Multi-component photoacoustic gas detection device and method based on photoluminescent material

Abstract

The invention discloses a multi-component photoacoustic gas detection device and method based on a photoluminescent material, and relates to the technical field of gas detection, and the device comprises a radiation light source, a two-dimensional optical adjustment device and a photoacoustic spectrum gas sensing device. A novel photoacoustic cell with multiple photoluminescent material coatings spin-coated on the inner surface is designed, and a single radiation light source and a two-dimensional optical adjusting device are matched, so that the function of generating light with multiple characteristic wavelengths by excitation of a single light source is realized, and online, real-time and multi-component trace gas detection is realized by combining a photoacoustic spectrum technology. According to the invention, single-light-source, multi-component and high-sensitivity online detection is realized, the system structure is simplified, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, specifically relating to a multi-component photoacoustic gas detection device and method based on photoluminescent materials. Background Technology

[0002] Based on their detection principles of interaction with gases, trace gas detection technologies are mainly divided into direct absorption spectroscopy (such as tunable laser absorption spectroscopy, TDLAS) and indirect absorption spectroscopy (such as photoacoustic spectroscopy, PAS). Among them, photoacoustic spectroscopy inverts the concentration by detecting the acoustic signal generated after the gas absorbs light energy. It has comprehensive advantages such as compact structure, high sensitivity, strong selectivity, fast response, and support for online real-time monitoring, and has become an important development direction in the field of trace gas detection.

[0003] In photoacoustic spectroscopy systems, the choice of radiation source directly affects system performance and feasibility. Existing light sources are mainly divided into incoherent sources (such as broadband continuous light sources) and coherent sources (such as near-infrared and mid-infrared lasers). To achieve the detection of multi-component gases, the system usually needs to have the radiation capability to cover multiple characteristic absorption bands, which is generally achieved by using multiple lasers or a single broadband light source combined with filtering or beam splitting elements. However, these mainstream solutions all face significant limitations: although mid-infrared lasers have high absorption line intensity, they are expensive, bulky, and often require water cooling or even liquid nitrogen cooling, resulting in complex systems and high energy consumption; although near-infrared lasers are relatively low in size and cost, their absorption line intensity is weak, limiting further improvement in detection sensitivity; and the solution of using a broadband continuous light source combined with a narrowband filter often suffers from low optical power, large system size, and poor signal-to-noise ratio, making it difficult to meet the requirements of high-sensitivity trace detection.

[0004] Therefore, current photoacoustic spectroscopy-based multi-component gas detection technologies, while pursuing high sensitivity, high selectivity, and online real-time monitoring capabilities, still face multiple challenges, such as complex light source systems, high costs, high power consumption, or limited sensitivity. Especially when using a single radiation source to achieve multi-component gas detection, it is often difficult to simultaneously achieve system structure simplification and detection performance optimization. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a multi-component photoacoustic gas detection device and method based on photoluminescent materials. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a multi-component photoacoustic gas detection device based on photoluminescent materials, comprising: a radiation source and a two-dimensional optical adjustment device, and a photoacoustic spectral gas sensing device; wherein, The radiation source and two-dimensional optical adjustment device include a laser modulation device, a radiation source, and a two-dimensional optical adjustment frame; the radiation source is used to output an excitation beam; the laser modulation device is used to modulate the intensity of the excitation beam; and the two-dimensional optical adjustment frame is used to adjust the incident angle of the excitation beam. The photoacoustic spectroscopy gas sensing device includes a photoacoustic cell, an acoustic sensor, and a signal processing unit. The inner surface of the photoacoustic cell is coated with at least two photoluminescent materials. The excitation beam output by the radiation source is adjusted at the incident angle by the two-dimensional optical adjustment frame and selectively irradiates a photoluminescent material coating on the inner surface of the photoacoustic cell. The currently irradiated photoluminescent material coating is excited to generate characteristic wavelength light. The characteristic wavelength light is used to excite the corresponding trace gas to generate photoacoustic signals. The acoustic sensor is used to detect the photoacoustic signals, and the signal processing unit is used to process the photoacoustic signals and invert the concentration of the trace gas.

