensor using a peak detection algorithm. Second FBG sensor wavelength The real-time wavelength value; Calculate the difference from the center wavelength:

[0014] in, The center wavelength of the first FBG sensor. The center wavelength of the second FBG sensor, Δ and Δ This indicates wavelength shift caused by changes in temperature and hydrogen gas. Establish the coupling matrix:

[0015] Based on the calibration coefficient matrix Temperature and hydrogen concentration are decoupled in real time using the least squares method:

[0016] in, K T1 , K H1 , K T2 , K H2 These represent the sensitivity coefficients of the first FBG sensor and the second FBG sensor when performing single-temperature and hydrogen detection, respectively; ΔT is the temperature change, Δ This represents the change in hydrogen concentration.

[0017] Compared with the prior art, the significant advantages of this invention are: This invention leverages the simple and compact structure of a Bragg fiber grating (FBG) that allows for multiplexing, employing spatial division multiplexing technology to simultaneously detect two parameters—temperature and hydrogen concentration—during the thermal runaway of lithium-ion batteries. Furthermore, to avoid the stress effects of battery deformation, the sensing grating structure is thermally conductive and breathable encapsulated, improving detection accuracy.

[0018] The grating structure of FBG was simulated, and FBG topology fiber structures with different working wavelengths were constructed. By utilizing the wavelength encoding characteristics of fiber optic gratings, temperature sensitivity and gas selectivity response were integrated into the same sensing unit. High-speed demodulation technology was used to achieve accurate decoupling and real-time output of the two parameters, which significantly improved detection efficiency and data consistency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a dual-parameter synchronous detection system for temperature and hydrogen concentration. Detailed Implementation

[0020] The principle of this invention is as follows: the grating structure of FBG is simulated, FBG topology fiber structures with different working wavelengths are constructed, and the temperature sensitivity and gas selectivity response are integrated into the same sensing unit by utilizing the wavelength encoding characteristics of fiber optic gratings. Through high-speed demodulation technology, the precise decoupling and real-time output of the two parameters are achieved, which significantly improves the detection efficiency and data consistency.

[0021] Example: like Figure 1As shown, a dual-parameter synchronous detection system for temperature and hydrogen concentration includes an ASE broadband light source 1. The output of the ASE broadband light source 1 is split into two paths via a coupler 2. One path enters a first circulator 3, and the other path enters a second circulator 4. The first circulator 3 and the second circulator 4 are three-port circulators. The output of the first circulator 3 enters a first FBG sensor 7, and the output of the second circulator 4 enters a second FBG sensor 8. The first FBG sensor 7 and the second FBG sensor 8 are disposed in a gas chamber 10. The first FBG sensor 7 and the second FBG sensor 8 are configured with FBG topology fiber structures with different operating wavelengths, exhibiting temperature sensitivity and gas selectivity response. The reflected signals from the first FBG sensor 7 and the second FBG sensor 8 are coupled to one path via a dual-channel wavelength division multiplexer 5 and sent to a spectrometer 6 for wavelength demodulation.

[0022] The ASE broadband light source 1 (power 20mW±0.5dB) serves as the illumination source, and its flattened spectral characteristics (fluctuation <1dB) ensure balanced detection of the dual FBG reflectance spectrum.

[0023] Coupler 2 is a fiber optic coupler that splits the input light into two paths at a specific ratio. Common splitting ratios include 50:50 or 90:10.

[0024] Preferably, the second FBG sensor 8 is surrounded by a porous stainless steel protective sleeve 9 with a pore size of 1-3 μm.

[0025] Preferably, the stainless steel protective sleeve is treated with PTFE for hydrophobicity.

[0026] Preferably, the gas chamber 10 is an aluminum alloy gas chamber, and the gas chamber is equipped with a gas path. The gas path is equipped with a three-way solenoid valve to realize the switching of measurement, calibration and nitrogen purging modes.

[0027] In a preferred embodiment, the grating structure parameters of the first FBG sensor and the second FBG sensor are obtained through simulation, including: A three-dimensional simulation model with dual FBG was established based on multiphysics simulation software. The parameters of the first FBG sensor of standard single-mode fiber were optimized by changing the grating period and refractive index modulation depth, and the effect on the reflection spectrum of 1550nm band was analyzed to finally determine its temperature sensitivity. For the second FBG sensor, based on the 1530nm band design, an additional multiphysics coupling model of the palladium film layer was established to analyze the strain transfer efficiency of palladium films of different thicknesses during hydrogen adsorption and calculate its impact on grating wavelength drift.

