月球工况下太空舱舱内空气稳定性的研究

On the inside air stability of the space flight capsule under the condition of lunar gravity

太空舱作为特殊的气密性空间,其室内空气品质的控制非常重要。为了获得太空舱内合理的空气分布规律,研究了月球重力工况下有限空间内空气稳定性对CO2传播的影响,初步建立了月球工况下的太空舱三维物理模型。采用计算流体动力学(CFD)方法计算月球工况下CO2在3种不同空气稳定性(稳定型、中性型、不稳定型)下的传播特性。结果表明:在月球重力工况下,不稳定型中CO2沿主流方向传播较慢,更易于与周围空气掺混,扩散能力较强,因此有限空间受污染区域大;与其相反,稳定型中CO2沿主流方向的传播比在不稳定型中快,CO2几乎完全沿着主流方向向前传播,难以向周围空气扩散,可以更快地到达出口,有限空间受污染区域小;而中性型中有限空间空气稳定性对CO2传播特性的影响介于稳定型和不稳定型之间。

This article is attempting to focus its study on the air envi- ronment in the space capsule under the condition of the lunar gravity in hoping to find a reasonable air distribution method. Since we know that the Space Capsule is airtight and enjoys a very narrow space without natural ventilation, there is no way but get the supplement of fresh air and exhaust the foul air totally dependent on the forced ven- tilation. It is just because of this reason that the air environment in the capsule is prone to the pollution caused by CO2 emission which comes from the metabolism of the astronauts. And, therefore, CO2 has to be the main pollutant in the space capsule, which makes it of great importance to control the air quality inside the capsule so as to keep the health of astronauts and enable them to work efficiently. Starting from the aforementioned needs, we have established a pre- liminary three-dimensional physical model to analyze the impacts of indoor air stability on the spread of CO2 based on the computational fluid dynamics（CFD） method. According to the said CFD method, it is possible to work out the pollutant transport characteristics under the three different working conditions （i. c. stable condition, neutral condition and unstable condition）. It is supposed that the contours of contamination distribution at 20 s, 60 s and 100 s can be compared when we analyze the differences among the said contours. The results of our calculation show that the CO2 produced under the unstable con- dition may have an obvious tendency to deviate from the mainstream direction and moving close to the two flanks. When the diffusion abil- ity of CO2 is strengthened, it would make the exhaust of CO2 more difficult to get eliminated from the space capsule, therefore the pol- luted area in the space capsule should be made much bigger. On the eontrary, when the CO2 under the stable condition can be transferred faster in the mainstream direction and arrives at the outlets more easi- ly, it would be easier to eliminate the exhaust air from the space cap- sule as compared with the unstable condition. What is more, the con- tours of pollution distribution in the transverse area in the capsule are also very compact. When CO2 is generated in the mainstream direc- tion of the space capsule, it would be better to set the outlets in the middle of the bottom so as to eliminate it more easily. In summary, it can be concluded that the internal air stability can be made reliable under lunar gravity condition by setting the outlets in the middle of the bottom so as to reduce the effects of pollutant transport.