A gas component detection device based on an acoustic waveguide cavity and a detection method thereof

Abstract

The application discloses a kind of gas component detection devices based on acoustic waveguide, including symmetrically arranged first acoustic waveguide and second acoustic waveguide, first acoustic waveguide and second acoustic waveguide are communicated by transition cavity between first acoustic waveguide and second acoustic waveguide, and the opening of transition cavity two ends is respectively sound wave incident port and sound wave emission port, first acoustic waveguide and second acoustic waveguide all include several grooves, the groove of first acoustic waveguide and second acoustic waveguide is communicated with transition cavity, and symmetric about transition cavity, the depth of several grooves gradually deepens and then gradually becomes shallow along the direction of sound wave incident port to sound wave emission port. eff The symmetric gradient structure with gradient change of groove depth first increases and then decreases makes the equivalent refractive index n eff of waveguide cavity inside present gradient change, which can support both transmission wave mode and surface wave mode, and when impedance matching condition is not satisfied, sound wave can also be converted and superimposed in various modes to penetrate waveguide cavity.

Description

Technical Field

[0001] This invention relates to gas detection, specifically to a gas composition detection device and method based on an acoustic waveguide cavity. Background Technology

[0002] With the continuous progress and development of modern science and technology, , , , Various gases are widely used in industry, medicine, and other fields. Therefore, the monitoring and detection of the composition and concentration of various gases is of paramount importance in industrial production and people's daily lives. In recent years, both domestically and internationally, corresponding detection methods have been developed based on the different application scenarios of various gases, such as optical methods, electrochemical methods, photoacoustic spectroscopy, semiconductor methods, and catalytic methods, etc.

[0003] Optical methods utilize the principles of spectroscopy. Light of a specific wavelength is incident on the gas to be measured. The emitted light is partially absorbed by the gas, and the concentration is measured using Lambert-Beer's law by calculating the absorbed intensity. Electrochemical methods involve oxidation or reduction reactions of the gas at electrodes. Gas parameters are further determined by measuring the current from a current sensor. Photoacoustic spectroscopy involves sealing the gas in a photoacoustic cell and shining a beam of high-intensity modulated light into the cell. The absorbed light energy is converted into heat and released. This released heat fluctuates periodically with the modulation frequency of the light, causing pressure fluctuations, which are detected by an acoustic sensor to calculate the gas parameters. Semiconductor methods involve reacting the gas with a metal oxide semiconductor surface. Gas parameters are measured based on the amount consumed in the reaction. Catalytic methods are often used in combustion and explosion scenarios. They utilize the thermal effect of combustion to cause a thermal reaction on the surface of a bridge circuit consisting of a detection element and a compensation element. This change in the resistance of the detection element generates an electrical signal for gas analysis.

[0004] The methods described above all have their own limitations. Optical methods are precise, but expensive and consume a lot of power. Electrochemical methods have low power consumption and high accuracy, but their application scenarios are limited and they cannot be effective for high-concentration gases. Wideband acoustic spectroscopy has high accuracy, but slow detection speed, high power consumption, and poor anti-interference ability. Semiconductor methods are low in cost, but have poor stability and linearity. Catalytic methods are inexpensive and precise, but they also have drawbacks such as high power consumption and slow reaction speed. Summary of the Invention

[0005] Purpose of the invention: To address the above-mentioned shortcomings, the present invention provides a gas composition detection device based on an acoustic waveguide cavity that features high sensitivity, high speed, and low power consumption.

[0006] The present invention also provides a detection method for a gas composition detection device.

[0007] Technical Solution: To solve the above problems, the present invention employs a gas composition detection device based on acoustic waveguides, comprising a first acoustic waveguide and a second acoustic waveguide symmetrically arranged, which are connected by a transition cavity. The two ends of the transition cavity are provided with an acoustic wave incident port and an acoustic wave exit port, respectively. Both the first and second acoustic waveguides include a plurality of grooves, which are connected to the transition cavity and are symmetrical about the transition cavity. The depth of the plurality of grooves gradually increases and then gradually decreases along the direction from the acoustic wave incident port to the acoustic wave exit port.

[0008] Furthermore, the grooves in the first and second acoustic waveguides are periodically and symmetrically distributed. The transition cavity is a rectangular cavity. The dispersion equation of the parallel metal plate acoustic SFS waveguide with a periodically symmetrical pleated structure is:

[0009]

[0010]

[0011] in, The width of the groove. For a single groove unit period, The depth of the groove. The distance between the first acoustic waveguide and the second acoustic waveguide. Let be the sound wave propagation constant. For the wave vector in the air, The wavelength of the sound wave;

[0012] When the first acoustic waveguide, the second acoustic waveguide, and the transition cavity are filled with a medium, the dispersion curve fitted by the dispersion equation generates a bandgap. Based on the dispersion curve, the frequency value of the lower limit of the bandgap is determined, thereby determining the deepest groove depth of the first and second acoustic waveguides. Along the direction from the sound wave incident port to the sound wave exit port, with the groove depth... Based on this, the depths of other grooves satisfy the arithmetic progression of the propagation constant in the first or second acoustic waveguide.