[0028] In a preferred embodiment, the method for fabricating the grating structures of the first FBG sensor and the second FBG sensor includes: A KrF excimer laser is used to write gratings on hydrogen-loaded optical fibers using a phase mask; the first FBG sensor is first written at a predetermined position using a precision displacement stage, and then the second FBG sensor is written after moving a certain distance. After the inscription is completed, the sample is placed in a programmable annealing furnace to eliminate residual stress; To enable hydrogen-sensitive functionalization of the second FBG sensor, a high-vacuum magnetron sputtering system was used to deposit a palladium film on its surface. During the sputtering process, substrate rotation and low-temperature cooling were used to ensure the uniformity of the film layer. Finally, a porous stainless steel protective sleeve was fabricated in the area of ​​the second FBG sensor using laser micromachining.

[0029] Another embodiment, a method for constructing a dual-parameter simultaneous detection system for temperature and hydrogen concentration, includes the following steps: Simulation of FBG grating structure parameters; FBG grating fabrication and functionalization; A detection system is constructed, comprising an ASE broadband light source. The output of the ASE broadband light source is split into two paths via a coupler: one path enters a first circulator, and the other path enters a second circulator. The first and second circulators are three-port circulators. The output of the first circulator enters a first FBG sensor, and the output of the second circulator enters a second FBG sensor. The first and second FBG sensors are disposed in a gas chamber and are configured with FBG topology fiber structures with different operating wavelengths, exhibiting temperature sensitivity and gas selectivity. The reflected signals from the first and second FBG sensors are coupled to one path via a dual-channel wavelength division multiplexer and sent to a spectrometer for wavelength demodulation.

[0030] The functions and implementation processes of each part of the construction method are as follows: Step 1: Simulation of FBG Grating Structure Parameters. A complete three-dimensional simulation model of the dual FBGs was established using COMSOL Multiphysics software. First, the parameters of FBG1 in the standard single-mode fiber (SMF-28) were optimized. By changing key parameters such as the grating period (set to the range of 525-535nm) and the refractive index modulation depth (controlled on the order of 10^-4), the influence on the reflection spectrum in the 1550nm band was analyzed, and its temperature sensitivity was finally determined. For the special requirements of FBG2, based on the 1530nm band design, a multiphysics coupling model of the palladium (Pd) film was additionally established. The strain transfer efficiency of Pd films of different thicknesses (30-100nm) during hydrogen adsorption was analyzed using the solid mechanics module, and its influence on grating wavelength drift was calculated using the wave optics module.

[0031] Step 2: FBG Grating Fabrication and Functionalization. FBGs were fabricated using a high-precision phase mask method. A 248nm KrF excimer laser (energy density 50mJ / cm²) was used to etch gratings onto hydrogen-loaded SMF-28 optical fibers through a phase mask (period 1060nm). Using a precision displacement stage, FBG1 (10mm length, refractive index modulation depth 2×10⁻⁴) was first etched at a predetermined position, followed by FBG2 (8mm length, refractive index modulation depth 3×10⁻⁴) after moving 5cm. After etching, the sample was placed in a programmable annealing furnace and heated to 300℃ at a rate of 1℃ / min, held for 4 hours to eliminate residual stress. For hydrogen-sensitive functionalization of FBG2, an 80nm thick Pd film was deposited on its surface using a high-vacuum magnetron sputtering system (background vacuum 5×10⁻⁶ Torr). During sputtering, substrate rotation (10rpm) and low-temperature cooling (-10℃) ensured film uniformity. Finally, laser micromachining technology was used to fabricate a porous stainless steel protective sleeve (5μm pore size, 30% porosity) in the FBG2 region, which ensured hydrogen permeability (response time <30s) and provided mechanical protection.

