Flow Field Analysis And Research Of Pressure-Fed Pneumatic Conveying Tree-Way Feeder

Pneumatic conveying is a technology that uses the kinetic energy formed by gas flow to transport bulk materials in closed pipelines,and has been widely used in petrochemical,food and pharmaceutical production and processing.In recent years,many scholars have studied pneumatic conveying,due to the complex non-uniform structure,multi-scale phenomenon and random two-phase interface characteristics between the gas-solid two phases in the conveying system,the flow characteristics between the gas-solid two phases in the pneumatic conveying system are more complicated;Especially in the mixed fluidization stage of material particles and gases and the accelerated transition stage of the formation of stable gas-solid two-phase flow,the complex non-uniform structure and interface characteristics between the gas-solid two phases are more obvious.Based on these,in order to have a clear and comprehensive understanding of the feeding stage of the pressure-fed pneumatic conveying tree-way feeder and the transition stage of the horizontal straight pipe segment to form a stable gas-solid two-phase flow,this paper studies the flow field of the tree-way feeder and the horizontal acceleration straight pipe based on the basic theory and particle dynamics theory of the gas-solid two-phase flow,and adopts the two-way coupling calculation model based on the Euler-Lagrange framework.Firstly,the characteristics of gas and material particles in the pneumatic conveying system are analyzed,and the force of the material in the feeding stage of the tree-way feeder and the horizontal acceleration transition stage is analyzed according to the basic theory of gas-solid two-phase flow and hertz contact theory,and the material particle contact collision model and the dynamic model of the material particle and the pipe wall collision are established,which provides a theoretical basis for the numerical calculation of the tree-way feeder and the horizontal straight pipe segment.The characteristics of the internal flow field of the tee feeder and the internal flow field of the tree-way feeder with different structural parameters under the same working conditions are studied,and the results show that the tree-way feeder has the greatest pressure loss in the mixed fluidization stage of material and gas;when the air flow speed and material mass flow are constant,the diameter of the horizontal conveying straight pipe has a greater impact on the pressure loss inside the tree-way feeder,and the both are negatively correlated.At the same time,the effect of different material mass flows on their internal flow fields at same air flow rates is studied.Aiming at the phenomenon that the material particles hits the pipe wall and the material particles is transported along the bottom of the pipe in the process of material gas mixing fluidization,a structural optimization scheme is proposed and simulated,the motion characteristics of the material particles before and after optimization were compared and analyzed,and the optimized three-way feeder was more conducive to the fluid conveying of the material particles..In this paper,the motion characteristics of the material particles in the horizontal straight tube acceleration transition stage are further analyzed,and the flow state of the material particles in the transition stage is described according to the combination of friction and collision dynamic stress.