对细颗粒在料仓内的重力卸料特性进行了实验研究,分别考察了颗粒粒径和料仓构型对卸料流率的影响,采用高速摄像仪对料仓出口处颗粒的卸料形态进行捕捉,并分析其周期性.结果表明,随着颗粒粒径的增大,颗粒卸料流率受逆向压力梯度和"空环效应"两种因素共同影响,先增大后基本保持恒定.另外,锥形和平底料仓中细颗粒的卸料形态,均随粒径增大由不稳定的间歇卸料向稳定的连续卸料过渡.在间歇卸料形态下,由于间歇卸料周期较长,锥形料仓的卸料流率要小于平底料仓;在连续卸料形态下,受料仓锥角影响,锥形料仓的卸料流率要大于平底料仓.最后,通过修正逆向压力梯度项,分别建立了适用于锥形和平底料仓的细颗粒重力卸料流率预测模型,卸料流率的预测值和实验值吻合很好.%An experiment study on the gravity discharge characteristics of fine particles from a hopper was performed. The effects of particle size and hopper geometry on the gravity discharge rate were investigated respectively. High speed camera was employed to capture the discharge pattern of particles from the hopper and the periodicity of discharge pattern was discussed. The results showed that with the increase of particle sizes,both the interstitial pressure gradient and empty annulus effect had significant influences on the discharge rate. Thus,the discharge rate increased with particle size at first and then kept stable. Besides,as particle size increased,a transition from unstable and intermittent discharge to stable and continuous discharge was found in the discharge patterns of fine particles from conical and flat-bottomed hoppers. For the case of intermittent discharge,the discharge rate in conical hopper was lower than that in flat-bottomed hopper,due to a longer intermittent discharge period. On the other hand,for the case of continuous discharge,the discharge rate in conical hopper was higher than that in flat-bottomed hopper,due to the conical angle. Finally,by modifying the interstitial pressure gradient,a new model was proposed to predict the discharge rate of fine particles from conical and flat-bottomed hoppers. The predicted values of discharge rate were in good agreement with the experimental values.
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