Study On The Character Of Dust Particles Based On Light Scattering

With the development of industry,the discharge of dust particles have caused a serious impact on the environmental pollution,so the concentration of dust particles and the measurement of particle size technology have become a hot spot.The composition of industrial dust is varied,and the dust particles filled with SiO₂ have a large proportion in the industrial dust.In this paper,we will study the characteristics of spherical particles filled with SiO₂ based on light scattering theory.First of all,we give the refractive index of SiO₂ varied with wavelength,with Helium-Neon laser as the incident light source,we study the characters of single particle based on the Mie light scattering theory,for different sizes of particles,we get the scattering intensity,extinction coefficient and scattering coefficient varied with size parameter.Due to the diameter of dust particles is not subject to single distribution,but subject to certain size distribution.Therefore,it is necessary to calculate the light scattering properties of the whole particles system.In this paper,we assumed the distribution of dust particles obeys to gamma distribution.Based on gamma distribution,we calculate the single scattering phase matrix,average extinction coefficient and asymmetry factor elements of dust particles varied with size parameters.Second,based on Monte Carlo method,we study the multiple scattering characteristics of laser and dust,and calculate the scattering intensity of dust particles varied with the concentration of dust.Calculation results show that when the concentration of dust is higher than1600mg/cm³,it is necessary to consider the effects of multiple scattering.Take ceramic industry for example,in the process of ceramic,the concentrations of dust are almost higher than this value,so in this case,using signal light scattering method will lead to large error.Third,when we use Monte Carlo method to simulate multiple scattering of dust particles,first of all,we assumed that the incident light is infinitely narrow collimated beam,without considering the shape of incident beam,if we only consider the scattering light varied with angles,this assumption can be application to incident plane wave,based on this,we studied the eflection and transmission function varied with scattering angles for different sizes of parameters and the optical thickness of the dust particle.The results show that,the bigger of optical thickness,the smaller of reflection,and the stronger of transmission;for the same optical thickness,the stronger of particle size parameter,the smaller of reflection,and the stronger of transmission.The last,because of the laser spot has a certain distribution,so for different incident beams—the Gauss beams and circularly flat beams,we studied the multiple scattering character of dust particles,the results show that the reflection function and the transmission function are very sensitive to the shape of laser beams.For the same effective radius and the same optical thickness of particles,the narrower radius of laser beam,the more concentrated of energy of the reflection function and the transmission function,whereas the more discreted.For the dust particles of same radius and different thinckness,the bigger of thinckness,the stronger of reflection intensity,the weaker of the transmission intensity.For the same thinckness and different radius of dust particles,the bigger of radius,the weaker of reflection intensity,the stronger of the transmission intensity.The research of this paper is applied for basic research,researing the laser measurement problems of the high concentration of dust particles,and this research provides a theroetic basis to the optimization and improvement of measuring system based on light scattering theory.