[0006] The present invention also provides a method for detecting multi-component photoacoustic gases based on photoluminescent materials, applicable to the multi-component photoacoustic gas detection device based on photoluminescent materials described in any of the above embodiments, the method comprising: The gas to be tested, containing trace amounts of various gases, is passed into the photoacoustic cell; The two-dimensional optical adjustment frame is controlled to change the incident angle of the excitation beam output by the radiation source, thereby sequentially exciting different photoluminescent material coatings; Detect the photoacoustic signals generated by the excited coatings of various photoluminescent materials; Based on the intensity and phase information of the photoacoustic signal, the concentration of each trace gas is obtained by inversion.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The multi-component photoacoustic gas detection device based on photoluminescent materials of the present invention abandons the traditional approach of relying on multiple lasers or complex spectral systems in multi-component gas detection. It achieves the function of generating multiple characteristic wavelengths of light using a single light source by designing a novel photoacoustic cell with a coating of multiple photoluminescent materials spin-coated on its inner surface, combined with a single radiation source and a two-dimensional optical adjustment device. This greatly simplifies the optical path and system structure, avoids the use of expensive, bulky, and powerfully cooled mid-infrared lasers, and significantly reduces the overall size, manufacturing cost, and operating power consumption of the device. 2. The multi-component photoacoustic gas detection device based on photoluminescent materials of the present invention, by precisely controlling the angle of the excitation beam, selectively irradiates a specific photoluminescent material coating on the inner wall of the photoacoustic cell, thereby exciting the generation of characteristic wavelength light that is only for a certain type or class of trace gases. Combining the high sensitivity and selectivity of photoacoustic spectroscopy, multiple gas components can be detected sequentially or on demand, providing a novel and efficient solution for online, real-time, multi-component trace gas detection using a single compact radiation source (such as a near-infrared laser or a broadband light source in a specific wavelength band). 3. In the multi-component photoacoustic gas detection device based on photoluminescent materials of the present invention, the type, quantity, and layout of the coating material on the inner wall of the photoacoustic cell can be flexibly designed and customized according to the type and quantity of the gas to be measured. By changing or adding / removing the coating material, the same core architecture of the device can adapt to different detection needs.

[0008] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0009] Figure 1 This is a structural block diagram of a multi-component photoacoustic gas detection device based on photoluminescent materials provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a photoacoustic cell provided in an embodiment of the present invention; Figure 3 These are infrared absorption spectra of common gases provided in embodiments of the present invention; Figure 4 This is a schematic diagram of a multi-component photoacoustic gas detection method based on photoluminescent materials provided in an embodiment of the present invention.

[0010] Icons: 1-Radiation source and two-dimensional optical adjustment device; 2-Photoacoustic spectroscopy gas sensing device; 3-Laser modulation device; 4-Radiation source; 5-Two-dimensional optical adjustment frame; 6-Sealed container for the gas to be measured; 7-Photoacoustic cell; 8-Acoustic sensor; 9-Inlet; 10-Outlet; 11-Lock-in amplifier; 12-Data acquisition card; 13-Computer; 14-21 are eight different photoluminescent material coatings. Detailed Implementation

[0011] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, describes a multi-component photoacoustic gas detection device and method based on photoluminescent materials proposed in accordance with the present invention.

[0012] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0013] In a first aspect, embodiments of the present invention provide a multi-component photoacoustic gas detection device based on photoluminescent materials. Its core lies in designing a novel photoacoustic cell with a coating of multiple photoluminescent materials spin-coated on its inner surface, combined with a single radiation source and a two-dimensional optical adjustment device, to achieve the function of generating multiple characteristic wavelengths of light using a single light source. This is further combined with photoacoustic spectroscopy technology to achieve online, real-time, multi-component trace gas detection.

