This research aims at studying experimentally the surface processes occurring during burning of a solid polymeric fuel containing a small fraction of expandable graphite (EG) particles/flakes (nominal size 150 μm). Solid polymeric fuels burning in oxidizer or air streams are found in propulsion devices such as hybrid rocket motors or solid fuel ramjets. It was revealed that the inclusion of EG particles in the fuel may increase its burning (regression) rate. Expandable graphite is a specific type of intercalated graphite, which, at elevated temperatures, tends to swell and form worm‐like strings several folds longer than the original particles. The behavior of these strings and the dynamic phenomena at the fuel surface subjected to a flame at atmospheric conditions have been visualized using high‐speed (1000 pictures per second) video photography. Formation and growth of the EG strings have been observed revealing characteristic times of tens of milliseconds and a typical length in a millimeter range. Individual EG strings emit from the surface and are eventually entrained by the gas flow without causing crumbling or detachment of layers from the fuel surface.

中文翻译：

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含可膨胀石墨的聚合物燃料的燃烧现象

这项研究的目的是实验研究包含少量可膨胀石墨（EG）颗粒/薄片（标称尺寸为150μm）的固体聚合物燃料燃烧过程中发生的表面过程。在诸如混合动力火箭发动机或固体燃料冲压喷气发动机等推进装置中发现了在氧化剂或气流中燃烧的固体聚合物燃料。揭示了在燃料中包含EG颗粒可以增加其燃烧（回归）速率。可膨胀石墨是一种特殊类型的插层石墨，在高温下，它易于膨胀并形成比原始颗粒长几倍的蠕虫状弦。这些串的行为以及在大气条件下受到火焰燃烧的燃料表面的动态现象已经通过高速（每秒1000张图片）视频摄影来可视化。已观察到EG弦的形成和生长，揭示了数十毫秒的特征时间和毫米范围内的典型长度。单独的EG弦从表面发出，并最终被气流夹带，而不会导致层从燃料表面塌陷或脱离。