Research On Particle Size Test Algorithm Based On Mie Theory

The laser particle size analyzer based on Mie scattering theory performs inversion of particle size distribution from scattered light intensity distribution of particles and resolved into the solution of Fredholm integral equation of the first kind. Since this is a typical ill-posed problem, particle size inverse algorithm becomes the key research content and hot spot of laser particle size analyzer. Thus it seems to be rather necessary and urgent to carry out this research.The research content of this article is concentrated in particle size test based on Mie theory. The main works completed are as follows, with the help of Visual C++6.0 and in combination with experiment platforms in laboratories:1) On the basis of mastering Mie theory and the working principle of laser particle size analyzer, light scattering modules for single particles and particle systems are established, theoretical derivation is carried out, and a program is written to perform simulation verification with Visual C++6.0 as the platform, including simulation of Mie scattered light intensity and distribution law, simulation of angular distribution law of scattered light of particles in different sizes, and so on. The specification parameters of corresponding annular photodetectors are designed according to different particle size measurement ranges, and simulation detection is performed to the scattered light intensity of their particle systems.2) Typical non-independent-mode and independent-mode particle size inverse algorithms are researched, and the respective characteristics of non-independent mode and independent mode are summarized. It is found out by simulation researches that the inverse algorithm of non-independent mode is easy to calculate, but it is necessary to suppose that the particle size distribution meets a certain function, which greatly limits its applications. The iterative inverse algorithm of independent mode, theoretically, can obtain the particle size application of any particle system, but is extremely sensitive to noise, so that it easily leads to distortion of particle size measurement result.3) The luminous energy distribution at the time of random noise simulation measurement is introduced into the luminous energy column vector. The iterative inverse algorithm of independent mode is extremely sensitive to noise, so that it easily leads to distortion of particle size measurement result. In depth research is conducted on this problem, the complexity of luminous energy distribution and the nonoperability of denoising the luminous energy in practical measurement are discussed, and data smoothing algorithm is introduced to make smoothing processing to the inversion results. This effectively eliminates the influence of errors, and improves the precision and reliability of particle size measurement.4) A great deal of tests are performed to standard samples on the existing experiment platforms, the error factors of the experiment system are analyzed in combination of the simulation research, and improvement proposals and requirements are proposed to the experiment system at last.With the researches of this thesis, system theoretical analysis and experiment researches on the laser particle size test based on Mie theory are completed. This proves that the theoretical model of it is feasible, and corresponding experimental researches and results are reliable. It also solves the problem that influence on practical application of particle size test inverse algorithm from noise leads to measurement distortion, and satisfies the requirements on high precision, reliability and stability of particle size measurement in modern powder industry. Experiments show that after smoothing processing, the error distribution reaches unanimity, and the errors will be further controlled through verification and calibration.