[0014] Please see Figure 1 , Figure 1 This is a structural block diagram of a multi-component photoacoustic gas detection device based on photoluminescent materials provided in an embodiment of the present invention. Figure 1 As shown, the multi-component photoacoustic gas detection device based on photoluminescent materials in this embodiment includes: a radiation source and a two-dimensional optical adjustment device 1, and a photoacoustic spectral gas sensing device 2. The radiation source and two-dimensional optical adjustment device 1 includes a laser modulation device 3, a radiation source 4, and a two-dimensional optical adjustment frame 5; the radiation source 4 is used to output an excitation beam; the laser modulation device 3 is used to modulate the intensity of the excitation beam; the two-dimensional optical adjustment frame 5 is used to adjust the incident angle of the excitation beam; the photoacoustic spectral gas sensing device 2 includes a photoacoustic cell 7, an acoustic sensor 8, and a signal processing unit. At least two types of photoluminescent material coatings are disposed on the inner surface of the photoacoustic cell 7; after the excitation beam output from the radiation source 4 is adjusted at the incident angle by the two-dimensional optical adjustment frame 5, it selectively irradiates one photoluminescent material coating on the inner surface of the photoacoustic cell 7. The currently irradiated photoluminescent material coating is excited to generate characteristic wavelength light, which is used to excite the corresponding trace gas to generate a photoacoustic signal. The acoustic sensor 8 is used to detect the photoacoustic signal, and the signal processing unit is used to process the photoacoustic signal and invert the concentration of the trace gas.

[0015] In this embodiment, the laser modulation device 3 modulates the frequency of the excitation beam to be equal to the acoustic resonant frequency of the photoacoustic cell 7. Exemplarily, the laser modulation device 3 may employ an acousto-optic modulator (AOM), an electro-optic modulator (EOM), or a scheme that directly modulates the driving current of the semiconductor laser.

[0016] Understandably, by using a laser modulation device to convert a continuously excited beam into a beam with periodically varying intensity, when the modulation frequency matches the resonant frequency of the photoacoustic cell, the periodic photoacoustic pressure waves generated within the cell are strongly amplified due to the acoustic resonance effect. This is similar to the resonance phenomenon in mechanical vibration; a weak periodic driving force can excite a large-amplitude vibration response at the resonant frequency. This means that under the same gas absorption light energy conditions, the resonant state can generate photoacoustic signals tens or even hundreds of times stronger than the non-resonant state, thereby directly improving the system's detection sensitivity. In the resonant state, the photoacoustic signal is confined to a specific frequency and spatial mode, while most environmental noise (such as mechanical vibration, airflow noise, and electrical noise) has a wide spectral distribution or frequency mismatch. By using detection techniques such as lock-in amplifiers, the signal can be extracted only within a narrow band of the resonant frequency, effectively suppressing out-of-band noise.

[0017] In this embodiment, the output wavelength of the radiation source 4 covers the effective absorption wavelength of all photoluminescent material coatings. Exemplarily, the radiation source 4 can be a blue / green semiconductor laser (such as a GaN-based laser diode) with an output wavelength in the range of 450-520 nm, which can effectively excite a variety of visible light-excited photoluminescent materials; it can be a near-infrared semiconductor laser with an output wavelength in the range of 790-850 nm, suitable for exciting upconversion luminescent materials with near-infrared responses; or it can be a superluminescent diode (SLED) or amplified spontaneous emission (ASE) source in a specific wavelength band, used as a broadband pump source.

[0018] This embodiment eliminates the reliance on expensive mid-infrared direct light sources, allowing the use of mature, inexpensive, small-sized, and low-power visible or near-infrared lasers as the core pump unit, fundamentally reducing system cost and power consumption and improving reliability.

[0019] In this embodiment, the two-dimensional optical adjustment frame 5 is used to adjust the pitch and azimuth angles of the excitation beam relative to the axis of the photoacoustic cell 7. The two-dimensional optical adjustment frame in this embodiment is a key mechanical component for achieving selective excitation. It can be a manually operated precision adjustment frame or an automatically adjusted frame driven by a motor (such as a stepper motor or piezoelectric ceramic drive). Its core function is to provide two mutually perpendicular rotational degrees of freedom (i.e., pitch and azimuth), with an adjustment accuracy better than 0.01°.

