Many efforts are being made to develop filters with high efficiency and high holding capacity but remaining a low pressure drop. A two-layer composite filter to achieve the goal was developed, in which the first layer was a charged coarse fibers to provide large void space for particle loading and the second was a thin layer of charged melt-blown with finer fibers to enhance the overall efficiency. Experimental results showed that although the new composite media had a lower initial efficiency than the other two HEPA filters (PTFE and glass fiber filter), its figure of merit (FOM) was the highest. Besides, the composite media had a better holding capacity for PM_2.5 than the other two. At a fixed mass load, i.e., 2 g m⁻², the PTFE (ΔP = 380 Pa) and glass fiber (ΔP = 165 Pa) required around 7.6 and 3.3 times more power, respectively, than the composite media (ΔP = 50 Pa). Due to the low charge level of the coarse fiber layer and the fine fiber diameter of the melt-blown layer, resulted in no efficiency reduction along the loading process. Theoretical analysis showed that the charge shielding and the loss of efficiency in the successive top-down layers were timely compensated by the efficiency enhancement caused by the loading effects, which made the composite media a much uniform deposition of PM_2.5 in layers. This was the main reason resulting in the high holding capacity and low pressure drop of the current composite media which acted like a perfect depth filtration media.

为了开发具有高效率和高保持能力但仍保持低压降的过滤器，人们已经做出了许多努力。开发了一种两层复合过滤器，以实现该目标，其中第一层是带电的粗纤维，可提供较大的空隙空间，以供颗粒装载；第二层是带电的熔喷薄层，具有较细的纤维，可提高整体性能效率。实验结果表明，尽管新的复合介质的初始效率低于其他两个HEPA过滤器（PTFE和玻璃纤维过滤器），但其品质因数（FOM）最高。此外，复合介质对PM _2.5的吸附能力比其他两种更好。在固定的质量负载下，即2 g m ^-2，PTFE（ΔP= 380 Pa）和玻璃纤维（ΔP= 165 Pa）所需功率分别是复合材料（ΔP= 50 Pa）的7.6和3.3倍。由于粗纤维层的低电荷水平和熔喷层的细纤维直径，导致在加载过程中效率没有降低。理论分析表明，由加载效应引起的效率提高可及时补偿连续的自上而下层的电荷屏蔽和效率损失，这使复合介质在各层中PM _2.5的沉积更加均匀。这是导致目前的复合介质具有高保持能力和低压降的主要原因，该复合介质的作用就像是理想的深度过滤介质。