Simulation Design and Performance Analysis of Two-Stage Buffer
Photoacoustic Cell
JIN Hua-wei1, 2, 3, WANG Hao-wei1, 2, LUO Ping1, 2, FANG Lei1, 2
1. School of Mechanical Engineering, Anhui University of Science and Technology, Huainan 232001, China
2. Institute of Environment-friendly Materials and Occupational Health of Anhui University of Science and Technology (Wuhu), Wuhu 241003, China
3. Key Laboratory of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Abstract：The photoacoustic cell is where the “light heat sound” coupling occurs. The performance of photoacoustic cells directly affects the accuracy and sensitivity of the detection system. In order to improve the performance of photoacoustic cells, a two-stage buffer photoacoustic cell is proposed based on the traditional cylindrical photoacoustic cell. Through the simulation of the thermal viscous acoustic physical field interface in COMSOL software, the effects of the height and number of buffer partitions on the sound field in the photoacoustic cell are analyzed.The results show that the resonance frequency of the photoacoustic cell decreases with the increase in the number and height of buffer partitions. When the number of buffer partitions is fixed, the height of the buffer partition is greater than 11mm, and the resonance frequency of the photoacoustic cell decreases sharply with the increase of the height of the buffer partition. In the required range of photoacoustic cell resonance frequency, the decrease of the resonance frequency is conducive to the increase of photoacoustic signal amplitude; When the height of the buffer partition is fixed, the sound pressure of the photoacoustic cell decreases with the increase of the number of buffer partition; When the height of the buffer partition is between 0 and 11mm, the sound pressure value remains relatively stable; When the height of the buffer partition is greater than 11mm, the sound pressure decreases sharply with the increase of the height of the buffer partition. Regarding flow field, the velocity gradient in the left buffer cavity can be reduced by setting a buffer partition in the cavity. Although the one-stage buffer can reduce the velocity gradient to a certain extent, there is velocity fluctuation at the buffer partition. The two-stage buffer reduces the velocity gradient in the photoacoustic cell and makes the gas flow more stable. Considering the photoacoustic signal amplitude, sound pressure and velocity gradient in the photoacoustic cell, the height of the buffer partition is 11mm and the number of buffer partitions is 2.Based on the optimal parameters given, the simulation and experimental results show that the sound pressure of the two-stage buffer photoacoustic cell is 3.34×10-5 compared with the cylindrical photoacoustic cell of the same size reduced to 3.32×10-5, background noise from (2.83±0.11) μV decreases to (1.26±0.03) μV. The resonance frequency is reduced from 1 344 to 1 299 Hz. Although the sound pressure is reduced by 1.2%, the sound-to-noise ratio is increased by 2.22 times, and the resonance frequency is reduced by 3.3% within the range meeting the requirements so that the amplitude of the photoacoustic signal is improved to a certain extent. Overall, the two-stage buffer photoacoustic cell stabilizes the gas flow noise and reduces the fluctuation range of the flow noise. The proposed two-stage buffered photoacoustic pool provides a new idea for the optimal design of a photoacoustic pool.
Key words：Photoacoustic spectroscopy; Photoacoustic cell; Finite element analysis; Optimal design
