This study evaluated the performance of different ventilation methods under varying limited space air stability conditions with respect to air distribution and pollutant transport in a space capsule. Two ventilation methods were adopted: mixing ventilation (MV) and displacement ventilation (DV). A seated thermal manikin was centred in a computational domain representing the capsule in order to simulate the floating state of a crewmember. Carbon dioxide (CO₂) was selected to represent the exhaled pollutant in the capsule macro-environment and the breathing micro-environment. The numerical results demonstrated that limited space air stability affects pollutant transport in the microgravity environment due to the gravitational sensitivity of capsule air. Moreover, the characteristics of the ventilation method depend on the limited space air stability condition. In the MV system, unstable conditions led to relatively stronger CO₂ diffusion perpendicular to the exhaled mainstream, resulting in a less polluted breathing micro-environment. Conversely, stable conditions confined the exhaled CO₂ to a limited layer near the level where it was released, resulting in a more polluted breathing micro-environment. Whereas in the DV system, very little difference was observed in the distribution of CO₂ between stable and unstable conditions. In addition, the effect of ventilation rate on the distribution of CO₂ was more obvious in the MV system than in the DV system. Under the same pollutant level in the MV system, the unstable condition consumed less energy than the stable condition. These results suggest that the unstable condition enables the more energy efficient removal of pollutants, and provides better air quality for crewmembers in a space capsule ventilated by MV. This study provides useful insights for ventilation design in space capsules.

中文翻译：

---

太空舱有限空间空气稳定条件下混合与置换通风的比较

这项研究评估了在不同的有限空间空气稳定性条件下，不同通风方法在太空舱中的空气分布和污染物输送方面的性能。采用两种通风方式：混合通风（MV）和置换通风（DV）。坐着的人体模型在代表胶囊的计算域中居中，以模拟机组人员的漂浮状态。二氧化碳（CO ₂选择）代表胶囊宏环境和呼吸微环境中的呼出污染物。数值结果表明，由于胶囊空气的重力敏感性，有限的空间空气稳定性会影响微重力环境中的污染物迁移。而且，通风方法的特性取决于有限的空间空气稳定性条件。在中压系统中，不稳定的条件导致垂直于呼出的主流垂直方向的CO ₂扩散相对较强，从而导致呼吸微环境污染较少。相反，稳定的条件限制了呼出的CO ₂到接近释放水平的有限层，导致呼吸微环境污染更严重。而在DV系统中，稳定条件和不稳定条件之间观察到的CO ₂分布差异很小。此外，通气速率对MV系统中CO ₂分布的影响比DV系统中更为明显。在中压系统中污染物水平相同的情况下，不稳定条件比稳定条件消耗的能量更少。这些结果表明，不稳定的条件能够更有效地去除污染物，并为使用MV通风的太空舱中的机组人员提供更好的空气质量。这项研究为太空舱通风设计提供了有用的见识。