Simulation And Design Of Photoacoustic Spectroscopy Trace Gas Detection System

Many gases play an important role in industrial and agricultural production and people’s daily lives,and the impact of certain trace gases on the human living environment is critical.Therefore,gas quantitative analysis has become an important part of modern detection technology.Among the many gas detection technologies,the photoacoustic spectrum detection technology has the advantages of good stability,high sensitivity,strong selectivity,and good real-time performance,and has broad application prospects.In this paper,through a systematic study of photoacoustic spectrum detection methods,an in-depth analysis and establishment of a microgas detection system based on photoacoustic spectra is established.The main contents of this article are as follows:(1)Starting from the principle of gas photoacoustic spectrum detection and the generation mechanism of photoacoustic signals,the internal relationship between photoacoustic signals and the structure and working mode of photoacoustic cells was analyzed.The typical structure of a first-order longitudinal cylindrical resonant photoacoustic cell is analyzed in detail.The three-dimensional relationship between the three characteristic parameters of the photoacoustic cell resonance frequency,figure of merit and cell constant and the geometric size of the photoacoustic cell was simulated by numerical calculation.Based on the distribution of sound pressure,a new type of photoacoustic cell with a buffer structure with rounded corners was designed,which laid the foundation for the optimization and design of the photoacoustic cell.(2)Using the HITRAN database,through a comparative analysis of methane,ammonia gas,and water and carbon dioxide absorption spectral lines,according to the radiation characteristics of the light source and the selection principle of gas absorption spectral lines,the characteristic absorption spectral lines of methane and ammonia gas were selected and modulated according to the wavelength And harmonic detection theory,the system is divided into three modules: light sourcemodulation,gas absorption,and data detection and processing.The above modules are simulated and modeled using visual virtual tools.The second harmonic detection technology is theoretically analyzed to improve the system.The necessity and feasibility of detection sensitivity.(3)A photoacoustic spectrum gas detection experimental platform was set up,and experimental parameters were used to measure the characteristics of the photoacoustic cell.The correspondence between the gas concentration,the laser power,and the photoacoustic signal was studied.The photoacoustic signal increases linearly with the increase of gas concentration and laser power.The theoretically derived formula of photoacoustic signal is well verified.