Dual-component gas detection device and method based on modular dual-resonance photoacoustic cell

Abstract

The invention provides a two-component gas detection device and a two-component gas detection method based on a modularized double-resonance photoacoustic cell, and belongs to the technical field of gas detection. Comprising a buffer structure module 1, a resonant structure module 2, a pickup mounting module 3, a first window fixed support 4, a second window fixed support 5, a first transmission lens 6 and a second transmission lens 7, the top of the resonant structure module 2 is provided with a first resonant cavity 21 and a second resonant cavity 22 which are the same in size and structure, and a first connecting cavity 23 is formed below the first resonant cavity 21; a second connecting cavity 24 is formed below the second resonant cavity 22, and the first connecting cavity 23 and the second connecting cavity 24 have the same length and different diameters and are equivalent to two Helmholtz resonant cavities with different inherent frequencies. The resonant frequency characteristic can be flexibly regulated and controlled through the modular design, and the concentrations of the two gases can be synchronously detected.

Description

Technical Field

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

[0002] Current photoacoustic spectroscopy gas detection devices generally employ a single-resonant-frequency photoacoustic cell. A single resonant cavity cannot simultaneously adapt to the optimal absorption frequencies of different gas molecules, severely limiting the sensitivity of multi-component detection. If a multi-cell series scheme is used, the system volume increases dramatically, and gas deceleration delays cause concentration measurement errors. Furthermore, fixing the resonant frequency makes it difficult to avoid mechanical vibration noise from 50Hz / 100Hz harmonics in industrial environments, while microfabrication dual-channel solutions are too costly due to complex manufacturing processes. Existing improved technologies, such as piezoelectrically tuned single-cavity or spatially split-beam detection, cannot achieve simultaneous dual-frequency resonance enhancement and long-term stable measurement.

[0003] The patent document with publication number CN222189110U discloses a resonant photoacoustic cell and a multi-component trace gas simultaneous detection device based on an integrating sphere photoacoustic cell. By installing acoustic tubes of different lengths on the integrating sphere, the sound signals of the corresponding frequencies are amplified to realize the detection of multi-component gas concentrations. However, this design is not conducive to integration. Therefore, there is an urgent need to develop a compact tunable dual-resonant photoacoustic cell to break through the technical bottleneck of synchronous high-precision detection of dual-component gases. Summary of the Invention

[0004] To address the problems in the prior art, this invention proposes a dual-component gas detection device and method based on a modular dual-resonant photoacoustic cell. By designing a symmetrically distributed dual-resonant structure with a shared buffer cavity, the synchronous detection of dual-component gases is achieved.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a two-component gas detection device based on a modular dual-resonant photoacoustic cell, comprising a modulation signal circuit, a first detection light source, a second detection light source, a modular dual-resonant photoacoustic cell, a signal demodulation circuit, and a host computer, wherein the modular dual-resonant photoacoustic cell comprises: The buffer structure module has an internal buffer cavity where the two-component gas to be tested and the probe light generate a photoacoustic effect. The resonant structure module is connected to the top of the buffer structure module. The top has two identical resonant cavities, a first resonant cavity and a second resonant cavity. A first connecting cavity is coaxially opened below the first resonant cavity, and a second connecting cavity is coaxially opened below the second resonant cavity. The first and second connecting cavities have the same length but different diameters and are connected to the buffer cavity. The sound pickup module is connected to the top of the resonant structure module and is used to pick up photoacoustic signals; The first window is fixed, and the first transmission lens is fixed on the left side of the buffer structure module; The second window is fixed, and the second transmission lens is fixed on the right side of the buffer structure module.

[0006] Furthermore, the resonant structure module is a replaceable module with different combinations of first and second connecting cavity diameters, and different diameter combinations are selected according to the optimal modulation frequency required by different components in the two-component gas to be tested.

[0007] Furthermore, the buffer structure module is provided with an air inlet and an air outlet on the front side, which are connected to the buffer chamber for introducing the two-component gas to be tested.

[0008] Furthermore, the buffer structure module is symmetrically provided with a first lens mounting slot and a second lens mounting slot on its left and right sides for mounting the first transmission lens and the second transmission lens.