[0013] Furthermore, the single groove unit periodicity The width of the groove The spacing between the first and second acoustic waveguides is g = 3.0 cm. Both waveguides have 30 grooves. Along the direction from the sound wave incident port to the sound wave exit port, the depth gradient of the first 15 grooves increases progressively, at 0.09, 0.134, 0.157, 0.17, 0.18, 0.188, 0.194, 0.199, 0.203, 0.206, 0.21, 0.212, 0.214, 0.216, and 0.218 (in dm). The depth gradient of the last 15 grooves decreases progressively, at 0.218, 0.216, 0.214, 0.212, 0.21, 0.206, and 0.203 (in dm). 0.199, 0.194, 0.188, 0.18, 0.17, 0.157, 0.134, 0.09, in dm.

[0014] This invention also employs a detection method using a gas composition detection device, characterized by comprising the following steps:

[0015] (1) Obtain standard band gap curves of different gases in a gas composition detection device;

[0016] (2) Fill the gas medium to be detected into the gas composition detection device;

[0017] (3) Input a sound wave at the sound wave incident port and detect the change curve of the band gap of the emitted sound wave at the sound wave exit port;

[0018] (4) Compare the measured bandgap change curve with the standard bandgap curve to obtain the gas characteristic parameters corresponding to the bandgap change curve and complete the gas composition detection.

[0019] Beneficial effects: Compared with the prior art, the significant advantage of this invention is that, based on the parallel metal plate acoustic waveguide, a symmetrical gradient metasurface acoustic waveguide with increasing and then decreasing groove depths is designed. This structure makes the effective refractive index inside the waveguide cavity... It exhibits a gradient variation, which can support both transmission wave modes ( It also supports surface wave mode. Even when impedance matching conditions are not met, sound waves can still be converted and superimposed in various modes to pass through the waveguide cavity. It is made of aluminum alloy, which is inexpensive, simple in structure, and easy to manufacture. Furthermore, it offers advantages such as high speed, high accuracy, and low energy consumption in gas detection applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the gas composition detection device in this invention;

[0021] Figure 2This is an XY cross-sectional view of the gas composition detection device in this invention;

[0022] Figure 3 This is a graph showing the relationship between the groove depth h and the propagation constant β in this invention.

[0023] Figure 4 Waveguide plate spacing in this invention Dispersion curve at cm;

[0024] Figure 5 Waveguide plate spacing in this invention Dispersion curve at cm;

[0025] Figure 6 Waveguide plate spacing in this invention Dispersion curve at cm;

[0026] Figure 7 The internal dielectric of the waveguide in this invention is The prohibited items map at that time;

[0027] Figure 8 The internal dielectric of the waveguide in this invention is The prohibited items map at that time;

[0028] Figure 9 The internal dielectric of the waveguide in this invention is The prohibited items map at that time;

[0029] Figure 10 The internal dielectric of the waveguide in this invention is The prohibited items map at that time;

[0030] Figure 11 This is the bandgap diagram when the internal medium of the waveguide in this invention is air;

[0031] Figure 12 This is a parameter diagram of the various gaseous media filling the waveguide cavity in this invention. Detailed Implementation

[0032] Example 1

[0033] like Figure 1 As shown, this embodiment of a gas composition detection device based on an acoustic waveguide cavity comprises two metal plates (5, 6) and a rectangular transition cavity 3 in the middle. The transition cavity 3 has openings at both ends, namely an acoustic wave incident port 31 and an acoustic wave exit port 32. A first acoustic waveguide 1 and a second acoustic waveguide 2 are respectively disposed inside the two metal plates (5, 6). The first acoustic waveguide 1 and the second acoustic waveguide 2 of the two metal plates (5, 6) are mirror-symmetrical in the X-direction. The two metal plates are made of aluminum alloy, and the dimensions of the metal plate with a groove on one side are... mm, while the external dimensions of the rectangular cavity in the middle of the waveguide are mm, internal dimensions are mm.

