Research On CO₂ Concentration Diagnostics Based On Near-infrared Laser Spectroscopy Technique

Carbon dioxide?CO₂?is an important part of the air,and it is also an important component of industrial raw materials,which is closely related to our production and our life.With the development of modern industrial production and urbanization,global carbon emissions have gradually spread.It makes the content of CO₂ in the atmosphere far exceed0.03%of the air component,which seriously disrupts the dynamic balance of CO₂ in the atmosphere,and forms a"greenhouse effect".Spectral measurement technology has the characteristics of strong selectivity,high detection sensitivity,fast and convenient,which is widely used in a variety of gas detection fields.Therefore,the research of near-infrared laser spectroscopy for the measurement of CO₂ concentration is carried out in this context.?1?Study on CO₂ concentration detection based on tunable diode laser and supercontinuum laserIt analyzed cross-interference of other trace gas absorption lines on CO₂ measurement in the near-infrared region,and selected the absorption line near 1432 nm as the target line.It measured the concentration of CO₂ based on DFB laser with a central wavelength of 1430 nm and supercontinuum?SC?laser from 1429 to 1435 nm.Firstly,the CO₂ gas absorption spectrum received by the photodetector,and the concentration of CO₂ was calculated using the sum method and peak method.The result showed that the measurement error of the inversion concentration by the summation method was the smallest,and the maximum relative error was 2.7%through comparative analysis.Secondly,the performance of the denoising effect was evaluated through performance parameters such as mean square error?MSE?and normalied correlation coefficient?NCC?.It was found that the MSE was 1.59×10^-77 and the NCC was 1.0032,indicating that the S-G digital smoothing filtering technology had better performanc denoising ability.Lastly,the performance parameters of CO₂ detection based on two types of laser sensing systems were compared.The detection limits of the DFB laser system and SC laser system were 0.59×10^-66 and 1.05×10^-3,and the accuracy were 1.64%and1.35%.The results provid an important references for the development of subsequent research content.?2?Quantitative analysis based on photodetector and spectrometer detected CO₂concentrationIn order to improve the detection probability and collection efficiency of the system's optical signals,a parallel gas detection system based on near-infrared laser spectroscopy technology has realized the simultaneous detection of CO₂ signals by photodetectors and spectrometers.Combined with the previous experiments,it was found that the changes in experimental parameters directly influenced the measurement results.First,the experimental parameters were tested to determine the best experimental parameters.Then the research analyzed the absorption spectrum obtained by detecting the CO₂ gas by the photodetector,and analyzed the performance parameters during the measurement.The linearity was 0.99634,the detection limit was 1.56 ppm,and the error of the system stability did not exceed 0.058%.Finally,the absorption spectrum of CO₂ obtained by spectrometer was explored.The data in the range of 1424¹434 nm was selected as the research object.The performance parameters such as linearity,repeatability and zero drift were analyzed.And repeatability was2.8×10^-44.2×10^-44 and zero drift was 0.496 ppm/h.The experimental results showed that the two detectors can stably and accurately measure the CO₂ signal.?3?Research on methods based on weighted fusion modelIn order to improve detection accuracy of the system and the robustness of the model,the concentration and signal intensity models obtained by the simultaneous detection of CO₂based on the photodetector and the spectrometer were weighted through standard deviation method.And finally it obtained a new combined measurement model in the data processing method.The measurement error of the combined model was reduced from 36.3%to 13.6%of the single model through comparative analysis.The results show that the combined model can effectively improve the concentration inversion capability and detection accuracy of the detection system.