ISS: Collaborative Research: Spherical Cool Diffusion Flames Burning Gaseous Fuels

球形冷扩散火焰是一种温度异常低的非凡火焰。它们对实际燃烧装置(如发动机)中的燃烧过程提供了有价值的见解。这些火焰是2012年在国际空间站(ISS)上发现的，从那时起，这一直是观察它们的唯一平台。到目前为止，国际空间站所有的低温火焰都涉及液滴燃料。这限制了观察燃料的数量和观察真正稳定火焰的能力。对于这个项目，国际空间站上的实验将使用气态碳氢燃料作为几乎稳定的球形火焰燃烧。这些火焰将由球形多孔燃烧器支撑。他们的观察，加上国际空间站上可用的最先进的燃烧诊断技术，将允许开发用于燃烧研究的新的化学动力学机制和计算工具。通过这些实验获得的对冷扩散火焰的更好的理解将导致实际燃烧装置的改进设计。冷扩散火焰的发现催生了一个迅速增长的研究领域，但在有限的条件下只有几个测量可用。因此，冷火焰化学动力学机制不能得到充分的测试或先进，但这种知识是设计更清洁和更高效的内燃机所必需的。该项目的目标是观察国际空间站上各种冷扩散火焰，用先进的计算模型模拟测试，并推进可以准确模拟这些火焰的化学动力学机制。国际空间站是观察球形冷扩散火焰的唯一平台，因为它们需要大约20 S的微重力才能建立，甚至需要更长时间才能达到稳定状态。火焰将由一个6毫米球形燃烧器支撑，供气为丙烷、正丁烷或正戊烷。将考虑正常火焰和反向火焰，包括广泛的稀释条件和压力。燃烧器、气体输送系统和诊断将是以前国际空间站飞行实验中使用的那些。诊断将支持彩色视频、激发的CH*和CH2O*的成像，以及气体温度、辐射发射、H2O和OH的光学发射以及环境气体组成的测量。这项研究将广泛传播给燃烧研究界和工业界。我们会举办外展活动，吸引中学生修读工程学。该项目将推进最先进的冷却火焰动力学机制，这反过来将导致更清洁，更高效的内燃机。

Spherical cool diffusion flames are remarkable flames with unusually low temperatures. They offer valuable insight into combustion processes in practical combustion devices, such as engines. These flames were discovered in 2012 aboard the International Space Station (ISS), and since then this has been the only platform for observing them. To date all the ISS cool flames have involved liquid droplet fuels. This has limited the number of fuels to be observed and the ability to observe truly steady flames. For this project, experiments aboard the ISS will be performed using gaseous hydrocarbon fuels burning as nearly steady spherical flames. These flames will be supported by spherical porous burners. Their observation, with the most advanced combustion diagnostics available aboard the ISS, will allow the development of new chemical kinetics mechanisms and computational tools for combustion research. The improved understanding of cool diffusion flames gained by these experiments will lead to improved designs of practical combustion devices.The discovery of cool diffusion flames has spawned a rapidly growing research field, but only a few measurements at limited conditions are available. Consequently, cool flame chemical kinetics mechanisms cannot be adequately tested or advanced, but such knowledge is needed to design cleaner and more efficient internal combustion engines. The objectives of this project are to observe diverse cool diffusion flames aboard the ISS, to simulate the tests with advanced computational models, and to advance chemical kinetics mechanisms that can accurately model these flames. The ISS is the only platform for observing spherical cool diffusion flames because they require about 20 s of microgravity to establish and even longer to reach steady state. The flames will be supported by a 6-mm spherical burner fed with propane, n-butane, or n-pentane. Normal and inverse flames will be considered, including a broad range of dilution conditions and pressures. The burners, gas delivery system, and diagnostics will be those used by the previous ISS flight experiments. The diagnostics will support color video, imaging of excited CH* and CH2O*, and measurements of gas temperatures, radiative emissions, optical emissions from H2O and OH, and ambient gas compositions. The research will be disseminated widely to the combustion research community and to industry. There will be outreach activities to attract secondary school students to engineering. This project will advance the state-of-the-art in cool flame kinetics mechanisms, which in turn should lead to cleaner, more efficient internal combustion engines.