新型铝/冰基燃料燃烧特性及机理研究

Al/Ice-based fuels are a new and green high-energy density fuel. It overcomes the problems of the short storage life and easy-to-chemical aging of Al/H2O-based fuels. The combustion of Al/Ice-based fuels can be used for space propulsion systems since its products are nontoxic and therefore considered as "green". At present, however, Al/Ice-based fuels has encountered problems such as the difficulty of ignition, the poor combustion performance and the low combustion efficiency although the nanosized Al powder is applied to the reaction with ice. The better combustion characteristics of propellants can be attainable by determining optimal oxygen/fuel ratio or by introducing other more additives such as combustion improver and catalyst. The combustion characteristcs of Al/Ice-based fuels will be studied as a function of the Al particle size, Al powder content, combustion improver and catalyst. Using advanced technology experiments with quantum chemistry computation, the unique combustion theory of Al/Ice-based fuels will be deeply investigated. At the same time, their combustion characteristics and internal combustion mechanism as well as combustion dynamics will be revealed. The advantages and disadvantages of the various factors are taken into consideration in order to improve the combustion efficiency of Al/Ice-based fuels. The purpose of this project is to look for the methods which improve the ignition and combustion performances through the experimental and theoretical studies and provide experimental basis and theoretical guidance for the formula ranges of new Al/Ice-based fuels. Therefore, the study not only has the academic value, but also has great significance to the application research of Al/Ice-based fuels.

铝/冰基燃料是一种新型的绿色高能量密度燃料，它克服了铝/水基燃料贮存困难，容易化学老化的问题。由于其燃烧产物的无毒性，使其可以作为绿色的环保型的推进剂用于太空推进系统中。但目前，虽然采用纳米铝粉和冰反应，铝/冰基燃料仍然存在点火困难，燃烧性能差，燃烧效率低的问题。在推进剂的燃烧中，确定最佳的氧燃比、添加少量助燃剂或催化剂等是调节推进剂燃烧性能的有效方法。本项目拟从铝粉粒度及含量、添加助燃剂或催化剂等方面，采用多种先进的实验技术结合量子化学计算，深入研究多种因素影响下的铝/冰基燃料独特的燃烧理论，揭示其燃烧特性与内在的燃烧机理以及燃烧反应动力学过程，综合权衡多种因素的利弊，提高铝/冰基燃料的反应效率。通过该项目的实验与理论研究，寻求改善铝/冰基燃料点火及燃烧性能的方法，为新型铝/冰基燃料配方研制提供实验依据和理论指导。因此，该项研究不仅具有学术价值，而且对铝/冰基燃料的应用研究具有重要意义。

针对当前铝/冰基燃料存在点火困难，燃烧性能差，燃烧效率低的问题，本项目采用多种实验技术，研究了铝粉粒度、添加剂对铝粉在高温水蒸汽中燃烧特性的影响。采用不同包覆剂对纳米铝粉进行包覆，研究了包覆纳米铝粉/冰在水蒸气气氛下的燃烧特性。同时，研究了铝粉粒度、添加剂对铝/冰燃料燃烧特性影响。研究结果表明，铝粉粒径对其在水蒸气气氛中的着火温度影响较大，但对其燃烧最高温度影响较小。纳米铝粉在水蒸气气氛中的着火温度比在空气气氛中的着火温度低，且最高温度也低。从燃烧现象发现，纳米铝粉在空气气氛中比在水蒸气气氛中燃烧剧烈，火焰亮度更强。添加KBH4和AP对纳米铝粉燃烧有明显促进作用，使铝粉燃烧强度变大，火焰更明亮，氧化燃烧过程中都发生铝颗粒多方向溅射现象。添加KBH4的铝粉燃烧过程尤为剧烈，燃烧持续时间最长，铝粉在管式炉内产生微爆。而添加NaCl抑制了纳米铝粉燃烧，持续时间明显缩短，且燃烧强度较小，整个燃烧过程较温和。硬脂酸包覆纳米铝粉后，铝颗粒分散更均匀，有效保持了活性铝粉含量，铝的质量分数提高了9.62%；在氧化剂相同的条件下，硬脂酸包覆的纳米铝粉比未包覆的纳米铝粉燃烧充分，并且包覆比例以m(硬脂酸):m(铝)为1:3的样品效果最好，燃烧产物中氧化铝含量最高，燃烧最充分。在铝/冰燃料中添加Mg粉后，燃料燃烧起始温度降低，燃烧反应加快，且效果最为明显的添加量介于3%~5%，但随着添加量的增加，燃烧剧烈程度逐渐减弱；添加AP后，其燃烧反应速率大大增加，缩短了点火延迟时间。但随着AP添加量的增加，燃烧不稳定性也随之增大，安全性能大大降低，添加NaF，在一定程度上减弱了铝/冰燃料的燃烧性能。镁的添加有利于铝/冰反应启动和燃速的提高。硼的添加不利于其反应的启动和燃速的提高，但能增加反应体系的能量性能。通过上述研究，建立了铝/冰燃料燃烧反应评价体系，分析了铝粉粒度、添加剂对铝/冰燃料燃烧过程中七个评价参数的影响，在此基础上，建立了铝/冰基燃料的燃烧模型。