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Method for measuring gas acoustic relaxation absorption coefficient

A technology of absorption coefficient and measurement method, applied in measurement devices, complex mathematical operations, material analysis using sonic/ultrasonic/infrasonic waves, etc., can solve the complex calculation and compensation process, difficult to meet the sensor accuracy, real-time and production cost requirements and other issues, to achieve the effect of reducing design complexity and cost, improving measurement accuracy, and simplifying cost

Pending Publication Date: 2020-12-08
张克声 +1
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Problems solved by technology

However, the calculation of acoustic classical absorption and attenuation caused by other reasons not only requires prior knowledge of gas composition and related gas molecular parameters (but this is often contrary to the purpose of gas detection), but also the calculation and compensation process is complicated [9][10]
[0005] Therefore, no matter from the hardware circuit design requirements of the test system or from the theoretical analysis of the measurement results, it is very challenging to accurately measure acoustic relaxation absorption in real time at low cost, and it is difficult to meet the requirements of practical gas detection. Requirements for the accuracy, real-time and production cost of sensors

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  • Method for measuring gas acoustic relaxation absorption coefficient
  • Method for measuring gas acoustic relaxation absorption coefficient
  • Method for measuring gas acoustic relaxation absorption coefficient

Examples

Experimental program
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Effect test

Embodiment 1

[0035] Measuring equipment can be placed in the gas to be tested, and the measuring equipment includes ultrasonic frequencies f 1 , f 2 and f 3Three sets of ultrasonic probes, barometers and thermocouples. Each set of ultrasonic probes includes an ultrasonic transmitting probe and an ultrasonic receiving probe.

[0036] Thermocouples are used to measure the temperature value of the gas to be measured;

[0037] The barometer is used to measure the pressure value of the gas to be tested;

[0038] Three pairs of ultrasonic probes are used to measure the ultrasonic frequency f 1 , f 2 and f 3 The sound velocity value of the ultrasonic wave in the gas to be measured is to obtain the acoustic measurement value, which is used to synthesize the acoustic relaxation absorption spectrum.

[0039] Ultrasonic frequency f 1 , f 2 and f 3 The gas can be set according to the gas type and the measured pressure range. For example, for CH 4 , CO 2 、CL 2 Equally strong relaxation ca...

Embodiment 2

[0062] In the present embodiment, the method of embodiment 1 is utilized: when the gas to be measured is 98% CH 4 -2% air, at three frequency points f 1 = 40kHz, f 2 = 215kHz, f 3 =1.4, the measured sound velocity is c(f 1 )=447.446m / s,c(f 2 )=450.626m / s and c(f 3 )=451.831m / s; the ambient temperature T=300K measured by the thermocouple; the pressure P=1atm measured by the barometer.

[0063] The relaxation intensity ε=0.0213 obtained by formula (7) is calculated, and then the relaxation frequency f is calculated by formula (8) m =1.241×10 5 Hz, and the absorption maximum μ calculated by formula (3) m = 0.0339. Then, based on the calculated f m , μ m and ε: Using formula (2), the sound velocity dispersion spectrum c(f) can be reconstructed (see figure 1 ); use formula (1) to reconstruct the acoustic relaxation absorption spectrum μ(f) (see figure 2 ); use (9) to reconstruct the frequency-dependent acoustic relaxation absorption coefficient (see image 3 ).

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Abstract

The invention discloses a method for measuring a gas acoustic relaxation absorption coefficient. The method comprises the following steps: measuring sound velocity values c (f1), c (f2) and c (f3) ofultrasonic waves with ultrasonic frequencies of f1, f2 and f3 in gas to be measured; calculating the relaxation intensity epsilon; calculating a relaxation frequency fm; calculating an absorption maximum value [mu] m; calculating a dimensionless acoustic relaxation absorption coefficient mu (f); calculating a sound velocity frequency dispersion spectrum c (f); and calculating an acoustic relaxation absorption coefficient alpha (f). According to the method, the acoustic relaxation absorption coefficient changing along with the frequency is calculated according to the acoustic velocity measurement values which are easily and accurately measured in real time on the three frequency points, and the calculated acoustic relaxation absorption result does not need to be compensated for other reasons; therefore, the technical bottleneck that the existing gas sensing technology based on the acoustic relaxation phenomenon is difficult to accurately measure acoustic relaxation absorption in real time at low cost can be solved.

Description

technical field [0001] The invention belongs to the field of ultrasonic gas sensing and detection, in particular to a method for measuring the acoustic relaxation absorption coefficient of gas. Applicable to the measurement of acoustic relaxation absorption in excitable gases (non-monatomic molecular gases, such as nitrogen, oxygen, chloromethane, carbon dioxide, sulfur hexafluoride). Background technique [0002] In excitable (non-monatomic molecular gas) gases, sound propagation causes inelastic collisions between gas molecules, making the temperature of the internal and external degrees of freedom of molecules change with the fluctuation of sound pressure; The change lags behind the fluctuation of the translational degree of freedom temperature, and it takes a period of relaxation time to complete the relaxation process to return to the thermal equilibrium state. The relaxation process makes the acoustic excitation energy trapped in the vibration mode undergo thermal rela...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/024G06F17/10
CPCG01N29/024G06F17/10
Inventor 张克声李岩
Owner 张克声
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