【作者】 张鑫；

【导师】 刘俊杰；

【作者基本信息】 天津大学 ， 土木工程， 2023， 博士

【摘要】 乘坐客机旅行的人数逐年增加,而客舱内的细菌、病毒和颗粒物等污染物对人体的健康和舒适造成极大困扰。为了节能,商用客机的环控系统(ECS)采用50%在巡航高度很干净的引气和50%来自舱内的循环空气,通过高效微粒空气(HEPA)过滤器对循环空气进行净化。该HEPA过滤器具有极高的气流阻力且采用了难以降解的玻璃纤维滤料,而静电纺丝纳米纤维滤料使用易降解的高分子聚合物制备,具有纳米级的纤维直径,可以实现高效低阻过滤,有可能取代玻璃纤维滤料而应用于新一代多电飞机的ECS。但是,目前我们缺少对真实客舱HEPA过滤器过滤性能的实测数据和预测模型,缺少对新材料的应用可行性的定量评估,用于纳米纤维过滤性能模拟的边界条件和纤维建模方法并不成熟。鉴于此,我们主要进行了如下工作:1)从市场上搜集了23款客舱HEPA过滤器样品,并进行了过滤器的外形尺寸、褶结构、压降、颗粒物捕集效率和容尘量等过滤性能的测试,建立了客舱HEPA过滤器的性能数据库并分析了造成其高阻力的原因。2)采用等效渗透系数(EPC)法对过滤器整体的运行性能进行预测,并基于EPC法对过滤器结构参数和表面颗粒物的分布规律进行了研究。3)定量分析了纳米纤维滤料在客舱HEPA过滤器中应用的可行性及存在的问题和可能的解决方法。4)建立了适用于纳米纤维流场CFD模拟的修正滑移边界模型,以及适用于纤维过滤介质的随机3D纤维模型建模方法,并实现了纳米纤维滤料和玻璃纤维滤料过滤性能的模拟。主要结论为:1)改进过滤器结构参数的降阻效果微乎其微,滤料纤维结构的设计是实现降阻的关键;2)EPC法可以实现过滤器运行性能预测且过滤器表面非均匀的颗粒物沉积对降阻有利;3)采用静电纺丝纳米纤维滤料预计可降低阻力66.4%～94.3%,品质因子提升4倍;4)修正滑移边界模型以及随机3D纤维建模方法可以用于纤维滤料的性能模拟,纤维表面滑移作用越强,其阻力越低且颗粒物捕集效率越高。更多还原

【Abstract】 The unmber of people who travel by air is increasing every year.Pollutants such as bacteria,viruses and particulate matter in the cabin cause great concerns to human health and comfort.To conserve energy,the environmental control systems(ECS)of commercial airliners typically use a mixture of 50%bleed air that is very clean at cruising height and 50%recirculated air.The recirculated air is purified through the HEPA filter.These HEPA filters have extremely high air flow resistance and use glass fiber filter medie that is difficult to degrade.The electrospun nanofiber filter media is made of easily degradable polymer.It has a nano-scale fiber diameter and can achieve high-efficient and low-resistance filtration.It is possible to replace the glass fiber filter media and apply it to the ECS of the new multi-electric aircraft.However,at present,we lack the measured data and prediction model of the filtration performance of the real cabin HEPA filters.We lack quantitative evaluation of the application feasibility of new materials.The boundary condition and fiber model used for the filtration performance simulation of nanofibers are not mature.Thus,we did the following work:1)We collected 23 cabin HEPA filters from the market and tested their filtration performance parameters,such as the apparent size,pleat structure,pressure drop,particulate capture efficiency and dust capacity.The performance database of cabin HEPA filters was established and the reasons for its high resistance were analyzed.2)The equivalent permeability coefficient(EPC)method is used to predict the operating performance of the filter.Based on the EPC method,the filters’structural parameters were optimized,and surface particle deposition law was studied.3)The feasibility,existing problems,and possible solutions of applying nanofiber filter media to cabin HEPA filters were quantitatively analyzed.4)We established a slip boundary model and a random 3D fiber model to realize the CFD simulation of flow field around nanofibers.The filtration performance simulation of nanofiber and glass fiber filter media was realized.Some main conclusions:1)It’s hard to reduce filter’s resistance by optimizing their structural parameters,and the key to reduce resistance is to optimize filter media’s fiber structure;2)EPC method can predict filter’s operation performance,and the uneven particle deposition on the filter surface is beneficial to the resistance reduction;3)The electrospun nanofiber filter media is expected to reduce the resistance by 66.4%～94.3%and improve the quality factor by 4 times;4)The modified slip boundary model and random 3D fiber model can be used to simulate the performance of fibrous filter media.The stronger the slip effect on the fiber surface,the lower the resistance and the higher the particle capture efficiency.更多还原