| In order to improve the efficiency of pneumatic filling in goaf,take the pneumatic filling discharge blow tank filled with fly ash as research object.The discharge blow tank serves as the core device of the pneumatic filling system,and its structural parameters directly affect the filling performance.Based on the drag reduction theory of flow field synergy,the geometric size and key structure of the top discharge blow tank are optimized,and use the Euler-Euler model to analyze the discharge characteristics.The results show that the nozzle can increase the synergy angle and discharge quantity,and the nozzle size R/r=1.2 to reach the peak of the discharge.The trend between the nozzle distance and the semi-top angle of the discharge blow tank is the same,which is increased first and then decreased.At the distance h=55mm and ?'=18° to reach the discharge peak respectively,the amount discharge of material increased 20% by the structural optimization.For different transport problems,equipment performance can be improved by optimizing correspond structural parameters.The drag force is a key parameter to represent the interaction between gas and solid phases.Based on the Euler two-fluid model,the Gidaspow,the Syamlal-O'Brien and the huilin drag model are taken as the object of study.The influence of different drag force model on the two-phase flow and the discharge characteristics of tank were analyzed.Then,the outlet mass flow rate at different inlet gas velocity is compared with the experimental data,analysis of different drag models can adapt to the inlet conditions.The calculation results show that the drag force model can be divided into three intervals according to the inlet velocity and the model matching degree.The Gidaspow model of G region has the highest velocity and turbulence degree in the tank and the highest degree of agreement with the experimental data.Syamlal-O'Brien calculated the results slightly smaller than the Gidaspow model.Only in the S region,Syamlal-O'Brien is close to the experimental value.The overall velocity and mass flow rate calculated by the huilin model is the smallest,and when the velocity increases to more than 0.15 m/s,the h region is close to the experimental result.This provides the theoretical basis for the study of the two-phase flow in the discharge blow tank.In order to study the stability and two-phase flow mechanism of the pulverized coal in the pneumatic conveying tank,fluent software was used as the platform.Based on the Realizable k-? Euler two-fluid model,the drag coefficient of Gidaspow model was user-defined according to the experimental data to obtain realistic simulation conditions.And then the stability of the fluctuation characteristics of mass flow rate and volumetric fraction of pulverized coal were analyzed.Finally,the flow mechanism of nitrogen-coal powder coupling in the tank is analyzed.It was found that with the increase of inlet gas velocity,the stability of coal discharge increased firstly and then decreased and the total time-consuming material is gradually reduced,when the inlet gas velocity exceeds 0.12m/s,the total time-consuming basically unchanged.While the inlet gas velocity has little effect on the lateral diffusion of pulverized coal and the movement is more intense in the near wall and center.It is found that the nitrogen in the tank moves mainly in the form of airflow vortex,which is caused by the collisions and superposition of the vortices of various scales to drive the transverse and vertical migration of the coal.The large size vortex in the main nitrogen gas field promotes the whole movement of the pulverized coal,and the small size vortex in the near wall promotes the local diffusion of the pulverized coal. |
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