颗粒群光散射法测量气溶胶质量浓度的分形理论模型及应用研究

Aerosol mass concentration is a very important parameter to evaluate the changes of atmospheric environment, and the light scattering of particles is an effective way of on-line and nonintrusive measurement of it. Particle mass and shape are the two main factors in the inversion of aerosol mass concentration by the light scattering method. In this project, considering the two aspects of particle shape and mass, the fractal theory will be applied to the light scattering method to further investigate the measurement theory. The specific content as follows: aerosols are equalized as a group of particle aggregates, and the statistical fractal characteristics of the aggregates group's signal amplitude distribution are analyzed. And then, the fractal model for aerosol mass concentration by using the optical equivalent diameter distribution of particles is presented,and the concepts of the factal dimension of random shape and the equivalent mass of the particle aggregates in a voltage channel are given. Besides, a clear physical fractal model for inversing aerosol mass concentration is established, which can improve the precision of measurement. Finnally, desiging the experimental device,the fractal dimension in the inversion algorithm can be calibrated by the intersection point calibration method proposed by the applicant. In a word, the study of this project will provide a new measurement method for on-line monitoring aerosol mass concentration based on the light scattering of particles.

气溶胶的质量浓度是评价大气环境变化的一个非常重要参数，颗粒群光散射法是在线非接触测量该参数的有效途径。颗粒质量和形貌在光散射法的质量浓度反演中是两个主要因素。本项目拟将分形理论应用于颗粒群光散射法，从颗粒质量和形貌两方面出发，进一步研究该方法的测量理论，具体内容包括：将气溶胶颗粒物等效为颗粒凝聚体集合，研究该集合对应光散射脉冲信号幅度分布的统计分形特性；提出利用颗粒物的光学等效粒度分布反演质量浓度的分形模型，并给出随机形貌分维数及与光散射脉冲信号通道对应的颗粒凝聚体等效质量概念，从而使模型的反演精度提高，物理概念清晰、完善；设计标定实验装置，利用申请人提出的交集点标定法解决反演算法中分维数的标定方法,实现对气溶胶质量浓度的实时监测。本项目的研究以期能够为颗粒群光散射法应用于在线监测气溶胶质量浓度提供一种新的测量方法

颗粒群光散射法是在线非接触测量气溶胶质量浓度的有效方法。本项目提出了将经过激光束的颗粒群等效为一颗凝聚体粒子，通过分析颗粒群光散射脉冲信号的统计分形特征，建立了采用凝聚体颗粒物的电压信号幅度分布反演气溶胶质量浓度的分形模型，该模型充分利用了凝聚体颗粒电压信号的幅度信息及数目信息，有利于提高反演精度。设计了用于采集散射光信号幅度分布的多通道分析电路，结合已有的光学传感器装置，建立了气溶胶浓度测试装置。通过对烟尘样品的多次标定测量，给出了分形模型中参数的分段标定法。实验结果表明：当相对湿度小于60%时，在0.5~13mg/m3的质量浓度范围内，将分段标定法的标定参数用于分形模型，气溶胶质量浓度测试装置的测量值与标准测量仪器的测量值吻合较好，两者多次测量的平均相对误差在6.0%以内。同时，本项目还对环境相对湿度高于60%的情况进行了理论分析和实验研究。基于Mie散射理论，计算分析了标定参数的变化规律；在实验上，提出了基于粒子群优化的BP神经网络补偿模型，对低浓度范围内的气溶胶在高湿度时的测量结果进行数据融合修正。本项目的研究成果为颗粒群光散射法应用于在线监测气溶胶质量浓度提供一种新的测量方法，也使得颗粒群光散射法测量气溶胶质量浓度的方法更加完善。