A surface acoustic wave gas leak detection method and system

Abstract

The present invention relates to a surface acoustic wave (SAW) gas leak detection method, comprising: inputting the same excitation signal, collecting the output signal of a SAW detection device in a background gas, recording it as a first signal; collecting the output signal of the SAW detection device in a gas to be detected, recording it as a second signal; calculating the energy difference between the second signal and the first signal, recording it as an energy attenuation difference; and calculating the volume concentration of the leaked gas based on the calculated energy attenuation difference. The method and system of the present invention also include an excitation unit, a SAW detection device, a collection unit, and a calculation unit. The method and system achieve rapid response to gas leak detection, a wide measurement range, and low power consumption.

Description

Technical Field

[0001] The present invention relates to the field of gas leakage detection, in particular to a surface acoustic wave gas leakage detection method and system. Background Art

[0002] Rapid and accurate detection of leaks of industrial gases such as hydrogen, argon, neon, and helium, and timely warnings are key to ensuring personnel safety, avoiding environmental pollution, and ensuring the safe production, transportation, and use of gases. Gas leak detection is crucial for early warning of leaks. Typical gas leak detection methods include photoacoustic spectroscopy, electrochemical methods, infrared methods, and acoustic methods. Among acoustic methods, surface acoustic wave (SAW) gas leak detection is gaining attention due to its high sensitivity, fast response, miniaturization, lightweight design, and ease of integration.

[0003] Typical surface acoustic wave gas leak detection methods can be roughly divided into two categories:

[0004] (1) Chemical formula: By depositing specific gas-sensitive materials on the sound propagation path, the gas-sensitive materials adsorb gas, causing changes in the sound propagation characteristics. Gas information can then be decoupled from the sound wave characteristics. This is generally achieved based on the load effect, viscoelastic effect, and acoustic-electric coupling effect, and often uses a surface acoustic wave detection device with a delayed structure. Currently, chemical methods have been used to detect a series of industrial gases such as ammonia, hydrogen sulfide, and hydrogen, demonstrating high sensitivity.

[0005] (2) Physical method: A micro heater is integrated on the surface of a piezoelectric crystal with a high temperature coefficient to increase the temperature of the surface acoustic wave (SAW) sensor. Due to the different thermal conductivities of different gases, the temperature of the SAW sensor changes in different gas atmospheres, causing the SAW velocity to change. This allows the detection of different gases. This detection method is also called a thermal conductivity SAW gas leak detection method. SAW detection devices generally use a resonator structure. Currently, hydrogen and helium gas detection can be achieved, showing a wide range of characteristics.

[0006] The two aforementioned surface acoustic wave (SAW) gas leak detection methods have developed rapidly. However, the chemical method, due to the use of gas-sensitive materials, has a limited lifespan of SAW detection devices, typically less than 10 years. Physical methods also consume high power, especially in low-temperature environments, and have a slow response speed. Summary of the Invention

[0007] In view of this, the main object of the present invention is to provide a surface acoustic wave gas leak detection method and system, which can achieve rapid response to gas leak detection, and has a wide measurement range and low power consumption.

[0008] To achieve the above-mentioned purpose, on the one hand, the present application provides a surface acoustic wave gas leakage detection method, comprising: inputting the same excitation signal,

[0009] collecting an output signal of the surface acoustic wave detection device in the background gas and recording it as a first signal;

[0010] collecting an output signal of the surface acoustic wave detection device in the gas to be detected, and recording it as a second signal;

[0011] Calculate the energy difference between the second signal and the first signal, and record it as the energy attenuation difference;

[0012] The volume concentration of the leaked gas is calculated using the calculated energy attenuation difference.

[0013] In one possible implementation, the first signal and the second signal are collected using the same surface acoustic wave detection device.

[0014] In another possible implementation, the formula for calculating the volume concentration of the leaked gas is expressed as:

[0015]

[0016] Where Δα is the calculated energy attenuation difference, ρ c is the density of the gas to be detected, V c is the wave velocity of the gas to be detected, ρ0 is the background gas density, V0 is the background gas wave velocity, ρ s is the piezoelectric crystal density, V s is the wave velocity of the piezoelectric crystal, f is the frequency of the surface acoustic wave detection device, L is the length of the sound propagation path, P is the ambient pressure, ρ1 is the leakage gas density, γ0 is the gas adiabatic coefficient, K s is the adiabatic compression coefficient, and C is the volume concentration of the leaked gas.

[0017] In another possible implementation, the acoustic propagation path length of the surface acoustic wave detection device is not less than 2λ, where λ is the wavelength of the acoustic wave.