[0009] Furthermore, the top of the buffer structure module is provided with a resonant structure mounting groove for mounting the resonant structure module.

[0010] Furthermore, the top of the pickup mounting module is provided with a first pickup mounting slot and a second pickup mounting slot for mounting photoacoustic signal receiving equipment; The first pickup mounting slot is coaxially connected to the first resonant cavity, and the second pickup mounting slot is coaxially connected to the second resonant cavity.

[0011] Furthermore, the photoacoustic signal receiving devices in the first and second pickup mounting slots respectively pick up photoacoustic signals of different frequencies in the first and second resonant cavities. The signal demodulation circuit separates the photoacoustic signals of different frequencies and demodulates them to obtain the concentration information of different gases.

[0012] Secondly, the present invention provides a method for detecting two-component gases based on a modular dual-resonant photoacoustic cell, comprising the following steps: The two-component test gas enters the buffer chamber through the air inlet, diffuses through the first connecting chamber and the second connecting chamber to the first resonant chamber and the second resonant chamber, and is discharged through the exhaust port; The modulation signal circuit uses the resonant frequencies of the first and second resonant cavities. f 1. f 2. Modulate the detection light frequency of the first and second detection light sources; The detection light from the first detection light source enters the buffer cavity through the first transmission lens, and the detection light from the second detection light source enters the buffer cavity through the second transmission lens, generating a photoacoustic signal. The first and second resonant cavities amplify the photoacoustic signals at their corresponding resonant frequencies. The photoacoustic signal receiving device picks up the photoacoustic signal and transmits it to the signal demodulation circuit to obtain the concentration results of the two-component gas to be measured; The gas concentration results are sent to the host computer for display.

[0013] Furthermore, the wavelengths modulated by the first and second detection light sources correspond to the absorption peak wavelengths of the two different gases in the two-component gas to be tested.

[0014] Furthermore, the data sampling rate of the signal demodulation circuit is greater than 5 times the highest resonant frequency.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The resonant cavity and connecting cavity of this invention are equivalent to a Helmholtz resonant cavity. By adjusting the inherent resonant frequency through two connecting cavities with different diameters, the separation of the two resonant frequencies is effectively achieved, thus enabling the synchronous detection of the concentrations of two target gases using a single photoacoustic cell. The photoacoustic cell features a modular design; by replacing the resonant structure modules with different combinations of first and second connecting cavity diameters, its resonant frequency characteristics can be flexibly adjusted, avoiding environmental noise at specific frequencies. The two resonant cavities share the same buffer cavity, which significantly reduces the internal volume of the photoacoustic cell. This not only greatly reduces the amount of gas sample consumed, but also significantly improves the engineering applicability of the system, while reducing system complexity and manufacturing costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a two-component gas detection device based on a modular dual-resonant photoacoustic cell; Figure 2 A three-dimensional perspective view of a modular dual-resonant photoacoustic cell; Figure 3 A schematic diagram of the modular dual-resonant photoacoustic cell's disassembled structure; Figure 4 A three-dimensional perspective view of the buffer structure module; Figure 5 A three-dimensional perspective view of the resonant structure module; Figure 6 A 3D perspective view of the microphone mounting module; The reference numerals in the figure indicate: 1. Buffer structure module; 2. Resonant structure module; 3. Pickup mounting module; 4. First window support; 5. Second window support; 6. First transmission lens; 7. Second transmission lens; 11. Air inlet; 12. Exhaust outlet; 13. Buffer cavity; 14. Resonant structure mounting slot; 15. First lens mounting slot; 16. Second lens mounting slot; 21. First resonant cavity; 22. Second resonant cavity; 23. First connecting cavity; 24. Second connecting cavity; 31. First pickup mounting slot; 32. Second pickup mounting slot. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] In the description of this specification, it should be understood that the terms "front", "left", "right", "top", etc., which indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are only for the convenience of describing the technical solution of this patent and simplifying the description, and do not imply or suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this patent application.

