Detection Of Mixed Gas Concentration Based On Acoustic Relaxation Method

With the continuous improvement of industrialization,people have more and more demand for gas concentration detection,and a large number of scholars have begun to study how to detect gas concentration.Because the relaxation acoustic method has low cost of detection,low service life,low energy loss,fast response,wide range of measurement concentration,real-time monitoring and other advantages.It shows superiority compared with other concentration detection.The advantage is respected by people.This paper describes the development of acoustic gas concentration measurement of mixed gas,and studies the classical sound velocity and sound attenuation theory,and introduces their relationship with relaxation attenuation theory.This paper mainly studies the measurement method of ultrasonic gas concentration based on relaxation attenuation theory.The main research work has the following contents:(1)Based on the basic laws of ultrasonic propagation,the principle of ultrasonic measurement of mixed gas concentration is clarified.Based on the attenuation of sound waves during propagation,including classical attenuation and relaxation attenuation,a reconstruction method for multi-component gas concentration distribution in three-dimensional space is proposed.A coupling model between gas concentration and acoustic wave propagation time and sound intensity attenuation is established.(2)The two methods of ultrasonic time of flight measurement are studied and analyzed.The principle of acoustic wave travel time measurement based on phase difference and the principle of sound wave travel time measurement based on phase difference are respectively described,and the advantages and disadvantages are compared.(3)Based on the coupled model of gas concentration and sound wave propagation time and sound intensity attenuation,a split Bregman iterative algorithm is proposed to solve this problem.Through the measured data of acoustic wave propagation attenuation in several common mixed gases,the spatial distribution of spatial mixed gas is reconstructed by simulation experiments in acoustic multipath measurement.(4)A measurement system for mixed gas concentrations is designed.The system uses FPGA as the central processing unit,as well as hardware devices such as ultrasonic transducer,transmitting circuit,receiving circuit,amplification filter circuit,digital/analog conversion circuit and multiple selection circuit.And through the preparation of VHDL program,the measurement of ultrasonic flight time and sound intensity attenuation parameters is realized.The communication between the coreboard and the host computer is realized,and the reason for the measurement error is analyzed.