Pickup, critical and wind threshold velocities of particles
Pickup, critical and wind threshold velocities of particles
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DOI：
10.1016/j.powtec.2007.01.033
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发表时间：
2007-07
影响因子：
5.2
通讯作者：
E. Rabinovich;H. Kalman
中科院分区：
文献类型：
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作者：
E. Rabinovich;H. Kalman
这项工作提出了各种颗粒固体在气体和液体中的拾取速度测量的实验结果。根据我们以前发表的实验结果，在管道中的气体流量回升的三区主曲线定义通过建立简单的关系，修改的雷诺数和阿基米德数。这些区域通过凝聚力（货车德瓦尔斯）区分：区域I代表可忽略的凝聚力，区域II代表增加单个颗粒所需拾取速度的相当大的凝聚力，区域III代表引起聚集体拾取的显著凝聚力。其他人先前发表的实验包括约121个测量范围广泛的颗粒大小，形状和密度的液体拿起，被添加到我们的主曲线具有良好的一致性。在液体-颗粒系统中，凝聚力不影响临界速度。因此，这些实验扩展了大颗粒干颗粒拾取速度的拟合线。在大多数情况下，临界剪切速度（报告的液体颗粒系统）必须转换为平均拾取速度。此外，在大型风洞中进行的额外16次拾取速度测量（空气中）被添加到主曲线中，具有良好的一致性。我们可以得出结论，我们的简单的主曲线是适当的阈值速度定义在三个流体颗粒系统的最大误差只有± 30%。
This work presents experimental results on pickup velocity measurements for a variety of particulate solids in gases and in liquids. Based on our previously published experimental results for pickup in gas flow in pipes a three-zone master-curve is defined by establishing simple relationships between modified Reynolds and Archimedes numbers. The zones are distinguished by cohesive forces (van der Waals): Zone I represents negligible cohesion forces, Zone II represents considerable cohesion forces that increase the required pickup velocity of individual particles, and Zone III represents significant cohesion forces that cause pickup of agglomerates. Previously published experiments by others encompassing about 121 measurements for a wide range of particle sizes, shapes and densities picked up by liquids, were added to our master-curve with excellent agreement. The cohesive forces did not affect the critical velocity in case of liquid–particle systems. Therefore, these experiments extend the line fitting the pickup velocity of big dry particles. In most cases, the critical shear velocity (reported for liquid–particle systems) had to be converted to the average pickup velocity. Furthermore, additional 16 measurements of pickup velocities (in air) conducted in big wind tunnels were added to the master-curve with excellent agreement. We can conclude that our simple master-curve is appropriate for threshold velocities defined in three fluid–particle systems with a maximum error of only ± 30%.