Lei Zhipeng, Yang James, Zhuang Ziqing, Roberge Raymond
Department of Mechanical Engineering, Human-Centric Design Research Laboratory, Texas Tech University, Lubbock, TX 79409, USA.
Ann Occup Hyg. 2013 May;57(4):493-506. doi: 10.1093/annhyg/mes085. Epub 2012 Dec 13.
This paper presents a computational fluid dynamics (CFD) simulation approach for the prediction of leakage between an N95 filtering facepiece respirator (FFR) and a headform and an infrared camera (IRC) method for validating the CFD approach. The CFD method was used to calculate leak location(s) and 'filter-to-faceseal leakage' (FTFL) ratio for 10 headforms and 6 FFRs.The computational geometry and leak gaps were determined from analysis of the contact simulation results between each headform-N95 FFR combination. The volumetric mesh was formed using a mesh generation method developed by the authors. The breathing cycle was described as a time-dependent profile of the air velocity through the nostril. Breathing air passes through both the FFR filter medium and the leak gaps. These leak gaps are the areas failing to achieve a seal around the circumference of the FFR. The CFD approach was validated by comparing facial temperatures and leak sites from IRC measurements with eight human subjects. Most leaks appear at the regions of the nose (40%) and right (26%) and left cheek (26%) sites. The results also showed that, with N95 FFR (no exhalation valves) use, there was an increase in the skin temperature at the region near the lip, which may be related to thermal discomfort. The breathing velocity and the viscous resistance coefficient of the FFR filter medium directly impacted the FTFL ratio, while the freestream flow did not show any impact on the FTFL ratio. The proposed CFD approach is a promising alternative method to study FFR leakage if limitations can be overcome.
本文提出了一种用于预测N95过滤式面罩呼吸器（FFR）与头模之间泄漏的计算流体动力学（CFD）模拟方法，以及一种用于验证CFD方法的红外热像仪（IRC）方法。CFD方法用于计算10种头模和6种FFR的泄漏位置和“滤材至面部密封处泄漏”（FTFL）率。通过分析每种头模与N95 FFR组合之间的接触模拟结果来确定计算几何形状和泄漏间隙。使用作者开发的网格生成方法形成体积网格。呼吸周期被描述为通过鼻孔的空气速度随时间变化的曲线。呼吸空气通过FFR过滤介质和泄漏间隙。这些泄漏间隙是FFR周边未能实现密封的区域。通过将IRC测量得到的面部温度和泄漏部位与8名人体受试者的情况进行比较，对CFD方法进行了验证。大多数泄漏出现在鼻子区域（40%）以及右脸颊（26%）和左脸颊（26%）部位。结果还表明，使用N95 FFR（无呼气阀）时，嘴唇附近区域的皮肤温度会升高，这可能与热不适有关。FFR过滤介质的呼吸速度和粘性阻力系数直接影响FTFL率，而自由流对FTFL率没有任何影响。如果能够克服局限性，所提出的CFD方法是研究FFR泄漏的一种有前景的替代方法。
