Experimental Study On Electrostatic Generation And Particle Behavior In Gas-solid Two-phase Elbow Flow

Pneumatic particle conveying device is widely used in chemical industry,food,medicine and other industrial fields.In the process of material transportation,particleparticle and particle-pipe interaction lead to the generation and accumulation of electrostatic charge on the surface of particles and pipe wall,which is harmful to the safe operation of industrial production.As a commonly used pipe structure in industry,the elbow can achieve the function of flow steering.However,due to the large loss of particle momentum at the elbow and the strong impact of particles on the wall,more static electricity often occurs and more static charge is accumulated,which is the most vulnerable part of pneumatic particle transport system.In this study,the particle motion mode and electrostatic generation mechanism are experimentally studied through the selfbuilt pneumatic conveying particle system.Considering the effects of particle material,particle size,shape,conveying wind speed,particle loading quality,elbow angle and elbow arrangement on electrostatic generation,the particle motion mode is photographed and recorded in real time by means of high-speed camera shooting and PTV analysis,then analyzed in combination with the electrostatic test results,finally the electrostatic charge generation mechanism is obtained.Through the comparative analysis of particle motion trajectories in different bend pipeline(90° and 45°),it has been found that the particle motion behavior in different pipe is quite different.The behavior of spiral wall rolling of particles in the elbow is different from that in the straight pipe.With the increase of wind velocity,the trend of spiral wall rolling of particles increases.The electrostatic generation experiment of pneumatic conveying particle system shows that the electrostatic generation of particles in elbow is significantly higher than that in straight pipe under the same conditions.The physical properties and motion state of particles have a great influence on the generation of electrostatic charge.The amount of electrostatic charge of particles in the spiral adhesion mode is significantly higher than that in the ordinary mode.In addition,with the increase of particle size,the specific surface area of particles will decrease and the electrostatic charge-to-mass ratio will decrease;With the increase of particle loading mass,the electrostatic charge mass ratio of particles increases.In the experiment of single particle electrostatic generation,it is found that the higher the collision height of particles,the greater the amount of electrostatic generation;In the experiment of metal plate,the amount of electrostatic charge under the condition of particle sliding is higher than that under the condition of rolling;Bipolar charging occurs between particles of different sizes of the same material,and particle powder contact leads to electrostatic polarity conversion.In short,through a large number of experiments,this paper compares the electrostatic generation of particle flow in different bends and the relationship between single particle electrostatic generation and particle motion mode,and reveals the mechanism of electrostatic generation in gas-solid two-phase bends.The research results provide important theoretical support for reducing the occurrence of electrostatic charge in pneumatic conveying particle system and ensuring industrial safety production.