Kumar A, Gautam S, Atri S, Tafreshi H V, Pourdeyhimi B
Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, North Carolina 27695-7910, United States.
The Nonwovens Institute, NC State University, Raleigh, North Carolina 27606, United States.
Langmuir. 2023 Dec 12;39(49):17653-17663. doi: 10.1021/acs.langmuir.3c02016. Epub 2023 Nov 29.
Electrostatic charge is a major part of modern-day aerosol filtration media (e.g., N95 respirators and surgical facemasks) that has remained poorly understood due to its complicated physics. As such, charging a fibrous material has relied on empiricism in dire need of a mathematical foundation to further advance product design and optimization. In this concern, we have conducted a series of numerical simulations to improve our understanding of how an electrostatically charged fiber captures airborne particles and to quantify how the fiber's dipole orientation impacts its capture efficiency. Special attention was paid to the role of Coulomb and dielectrophoretic forces in the capture of particles of different charge polarities (e.g., particles having a Boltzmann charge distribution). Simulation results were compared with the predictions of the popular empirical correlations from the literature and discussed in detail. Predictions of the empirical correlations better agreed with the simulation results obtained for fibers with a dipole perpendicular to the flow direction rather than for fibers with a dipole parallel to the flow. This indicates that such empirical correlations are more suitable for filters charged via contact electrification (friction charging), where the dipoles are mostly perpendicular to the flow direction, and less suitable for corona-charged media, where the fiber dipoles are generally parallel to the flow direction.
静电荷是现代气溶胶过滤介质（如N95口罩和医用外科口罩）的一个主要组成部分，由于其复杂的物理原理，人们对其了解甚少。因此，对纤维材料进行充电一直依赖于经验主义，迫切需要一个数学基础来进一步推进产品设计和优化。在这方面，我们进行了一系列数值模拟，以加深对带静电纤维如何捕获空气中颗粒的理解，并量化纤维偶极方向如何影响其捕获效率。特别关注了库仑力和介电泳力在捕获不同电荷极性颗粒（如具有玻尔兹曼电荷分布的颗粒）中的作用。将模拟结果与文献中流行的经验关联式的预测结果进行了比较，并进行了详细讨论。经验关联式的预测结果与偶极垂直于流动方向的纤维的模拟结果更吻合，而不是与偶极平行于流动方向的纤维的模拟结果。这表明，这种经验关联式更适用于通过接触起电（摩擦起电）充电的过滤器，其中偶极大多垂直于流动方向，而不太适用于电晕充电介质，其中纤维偶极通常平行于流动方向。
