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

球形冷扩散火焰是具有异常低温的非凡火焰。他们提供了宝贵的见解，燃烧过程在实际的燃烧装置，如发动机。这些火焰是2012年在国际空间站（ISS）上发现的，从那以后，国际空间站一直是观测它们的唯一平台。迄今为止，国际空间站的所有冷却火焰都涉及液滴燃料。这限制了可观察的燃料数量和观察真正稳定火焰的能力。在这个项目中，国际空间站上的实验将使用气态碳氢化合物燃料燃烧成几乎稳定的球形火焰。这些火焰将由球形多孔燃烧器支撑。他们的观察，加上国际空间站上最先进的燃烧诊断技术，将为燃烧研究提供新的化学动力学机制和计算工具。这些实验提高了对冷扩散火焰的认识，将有助于改进实际燃烧装置的设计。冷扩散火焰的发现已经催生了一个快速发展的研究领域，但只有在有限条件下的一些测量是可用的。因此，冷焰化学动力学机制无法充分测试或改进，但需要这样的知识来设计更清洁、更高效的内燃机。该项目的目标是观察国际空间站上不同的冷扩散火焰，用先进的计算模型模拟测试，并推进能够准确模拟这些火焰的化学动力学机制。国际空间站是观测球形冷扩散火焰的唯一平台，因为它们需要大约20秒的微重力来建立，甚至更长的时间才能达到稳定状态。火焰将由一个6毫米的球形燃烧器支撑，燃烧器装有丙烷、正丁烷或正戊烷。将考虑正常火焰和反火焰，包括广泛的稀释条件和压力。燃烧器、气体输送系统和诊断仪将是之前国际空间站飞行实验中使用的。该诊断系统将支持彩色视频、激发态CH*和CH2O*的成像，以及气体温度、辐射发射、H2O和OH的光学发射和环境气体成分的测量。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，吸引中学生研习工程。该项目将推进最先进的冷火焰动力学机制，这反过来应该导致更清洁，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.