Study On Dissipation And Flow Characterics Of Free Falling Particle From Slit Based On Cfd-dem Coupling

When the loose particles fall freely under the action of gravity and impact the hard wall or stock pile,the squeezed high-speed airflow will carry the material particles around to splash,and a large amount of productive dust will escape,which is one of the most important pollution sources in the industrial environment.If the emitted dust particles are not controlled,it will affect the normal operation of the equipment and endanger the health of the staff.The results of the current research are mainly point-like particle sources,but the research on the more common linear particle sources in industrial production has rarely been studied.Therefore,based on previous studies,the author analyzed the free falling particle dispersion and flow characteristics of free falling particles from a slit dust source.This paper provides guidance for the control of the free-falling dusts.Based on the industrial production background,the CFD-DEM coupling model combining computational fluid dynamics(CFD)and discrete element method(DEM)is used to simulate the free falling process of industrial dust,such as alumina.The main work of this paper is as follows:(1)The free-falling process of the circular hole is simulated,and the method of calculating the particle velocity and the amount of entrained air is given.The CFD-DEM coupling model was validated by combining the previous experimental data and the air entrainment models.(2)The free falling particle from slit was simulated,and the changes of particle and entrainment air velocity and entrained air volume during the falling the granular flow were analyzed at different heights,different outlet sizes and different particle sizes.(3)The process of granular flow impacting on the horizontal and inclined wall is studied,andcompare and analyze the differences of granular flow impacting under different impact heights,different tilt angles and different particle sizes.The results show that the diffusion width of the granular flow in the short-side direction increases more than the long side,and the width of the entrained air is much larger than the diffusion width of the granular flow.As the drop height increases,the particle velocity distribution in different directions at 900 mm away from the exit gradually becomes uniform.As the size of the outlet increases,the velocity of the particles and the entrained air also increases,but as the length increases,the velocity of the particles and the entrained air at the center of the particle flow grows slowly and gradually becomes constant after the outlet length is greater than 30 mm.The amount of entrained air increases as the size of the outlet increases,but the amount of air entrained per unit mass flow decreases.With the same outlet size,the larger the particle size,the greater the particle velocity and the smaller the entrainment air velocity at the same height.The amount of entrained air and the amount of entrained air per unit mass flow decrease as the particle size increases.The degree of escape of the granular flow impinging on the horizontal wall gradually decreases as the particle stacks pile up.The entrained air forms a deposition vortex at the near wall surface and gradually moves outward and high over time.The larger the drop height of the granular flow and the larger the particle size,the larger the granular flow escape width at the same height of the near wall surface,which means that the escape is more serious.After the granular flow is in contact with the inclined wall,it is divided into two parts,one part flows down the inclined wall,and the other part bounces off and exits the wall surface and falls onto the inclined surface again.The velocity of the granular flow on the inclined wall conforms to the Gaussian distribution law.At the upper corner of the granular flow in contact with the ramp,a entrained air vortex is formed.The higher the height of the granular flow impinging on the slope,the smaller the inclination angle,and the smaller the particle size,the more obvious the diffusion width of the granular flow on the slope.