The Research Of Air Entrainment And Particle Movement Characteristic In Free Falling Particle Stream

In the process of industrial production and bulk material transportation, we can see powders falling from a height to the ground, stockpile, bin or on the conveyor belt regularly.This way that operation by free falling which materials falls only rely on gravity becomes both energy saving and efficient method.Because of the free falling buck materials and impact on the stockpile,there will be a large number of particles diffusion into the surrounding air, these free particles not only cause the air pollution but also do a great harm to the human body and equipment. Therefore,for both on the health of the workers and normal operation of the equipment, the emission of fugitive dust and pollution to the environment during the process of dumping become an urgent problem which must be solved.So,it is extremely important to design a reasonable and effective dust control system.This paper summarizes the research status of free falling particle stream, and based on the related analysis of the theoretical, experimental research and simulation, we try to determine the gas-solid two-phase flow model, physical model and boundary conditions for the free falling particle stream. By analyzing the air jet entrainment mechanism of particle flow, we research the air velocity distribution, the air entrainment, the particle movement characteristics and the particle diffusion concentration during the process of free falling.The DPM two-way coupling model is used to model different size diameter, particle density and particle size particles flow. Through the numerical simulation calculation, different height distribution of air velocity is obtained, and through integrating each air velocity curve in the whole section, air entrainment is determined. Besides,we also obtain the particle movement characteristics and particle concentration distribution. All of them provide the basis for later design of dust control system.We have done a lot of experiments to record the movement forms and inhalable particles dust generation rate. Besides, we have obtained the relationship between the dust generation rate and some influence factors, which concluding the difference of the material, height, mass and hopper diameter.