可调谐半导体激光吸收光谱（TDLAS）技术具有很高的选择性和灵敏度,能够实现污染区域环境中痕量氨气（NH_3）的在线检测。影响TDLAS系统测量精度的因素有很多,温度和压力是最基本的两个影响条件。首先介绍了TDLAS原理和实验系统,然后研...可调谐半导体激光吸收光谱（TDLAS）技术具有很高的选择性和灵敏度,能够实现污染区域环境中痕量氨气（NH_3）的在线检测。影响TDLAS系统测量精度的因素有很多,温度和压力是最基本的两个影响条件。首先介绍了TDLAS原理和实验系统,然后研究了温度变化对检测结果的影响,温度在-10℃~50℃之间,使用空芯波导（Hollow Waveguide,HWG）气体池对浓度为50 ppm的NH3进行检测,得到其二次谐波光谱图,从图中可以得出在该温度范围内,NH_3二次谐波信号幅度随温度升高而减小。温度不变,气体池内压力从0 k Pa变化到100 k Pa时,二次谐波信号的幅度随着压力增加而减小。根据实验结果,给出了该系统的温度压力修正公式。修正后,50 ppm的NH_3在不同温度下的最大检测相对误差为-5.5%。对30 ppm的NH_3长时间监测结果表明,修正后系统能够适应现场监测需求。展开更多
Regularization methods were combined with line-of-sight tunable diode laser absorption spectroscopy(TDLAS)to measure nonuniform temperature distribution.Relying on measurements of 12 absorption transitions of water va...Regularization methods were combined with line-of-sight tunable diode laser absorption spectroscopy(TDLAS)to measure nonuniform temperature distribution.Relying on measurements of 12 absorption transitions of water vapor from 1300 nm to 1350 nm,the temperature probability distribution of nonuniform temperature distribution,for which a parabolic temperature profile is selected as an example in this paper,was retrieved by making the use of regularization methods.To examine the effectiveness of regularization methods,truncated singular value decomposition(TSVD),Tikhonov regularization and a revised Tikhonov regularization method were implemented to retrieve the temperature probability distribution.The results derived by using the three regularization methods were compared with that by using constrained linear least-square fitting.The results show that regularization methods not only generate closer temperature probability distributions to the original,but also are less sensitive to measurement noise.Particularly,the revised Tikhonov regularization method generate solutions in better agreement with the original ones than those obtained by using TSVD and Tikhonov regularization methods.The results obtained in this work can enrich the temperature distribution information,which is expected to play a more important role in combustion diagnosis.展开更多
文摘可调谐半导体激光吸收光谱（TDLAS）技术具有很高的选择性和灵敏度,能够实现污染区域环境中痕量氨气（NH_3）的在线检测。影响TDLAS系统测量精度的因素有很多,温度和压力是最基本的两个影响条件。首先介绍了TDLAS原理和实验系统,然后研究了温度变化对检测结果的影响,温度在-10℃~50℃之间,使用空芯波导（Hollow Waveguide,HWG）气体池对浓度为50 ppm的NH3进行检测,得到其二次谐波光谱图,从图中可以得出在该温度范围内,NH_3二次谐波信号幅度随温度升高而减小。温度不变,气体池内压力从0 k Pa变化到100 k Pa时,二次谐波信号的幅度随着压力增加而减小。根据实验结果,给出了该系统的温度压力修正公式。修正后,50 ppm的NH_3在不同温度下的最大检测相对误差为-5.5%。对30 ppm的NH_3长时间监测结果表明,修正后系统能够适应现场监测需求。
基金support by the National Science Foundation for Distinguished Youth Scholars of China(Grant No.61225006)National Natural Science Foundation of China(Grant No.60972087)Natural Science Foundation of Beijing,China(Grant No.3112018).
文摘Regularization methods were combined with line-of-sight tunable diode laser absorption spectroscopy(TDLAS)to measure nonuniform temperature distribution.Relying on measurements of 12 absorption transitions of water vapor from 1300 nm to 1350 nm,the temperature probability distribution of nonuniform temperature distribution,for which a parabolic temperature profile is selected as an example in this paper,was retrieved by making the use of regularization methods.To examine the effectiveness of regularization methods,truncated singular value decomposition(TSVD),Tikhonov regularization and a revised Tikhonov regularization method were implemented to retrieve the temperature probability distribution.The results derived by using the three regularization methods were compared with that by using constrained linear least-square fitting.The results show that regularization methods not only generate closer temperature probability distributions to the original,but also are less sensitive to measurement noise.Particularly,the revised Tikhonov regularization method generate solutions in better agreement with the original ones than those obtained by using TSVD and Tikhonov regularization methods.The results obtained in this work can enrich the temperature distribution information,which is expected to play a more important role in combustion diagnosis.
文摘基于仿真平台,搭建了TDLAS氢气检测系统,对4 712.905 cm^(-1)处的吸收光谱进行调制并利用锁相放大器提取出二次谐波信号。通过比较不同激光调制参量对二次谐波信号波形的影响进而选取最佳参数,调制幅度参量取值范围为0.1~0.35 V,观测二次谐波波形,结合波峰和波形对称性两个评估条件,确定最佳调制幅度为0.25 V。调制频率参量取值范围0.5~30 k Hz,结合二次谐波信号幅值和对噪声的抑制效果两个评估条件,选取调制频率为10 k Hz。结果表明,通过激光调制参量的优化选择可以获得更理想的二次谐波信号。该研究为开展氢气激光检测TDLAS系统调制参数的选取提供了理论依据,对改善实际应用中系统测量精度提供理论指导。