[0020] Optionally, the two-dimensional optical adjustment frame 5 includes a precision micrometer head driver with an integrated locking mechanism, a two-dimensional angular displacement mechanism based on orthogonal flexible hinges, an optical element mounting interface, and a rigid base.

[0021] The two-dimensional optical adjustment frame in this embodiment can repeatedly control the incident direction of the laser beam, ensuring that the beam is accurately aligned with a specific annular coating area on the inner wall of the photoacoustic cell. This enables precise and rapid switching between different gas detection channels, laying the foundation for sequential measurement of multi-component gases.

[0022] like Figure 1 As shown, the photoacoustic spectroscopy gas sensing device 2 in this embodiment also includes a sealed gas container 6, which serves as a sample gas source and can be connected to an external gas bag, gas cylinder, or online sampling pipeline. An inlet 9 and an outlet 10 are provided on the side wall of the photoacoustic cell 7. Gas flows into the photoacoustic cell 7 through the inlet 9 and is discharged through the outlet 10 after detection. Flow controllers (such as mass flow controllers, MFCs) or flow limiting elements (such as capillaries) can be installed at the inlet 9 and outlet 10 to maintain stable gas pressure and constant flow rate within the photoacoustic cell 7.

[0023] In this embodiment, the photoacoustic cell 7 is primarily an acoustic resonant cavity, providing a confined, sealed acoustic space that can constrain and amplify pressure fluctuations (sound waves) generated by gas absorbing light energy, greatly improving the detection sensitivity of weak photoacoustic signals. The photoacoustic cell 7 is preferably a circular straight-cavity (cylindrical) resonant cavity. Optionally, the diameter of the circular straight-cavity photoacoustic cell 7 is 2-20 mm.

[0024] It is understood that other cavity structures that can form a stable sound field and have a high quality factor Q are also within the scope of protection of this invention, such as: elliptical cavity, multi-resonance cavity, T-shaped resonant cavity, annular resonant cavity or spherical resonant cavity.

[0025] In this embodiment, a photoluminescent material coating is applied to the inner wall of the photoacoustic cell 7 to form a ring structure. At least two types of photoluminescent material coatings are arranged alternately along the axial direction of the photoacoustic cell 7, and a gap is provided between adjacent coatings.

[0026] Please see Figure 2 , Figure 2 This is a schematic diagram of a photoacoustic cell provided in an embodiment of the present invention, as shown below. Figure 2 As shown, in this embodiment, the inner surface of the photoacoustic cell 7 is coated with eight types of photoluminescent material coatings. The annular coatings are arranged alternately along the axial direction of the photoacoustic cell, with a gap of approximately 1-3 mm between adjacent coatings to prevent optical and thermal crosstalk. The width of the photoluminescent material coating can be 3-10 mm, and the thickness can be 10-100 μm to ensure sufficient luminous intensity and mechanical stability.

[0027] For example, the eight photoluminescent materials can be HgCdTe epitaxial films, InAs / GaSb superlattices, HgTe / HgCdTe superlattices, InGaNAs / GaAs quantum wells, InGaP / AlGaInP quantum wells, InAsSb dual heterostructures, GaSbBi quantum wells, and InAs nanowires. HgCdTe epitaxial films and InAs / GaSb superlattices can generate light in the 3–30 μm band. The wavelength of light generated by HgCdTe can also be adjusted by changing the Cd composition. HgTe / HgCdTe superlattices can generate light in the 10–30 μm band, InGaNAs / GaAs quantum wells can generate light in the 1.2–1.6 μm band, InGaP / AlGaInP quantum wells can generate light in the 630–700 nm band, InAsSb double heterostructures can generate light in the 3–5 μm band, GaSbBi quantum wells can generate light in the 1.8–2.5 μm band, and InAs nanowires can generate light in the 2–3.5 μm band.

