Gas Detection Technology Based On TDLAS

Environmental pollution is a problem that must be faced on the process of reform and development,and it is closely related to the development of industrialization.The detection of pollutants is the first step to solve environmental problems.After decades of development,the demand for gas detection has also been upgrading and gradually developing towards high precision,fast response speed and strong adaptability.In order to adapt to the development trend,Tunable Diode Laser Absorption Spectroscopy technology develope rapidly and have been widely used in many fields,such as the detection of atmospheric pollutants,the monitoring of denitrification process in power plants and other industrial gas detection fields.In this paper,starting from the theory of absorption spectrum,the basic principle of TDLAS technology is expounded.Two main methods,direct absorption and wavelength modulation spectroscopy,are theoretically deduced.The expressions of second harmonic and 2f/1f are obtained.Taking the CO2 absorption peak near 1572nm as the research object,an experimental platform for gas measurement is set up,and the selection of experimental elements is introduced in detail.On the basis of theoretical deduction and experimental system,TDLAS simulation model is built with Simulink software.Secondary harmonic and calibration-free 2f/1f signals are simulated based on the simulation model,and the simulation results are consistent with the theoretical deduction.Direct absorption of CO2 is measured based on the experimental platform,and the measurement accuracy of direct absorption is optimized by modifying the integral range of lineshape function.Singular value decomposition(SVD)is used to analyze the noise of the experimental system,and the second harmonic signal is obtained without the high frequency noise signal,which improves the signal-to-noise ratio of the experimental system.