Study On Effects Of Inserts In Hopper On Powder Discharge

The introduction of insert can cope with various abnormal flow behaviors during hopper discharge.In this thesis,firstly,the effects of insert on the granular flow and the solid flow rate were investigated by experiments.In addition,the solid flow rate of the hopper with complicated flow channels formed by the insert was predicted.Finally,the numerical method of computational particle fluid dynamic(CPFD)was employed to analyze the influences of insert on the flow parameters.By means of perspex hopper platform built in the laboratory,the discharge behaviors of powders with different properties were compared and the increase of solid flow rate was analyzed quantitatively under the action of various flow channel structures in hoppers without insert(No-In),with confined insert(Con-In)and with unconfined insert(Ucon-In).The results show that the introduction of insert are beneficial to the increase of the solid flow rate.Con-In has the more significant effects and powders flow out in a specific sequential order under the action of Ucon-InFor No-In,based on the division of flow zones,the minimum energy theory equation was modified by a correction factor F.By taking the effects of the shear flow zone into consideration,the ideal hopper discharge model was extended to actual situations.Regarding Con-In,according to the structural characteristics of the flow channels and the force analysis on powders,the term relating to conical angle in the model was modified.In terms of Ucon-In,based on the flow competition mechanism,a correlation between the flow rate of inner layer and that of interlayer was proposed.Finally,a model to predict the solid flow rate in hopper with an insert was established.The model took into account the effects of powder properties,flow patterns and structural parameters,which can effectively predict the discharge rate in a hopper with an insert with the deviation less than 10%.CPFD numerical method was used to investigate the flow behaviors in No-In and Con-In.Compared with No-In,the particles volume fraction became smaller and the pressure became higher in Con-In.The particles in Con-In took advantage of a shorter route to the hopper outlet and less energy dissipation cause by vortex motion.