[0028] Based on the aforementioned eight photoluminescent materials and their typical wavelength ranges, combined with photoacoustic spectroscopy, highly sensitive detection of various gases can be achieved. For example, using materials such as HgCdTe epitaxial films or InAs / GaSb superlattices to emit lasers of approximately 4.53 μm can achieve N2O gas detection; using materials such as InAsSb double heterostructures to generate lasers of approximately 4.61 μm is suitable for CO gas detection; and the approximately 1.56 μm laser emitted by InGaNAs / GaAs quantum wells can be used for C2H2 gas detection. Furthermore, by adjusting the material composition or structure, the detection of even more gases can be achieved, such as using approximately 1.13 μm lasers for H2O gas detection and approximately 4.3 μm lasers for CO2 gas detection.

[0029] In this embodiment, electrons in the photoluminescent material coating transition to a high-energy excited state after absorbing incident photons, and then generate light output of a specific wavelength through radiative transition. The wavelength of this specific wavelength light corresponds to the absorption spectrum of the trace gas to be measured. After absorbing the specific wavelength light radiated by the photoluminescent material coating, the trace gas to be measured will generate a photoacoustic signal, which is detected by the acoustic sensor in the photoacoustic spectroscopy gas sensing device. By analyzing the phase and intensity information of the photoacoustic signal, the concentration information of the trace gas to be measured can be deduced.

[0030] It is understandable that each photoluminescent material coating on the inner wall of the photoacoustic cell emits light of a specific wavelength when irradiated with excitation light of a specific wavelength. Each specific wavelength corresponds to the absorption spectral line of a trace gas being measured. Infrared absorption spectra of common gases are shown below. Figure 3 As shown.

[0031] The photoacoustic cell coated with photoluminescent material in this embodiment can convert a single pump light into multiple characteristic excitation lights for specific gases, eliminating the need for complex external beam splitting or multiple laser systems. At the same time, its spatial arrangement combined with beam angle control constitutes a natural, addressable multi-channel excitation source, which is the physical basis for realizing single-source multi-component gas detection.

[0032] In this embodiment, the acoustic sensor 8 is a microphone or a tuning fork quartz crystal oscillator. For example, a high-sensitivity capacitive microphone can be used, which has a wide frequency response and good stability. The acoustic sensor 8 can convert weak gas pressure fluctuations into electrical signals. By selecting a suitable sensor and matching it with the photoacoustic cell resonance mode, signal extraction efficiency can be maximized.

[0033] like Figure 1 As shown, in this embodiment, the signal processing unit includes a lock-in amplifier 11, a data acquisition card 12, and a computer 13 connected in sequence; the lock-in amplifier 11 is connected to the acoustic sensor 8. The lock-in amplifier 11 is used to extract a small photoacoustic signal synchronized with the modulation frequency in a strong noise background. The data acquisition card 12 performs analog-to-digital conversion. The computer 13 uses data processing algorithms to invert the concentration of trace gases. It is understood that the computer 13 can also run control software, such as controlling light source modulation, two-dimensional adjustment frame movement, and gas path control.

[0034] In this embodiment, the calculation steps for retrieving the concentration of trace gases are as follows: Assume there are 8 types of trace gases in the gas to be tested, namely... The different angles between the excitation beam and the axis of the photoacoustic cell are respectively... .

[0035] In the initial design, a strict correspondence was established between the radiation wavelength of each photoluminescent material and each trace gas. This allows for the derivation of the absorption coefficient of the trace gas and the type of trace gas to be measured. This is related to the angle between the excitation beam and the axis of the photoacoustic cell, and thus to the different angles between them. Related, recorded as The absorption cross section of trace gases and the concentration of the trace gas being measured are related to their type, and thus differ from the angle between the excitation beam and the axis of the photoacoustic cell. Related, can be recorded as follows: and The intensity of the photoacoustic signal measured by the photoacoustic spectroscopy gas sensing device and Related, recorded as The laser intensity is related to the effective wavelength band of the characteristic wavelength light generated by the absorption of the trace gas by the photoluminescent material, denoted as . .

[0036] The trace gas absorption coefficient is already known. Same trace gas concentration The relationship can be represented as: (1); Photoacoustic signal intensity measured by photoacoustic spectroscopy gas sensing device Same trace gas absorption coefficient The relationship is: (2); In the formula, This is the photoacoustic cell constant, which is related to the photoacoustic cell quality factor. The effective wavelength range for radiation light generated by photoluminescent materials that absorb trace gases.

