Study on a photoacoustic spectroscopy trichloromethane gas detection method based on an arched photoacoustic cavity

Abstract

As an important component in photoacoustic spectroscopy gas detection systems, the performance of the photoacoustic cavity directly affects the sensitivity and resolution of the system. Based on a study of photoacoustic cavity performance, a new type of arched photoacoustic cavity is proposed. Finite element simulation software is used for modeling. By comparing the influences of the position and radius of the central sphere, the length and radius of the resonant cavity, and the radius of the buffer chamber on the performance of the photoacoustic cavity, the optimal structural size of the arched photoacoustic cavity is determined. Compared to a traditional cylindrical photoacoustic cavity with the same size, and considering the thermal viscous acoustic loss, a thermal-acoustic coupling multiphysical field simulation of the two models is carried out. The acoustic pressure signal of the arched photoacoustic cavity is 6 times that of the cylindrical photoacoustic cavity, the resonant frequency increases by 300 Hz, and the quality factor is 2.6 times that of the cylindrical photoacoustic cavity. The performance of the arched photoacoustic cavity is significantly improved. A photoacoustic spectroscopy system for the detection of chloroform gas (CHCl₃) is built based on an arched photoacoustic cavity. Detection experiments are carried out with different concentrations of chloroform. At room temperature (25 °C) and atmospheric pressure, the linear coefficient R₂ is 0.9975, and the detection sensitivity is 0.28 ppm. The system has great practical value for the detection of chloroform gas in industrial and agricultural applications.