Research On Praticle Diffusion Characteristics Of Roping Phenomenon In Pneumatic Conveying

In the pneumatic conveying,the particles are concentrated in the downstream pipe after the bend due to the centrifugal force,and a relatively dense phase structure is formed on the outer wall of the bend,which is called Roping phenomenon.Although domestic and foreign scholars have done some research on Roping phenomenon,the research on the diffusion mechanism of Roping phenomenon is still insufficient.In order to study the diffusion of particles in the dilute phase pneumatic conveying system after passing through the bend,this paper uses high-definition cameras to obtain particles on different height sections after the bend(R / D = 1.3,R is the bending radius of 100 mm,and D is the diameter of the pipe 75mm)(The particle size distribution is 0-300?m,the average particle size is 172.4?m,and the density is 2550kg/m3)The spatial distribution law and the numerical simulation CFDDEM are used to analyze the diffusion mechanism of the Roping phenomenon.The specific content and conclusion are as follows:The experimental results show that the diffusion speed of particles with different particle sizes is different.The diffusion speed of large particles(200-300?m)and small particles(0-100?m)is faster than that of medium particles(100-200?m);It is divided into two stages: rapid diffusion stage and uniform distribution stage.In the rapid diffusion stage,the mass flux of the dimensionless particles in the dense phase zone drops to 43%,while the mass flux of the dimensionless particles in the transition zone rises to 42%;in the uniform diffusion stage,The mass fluxes of dimensionless particles in the three regions are similar.Finally,based on the Fluent-EDEM platform to explore the effect of particle size,gas flow rate and bending diameter ratio on Roping diffusion.The simulation results show as follws:(1)When the solid load ratio is 1%-10%(dilute phase pneumatic conveying)and the bend diameter ratio of the elbow is 1-2,for the Geldart A type particles,the larger the particle size,the smaller the segregation height of the rope diffusion For Geldart B and D particles,the rope phenomenon is not obvious.In fact,the main factor affecting the diffusion of the rope is the Stoke number of the particles.When the Stokes number of the particles is below 7.171,the rope phenomenon diffuses significantly.(2)For Geldart A-type and B-type particles,when the Stokes number of the particles is the same and the bending diameter ratio of the elbow is 1-2,as the bending diameter ratio increases,the segregation height of the rope phenomenon diffusion increases.(3)When the Stokes number of the particles is the same,and the bend diameter ratio of the elbow is 1-2,for Geldart A particles,the gas flow rate has little effect on the rope diffusion;while for Geldart B particles,the gas flow rate is greater,The smaller the segregation height of the rope diffusion...