[0037] Once the photoacoustic cell constant is known, the photoacoustic signal intensity only needs to be measured using a photoacoustic spectroscopy gas sensing device. Substituting it into equation (2) yields the absorption coefficient of the trace gas being measured on the radiation emitted by the photoluminescent material. Then the absorption coefficient Substituting into equation (1) will allow us to invert the gas to be tested. concentration .

[0038] It is understood that the multi-component photoacoustic gas detection device based on photoluminescent materials in this embodiment effectively suppresses background noise and improves the signal-to-noise ratio by matching the laser modulation frequency to the resonant frequency of the photoacoustic cell and extracting the photoacoustic signal using techniques such as lock-in amplification. Simultaneously, each photoluminescent material can theoretically be designed to have a characteristic absorption response to only one gas, reducing cross-interference between gases and improving the accuracy and reliability of multi-component gas detection. When multiple analytes exhibit overlapping absorption in the light band generated by a photoluminescent material coating, the individual concentration of each gas can be calculated through decoupling multi-dimensional analysis and data processing.

[0039] This invention relates to a multi-component photoacoustic gas detection device based on photoluminescent materials. By integrating various photoluminescent materials into the inner wall of the photoacoustic cell and combining them with a controllable gas path system, high-precision angle control, and advanced signal processing, a highly integrated and low-cost single-source multi-component photoacoustic gas online real-time detection platform is constructed. This provides a novel and efficient solution for realizing online, real-time, multi-component trace gas detection. By selecting relatively mature, inexpensive, and compact near-infrared or visible light lasers as pump sources, and utilizing photoluminescent materials to convert the required mid-infrared and other characteristic wavelengths of light, many problems associated with directly using mid-infrared light sources are avoided. This provides a new technical approach for optimizing the selection of light sources in photoacoustic spectroscopy systems.

[0040] Secondly, embodiments of the present invention provide a method for detecting multi-component photoacoustic gases based on photoluminescent materials, applicable to the multi-component photoacoustic gas detection device based on photoluminescent materials provided in the first aspect.

[0041] Please see Figure 4 , Figure 4 This is a schematic diagram of a multi-component photoacoustic gas detection method based on photoluminescent materials provided in an embodiment of the present invention; as shown. Figure 4 As shown, the multi-component photoacoustic gas detection method based on photoluminescent materials in this embodiment includes the following steps: Step 1: Pass the gas to be tested, which contains trace amounts of various gases, into the photoacoustic cell; Step 2: Control the two-dimensional optical adjustment frame to change the incident angle of the excitation beam output by the radiation source, and excite different photoluminescent material coatings in sequence; Step 3: Detect the photoacoustic signals generated by the excitation of each photoluminescent material coating; Step 4: Based on the intensity and phase information of the photoacoustic signal, the concentration of each trace gas is obtained by inversion.

[0042] In this embodiment, the inversion step for the concentration of trace gases includes: Step (1): Calculate the absorption coefficient of trace gas for characteristic wavelength light based on the intensity of the detected photoacoustic signal.

[0043] in In the formula, The intensity of the detected photoacoustic signal, The photoacoustic cell constant is... The intensity of light at the characteristic wavelength. The effective wavelength range for radiation light generated by photoluminescent materials that absorbs trace gases. is the absorption coefficient of trace gases for light of a characteristic wavelength. The angle between the excitation beam and the axis of the photoacoustic cell.

[0044] Step (2): Based on the absorption coefficient of the trace gas to the characteristic wavelength light, the concentration of the trace gas is obtained by inversion.

[0045] in In the formula, The concentration of trace gases. This represents the absorption cross section of trace gases at a characteristic wavelength.

[0046] Furthermore, the multi-component photoacoustic gas detection method based on photoluminescent materials of the present invention will be described through specific examples.

[0047] Example 1 Assume the gas to be tested is a trace gas, for example, methane (CH4). Assume the inner wall of the photoacoustic cell is coated with only one photoluminescent material sensitive to CH4, which can be a complete coverage or only one type of material.

