Research On Particle Size Measurement Technology Based On Light Scattering

Particulate matter is closely related to the production and life of today's society.As an important characteristic parameter of particles,accurate measurement of particle size is of great significance to the development of related fields.Based on Mie scattering theory,Fraunhofer diffraction theory and small-angle forward scattering method,the following works have been done in this paper:(1)The mathematical models of Mie scattering theory and Fraunhofer diffraction theory are studied.The Mie scattering coefficient matrix and Fraunhofer diffraction coefficient matrix are solved by MATLAB,and the particle environment used in the two theories is clarified.(2)On the basis of Mie scattering theory,the small-angle forward scattering model is studied in depth,the particle size measurement model based on polarization ratio method is proposed,and the objective function of polarization ratio method based on small-angle forward scattering method is constructed.The model uses the ratio of light energy in different polarization directions to retrieve particle size,avoiding the influence of other components in the optical path on particle size measurement,and can be better applied to on-line detection.(3)In the aspect of inversion algorithm,for independent mode algorithm,an iterative non-negative PT(INNPT)algorithm based on traditional non-negative PT(NNPT)algorithm is derived by combining iterative regularization with small-angle forward scattering method.It is analyzed and determined that the INNPT algorithm has higher inversion accuracy and stability than the NNPT algorithm when inversion particles with wide distribution.For dependent mode algorithm,the artificial fish swarm algorithm is used to retrieve the objective function of small-angle forward scattering method,regularization method and small-angle forward scattering polarization ratio method.The comparison analysis shows that the small-angle forward scattering polarization ratio method has better inversion accuracy,anti-noise ability and repeatability than the other two objective functions.(4)The traditional particle measurement system based on small angle forward scattering method is built,and the particle measurement system based on small angleforward scattering polarization ratio method is designed and built.When calibrating the measuring system,the method of replacing standard particles with pinholes is proposed for the first time,which avoids the disadvantage that the calibration results are easily affected by the standard particle concentration,and the pinhole calibration is easy to operate and can be reused.The inversion results of national standard particles are calibrated by pinhole calibration results.The reliability and superiority of the proposed objective function,inversion algorithm and measurement system are verified,and the reconstruction of national standard particle size distribution is realized.