[0018] In another possible implementation, the frequency of the surface acoustic wave detection device is not less than 10 MHz.

[0019] In another possible implementation, the surface acoustic wave detection device adopts an extended line structure, a reflection delay line structure, or a resonator structure.

[0020] On the other hand, the present application also provides a surface acoustic wave gas leakage detection system, comprising: an excitation unit, a surface acoustic wave detection device, a collection unit, and a calculation unit; wherein,

[0021] an excitation unit, inputting the same excitation signal to the surface acoustic wave detection device;

[0022] an acquisition unit for acquiring an output signal of the surface acoustic wave detection device in a background gas, which is recorded as a first signal; and an output signal of the surface acoustic wave detection device in a gas to be detected, which is recorded as a second signal;

[0023] The calculation unit calculates the energy difference between the second signal and the first signal, which is recorded as an energy attenuation difference; and calculates the volume concentration of the leaked gas based on the calculated energy attenuation difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of a surface acoustic wave gas leak detection method according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic structural diagram of an extended linear surface acoustic wave detection device according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the circuit principle of the extended linear surface acoustic wave detection device for collecting signals according to an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of the structure of a reflection delay line surface acoustic wave detection device according to an embodiment of the present invention;

[0028] Figure 5 Schematic diagram of the structure of a resonator-type surface acoustic wave detection device according to an embodiment of the present invention;

[0029] Figure 6 A schematic diagram of the response / recovery time for verifying different hydrogen concentrations;

[0030] Figure 7 Schematic diagram of response / recovery time for verifying a 30% hydrogen concentration;

[0031] Figure 8 Schematic diagram to verify the frequency response of the second detection device exposed to air;

[0032] Figure 9 Schematic diagram to verify the frequency response of the second detection device exposed to helium;

[0033] Figure 10 Schematic diagram for verifying the frequency response of the three detection devices;

[0034] Figure 11 Schematic diagram of the energy attenuation of surface acoustic waves in air / carbon dioxide gas mixtures with different hydrogen concentrations. DETAILED DESCRIPTION

[0035] The implementation principle and advantages of the present invention are as follows:

[0036] Gas leakage changes the acoustic impedance of the gas surrounding the surface acoustic wave detection device, thereby changing the energy radiated by the surface acoustic wave into the gas. Therefore, the present invention obtains the difference in energy attenuation of the surface acoustic wave in the gas to be detected and the background gas by collecting the first signal and the second signal and calculating the difference in the energy of the two signals. The volume concentration of the leaked gas is calculated based on the obtained difference in energy attenuation.

[0037] That is, the present invention detects gas leakage based on the change in the energy radiated into the gas by the surface acoustic wave caused by the detection of gas leakage, rather than the change in the sound propagation characteristics of specific components of the surface acoustic wave detection device, such as gas-sensitive films, piezoelectric crystals with high temperature coefficients, etc., and the surface acoustic wave detection device does not need to be provided with such components, thereby avoiding the problems of poisoning and limited life of the surface acoustic wave detection device caused by gas-sensitive materials, and also avoiding the problems of high power consumption, increased power consumption in low-temperature environments, and low response speed caused by the use of piezoelectric crystals with integrated micro-heaters. In addition, the surface acoustic wave detection device proposed in the present application can have the characteristics of high repeatability, high consistency, miniaturization, light weight, and mass production.

[0038] The detection method of the present invention has higher detection sensitivity for gas leaks with greater acoustic impedance difference from the background gas. For example, using the air in the site where gases are packaged, transported, and used as the background gas, the detection sensitivity is higher for leaks of gases such as hydrogen, helium, argon, hydrogen sulfide, ammonia, carbon monoxide, carbon dioxide, and methane.

[0039] Specifically, the process of a surface acoustic wave gas leakage detection method according to an embodiment of the present invention is as follows: Figure 1 As shown, it includes steps 101 to 104.

[0040] Step 101: input an excitation signal, and collect an output signal of a surface acoustic wave detection device in a background gas, which is recorded as a first signal.

[0041] Step 102: Input the same excitation signal as in step 101, and collect the output signal of the surface acoustic wave detection device in the gas to be detected, which is recorded as the second signal.

[0042] Step 103: Calculate the energy difference between the second signal and the first signal, and record it as the energy attenuation difference.

[0043] Step 104: Calculate the volume concentration of the leaked gas using the calculated energy attenuation difference.

[0044] Here, in an actual usage scenario, step 101 is performed in advance and the first signal is stored, and steps 102 to 104 are performed in real time or periodically to determine whether there is a gas leak.