[0034] Figure 2 As shown, both metal plates (5 and 6) are provided with several grooves 4. In this embodiment, each metal plate has 30 gradient groove structure units inside, and the groove openings face the YZ plane. The metal plate spacing g = 3.0 cm, and the period... , slot width ,in m is the wavelength of the sound wave. The groove structure units are arranged periodically along the Y direction, and the groove depth is [insert value here]. ~ The refractive index varies gradually. This is because the gas composition detection device needs to ensure that adjacent metal grooves along the direction of sound wave propagation meet the equivalent refractive index requirement. The effective refractive index is gradually varied to support high transmission of sound waves over a wider frequency band. This gradual variation is reflected in the propagation constant. On the arithmetic progression, along the direction from the sound wave incident port to the sound wave exit port, with the groove depth... Based on this, the depths of other grooves gradually change arithmetically in accordance with the propagation constants in the first or second acoustic waveguide. For example... Figure 3 As shown, considering that the designed structure operates in the 2000-6000Hz frequency range, and combining the frequency value of the lower bandgap determined by the dispersion curve, extensive inversion verification was performed based on the dispersion curve to obtain the groove depths corresponding to 15 gradually changing propagation constants in a single metal groove structure. These values, from smallest to largest, are 0.09, 0.134, 0.157, 0.17, 0.18, 0.188, 0.194, 0.199, 0.203, 0.206, 0.21, 0.212, 0.214, 0.216, and 0.218, in dm. Simultaneously, the latter 15 groove depth values ​​also... ~ The 15 groove depth values, decreasing in size, are 0.218, 0.216, 0.214, 0.212, 0.21, 0.206, 0.203, 0.199, 0.194, 0.188, 0.18, 0.17, 0.157, 0.134, and 0.09, respectively, in dm.

[0035] Figure 4 It is based on the dispersion equation of a parallel metal plate acoustic (SFS) waveguide with an internal periodic symmetrical pleated structure (in the case of a vacuum cavity):

[0036]

[0037]

[0038] For different trench depths The dispersion curve plotted under the condition (where) For the width of the groove, For a single slot unit cycle, The depth of the groove. The spacing between the metal plates. Let be the sound wave propagation constant. For the wave vector in the air, (Where the wavelength is called the acoustic wavelength). It is evident that the SFS waveguide can support both transmission wave modes (…). It also supports surface wave mode. When the cavity is filled with a medium, the equivalent refractive index within the groove changes, thus altering the dispersion curve. Therefore, different gaseous media will produce different band gap curves. When the cavity is filled with air, when... (Without the metal groove), the surface wave mode is no longer supported, and the dispersion equation always has a solution, so no band gap exists. When When the surface wave mode is excited in the metal groove, a band gap is generated, such as... Figure 4 The shaded area is shown. The frequency value of the lower bandgap limit is determined based on the dispersion curve, thereby determining the deepest groove depth of the first and second acoustic waveguides. .

[0039] Figure 4 The shaded area shown is The forbidden band area is defined by the shaded area, with the upper and lower bounds corresponding to the upper and lower limits of the forbidden band area. (From the diagram...) The effect of changes in depth on surface wave dispersion can be seen to be that, with the depth value... As the bandgap increases, the lower bandgap frequency undergoes a red shift, because each metal groove can be considered as a depth of... The resonant cavity, inside the cavity ( (where the propagation mode order is), so The smaller the value, the higher the resonant frequency.

[0040] Based on the aforementioned dispersion characteristics, in order to create a bandgap for sound waves in the designed acoustic waveguide, we designed a parallel metal plate with 30 slots. The depth of the slots in the Y direction is respectively from... Increment to Then by Decrease to That is, gradient symmetry, this structure can support transmission wave modes ( It also supports surface wave mode. Even when impedance matching conditions are not met, sound waves can still be converted and superimposed in various modes to pass through the waveguide cavity.

[0041] Figure 4 ,5 6 is based on the relationship satisfied by the waveguide propagation mode:

[0042]

[0043] Based on the relationship between the metal plate spacing and the band gap curve, the shaded area in the figure is... The corresponding prohibited items, Figure 4 , 5 6 and 6 correspond to the cases when g = 3.0cm, 4.0cm, and 5.0cm, respectively. From Figure 4 , 5 A comparison of points 6 and 7 shows that the upper bandgap depends on the spacing between the parallel waveguides. , The larger the value, the smaller the upper bandgap frequency ( ). When the value exceeds a certain threshold, the bandgap disappears, such as... Figure 6 As shown, the upper and lower limits coincide, and the no-band restriction disappears.

[0044] Figures 7 to 11 Based on the aforementioned theories, models, and gas measurement methods, the filling... , , , And air (gas parameters such as) Figure 12 As shown, the bandgap curves for different gas media obtained from simulation under the condition that the ambient temperature is set to 15° are shown.

[0045] Based on the bandgap curves in the figure and the aforementioned theory, it can be seen that below the lower bandgap frequency, due to the continuous and smooth gradient phase shift generated between the waveguide gradient surface and the air, the waveguide operates in surface wave mode, either without reflection or generating higher-order modes, thus achieving high-energy transmission. Above the lower bandgap frequency, because neither the surface wave mode nor the propagation mode is supported in certain regions, surface waves cannot continue to propagate to the right, and the waveguide operates in a high-energy reflection state.

