Research On The Flow Property In The Pneumatic Conveying System

Pnematic conveying means transforming the solid particles with the gas power., which is widely used in the electric, chemical, food precessing, iron and steel, metuallgy engineering etc. The pneumatic conveying is related several aspects and meanining in the industry. In this paper, the theoretical anlysis, numerical simulation and experiment are used to study the flow property in the pneumatic system.First, the background about the thesis is explained, the constitution of pneumatic conveying system is introduced. Then the property of pneumatic conveyingsystem is summarized. Finally, the classification of pneumatic conveying system is made.In this paper, the motion of suspended particles that move from initial to a stable state in pneumatic conveying system is studied by considering the effect of friction force on the particles. The relationship of particle velocity and moving time, distance under the different conditions is given. The effect of ratio of initial gas and particle velocity on the particle velocity is analyzed.Gas-solid two-phase flow with different initial state in accelerating zone is simulated in pneumatic conveying system. Inter-Phase-Slip Algorithm method (IPSA) is used to solve N-S equations, while turbulence is considered with modified k-e model. The equations of particle velocity are deduced when the initial velocities are different for both the temporal model and the spatial model. Through the synthesis of the analyzed relations and simulation results, several important results are gained about effect of ratio of initial gas and particles velocity in accelerating zone on time, distance and acceleration of particles.The motion of suspended dense particles with different initial conditions in pneumatic conveying system is studied by considering the effect of friction force on the particles. The process of particles from initial to stable state is investigated. The relationship of the initial gas and particle velocity ratio and suspended velocity, friction coefficient is analyzed. The motion property of particles with different initial velocity in the process of acceleration is stressed. The results are helpful to pre-calculate develocity of particle in the practical usage.The fluid fluctuating velocity equations which include the term of cylinder particles are established. The turbulent intensity and Reynolds stress of fluid are obtained by averaging fluctuating velocity based on the solution of the fluctuating velocity equations. Above equation approach are used to solve the channel turbulent flows, and computational results are compared with the experimental ones for the case of single phase flow. The effects of volume fraction of particles, the ratio of particle length to diameter and the particle relaxation time on turbulent properties are illustrated by changing cylinder particle parameters. It is shown that particles play a restraining role to turbulent properties in flow field. The degree of restraint is directly proportional to the volume fraction of particle, the ratio of particle length to diameter and inversely proportional to particle relaxation time.The background and problems of gas-solid two-phase fan are analyzed. The relationship between flow properties near blade surface and blade erosion is built up based on the comparison of blade erosion when solid particles flow through turbulent boundary layer and laminar boundary layer. It is illustrated that the flows with higher turbulent intensity can reduce the blade erosion struck by particles, and blade surface with rib-welded can result in higher turbulent intensity so as to reduce erosion.The effect of second gas flow on the conveying pipe gas-solid flow in pneumatic dense plug-flow conveying is numerically simulated. Considering different second gas flow velocities, high and low second gas flow velocity disturbance effects on main pipe flow pressure, gas-phase and solid-phase velocities are obtained. Different second gas flow parameters have different impact on gas-phase and solid-phase velocities. Inter-Phase-Slip Algorithm metho...