Theoretical And Experimental Research Of Irregular Particles Based On IPI System

Particles widely exist in atmosphere,industry,manufacture and other fields,and the size,velocity,position,phase state,concentration of particle are main parameters in the measurement of particles.Interferometric particle imaging(IPI)is an robust technique to measure the droplets,bubbles,spray field,cloud particles and other particle fields because of its high precision,non-contact,real-time capability and etc.In this paper,the transparent spheroidal particle and non-transparent irregular sand particle are chosen as research objects;Based on the analysis of the scattering characteristic of these two kinds of particles,the infocused image and defocused image are obtained and the method to measure the irregular particles is given.Then the IPI experiments are conducted to measure the particles.Main work of this paper:1.Based on the scattering characteristic of the spherical particle,ray tracing is conducted to the spheroidal particle to describe the transmission of scattering light;The infocused image of transparent spheroidal particle are several glare points,and the correspond defocused image is fringes or speckle;For defocused image shown as fringes,we give the method to measure the size of spheroidal particle based on the infocused image;For defocused image shown as speckle,we give the method to measure the size of spheroidal particle based on the 2D-atutocorrelaiton of defocused image;Experimental verification is conducted by spheroidal particle made from spherical particle by hot stretch.2.For non-transparent irregular particles,theoretical analysis of interferometric particle imaging and the method to calculate the size of particles by defocused image are given.We choose the assemble of multiple Dirac function to describe the irregular particle,and the characteristic of infocused image and defocused image is analyzed.We could make a conclusion by simulation analysis: the minimum width of the central peak of 2D-autocorrelation of defocused image is always corresponding to the maximum size of particle,whatever the particle's shape is;The shape of particle could be obtained by the 2D-atutocorrelaiton of infocused image or 2D-FFT of defocused image,and the size of particle could obtained by the 2D-atutocorrelaiton of defocused image.3.The IPI system with double receiving unit to collect the infocused image and defocused image simultaneously is established.Sand particles with different shapes are illuminated by a laser sheet to have an interference imaging experiment,and the shape of particle could be obtained by the infocused image and the size of particle could be obtained by the 2D-atutocorrelaiton of defocused image;We rotate the sand to different orientations to search for the maximum size by IPI technique,and the measurement error is lower than 10%.