基于可调谐激光吸收光谱技术的多条吸收谱线重建气体浓度二维分布的研究

摘要

针对二维气体浓度分布，主要选用多条 H2 O的吸收谱线，采用代数迭代重建算法，研究了在激光光束较少且假定温度分布已知的情况下，即不考虑燃烧场中温度对谱线强度的影响时，不同谱线条数对二维浓度重建结果的影响，对比了在同一浓度模型下通过增加激光光束与增加 H2 O吸收谱线条数对气体浓度重建结果的影响；研究了增加谱线条数重建气体浓度分布对不同温度与浓度分布模型的适应情况，其中，文中所选取的多条吸收谱线可以由一个激光器同时扫描得到。浓度测量区域采用10×10的网格划分，测量区域中的温度和浓度分布采用单峰不均匀分布与双峰不均匀分布，重建过程中计算了吸收谱线与激光光束的有效利用率。重建结果表明在激光光束较少时，增加吸收谱线条数可以获得更多与浓度相关的谱线参数信息，且与增加激光光束相比可以明显改善浓度重建结果，更主要的是增加谱线条数可以有效降低实验中硬件设备的成本投入以及测量系统的复杂性。%The two-dimensional concentration distribution was reconstructed by using algebraic iterative reconstruction algorithm.This paper mainly focused on the effects of multispectral H2 O absorptions on condition that the laser beam was less and the temperature was known,i.e.the influence of temperature on spectral line-strength was not considered as to this concen-tration distribution.Based on ART algorithm,increased spectral lines and increased laser beam were compared under the same concentration model.Three H2 O lines were selected to reconstruct two-dimensional distribution of non-uniform gas concentra-tion,and these three transitions were selected within the external cavity diode laser turning range in the simulated system.The interested region was discretized to 10×10 grid points,and the temperature and concentration of the reconstruction model were not evenly distributed,so the unimodal distribution and bimodal distribution were used to describe the concentration distribution. The simulated system also calculated the effective utilization of laser beams and absorption lines.The results showed that the re-construction quality quickly increased with increasing H2 O absorption lines when the laser beams were very few,the increased absorption lines could get more spectral information related to the concentration.The increased laser beam is also effective to im-prove the accuracy of reconstruction results,but increasing the absorption lines can better reconstruct a two-dimensional concen-tration distribution.Improving the absorption lines can also effectively reduce the costs of the hardware and the complexity of the measurement system,which shows that the multispectral absorption lines are applicable to in-situ measurements.