Study On Collision And Rebounding Behavior Of Particle Impact On The Wall Surface

Collision rebound between particles and walls often occurs inside pipeline transportation systems,fluidized reactors and other equipments.Different forms of collision rebound behavior between particles and wall can cause the consequences of particle adhesion,particle accumulation and other consequences,affecting the efficiency of industrial production.In order to explore the characteristics of particle-wall collision rebound process,this paper mainly used experimental methods to study the dry and wet collision between particles and wall in industrial production.By means of high-speed photography technology,the recovery coefficient,trajectory of motion and the law of change of liquid bridge after particle-wall collision were analyzed.The variation law of particle rebound recovery coefficient under two kinds of collision conditions was revealed.The main reasons of particle energy loss after dry and wet collision were discussed.The mathematical models of particle rebound in two kinds of collisions are summarized.The main research contents are as follows:(1)Design and implementation of collision rebound experiment: Particle ejection device was designed and developed to ensure that the spherical particles impact the target wall at a certain speed and angle.High-speed camera was used to record the process of collision rebound between the particles and the wall,and image processing software was used to process and analyze the movement of particles.(2)Collision rebound characteristics between particles and drying wall: When both particles and drying wall were dry,the normal recovery coefficient decreased slightly with the increase of incident velocity,which was due to the plastic deformation of aluminum wall and the dissipation of elastic wave in contact process;Because of the gradual change of the contact mode between particles and wall from rolling to sliding,the tangential recovery coefficient increased first and then decreased with the increase of incident angle.(3)Collision and rebound characteristics between particles and the wall with liquid film: When the target wall was covered with liquid film,the rebound of particles would pull out a dynamic liquid bridge on the wall,thus affected the particle trajectory.Different from the results of dry collision,the normal recovery coefficient of wet collision was affected by particle size,incident velocity,liquid film thickness and viscosity,while the tangential recovery coefficient was only related to the existence of liquid film.At the same time,it could be found that there was a critical rebound velocity when the liquid film exists.When the incident velocity was lower than that,the particle woud be pulled back to the wall by the liquid bridge.The energy dissipation of particles increased with the decreased of particle size and the increase of viscosity and thickness of liquid film.