Experimental Study On The Characteristics Of Near-Infrared High-Temperature Spectroscopy Of CO

With the rapid development of China’s economy, the issues of environmental safety caused by air pollution have become more and more prominent. CO is a typical air pollution component associated with the combustion process, therefore the accurate measurement of CO in the combustion flow field is important for energy conservation and emission reduction in industrial combustion processes and engine combustion state diagnosis. Spectroscopy method is an ideal tool for combustion process diagnosis. It can satisfy the need for on-line measurement in situ of the key parameters including combustion temperature and atmosphere conditions. But the lack of accurate experimental data of gas spectroscopy parameters at high temperature has been one of the most important factor that limit the measurement accuracy of spectrum detection technology in combustion process.Aiming at these problems, the characteristics of near-infrared absorption spectroscopy of CO at high temperature is analyzed and the experimental research on it is carried out based on the tunable diode laser absorption spectroscopy (TDLAS) technique in this paper. According to the near-infrared absorption spectroscopy theory, the vibration and rotation spectrum of diatomic molecules and line shape functions are analyzed in theory. The charateristics of infrared absorption spectroscopy of CO is introduced systematically. The model of gas absorption spectroscopy charateristics of high temperature in theory is established based on direct absorption spectroscopy technique. The different calculation methods of partition function and the theoretical method of linestrength and the relationship between linestrength and temperature are studied in emphasis.According to these principles and methods, the experimental setup for the spectroscopy measurement of CO at high temperature was established based on direct absorption spectroscopy technique. The R(12), R(13), R(14) transition in the second overtone of CO were selected as research objects for the application need of near-infrared laser spectroscopy with high resolution on-line measurement of CO in combustion process. And the absorption spectroscopy of the three transitions in different conditions at the temperatures of 323-973K were obtained through a series of spectroscopy measurement experiments; The extraction algorithm of gas infrared spectroscopy parameters at high temperatures based on the direct absorption spectroscopy with high resolution was studied. The linestrengths of R(12), R(13), R(14) transitions in the second overtone at the temperatures of 323-973K and the accurate experimental data about the relationship between linestrength and temperature were obtained. Then the results were compared with theoretical calculation results. According to the broadening charateristics under different pressures and temperatures, the self-broadening coefficients, N2-CO broadening coefficients and temperature dependence coefficients at high temperature were obtained; The temperature correction algorithm model was established in the end and the model was applied for the measurement of gas concentration at high temperature.