| With the rapid development of the chemical industry,acetylene has become one of the most important raw materials for organic synthesis in the chemical production process.However,due to its flammable characteristics,it is easy to mix with air to form an explosive mixed gas.Compared with other flammable and explosive gases,acetylene has a larger explosion range and a lower explosion limit,which seriously threatens the safety of chemical production.Therefore,real-time and accurate detection of the concentration of acetylene gas is of great significance to ensure the safety of industrial production.Photoacoustic spectroscopy detection technology is a spectral technology developed based on photoacoustic effect.Photoacoustic spectroscopy detection technology has the advantages of high detection resolution,high sensitivity,strong antiinterference ability,no consumption of gas samples and wide detection range.It is an effective method to realize real-time and accurate detection of gas.In the photoacoustic spectroscopy detection system,the resonant cavity is one of the important detection units.The structure and shape of the resonant cavity directly affect the sensitivity of the entire detection system.At present,the research based on the shape and structure of the resonant cavity has not yet formed a conclusion.In view of this problem,the simulation software is used to study and design,the performance of the optimized resonator is tested in the detection system.The main research work is as follows:Firstly,the basic principle of photoacoustic spectroscopy detection technology is described.The energy conversion between gas molecules,light absorption,photoacoustic signal generation,wavelength modulation technology and second harmonic technology are analyzed in detail.The mathematical model of the classical cylindrical cavity is established,and the influence of the structure and shape of the cavity on the quality factor,resonant frequency and cavity constant is simulated and analyzed.Secondly,the shape of the resonant cavity is optimized.The structure and performance of the classical cylindrical resonator are analyzed in detail.On this basis,a symmetric ellipsoid cylindrical resonator is proposed.Compared with the cylindrical resonator,when the laser is injected into the resonator,the light diffuses in the convex part,which can reduce the friction between the laser and the inner wall,reduce the loss of light energy,and improve the sensitivity of the detection system.Compared with the symmetrical ellipsoid cylindrical cavity,the parameters of the asymmetric ellipsoid cylindrical cavity increase,and the structural variables increase.It can accurately simulate the convex part of the cavity,which is beneficial to improve the sensitivity of the detection system.According to the design principle of the resonant cavity,the finite element analysis simulation software is used to model.The symmetric ellipsoid cylindrical resonant cavity and the asymmetric ellipsoid cylindrical resonant cavity are established by COMSOL software.The optimal size of the two resonant cavities is obtained by simulation and manufactured.Then,the acetylene gas detection system is built with the fabricated resonant cavity for experiment.The performance of the detection system is analyzed,and the frequency characteristics,linearity and sensitivity of the detection system are obtained.The influence of environmental factors on the detection system is analyzed,including ambient temperature,pressure and buffer gas types.Finally,the two ellipsoidal cylindrical resonators are compared with the cylindrical resonator.After modeling the cylindrical cavity,it is compared with the performance of two ellipsoidal cylindrical cavities.The sound pressure value,quality factor,linearity and sensitivity of the two ellipsoidal cylindrical cavities are higher than those of the cylindrical cavity.Therefore,compared with the classical cylindrical cavity,the proposed new elliptical cylindrical cavity improves the performance of the photoacoustic spectroscopy gas detection system. |
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