[0048] The specific testing method includes the following steps: S1: After connecting the detection device, introduce CH4 standard gas of known concentration, turn on the radiation source, such as a 488nm laser, and set its modulation frequency to the resonant frequency of the photoacoustic cell using a laser modulation device. Operate the two-dimensional optical adjustment frame to adjust the excitation beam to an optimal fixed angle that can completely illuminate the CH4-sensitive coating. .

[0049] S2: The gas to be tested (which may contain CH4) is introduced into the photoacoustic cell through the inlet, and the flow rate is kept stable.

[0050] S3: Modulated 488 nm laser at an angle Incident light excites the coating and produces characteristic fluorescence corresponding to the absorption band of CH4 at approximately 3.3 μm. The CH4 gas absorbs this fluorescence energy to generate a photoacoustic signal, which is detected by a microphone.

[0051] S4: The lock-in amplifier extracts the amplitude of the photoacoustic signal that is in phase with the modulation frequency. Based on the pre-calibrated photoacoustic cell constant Intensity of light with characteristic wavelength and the absorption cross section of CH4 near 3.3 μm. The concentration of CH4 in the gas to be tested was calculated. .

[0052] Example 2 Assume the analyte gases are two trace gases, for example, carbon monoxide (CO) and carbon dioxide (CO2). Assume the inner wall of the photoacoustic cell is alternately spin-coated with two annular photoluminescent material coatings, wherein coating A, when excited, produces light with a center wavelength of approximately 4.6 μm (corresponding to the strong absorption band of CO), and coating B, when excited, produces light with a center wavelength of approximately 4.3 μm (corresponding to the strong absorption band of CO2).

[0053] The specific testing method includes the following steps: S1: Control the two-dimensional optical adjustment frame to finely adjust the incident angle and calibrate the angle at which the center of the excitation beam is aligned with coating A. and the angle at which the excitation beam center is aligned with coating B. .

[0054] S2: The test gas mixture containing CO and CO2 is introduced into the photoacoustic cell. The excitation beam is adjusted to the desired angle. The coating A was excited to produce 4.6 μm light. At this time, CO molecules in the mixed gas absorbed this wavelength of light, generating a photoacoustic signal, while CO2 absorption of this wavelength was negligible. The amplitude of this photoacoustic signal was measured. .

[0055] S3: Adjust the excitation beam to the desired angle The coating B is excited to produce 4.3 μm light. At this time, CO2 molecules absorb the light, generating a photoacoustic signal; CO absorption at this wavelength is negligible. The amplitude of this photoacoustic signal was measured. .

[0056] S4: Combination and calibrated photoacoustic cell constant Intensity of characteristic wavelength light , and the absorption cross section of CO near 4.6 μm The absorption cross section of CO2 is around 4.3 μm. They can be calculated separately. and .

[0057] It should be noted that during the calibration process of S1, it is necessary to ensure that the spot of the excitation beam falls completely on the target photoluminescent material coating and avoid irradiating adjacent coatings.

[0058] Understandably, the measurement order of S2 and S3 can be adjusted arbitrarily, and the two-dimensional adjustment frame can be automatically switched through program control.

[0059] It should be noted that when multiple trace gases exhibit overlapping absorption in the light band produced by a certain photoluminescent material coating, multi-dimensional analysis and data processing can be used to accurately decouple and calculate the individual concentration of each gas. Alternatively, a special photoluminescent material coating can be selected to avoid cross-absorption.

[0060] This invention relates to a multi-component photoacoustic gas detection method based on photoluminescent materials. It can be easily extended to more gas components by simply adding coating types and measuring them sequentially. The system has strong scalability and provides a highly promising and practical solution for online analysis of multi-component trace gases.

[0061] For details regarding the multi-component photoacoustic gas detection method based on photoluminescent materials and its corresponding beneficial effects, please refer to the relevant content of the multi-component photoacoustic gas detection device based on photoluminescent materials provided in the first aspect, which will not be repeated here.

