| Dust is easy invariably produced during the transportation and loading of bulk materials.In order to control dust pollution during the bulk materials transportation process,the transportation device for passive dust suppression based on the particle flow characteristics should be developed.Therefore,the dust suppression hopper with material core structure is taken as the research object.Aiming at the main structural geometric parameters affecting dust emission,the particle motion characteristics,flow field distribution and dust concentration variation of the bulk materials transportation process in the dust suppression hopper are analyzed using CFD-DEM coupling numerical simulation and experiment.The dust suppression principle and the influencing factors of dust suppression hopper are explored.And the design basis of dust suppression hopper is obtained by analysing the semi empirical model of discharge mass flow,which is established based on the dimensional analysis method.The main research contents and results of this thesis are as follows:(1)On the basis of reasonably simplifying the dust suppression hopper model,the numerical simulation models of dust suppression hopper,semi core hopper,equal area hopper and equal diameter hopper are established,and the dust suppression principle of dust suppression hopper is explored by comparing the particle profile,particle velocity and flow field distribution.The results show that the particle transportation in the dust suppression hopper can be divided into rapid falling stage,transition stage and stable stage,and the dust suppression effect of the stable stage is better.Compared with the other three kinds of hoppers,the primary and secondary dust emission of the dust suppression hopper are reduced due to the advantages of higher material column density,lower particle and air velocity.In addition,the lateral airflow influence for the dust suppression effect of the dust suppression hopper is lower.Then,it can be noted that bulk materials falling form rest and the annular channel formed by the lower conical material distribution insert and the hopper in the dust suppression hopper are conducive to controlling dust emission.(2)The characteristics of particle mass flow,particle velocity,flow field distribution and dust concentration are explored using numerical simulation and experiment under the working conditions of three structural geometric parameters,which are the cone angle of the dust suppression hopper,the horizontal distance between distribution core and hopper,and the opening diameter at the hopper bottom,respectively.The results show that a smaller cone angle is beneficial for the particle flow of stable stage to reduce dust emission under 20°～45° cone angle working condition.Under the working condition of 20 mm～60 mm horizontal distance,the dust suppression effect increases rapidly,and then slightly decreases due to the compression limitation of annular channel,but the overall effect is preferred.The dust suppression effect is significantly improved for the dust suppression hopper with 40mm～160 mm opening diameter,when the small opening diameter is increased.However,due to the particle mass flow of the large opening diameter is limited by the annular channel,the increase of dust suppression effect is weakened and maintained at a good level.Therefore,the dust suppression hopper can achieve the maximum dust suppression effect by selecting a smaller cone angle within the appropriate cone angle range and keeping the spacing close to the outlet radius.(3)The basic physical parameters affecting the discharge mass flow of the dust suppression hopper are combined and solved by the dimensional analysis method,and the semi-empirical model is established,and that the empirical constants are summarized.The results show that the experimental value with obvious dust suppression effect is within ±20% error of the theoretical model,and it can be drawn that the semi-empirical model has better applicability in practical engineering. |
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