[0045] In steps 101 and 102, in order to offset the energy attenuation of the surface acoustic wave in the surface acoustic wave detection device, that is, the energy loss in the piezoelectric crystal, so that the energy attenuation difference is the difference between the energy attenuation of the surface acoustic wave in the gas to be detected and the background gas, the same surface acoustic wave detection device is used to collect the first signal and the second signal.

[0046] In one possible implementation, in step 103, the formula for calculating the volume concentration of the leaked gas is expressed as:

[0047]

[0048] Where Δα is the calculated energy attenuation difference, ρ c is the density of the gas to be detected, V c is the wave velocity of the gas to be detected, ρ0 is the background gas density, V0 is the background gas wave velocity, ρ s is the piezoelectric crystal density, V s is the wave velocity of the piezoelectric crystal, f is the frequency of the surface acoustic wave detection device, L is the length of the sound propagation path, P is the ambient pressure, ρ1 is the leakage gas density, γ0 is the gas adiabatic coefficient, K s is the adiabatic compression coefficient, and C is the volume concentration of the leaked gas.

[0049] In another possible implementation, to increase the difference in SAW energy attenuation between the target gas and the background gas, thereby ensuring detection sensitivity, the SAW detection device has an acoustic propagation path length of no less than 2λ, where λ is the wavelength of the acoustic wave. In the design of SAW detection devices, increasing the acoustic propagation path length can improve detection sensitivity.

[0050] In another possible implementation, the frequency of the surface acoustic wave detection device is not less than 10 MHz. The higher the frequency of the surface acoustic wave detection device, the greater the acoustic impedance effect. Therefore, using a surface acoustic wave detection device with a high frequency can improve detection sensitivity.

[0051] In another possible implementation, the surface acoustic wave detection device adopts an extended line structure, a reflection delay line structure, or a resonator structure.

[0052] Specifically, such as Figure 2 The extended line type surface acoustic wave detection device shown includes a piezoelectric crystal 1, and an input interdigital transducer 2 and an output interdigital transducer 3 arranged on one side surface of the piezoelectric crystal 1. The distance between the input interdigital transducer 2 and the output interdigital transducer 3 is the sound propagation path 4.

[0053] The circuit principle of using an extended line type surface acoustic wave detection device to collect the first signal and the second signal respectively is as follows Figure 3 shown.

[0054] like Figure 4 The reflection delay line type surface acoustic wave detection device shown includes a piezoelectric crystal 1, an interdigital transducer 2 arranged on one end of one side surface of the piezoelectric crystal 1, and a first reflection grating 3 and a second reflection grating 4 arranged on one side of the interdigital transducer 2 on the side surface.

[0055] like Figure 5 The resonator-type surface acoustic wave detection device shown includes a piezoelectric crystal 1, an interdigital transducer 2 arranged at the center of one side surface of the piezoelectric crystal 1, and a left reflection grating 3 and a right reflection grating 4 symmetrically arranged on both sides of the interdigital transducer 2 on the side surface.

[0056] The embodiment of the present invention verifies

[0057] Taking the acquisition of the first and second signals using an extended linear surface acoustic wave (SAW) detection device as an example, the SAW detection device features a Y-cut piezoelectric quartz crystal with dimensions of 20 mm x 4 mm x 0.5 mm. Electron beam evaporation is used to deposit 100 nm thick aluminum input and output IDTs on its surface. The input and output IDTs are 1 mm apart from the longitudinal edge of the piezoelectric crystal. The input IDT utilizes a unidirectional, single-phase transducer structure, while the output IDT utilizes a uniform finger structure. The acoustic aperture is 100λ for both IDTs, with 100 pairs of fingers and 40 pairs of fingers for the output IDT. The acoustic propagation path is set to 800λ, with a wavelength of λ = 15.8 μm.

[0058] The surface acoustic wave detection device was placed in an air / hydrogen mixed gas with different hydrogen concentrations and Figure 3 The circuit shown collects signals such as Figure 6 As shown in Figure 2, the output signal of the surface acoustic wave detection device, that is, the response, changes with the change of hydrogen leakage concentration. Figure 7 The figure shows the response T90: 1s and recovery time T10: 0.8s of the surface acoustic wave detection device tested at a hydrogen concentration of 30%, with sub-second fast response and recovery capabilities.