[0046] The gas composition detection device is made of aluminum alloy, which is inexpensive, simple in structure, and easy to manufacture. Furthermore, it offers advantages such as high speed, high accuracy, and low energy consumption in gas detection.

[0047] Example 2

[0048] This embodiment describes a detection method using the gas composition detection device described in Embodiment 1 above, the specific details of which are as follows:

[0049] First, different gas media have different bandgap curves. Therefore, in industrial or medical fields, finite element simulations can be performed on waveguide cavities filled with various gases. Since different gas media will produce different equivalent refractive indices in the cavity, standard bandgap curves for different gas fillings can be recorded and obtained.

[0050] Secondly, the gas medium to be tested is filled into the waveguide cavity, and then an acoustic wave is input into the incident port of the waveguide cavity. A high-sensitivity acoustic detector is then connected to the exit port of the waveguide cavity. The detector is used to detect the bandgap change curve of the exit acoustic wave. The bandgap curve measured at the exit port is compared with the standard bandgap curve to find the standard bandgap curve that matches the measured value. The gas characteristic parameters corresponding to the standard bandgap curve are the gas parameter values ​​of the gas to be tested, thereby realizing the detection of gas composition.

Claims

1. A gas composition detection device based on acoustic waveguides, characterized in that, The device includes a first acoustic waveguide and a second acoustic waveguide arranged symmetrically. The first acoustic waveguide and the second acoustic waveguide are connected by a transition cavity. The two ends of the transition cavity are provided with an acoustic wave incident port and an acoustic wave exit port, respectively. The first acoustic waveguide and the second acoustic waveguide each include a number of grooves. The grooves of the first acoustic waveguide and the second acoustic waveguide are connected to the transition cavity and are symmetrical about the transition cavity. The depth of the grooves gradually increases and then gradually decreases along the direction from the acoustic wave incident port to the acoustic wave exit port. The grooves in the first and second acoustic waveguides are periodically and symmetrically distributed. The transition cavity is a rectangular cavity; The dispersion equation for a parallel metal plate acoustic SFS waveguide with a periodically symmetrical pleated structure is: in, The width of the groove. For a single groove unit period, The depth of the groove. The distance between the first acoustic waveguide and the second acoustic waveguide. Let be the sound wave propagation constant. For the wave vector in the air, The wavelength of the sound wave; When the first acoustic waveguide, the second acoustic waveguide, and the transition cavity are filled with a medium, the dispersion curve fitted by the dispersion equation generates a bandgap. Based on the dispersion curve, the frequency value of the lower limit of the bandgap is determined, thereby determining the deepest groove depth of the first and second acoustic waveguides. ; Along the direction from the sound wave incident port to the sound wave exit port, with the groove depth Based on this, the depths of other grooves satisfy the arithmetic progression of the propagation constant in the first or second acoustic waveguide. The single groove unit period The width of the groove .

2. The gas composition detection device according to claim 1, characterized in that, For the spacing g between the first acoustic waveguide and the second acoustic waveguide, The first and second acoustic waveguides are each 3.0 cm in diameter and have 30 grooves. Along the direction from the sound wave incident port to the sound wave exit port, the depth gradient of the first 15 grooves increases progressively, and is 0.09, 0.134, 0.157, 0.17, 0.18, 0.188, 0.194, 0.199, 0.203, 0.206, 0.21, 0.212, 0.214, 0.216, and 0.218 respectively (in dm). The depth gradient of the last 15 grooves decreases progressively, and is 0.218, 0.216, 0.214, 0.212, 0.21, 0.206, 0.203, 0.199, 0.194, 0.188, 0.18, 0.17, 0.157, 0.134, and 0.09 respectively (in dm).

3. The gas composition detection device according to claim 1, characterized in that, The first and second acoustic waveguides are made of aluminum alloy.

4. A detection method using the gas composition detection device according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Obtain standard band gap curves of different gases in a gas composition detection device; (2) Fill the gas medium to be detected into the gas composition detection device; (3) Input a sound wave at the sound wave incident port and detect the change curve of the band gap of the emitted sound wave at the sound wave exit port; (4) Compare the measured bandgap change curve with the standard bandgap curve to obtain the gas characteristic parameters corresponding to the bandgap change curve and complete the gas composition detection.

5. The detection method according to claim 4, characterized in that, In step (1), the gas composition detection device under various gas filling conditions is simulated by finite element method. Due to different gas media filling, the cavity of the gas composition detection device produces different equivalent refractive indices, thereby obtaining the standard bandgap curve when filled with different gases.

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