[0019] Example 1 This embodiment provides a dual-component gas detection device based on a modular dual-resonant photoacoustic cell, such as... Figure 1 As shown, the system includes a modulation signal circuit, a first detection light source, a second detection light source, a modular dual-resonant photoacoustic cell, a signal demodulation circuit, and a host computer. The modulation signal circuit generates a modulation signal that modulates the detection light frequencies of the first and second detection light sources. The detection light enters the modular dual-resonant photoacoustic cell and reacts with the two-component gas to generate a photoacoustic signal. After resonance enhancement, the photoacoustic signal is transmitted to the signal demodulation circuit. The signal demodulation circuit processes the enhanced photoacoustic signal to obtain the concentration result of the two-component gas, which is then transmitted to the host computer for display.

[0020] like Figure 2 and Figure 3 As shown, the modular dual-resonant photoacoustic cell includes a buffer structure module 1, a resonant structure module 2, a pickup mounting module 3, a first window support 4, a second window support 5, a first transmission lens 6, and a second transmission lens 7; the resonant structure module 2 is installed on the top of the buffer structure module 1; the pickup mounting module 3 is installed on the top of the resonant structure module 2; the first transmission lens 6 is installed on the left side of the buffer structure module 1 and fixed with the first window support 4; the second transmission lens 7 is installed on the right side of the buffer structure module 1 and fixed with the second window support 5.

[0021] like Figure 4 As shown, the buffer structure module 1 has a buffer cavity 13 inside, and an air inlet 11 and an exhaust 12 are provided on the front side to communicate with the buffer cavity 13. The left and right sides are symmetrically provided with a first lens mounting groove 15 and a second lens mounting groove 16 with identical structures. The top is provided with a resonant structure mounting groove 14, which communicates with the buffer cavity 13. like Figure 5 As shown, the top of the resonant structure module 2 is symmetrically provided with a first resonant cavity 21 and a second resonant cavity 22 with identical dimensions and structures. The first resonant cavity 21 and the second resonant cavity 22 are respectively provided with a first connecting cavity 23 and a second connecting cavity 24 at their coaxial positions. The first connecting cavity 23 and the second connecting cavity 24 have the same length but different diameters, which are used to connect the first connecting cavity 23 and the second connecting cavity 24 with the buffer cavity 13. like Figure 6 As shown, the top of the pickup mounting module 3 is symmetrically provided with a first pickup mounting slot 31 and a second pickup mounting slot 32 for mounting photoacoustic signal receiving devices, such as pickups or microphones; the first pickup mounting slot 31 is coaxially connected to the first resonant cavity 21, and the second pickup mounting slot 32 is coaxially connected to the second resonant cavity 22.

[0022] The modular dual-resonant photoacoustic cell described in this invention is based on the acoustic principle of a Helmholtz resonator. Through a specific structural design, it achieves two independent resonant frequencies and synchronously enhances the photoacoustic signals of different target gas molecules. The specific principle is as follows: The essence of photoacoustic effect is that light absorption induces thermal expansion to generate sound waves (pressure waves). When the frequency of the sound wave matches the inherent acoustic resonant frequency of the photoacoustic cell, an acoustic standing wave is generated, and the sound pressure signal is significantly amplified, that is, acoustic resonance occurs.

[0023] A Helmholtz resonant cavity consists of a resonant cavity and a connecting cavity, and its natural resonant frequency is... f 0 is approximately described by the following formula: ; in, c The speed of sound in a gas is related to ambient temperature and gas composition. S This represents the cross-sectional area of ​​the connecting cavity; V The volume of the resonant cavity; L The effective length of the connecting cavity; The natural resonant frequency of a Helmholtz resonator f 0 and the cross-sectional area of ​​the connecting cavity S It is proportional to the square root and to the effective length of the connecting cavity. L and resonant cavity volume V It is inversely proportional to the square root.

