二次流驱动气力输送中摩擦电粉体充电
Secondary flows drive triboelectric powder charging in pneumatic conveying
AI总结：
本研究发现二次流通过促进颗粒混合和减少碰撞，使气力输送中粉体充电速度加快并改善电荷分布。
摘要：
高分辨率模拟揭示了载体流体的流动动力学对摩擦电粉体充电的根本影响。我们发现，通过方形管道运输的颗粒比在通道流中充电更快，这是由于二次流导致更严重的颗粒-壁碰撞。具体而言，斯托克斯数为4.69的颗粒在管道流中达到平衡电荷约85%的时间比在通道流中快1.5倍。此外，管道横截面的电荷分布比通道横截面更均匀。在通道流中，颗粒由于在壁法向方向上的运动受限而靠近墙壁并频繁碰撞，导致局部电荷积累。相反，管道流通过二次流促进更好的混合，减少重复碰撞，并在横截面内提供均匀的电荷分布。在充电过程中，静电力显著改变颗粒的行为和分布。一旦粉体达到平衡电荷的一半，颗粒越来越多地聚集在墙壁上，导致中心区域浓度降低。这些颗粒分布的变化对周围流体相有明显影响，并改变整体流动动力学。这些发现为通过施加特定模式来控制粉体充电提供了新的可能性。
英文摘要：
Highly resolved simulations reveal the fundamental influence of a carrier fluid's flow dynamics on triboelectric powder charging. We found that particles transported through a square-shaped duct charge faster than in a channel flow caused by secondary flows that led to more severe particle-wall collisions. Specifically, particles with a Stokes number of 4.69 achieve 85 % of their equilibrium charge approximately 1.5 times faster in duct flow than in channel flow. Also, charge distribution is more uniform in a duct cross-section compared with a channel cross-section. In channel flow, particles are trapped near the walls and collide frequently due to limited movement in the wall-normal direction, causing localized charge buildup. In contrast, duct flow promotes better mixing through secondary flows, reducing repeating collisions and providing uniform charge distribution across the cross-section. Upon charging, electrostatic forces significantly reshape particle behaviour and distribution. Once the powder achieves half of its equilibrium charge, particles increasingly accumulate at the wall, leading to a reduced concentration in the central region. These changes in particle distribution have a noticeable impact on the surrounding fluid phase and alter the overall flow dynamics. These findings open the possibility for a new measure to control powder charging by imposing a specific pattern.
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