Research On The Mechanism And Method Of Multi-component Gas Concentration Detection Based On Acoustic Characteristics

All kinds of toxic,harmful and dangerous gases will cause great safety hazards to people’s life and industrial production.Accurate quantitative analysis of various gas concentrations is an important guarantee for the orderly development of society.At present,Gas concentration detection methods mainly include optics,chemistry,heat and materials science.However,these methods have some limitations under the specific conditions of high humidity,no oxygen,strong vibration and high dust.Acoustic gas detection method has the advantages of low cost,low power consumption,high speed and good stability,which can work normally without the influence of the above special environment.However,the theory and application research of acoustic gas detection technology is relatively backward.The research on detection mechanism and method of acoustic gas sensor is of great significance to promote the development of gas sensing technology.In this dissertation,the acoustic characteristics based on the microstructure of gas molecules are studied,and the mathematical models of the relationship between the sound velocity,sound attenuation and gas concentration of complex gas molecules are established.A multicomponent gas concentration detection method based on acoustic characteristics is proposed,which pushes the gas detection technology to a new development stage.The mechanism of gas acoustic detection is studied and a gas concentration detection model based on acoustic characteristics is established.The sound velocity characteristics and sound attenuation characteristics of gas are analyzed systematically.The gas concentration detection mechanism based on sound velocity measurement and sound attenuation measurement is studied.The relationship models of sound velocity,sound attenuation and gas concentration are established.The relationship between gas molecular structure and gas sound attenuation characteristics is studied.The gas sound attenuation models suitable for different molecular structures are established,to provide the necessary theoretical support for the follow-up theoretical research.The ultrasonic phase difference measurement method based on mixingfrequency operation and multi-frequency driving is studied.The problems existing in the detection of gas sound velocity phase difference are deeply studied.In order to solve the problem of low resolution of gas sound velocity phase difference measurement,the mixing-frequency technology is used to convert the highfrequency phase difference into low-frequency phase difference to realize the highresolution measurement of sound velocity phase difference,so as to achieve high accuracy identification of gas concentration.In order to solve the problem that the cross-cycle phase difference of high concentration gas can not be identified in the detection of sound velocity phase difference,a multi-frequency driving method is proposed to extract the phase difference of low frequency envelope signal and realize the extraction of ultrasonic cross-cycle phase difference.The low frequency envelope signal is digitally detected and the phase difference is extracted.Combined with the phase difference correction algorithm,the total cross-cycle phase difference detection is realized.High resolution and full range detection of gas concentration is realized by using mixing-frequency and multi-frequency driving technology.The gas concentration measurement method based on sound attenuation is studied.The detection mechanism of gas acoustic attenuation is studied.Aiming at the problem that the solution of relaxation frequency in gas acoustic attenuation is complex and can not be applied to real-time concentration measurement,the calculation method of gas concentration relaxation attenuation is proposed.By establishing the relationship between specific heat,acoustic frequency and gas acoustic velocity,the solution algorithm of specific heat value is determined,and the concentration relationship model of gas relaxation attenuation based on gas specific heat calculation is established.The measurement method of gas concentration based on relaxation attenuation is established.The multi-component gas detection method based on the combination of sound velocity and sound attenuation is studied.In order to solve the problem that single acoustic parameter can’t realize multi-component gas concentration detection,a multi-component gas detection method combining sound velocity and sound attenuation is proposed.And for the problem that the relaxation frequency cannot be solved in the relaxation attenuation process of the multi-component mixed gas,the relationship between effective equivalent specific heat,sound velocity and sound frequency is established.The gas sound velocity model and gas relaxation attenuation model in the relaxation process are reconstructed.The measurement method of relaxation frequency and gas concentration of multi-component gas based on dual-frequency eigenvalue method is proposed.The datas of sound velocity and sound attenuation of multi-component gas at two frequencies are calculated and processed.A multi-component gas concentration detection model combining sound velocity and sound attenuation is established,and the concentration of multicomponent gas is obtained through data processing of the model.In this dissertation,the mechanism of gas detection based on acoustic characteristics is systematically studied,and the gas concentration detection methods based on sound velocity measurement and sound attenuation measurement are established.Multi-component gas concentration measurement methods are established.The effectiveness and accuracy of the methods are verified by actual measurement.The research work in this dissertation makes it possible to detect gas concentration by acoustic technology,and will further promote the development of gas sensing technology.