[0024] In this embodiment, the first resonant cavity 21 and the first connecting cavity 23, the second resonant cavity 22 and the second connecting cavity 24 essentially each constitute an independent Helmholtz resonant cavity. The volume of the first resonant cavity 21 is... V 1. The volume of the second resonant cavity 22 is V 2. The effective length of the first connecting cavity 23 is L 1. The cross-sectional area is S 1. The effective length of the second connecting cavity 24 is L 2, cross-sectional area is S 2; The first resonant cavity 21 and the second resonant cavity 22 have the same size and structure, that is V 1= V 2; The first connecting cavity 23 and the second connecting cavity 24 have the same effective length, that is L 1= L 2; The first connecting cavity 23 and the second connecting cavity 24 have different diameters, therefore their cross-sectional areas are different. S 1≠ S 2. Based on the Helmholtz resonant frequency formula, two independent and separate resonant frequencies were directly achieved by connecting cavities of different diameters. f 1 and f 2; The modulation signal circuit modulates the frequency of the first detection light source to the inherent resonant frequency of the first resonant cavity 21. f 1. Modulate the frequency of the second detection light source to the inherent resonant frequency of the second resonant cavity 22. f 2; The photoacoustic signal excited by the first probe light undergoes strong acoustic resonance in the first resonant cavity 21, and the sound pressure signal is significantly amplified. The photoacoustic signal excited by the second probe light undergoes strong acoustic resonance in the second resonant cavity 22, and the sound pressure signal is significantly amplified. The two resonant cavities are physically isolated, and the two frequency resonance enhancement processes occur independently in their respective resonant cavities without interfering with each other.

[0025] Two microphones are respectively installed in the first microphone mounting slot 31 and the second microphone mounting slot 32. The two microphones pick up photoacoustic signals of different gases in the two-component gas. Since the resonant frequencies are separate and the microphones are close to their respective resonant cavity sound sources, the signal demodulation circuit can easily separate the components of the corresponding gases in the signals output by the two microphones through frequency selection or phase-locked loop amplification technology, and demodulate to obtain the concentration information of the two gases.

[0026] Based on the natural resonant frequency of the Helmholtz resonator f The formula for 0 is obtained by changing the cross-sectional area of ​​the connecting cavity. S or length L Or change the volume of the resonant cavity V Both can change the resonant frequency. f 0; This invention features a modular design, particularly the replaceable resonant structure module 2. By replacing the resonant structure module 2 with different combinations of the diameters of the first connecting cavity 23 and the second connecting cavity 24, the cross-sectional area of ​​the two connecting cavities can be easily changed. S 1 and S 2. This allows for the alteration of the resonant frequencies of the two resonant cavities, enabling flexible adjustment of the resonant frequency. This allows the system to adapt to the optimal modulation frequency required by different target gas molecules and actively avoid strong noise frequencies present in the environment, thereby improving the signal-to-noise ratio and detection sensitivity.

[0027] Example 2 This embodiment provides a method for detecting two-component gases based on a modular dual-resonant photoacoustic cell, including the following steps: The two-component gas enters the buffer chamber 13 through the air inlet 11, diffuses to the first resonant chamber 21 and the second resonant chamber 22 via the first connecting chamber 23 and the second connecting chamber 24, and is discharged through the exhaust port 12. The modulation signal circuit uses the resonant frequencies of the first resonant cavity 21 and the second resonant cavity 22. f 1. f 2. Modulate the detection light frequency of the first and second detection light sources; The detection light from the first detection light source enters the buffer cavity 13 through the first transmission lens 6, and the detection light from the second detection light source enters the buffer cavity 13 through the second transmission lens 7, generating a photoacoustic signal. The first resonant cavity 21 and the second resonant cavity 22 amplify the photoacoustic signal at the corresponding resonant frequency; The photoacoustic signal receiving device collects photoacoustic signals and transmits them to the signal demodulation circuit to obtain the concentration results of the two-component gas. The gas concentration results are sent to the host computer for display.

[0028] Preferably, the wavelengths modulated by the first and second detection light sources correspond to the absorption peak wavelengths of the two different gases in the two-component analyte gas, respectively. Preferably, the data sampling rate of the signal demodulation circuit is greater than 5 times the highest resonant frequency. The high sampling rate can clearly restore the signal characteristics of the two frequencies, improve the signal-to-noise ratio, and ensure that the gas concentration results are stable and reliable.