[0032] Step 3: Construction of the temperature and hydrogen dual-parameter detection system. The optical part of the demodulation system adopts a modular design, using an ASE broadband light source (power 20mW±0.5dB) as the illumination source. Its flattened spectral characteristics (fluctuation <1dB) ensure balanced detection of the dual FBG reflection spectrum. The light source output passes through a coupler and two three-port circulators (Thorlabs 6015-3-APC, insertion loss <0.5dB) into the sensing fiber. The reflected signal is coupled to one channel through a high-isolation dual-channel wavelength division multiplexer (WDMI-1550-1530-50-APC) and sent to a high-resolution spectrometer for wavelength demodulation. The gas path is equipped with a three-way solenoid valve to switch between measurement / calibration / nitrogen purging modes. A customized aluminum alloy gas chamber and a porous stainless steel protective sleeve (PTFE hydrophobic treatment) with a pore size of 1-3μm for the internal FBG2 sensor ensure rapid hydrogen permeation.

[0033] Step 4: Data Analysis and Processing. Extract peak data using peak detection algorithms (such as Gaussian fitting). and The real-time wavelength value. Establish the following coupling matrix:

[0034] Based on the calibration coefficient matrix, temperature and hydrogen concentration are decoupled in real time using the least squares method:

[0035] in, K T1 , KH1 , K T2 , K H2 These represent the sensitivity coefficients of FBG1 and FBG2 when performing single temperature / hydrogen detection, respectively, and have been calibrated before performing dual-parameter detection.

[0036] Calibration process

[0037] Before testing begins, the center wavelength (reference wavelength) of each FBG sensor is determined and calibrated to determine the sensitivity coefficient.

[0038] Under reference conditions (such as standard temperature) =25°C, hydrogen concentration The initial Bragg wavelength read at 0 ppm is defined as the center wavelength of each FBG. First FBG sensor (temperature dominant) center wavelength. Designed in the 1550nm wavelength band, primarily responding to temperature changes. Second FBG sensor (dual response to hydrogen and temperature): center wavelength. The design utilizes a palladium-palladium film to achieve hydrogen sensitivity in the 1530nm wavelength band.

[0039] The sensor is placed in a temperature-controlled environment, and the temperature (ΔT) is changed to measure the wavelength drift Δ of each FBG. and Δ Calculate the temperature sensitivity coefficient K T1 and K T2 (Unit: pm / °C). For example: K T1 = Δ / ΔT (only temperature changes, hydrogen concentration remains constant).

[0040] At a constant temperature, the hydrogen concentration (Δ) is changed. ), measuring wavelength drift Δ Calculate the hydrogen sensitivity coefficient K H2 (Unit: pm / ppm), and simultaneously verify the cross-sensitivity K of the first FBG. H1 (Usually small, can be approximated as 0).

[0041] The calibration results form a coefficient matrix: .

[0042] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A dual-parameter synchronous detection system for temperature and hydrogen concentration, characterized in that, The application relates to a FBG sensor for measuring the concentration of hydrogen in a gas chamber, comprising an ASE broadband light source, the output of which is split into two paths by a coupler, one path entering a first circulator and the other path entering a second circulator, the first and second circulators being three-port circulators, the output of the first circulator entering a first FBG sensor and the output of the second circulator entering a second FBG sensor, the first and second FBG sensors being arranged in a gas chamber, the first and second FBG sensors being provided with FBG topological fiber structures with different working wavelengths, temperature sensitivity and gas selective response, the reflection signals of the first and second FBG sensors being coupled to one path by a double-channel wavelength division multiplexer and sent into a spectrum analyzer for wavelength demodulation.

2. The dual-parameter synchronous detection system of temperature and hydrogen concentration according to claim 1, characterized in that, The second FBG sensor is provided with a porous stainless steel protective sleeve with a pore size of 1-3 microns.

3. The dual-parameter synchronous detection system of temperature and hydrogen concentration according to claim 2, characterized in that, The stainless steel protective sleeve is subjected to PTFE hydrophobic treatment.

4. The dual-parameter synchronous detection system of temperature and hydrogen concentration according to claim 1, characterized in that, The gas chamber is an aluminum alloy gas chamber, and the gas chamber is provided with a gas path, and the gas path is provided with a three-way electromagnetic valve to realize measurement, calibration and nitrogen purging mode switching.

5. The dual-parameter synchronous detection system of temperature and hydrogen concentration according to claim 1, characterized in that, The grating structure parameters of the first and second FBG sensors are obtained through simulation, including: A three-dimensional simulation model of the double FBG is established based on a multi-physical field simulation software; The first FBG sensor of the standard single-mode fiber is optimized in parameters, the influence of grating period and refractive index modulation depth on the reflection spectrum of the 1550nm wave band is analyzed, and the temperature sensitivity is finally determined; For the second FBG sensor, a multi-physical field coupling model of the palladium film layer is additionally established on the basis of the design of the 1530nm wave band, the strain transmission efficiency of the palladium film with different thicknesses when absorbing hydrogen is analyzed, and the influence of the grating wavelength drift is calculated.