[0059] Verification of the embodiment of the present invention

[0060] Taking the acquisition of the first and second signals using a reflective delay line surface acoustic wave (SAW) detection device as an example, the SAW detection device's piezoelectric crystal is a Y-cut piezoelectric quartz crystal measuring 40mm x 4mm x 0.5mm in length, width, and height. Electron beam evaporation is used to deposit a 100nm-thick aluminum input IDT, as well as a first and second reflection grating. The input IDT employs a uniform finger structure with 40 pairs of fingers, while the first and second reflection gratings also employ a uniform finger structure, each with an acoustic aperture of 100λ. The spacing between the first reflection grating and the input IDT is 100λ, and the spacing between the second reflection grating and the input IDT is 150λ. The wavelength λ is 15.8μm. Figure 8 The figure shows the frequency response of the surface acoustic wave detection device exposed to air, with the first reflection peak signal intensity being 42.26 dB; Figure 9 The frequency response of the surface acoustic wave detection device placed in 100% helium shows that the energy of the first reflection peak is reduced to 40.772 dB. Compared with air, helium significantly reduces the surface acoustic wave echo energy. This shows that helium information can be decoupled from energy changes.

[0061] Verification of the third embodiment of the present invention

[0062] Taking the acquisition of the first and second signals using a resonator-type surface acoustic wave (SAW) detection device as an example, the SAW detection device's piezoelectric crystal is a Y-cut piezoelectric quartz crystal with dimensions of 20 mm x 4 mm x 0.5 mm in length, width, and height. Electron beam evaporation is used to deposit 100 nm thick aluminum on its surface, forming the input IDT, as well as the left and right reflectors. The input IDT employs a uniform finger structure with 40 pairs of fingers, while the left and right reflectors employ a uniform finger structure. The acoustic aperture is 100 λ, and the spacing between the left reflector and the input IDT is 2 λ, while the spacing between the right reflector and the input IDT is also 2 λ. The wavelength λ is 15.8 μm. Figure 10 The figure shows the frequency response of the surface acoustic wave detection device, with a center frequency of 199.2MHz and a device loss of -8dB. Figure 11 The figure shows that the surface acoustic wave detection device is placed in an air / carbon dioxide gas mixture containing different carbon dioxide concentrations. The energy attenuation, i.e., the loss, of the surface acoustic wave under different carbon dioxide concentrations gradually decreases with increasing carbon dioxide concentration and has good linearity.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A surface acoustic wave gas leak detection method, characterized in that: include: Input the same excitation signal, collecting an output signal of the surface acoustic wave detection device in the background gas and recording it as a first signal; collecting an output signal of the surface acoustic wave detection device in the gas to be detected, and recording it as a second signal; Calculate the energy difference between the second signal and the first signal, and record it as the energy attenuation difference; The volume concentration of the leaked gas is calculated using the calculated energy attenuation difference.

2. The method according to claim 1, characterized in that The first signal and the second signal are collected by using the same surface acoustic wave detection device.

3. The method according to claim 1, characterized in that The formula for calculating the volume concentration of leaked gas is expressed as: Where Δα is the calculated energy attenuation difference, ρ c is the density of the gas to be detected, V c is the wave velocity of the gas to be detected, ρ0 is the background gas density, V0 is the background gas wave velocity, ρ s is the piezoelectric crystal density, V s is the wave velocity of the piezoelectric crystal, f is the frequency of the surface acoustic wave detection device, L is the length of the sound propagation path, P is the ambient pressure, ρ1 is the leakage gas density, γ0 is the gas adiabatic coefficient, K s is the adiabatic compression coefficient, and C is the volume concentration of the leaked gas.

4. The method according to claim 3, characterized in that The acoustic propagation path length of the surface acoustic wave detection device is not less than 2λ, wherein λ is the wavelength of the acoustic wave.

5. The method according to claim 3, characterized in that The frequency of the surface acoustic wave detection device is not less than 10 MHz.

6. The method according to claim 1, characterized in that The surface acoustic wave detection device adopts an extended line structure, a reflection delay line structure or a resonator structure.

7. A surface acoustic wave gas leak detection system, characterized in that: include: Excitation unit, surface acoustic wave detection device, acquisition unit, calculation unit; wherein, an excitation unit, inputting the same excitation signal to the surface acoustic wave detection device; an acquisition unit for acquiring an output signal of the surface acoustic wave detection device in a background gas, which is recorded as a first signal; and an output signal of the surface acoustic wave detection device in a gas to be detected, which is recorded as a second signal; The calculation unit calculates the energy difference between the second signal and the first signal, which is recorded as an energy attenuation difference; and calculates the volume concentration of the leaked gas based on the calculated energy attenuation difference.

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