【作者】 顾芳；

【导师】 贺安之； 卞保民；

【作者基本信息】 南京理工大学 ， 光学工程， 2008， 博士

【摘要】 单粒子光散射法因具有测量速度快、精度高、重复性好及适用于在线非接触测量等优点而在颗粒测量领域得到了广泛应用。本文结合实验,对单粒子光散射法测量悬浮颗粒物质量浓度的理论进行了深入研究,取得的主要成果如下:提出了与光散射信号计数通道对应的颗粒平均质量、等效球形颗粒数、单粒子光学等效直径概念,这些概念揭示了颗粒物散射光信号幅度分布与质量之间的内在规律,从而建立了悬浮颗粒物质量浓度的理论模型,为应用粒子计数器测量的颗粒物电压脉冲信号幅度分布反演质量浓度提供了理论基础。结合单粒子光散射法悬浮颗粒物质量浓度的理论模型,进一步深入研究颗粒物散射光信号幅度分布与颗粒物形貌之间的关系,并考虑颗粒物的分形特征,提出了光散射等效截面分形维数的概念,给出了光散射信号计数通道中的颗粒平均质量与对应通道的电压信号幅度之间的关系,发现单粒子光散射法测量悬浮颗粒物质量浓度算法有两个待标定的特征参数:灵敏度系数k和光散射等效截面分形维数α。本文从理论和实验两个方面对悬浮颗粒物质量浓度反演算法中特征参数的标定方法进行了深入研究。分析了颗粒物质量浓度反演精度与小样本颗粒物的光散射等效截面分形维数α₁之间的关系,发现与反演误差极小值对应的小样本颗粒物的α₁不能很好地反映整个颗粒物的光散射等效截面分形维数α特征。通过分析颗粒物的α与小样本的α₁之间内在联系,提出小样本的α₁交集点是颗粒物的α最佳值的观点,解决了特征参数的标定问题。实验结果表明,在0.001～5mg/m³质量浓度范围内,粒子计数器测量的质量浓度值与标准参照仪器的测量值十分吻合。本文将信息熵用于评价粒子计数器计数通道的优化问题。提出了均匀和非均匀计数通道划分法,实验结果表明质量浓度反演精度稳定时非均匀划分法所需的计数通道较少。利用信息熵计算发现计数通道数相同时非均匀划分法提取的颗粒物电压脉冲信号幅度分布信息熵明显较大,表明信号幅度分布信息熵大小决定了颗粒物质量浓度反演精度的稳定速度。本文建立了一个较为全面的利用单粒子光散射法测量悬浮颗粒物质量浓度的理论,并将该理论应用于实际测量,实证了它的正确性,该研究成果为单粒子光散射法的深入发展提供了有价值的参考。本文的单粒子光散射法可用于实现工业在线测量悬浮颗粒物质量浓度。更多还原

【Abstract】 The single particle scattering method is widely employed due to fast,high precision, nonintrusive and suitable for on-line measurement.In this paper,the theory for aerosol mass concentration by using the single particle scattering method is investigated combining with experiments.The innovation achievements are listed as following:The concepts of the average mass of particles in a voltage channel,the equivalent number of spherical particles and the optical equivalent diameter of a particle are presented, respectively,which reveal inherent law between the pulse height distribution of particles and mass.The theoretical model for inversion aerosol mass concentration is then established,which provides theoretical basis for inversion aerosol mass concentration using the pulse height distribution of particles measured by an optical particle counter.Combining the theoretical model for aerosol mass concentration by using the single particle scattering method and the relationship between the pulse height distribution of particles and particle shape,the conception of fractal dimension of scattering equivalent section is put forward by taking the fractal characteristic of particles into account,then the relationship between the average mass of particles in a voltage channel and the signal amplitude of corresponding voltage channel is given.It is found that inversion algorithm of aerosol mass concentration using the single particle scattering method has two characteristic parameters needed to be calibrated,that is,the sensitivity coefficient k and the fractal dimension of scattering equivalent sectionα.The calibration method of the two characteristic parameters in the inversion algorithm for aerosol mass concentration is further researched theoretically and experimentally.The relationship of inversion precision of aerosol mass concentration and fractal dimension of scattering equivalent sectionα_l of a small sample aerosol is analyzed,and it is found that fractal dimension of scattering equivalent sectionαof aerosol cannot be replaced byα_l obtained by the minimum method.Through analyzing the inherent relation betweenαandα_l,the conclusion that the intersection point ofα_l for different small samples is equal toαof aerosol is obtained,thus,the calibration problem of characteristic parameters are solved.The experimental results demonstrate that mass concentrations measured by an optical particle counter agree well with actual mass concentrations in the range from 0.001 to 5 mg/m~3. In order to evaluate the optimization problem of voltage channels of an optical particle counter,the information theory is applied to analyze the reason for the difference of the stable velocities of inversion accuracy of mass concentration obtained using linear and non-linear division methods,respectively.The result indicates that in the case of same number of voltage channels,the information entropy of non-linear division method is obviously larger,leading to the number of voltage channels is fewer when the inversion accuracy of mass concentration is stable.This conclusion indicates that information entropy of the pulse height distribution of particles directly determines the stable velocity of inversion accuracy of mass concentration.In this paper,an overall theory for aerosol mass concentration by using the single particle scattering method is established,whose validity is justified by experiments,and the research of this paper provides a valuable reference for the further development of the single particle scattering method.The method in this paper can be applied to measure aerosol mass concentration in real time.更多还原