6. The dual-parameter synchronous detection system of temperature and hydrogen concentration according to claim 5, characterized in that, The grating structure preparation method of the first and second FBG sensors comprises: A KrF excimer laser is used to write a grating on a hydrogen-loaded treated optical fiber through a phase mask; a precision displacement table is controlled to first write the first FBG sensor at a predetermined position, and then write the second FBG sensor after moving a certain distance; After writing, the sample is placed in a programmed annealing furnace to eliminate residual stress; For the hydrogen-sensitive functionalization of the second FBG sensor, a high-vacuum magnetron sputtering system is used to deposit a palladium film on the surface of the second FBG sensor; during the sputtering process, the substrate rotation and low-temperature cooling are used to ensure the uniformity of the film layer; finally, a laser micro machining is used to manufacture a porous stainless steel protective sleeve in the second FBG sensor area.

7. A method for constructing a dual-parameter synchronous detection system for temperature and hydrogen concentration, characterized in that, The application comprises the following steps: FBG grating structure parameter simulation; FBG grating preparation and functionalization treatment; A detection system is constructed, which includes an ASE broadband light source, the output of which is split into two paths by a coupler, one of which enters a first circulator and the other enters a second circulator, the first and second circulators being three-port circulators, the output of the first circulator entering a first FBG sensor, the output of the second circulator entering a second FBG sensor, the first and second FBG sensors being arranged in a gas chamber, the first and second FBG sensors being provided with FBG topological fiber structures of different operating wavelengths, having temperature sensitivity and gas selective response, the reflected signals of the first and second FBG sensors being coupled to a single path by a dual-channel wavelength division multiplexer and sent to a spectrum analyzer for wavelength demodulation.

8. The method according to claim 7, wherein FBG grating structure parameter simulation includes: Based on multi-physical field simulation software, a three-dimensional simulation model of double FBG is established; The first FBG sensor of the standard single-mode fiber is optimized in parameters, the influence of grating period and refractive index modulation depth on the reflection spectrum of the 1550 nm waveband is analyzed, and the temperature sensitivity is finally determined; For the second FBG sensor, a multi-physical field coupling model of the palladium film layer is additionally established based on the design of the 1530 nm waveband, the strain transmission efficiency of different thickness palladium films during hydrogen adsorption is analyzed, and the influence of the grating wavelength drift is calculated.

9. The method according to claim 7, wherein FBG grating preparation and functionalization treatment includes: A KrF excimer laser is used to write gratings on hydrogen-loaded treated optical fibers through a phase mask; through precise displacement table control, the first FBG sensor is first written at a predetermined position, and then the second FBG sensor is written after moving a certain distance; After writing, the sample is placed in a programmed annealing furnace to eliminate residual stress; For the hydrogen-sensitive functionalization of the second FBG sensor, a high-vacuum magnetron sputtering system is used to deposit a palladium film on its surface, and the film uniformity is ensured by substrate rotation and low-temperature cooling during sputtering; finally, a laser micro-machining is used to make a porous stainless steel protective sleeve in the second FBG sensor area.

10. A method for simultaneous detection of temperature and hydrogen concentration, applied to the system for simultaneous detection of temperature and hydrogen concentration according to any one of claims 1-6, characterized in that, The following steps are included: The spectral analyzer wavelength demodulates the obtained reflection signal, and extracts real-time wavelength values of the first FBG sensor wavelength and the second FBG sensor wavelength through a peak detection algorithm. Calculate the difference from the center wavelength: wherein is the center wavelength of the first FBG sensor, is the center wavelength of the second FBG sensor, Δ and Δ denotes the wavelength shift due to temperature and hydrogen variations; Establish a coupling matrix: According to the calibration coefficient matrix , the temperature and hydrogen concentration are decoupled in real time by the least square method: Wherein, K T1 , K H1 , K T2 , K H2 respectively represent the sensitivity coefficient of the first FBG sensor and the second FBG sensor when detecting single temperature and hydrogen; ΔT is the temperature change amount, and Δ is the hydrogen concentration change amount.

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