[0062] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0063] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0064] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A multi-component photoacoustic gas detection device based on photoluminescent materials, characterized in that, include: A radiation source and a two-dimensional optical adjustment device (1) and a photoacoustic spectroscopy gas sensing device (2); wherein, The radiation source and two-dimensional optical adjustment device (1) include a laser modulation device (3), a radiation source (4), and a two-dimensional optical adjustment frame (5); the radiation source (4) is used to output an excitation beam; the laser modulation device (3) is used to modulate the intensity of the excitation beam; and the two-dimensional optical adjustment frame (5) is used to adjust the incident angle of the excitation beam. The photoacoustic spectroscopy gas sensing device (2) includes a photoacoustic cell (7), an acoustic sensor (8), and a signal processing unit. The inner surface of the photoacoustic cell (7) is coated with at least two photoluminescent materials. The excitation beam output by the radiation source (4) is adjusted at the incident angle by the two-dimensional optical adjustment frame (5) and selectively irradiates a photoluminescent material coating on the inner surface of the photoacoustic cell (7). The currently irradiated photoluminescent material coating is excited to generate characteristic wavelength light. The characteristic wavelength light is used to excite the corresponding trace gas to generate photoacoustic signals. The acoustic sensor (8) is used to detect the photoacoustic signals. The signal processing unit is used to process the photoacoustic signals and invert the concentration of the trace gas.

2. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The laser modulation device (3) modulates the frequency of the excitation beam to be equal to the acoustic resonance frequency of the photoacoustic cell (7).

3. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The output band of the radiation source (4) covers the effective absorption band of all photoluminescent material coatings.

4. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The two-dimensional optical adjustment frame (5) is used to adjust the pitch and azimuth angles of the excitation beam relative to the axis of the photoacoustic cell (7).

5. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The photoluminescent material coating is applied to the inner wall of the photoacoustic cell (7) to form a ring structure; At least two photoluminescent material coatings are arranged alternately along the axial direction of the photoacoustic cell (7), and a gap is provided between adjacent coatings, the width of the gap being 1-3 mm; The width of the photoluminescent material coating is 3-10 mm, and the thickness is 10-100 μm.

6. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The structure of the photoacoustic cell (7) is one of the following: circular straight cavity, elliptical, multi-resonance cavity, T-shaped, annular, or spherical.

7. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The acoustic sensor (8) is a microphone or a tuning fork quartz crystal oscillator.

8. The multi-component photoacoustic gas detection device based on photoluminescent materials according to claim 1, characterized in that, The signal processing unit includes a lock-in amplifier (11), a data acquisition card (12), and a computer (13) connected in sequence; the lock-in amplifier (11) is connected to the acoustic sensor (8).

9. A method for detecting multi-component photoacoustic gases based on photoluminescent materials, characterized in that, The method applicable to the multi-component photoacoustic gas detection device based on photoluminescent materials according to any one of claims 1-8, the method comprising: The gas to be tested, containing trace amounts of various gases, is passed into the photoacoustic cell; The two-dimensional optical adjustment frame is controlled to change the incident angle of the excitation beam output by the radiation source, thereby sequentially exciting different photoluminescent material coatings; Detect the photoacoustic signals generated by the excited coatings of various photoluminescent materials; Based on the intensity and phase information of the photoacoustic signal, the concentration of each trace gas is obtained by inversion.

10. The method for detecting multi-component photoacoustic gases based on photoluminescent materials according to claim 9, characterized in that, The inversion step for the concentration of the trace gas includes: Based on the intensity of the detected photoacoustic signal, the absorption coefficient of the trace gas for characteristic wavelength light is calculated, where... ; In the formula, The intensity of the detected photoacoustic signal, The photoacoustic cell constant is... The intensity of light at the characteristic wavelength. The effective wavelength range for radiation light generated by photoluminescent materials that absorbs trace gases. is the absorption coefficient of trace gases for light of a characteristic wavelength. To determine the angle between the excitation beam and the axis of the photoacoustic cell; The concentration of the trace gas is obtained by inversion based on the absorption coefficient of the trace gas to the characteristic wavelength light, wherein... ; In the formula, The concentration of trace gases. This represents the absorption cross section of trace gases at a characteristic wavelength.

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