A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central fre...A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.展开更多
An improved algebraic reconstruction technique（ART） combined with tunable diode laser absorption spectroscopy（TDLAS） is presented in this paper for determining two-dimensional（2D） distribution of H2O concentrati...An improved algebraic reconstruction technique（ART） combined with tunable diode laser absorption spectroscopy（TDLAS） is presented in this paper for determining two-dimensional（2D） distribution of H2O concentration and temperature in a simulated combustion flame.This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy.It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid,and after that point,the number of projection rays has little influence on reconstruction accuracy.It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method.In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed,and the capability of this new method is evaluated by using appropriate assessment parameters.By using this new approach,not only the concentration reconstruction accuracy is greatly improved,but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation.Finally,a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method.Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles.This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices.展开更多
研究高温下待测气体的谱线属性,如谱线强度、自加宽系数、空气加宽系数、温度系数等,为高温环境中可调谐半导体激光吸收光谱技术反演温度、浓度、速度及其场分布提高精度和可靠性起着十分重要的作用.HITEMP数据库中的数据基本上是理论...研究高温下待测气体的谱线属性,如谱线强度、自加宽系数、空气加宽系数、温度系数等,为高温环境中可调谐半导体激光吸收光谱技术反演温度、浓度、速度及其场分布提高精度和可靠性起着十分重要的作用.HITEMP数据库中的数据基本上是理论计算结果,与实际情况存在相当的误差.为了获得所选2.0μm处的可用于燃烧诊断的CO2谱线参数,本文采用半导体激光器作为光源,结合实验室的高温测量系统,记录了700—1300 K温度范围内所选谱线的高温吸收光谱,获得了各谱线在相应温度下的谱线强度、自展宽系数及温度系数等谱线参数.测量得到CO2的5006.978 cm 1和5007.7874 cm 1谱线强度与理论计算值相对误差小于11%;获得了现有数据库缺少的温度系数和高温下自展宽系数数据.所有各项参数对以后将要进行的燃烧诊断中的CO2浓度检测有很大帮助.展开更多
基金Project supported by the National Key Scientific Instrument and Equipment Development,China(Grant No.2014YQ060537)the National Key Research and Development Program,China(Grant No.2016YFC0201103)
文摘A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61205151)the National Key Scientific Instrument and Equipment Development Project of China(Grant No.2014YQ060537)the National Basic Research Program,China(Grant No.2013CB632803)
文摘An improved algebraic reconstruction technique（ART） combined with tunable diode laser absorption spectroscopy（TDLAS） is presented in this paper for determining two-dimensional（2D） distribution of H2O concentration and temperature in a simulated combustion flame.This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy.It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid,and after that point,the number of projection rays has little influence on reconstruction accuracy.It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method.In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed,and the capability of this new method is evaluated by using appropriate assessment parameters.By using this new approach,not only the concentration reconstruction accuracy is greatly improved,but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation.Finally,a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method.Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles.This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices.
文摘研究高温下待测气体的谱线属性,如谱线强度、自加宽系数、空气加宽系数、温度系数等,为高温环境中可调谐半导体激光吸收光谱技术反演温度、浓度、速度及其场分布提高精度和可靠性起着十分重要的作用.HITEMP数据库中的数据基本上是理论计算结果,与实际情况存在相当的误差.为了获得所选2.0μm处的可用于燃烧诊断的CO2谱线参数,本文采用半导体激光器作为光源,结合实验室的高温测量系统,记录了700—1300 K温度范围内所选谱线的高温吸收光谱,获得了各谱线在相应温度下的谱线强度、自展宽系数及温度系数等谱线参数.测量得到CO2的5006.978 cm 1和5007.7874 cm 1谱线强度与理论计算值相对误差小于11%;获得了现有数据库缺少的温度系数和高温下自展宽系数数据.所有各项参数对以后将要进行的燃烧诊断中的CO2浓度检测有很大帮助.
