Experimental And Numerical Study On Hopper Discharge

This study investigated the applicability of computational particle fluid dynamic (CPFD) numerical scheme for simulating flows in a3-D hopper on the basis of the experiments. Firstly, the parameters in CPFD model for hopper discharge process were studied. In addition, the effects of hopper geometries, particle properties and aerate hopper were in vestigated. Finally, the applicability of simulating process of discharging pulverized coal in industrial-grade hopper by CPFD model was discussed.Based on particle volume fraction distribution by the simulation results, three flow regions (granular regime region, suspended regime region and standpipe region) were divided and flow characteristics in these regions were analyzed. It shows dense-flow and slow increase of particle and fluid velocity in the granular regime region, dilute-flue and fast increase of particle velocity in the suspended regime region and the negative pressure gradient in the standpipe, which was caused by the difference of gas-solid velocities.The relative height of critical surface decreased with increase of the outlet diameter of hopper, approaching the extreme value1.4. The particle exit velocity increased with the increase of hopper diameter0.5-power law. As hopper angle increased, the flow pattern in hopper transformed from mass-flow to funnel-flow. But the height of the critical surface hardly changed with the hopper angle. The discharge characteristics types of particle were found:Group D particle expansion rate was largest at hopper outlet. Group C particle volume fraction almost didn’t change at outlet in hopper. The absolute negative pressure at outlet in hopper was largest with group A particle discharge process,The discharge of glass beads from an aerated hopper under several aeration height and rates was studied. There were the economic aerating flow rate, the optical aerated height (Ho/D) and the largest discharge rate in aerated hopper. The optical aerated height was increased with the increase of the aerate flow rate. Three flow regions were developed by gravity discharge critical height Hgc/D and the optical aerated height (Ho/D).(1)HL/D<Hggc/D, the discharge rate is slow and poor stability;(2) Hgc/D<HL/D<Ho/D, the discharge rate and critical surface height increase with the aeration height.(3) HL/D≥Ho/D, as the aeration height increased, the discharge rate decreased and stability gradually increased.