ABSTRACT

The burning process of multiple liquid fuels with various nanoenergetic additives is investigated experimentally in the suspended droplet configuration. Specifically, the burning rate constant $K$ and ignition delay ${\tau }_{\mathrm{i}\mathrm{g}\mathrm{n}}$ are measured for two base fuels, rocket grade kerosene (RP-2) and ethanol, with seven energetic additives; the investigated additives include aluminum (Al), magnesium oxide (MgO), graphene, graphene nano-platelet (GNP), as well as numerous soluble additives including ammonia borane (AB), ammonium nitrate (NaAN) and sodium borohydride ($\mathrm{N}\mathrm{a}\mathrm{B}{\mathrm{H}}_4$), all of which do not exceed 6 wt.% loading concentration. Results from these experiments show that in general, there is not a significant modification to the steady burning rate for these nanofuel combinations (averaging $<$10%) for the loading concentrations considered. Instead, the additives exhibit a majority of particle burning during the end of the droplet lifetime, which generally are short-lived events that do not affect the overall $K$. This is illustrated by calculating the instantaneous burning rate $\tilde{K}$ for these nanofuels, where $\tilde{K}$ is 2% to 18% higher than pure fuels during the last half of the droplet burn time depending on the additive type. Similarly, nanofuel ignition delays generally only exhibit modest changes for a majority of the investigated combinations, causing only a $\pm$5% change on average. However, two nanofuels consisting of ethanol with 5 wt.% soluble ammonia borane and RP-2 with 1 wt.$\mathrm{\%}$ suspended graphene do exhibit increases in ${\tau }_{\mathrm{i}\mathrm{g}\mathrm{n}}$ of approximately 20 and 30$\mathrm{\%}$, respectively. These nanofuel compounds also exhibit substantial qualitative combustion behavioral changes including flame color changes and micro-droplet shedding events for ethanol with ammonia borane, as well as a notable reduction in the average burning rate of 20$\mathrm{\%}$ for RP-2 with graphene. Therefore, these two nanofuel combinations may be candidates for further study as a means to garner control of combustion dynamics in a reacting liquid rocket spray environment.

摘要

在悬浮液滴配置中实验研究了具有各种纳米能量添加剂的多种液体燃料的燃烧过程。具体来说，燃烧速率常数$钾$ 和点火延迟 ${\tau }_{\mathrm{一世}\mathrm{G}\mathrm{n}}$测量两种基础燃料，火箭级煤油 (RP-2) 和乙醇，以及七种高能添加剂；研究的添加剂包括铝 (Al)、氧化镁 (MgO)、石墨烯、石墨烯纳米片 (GNP)，以及许多可溶性添加剂，包括氨硼烷 (AB)、硝酸铵 (NaAN) 和硼氢化钠 ($\mathrm{N}\mathrm{一种}\mathrm{乙}{\mathrm{H}}_4$)，所有这些都不超过 6 wt.% 的负载浓度。这些实验的结果表明，总的来说，这些纳米燃料组合的稳定燃烧速率没有显着改变（平均$<$10%) 对于所考虑的负载浓度。相反，添加剂在液滴寿命结束时表现出大部分颗粒燃烧，这通常是短暂的事件，不会影响整体$钾$. 这可以通过计算瞬时燃烧率来说明$\stackrel{～}{钾}$ 对于这些纳米燃料，其中 $\stackrel{～}{钾}$根据添加剂类型，在液滴燃烧时间的后半段时间比纯燃料高 2% 至 18%。类似地，对于大多数研究的组合，纳米燃料点火延迟通常只表现出适度的变化，仅导致$\pm$平均变化 5%。然而，两种纳米燃料由含有 5 重量％可溶性氨硼烷的乙醇和含有 1 重量％可溶性氨硼烷的 RP-2 组成。$\mathrm{\%}$ 悬浮石墨烯确实表现出增加 ${\tau }_{\mathrm{一世}\mathrm{G}\mathrm{n}}$ 大约 20 和 30$\mathrm{\%}$， 分别。这些纳米燃料化合物还表现出显着的定性燃烧行为变化，包括火焰颜色变化和含氨硼烷的乙醇的微液滴脱落事件，以及平均燃烧速率显着降低 20$\mathrm{\%}$对于带有石墨烯的 RP-2。因此，这两种纳米燃料组合可能是进一步研究的候选者，作为在反应液体火箭喷雾环境中控制燃烧动力学的一种手段。