[0029] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A dual-component gas detection device based on a modular dual-resonance photoacoustic cell, comprising a modulation signal circuit, a first probe light source, a second probe light source, a modular dual-resonance photoacoustic cell, a signal demodulation circuit and an upper computer, characterized in that, The modular dual-resonance photoacoustic cell comprises: a buffer structure module (1) having a buffer cavity (13) opened inside, in which a dual-component gas to be measured and probe light generate photoacoustic effect; a resonance structure module (2) connected to the top of the buffer structure module (1), having two first and second resonance cavities (21, 22) of the same size opened on the top, a first connecting cavity (23) coaxially opened below the first resonance cavity (21), a second connecting cavity (24) coaxially opened below the second resonance cavity (22), the first and second connecting cavities (23, 24) having the same length and different diameters, and being in communication with the buffer cavity (13); a pickup mounting module (3) connected to the top of the resonance structure module (2) for picking up photoacoustic signals; a first window fixed support (4) for fixing a first transmission lens (6) on the left side of the buffer structure module (1); a second window fixed support (5) for fixing a second transmission lens (7) on the right side of the buffer structure module (1).

2. The dual-component gas detection device based on a modular dual- resonant photoacoustic cell of claim 1, wherein, The resonance structure module (2) is a replaceable module having different diameter combinations of the first and second connecting cavities (23, 24), and different diameter combinations are selected according to the optimal modulation frequency required by different components in the dual-component gas to be measured.

3. The dual-component gas detection device based on a modular dual- resonant photoacoustic cell of claim 1, wherein, The buffer structure module (1) is provided with an air inlet hole (11) and an air outlet hole (12) on the front side, the air inlet hole (11) and the air outlet hole (12) are in communication with the buffer cavity (13), and are used for introducing the dual-component gas to be measured.

4. The dual-component gas detection apparatus based on a modular dual- resonant photoacoustic cell of claim 1, wherein, The buffer structure module (1) is symmetrically provided with a first lens mounting groove (15) and a second lens mounting groove (16) on the left and right sides, and is used for mounting the first and second transmission lenses (6, 7).

5. The dual-component gas detection apparatus based on a modular dual- resonant photoacoustic cell of claim 1, wherein, The buffer structure module (1) is provided with a resonance structure mounting groove on the top, and is used for mounting the resonance structure module (2).

6. The dual-component gas detection apparatus based on a modular dual- resonant photoacoustic cell of claim 1, wherein, The pickup mounting module (3) is provided with a first pickup mounting groove (31) and a second pickup mounting groove (32) on the top, and is used for mounting photoacoustic signal receiving equipment; The first pickup mounting groove (31) is coaxially communicated with the first resonance cavity (21), and the second pickup mounting groove (32) is coaxially communicated with the second resonance cavity (22).

7. The dual-component gas detection apparatus based on a modular dual- resonant photoacoustic cell of claim 6, wherein, The photoacoustic signal receiving equipment in the first and second pickup mounting grooves (31, 32) picks up photoacoustic signals of different frequencies in the first and second resonance cavities (21, 22) respectively, a signal demodulation circuit separates photoacoustic signals of different frequencies, and demodulates to obtain concentration information of different gases.

8. A method of two-component gas detection based on a modular dual-resonance photoacoustic cell, characterized in that, The method comprises the following steps: The dual-component gas to be measured enters the buffer cavity (13) through the air inlet hole (11), diffuses to the first and second resonance cavities (21, 22) through the first and second connecting cavities (23, 24), and is discharged through the air outlet hole (12); The modulation signal circuit modulates the resonant frequency of the first resonant cavity (21) and the second resonant cavity (22) f 1、 f 2 modulating the probe light frequency of the first probe light source and the second probe light source; Probe light of a first probe light source is emitted into the buffer cavity (13) from the first transmission lens (6), and probe light of a second probe light source is emitted into the buffer cavity (13) from the second transmission lens (7), to generate photoacoustic signals; The first and second resonance cavities (21, 22) enhance photoacoustic signals of corresponding resonance frequencies; The photoacoustic signal receiving device picks up the photoacoustic signal and transmits to the signal demodulation circuit to obtain a dual-component gas concentration result; The gas concentration result is sent to a host computer for display.

9. The method according to claim 8, wherein, The modulated wavelengths of the first probe light source and the second probe light source correspond to the absorption peak wavelengths of two different gases in the dual-component gas to be measured.

10. The method of claim 8, wherein, The data sampling rate of the signal demodulation circuit is greater than 5 times the highest resonant frequency.

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