Study On Characteristics Of Bubble Behaviors In Aerated Hopper And Feeding Of Parallel Hopper System

In this thesis,based on the background of the application of aerated hopper,the characteristics of bubble behaviors during the powder discharge process in a two-dimensional aerated hopper were studied by a high-speed camera system.And,the impacts on switching methods of the feeding of parallel hopper system were investigated preliminarily.The results are as follows:With the increase of the gas velocity,three typical discharge states can be found:stable discharge without bubbling?stable discharge with bubbling and unstable discharge with bubbling;and the proportion of downward bubble increased,the bubble above the outlet of the hopper increased significantly,and the volatility of the flow column also increased.When the gas velocity(u)exceeded the maximum discharge gas velocity(umax),the discharge of particles started to be suppressed by the downward bubbles,and the barometric arch occurred.Both minimum bubble velocities and minimum bubble downward velocity increased with the increase of particle size.A bubble frequency model with a relative deviation within±20%was established,which could provide a basis for the design of aeration hoppers.The increase of aeration height and half angle of aeration hoppers could significantly influence the discharge rate of aerated hoppers,reduce the downward frequency of bubbles and the fluctuating frequency of the flow column,which reflected the significant influences of the size of hopper structures on the characteristics of bubbles behaviors.The switching modes of hoppers were very important to the parallel hopper feeding system.The switching method of "closing before opening" and "simultaneous opening and closing"resulted in obvious flow interruption in the pipeline,only switching in the form of "open before close" could effectively meet the requirement of continuous flow in the pipeline.Although during the switching of parallel hoppers by this mode,the discharge rates produced certain fluctuations,and the fluctuation increased with the increase of the discharge rate of hoppers,reasonable setting of the throttle device could effectively reduce the fluctuation.