| Various methods for measuring particle size distribution of the suspended particulate matter are developed home and abroad, the main existing measuring methods based on optics for the suspended particulate matter are transmission method, scattering method, transmission light-scattering comparison of optical measuring method. Scattering method is confirmed to be a standard method for the measurement of particle size distribution of suspended particles due to its high sensitivity, less affected by ambient noise and other advantages, which can be widely used in blood cell analysis, atmospheric concentration measurement, water quality suspended particulate matter measurement and so on.In the optical measurement process of the concentration of suspended particulate matter, aiming at monitoring the particle size distribution of coarse suspended particles in real time and improve the measurement accuracy of the coarse particles scattering coefficient, the influence of the particles refractive index to the light intensity is analyzed and research shows that the refractive index within a small angular range has little effect based on Mie scattering theory in this article. Through the hypothesis of suspended particles of light intensity and wavelength, smooth Chahine iterative algorithm and the least square method are respectively used to invert the suspended particles size distribution, the result smooth Chahine iterative algorithm for the inversion of particle size distribution is more consistent with the original distribution is obtained. The determining denoising factor is confirmed for 200 by using wavelet method to deal with the noise signal. The variation curves of scattering coefficient with concentration were obtained by measuring the polystyrene solutions of three different particle sizes at different concentration and different scattering angles and different light wavelengths through the analysis and comparison, it is concluded that the scattering coefficient and the concentration have very good monotonic increasing when the scattering angle is 15 degree and the band range is 450.03nm-700.03nm parameter. The scattering coefficient of three kinds of polystyrene solution is mixed with 1:1:1 ratio and the sum of the scattering coefficients of three kinds of single particle size are at the same concentration. The coefficients of the same items in the simulation curve are basically the same multiples and they all have a strong linear correlation, which shows the applicability of the inversion method. Through the measurement of the light scattering coefficient of suspended particles, using smooth Chahine iterative algorithm to invert the suspended particles size distribution, and compared with the experimental results, we can obtain in the suitable band that the inversion error is small, which shows that the real-time monitoring technique is of high precision and high practicability. |
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