Study of evaporation, micro-explosion, and combustion of nanofluid fuel droplets

许多工业应用涉及蒸发含有小颗粒的液体。一个例子是以一种容易吸入或摄入的方式制造药物粉末聚集体。在这种应用中，聚集体的形状和密度决定了患者服药的容易程度。燃烧含有颗粒的燃料，如重油或火箭推进剂，也涉及类似的蒸发过程。在燃烧燃料的情况下，颗粒聚集体的形状和密度也会影响捕获颗粒以将污染物排放降至最低的方法和效果。在这个项目中，将表征颗粒大小和浓度对液体蒸发和燃烧的影响。这项工作将主要是实验，辅之以理论分析，以全面了解蒸发、燃烧和聚集体形成机制。这项研究将招募不同背景的本科生和研究生参与该项目。该研究结合电喷雾技术产生含有纳米级能量粒子的燃料液滴，通过电动平衡将其自由悬浮在空间中。然后，液滴将被点燃进行燃烧研究，并将结果与没有添加纳米颗粒的结果进行比较。拟议的研究将回答以下具体问题：(1)由于粒子的存在，液滴的燃烧是否遵循传统的d-平方定律？为什么？(2)现有的理论能否解释非d-平方行为？(3)液滴带电时液滴如何燃烧？(4)由于瑞利电荷极限(液滴的临界电荷密度)，在单液滴蒸发过程中是否存在二次雾化？(5)铝颗粒对二次雾化、瑞利极限、点火和燃烧有何影响？该研究对提高能源系统的功率密度具有重要意义。这项工作在推进中的主要应用是在液体推进剂中添加金属含能粒子，可以增加推进剂的重量和体积能量密度，从而增加大气飞行和空间飞行器的射程。除了燃烧，这项工作还与功能液滴、喷雾和热/质传递的动力学有关。研究结果还对食品、制药、陶瓷、化学和纳米技术等其他应用领域具有重要意义。

Many industrial applications involve evaporating liquid containing small-size particles. One example is to manufacture pharmaceutical powder aggregates in a way that they would be easily inhaled or ingested. In this application, the shape and density of aggregates determine the easiness with which the patient take the medication. Burning fuels containing particles, such as heavy fuel oils or rocket propellants, also involves similar evaporation process. In the case of burning fuels, the shape and density of the particle aggregates also affect the means and effectiveness with which particles are captured to minimize pollutant emissions. In this project, effects of particle size and concentration on liquid evaporation and burning will be characterized. The effort will be mainly experimental, aided by theoretical analysis for a full understanding of the evaporation, burning, and aggregate formation mechanisms. Both undergraduate and graduate students with diverse backgrounds will be recruited and involved in this project.The proposed study uses the combination of the electrospray technique to generate fuel droplets containing nano-size energetic particles, which are freely suspended in space by the electro-dynamic balance. The droplet will then be ignited for combustion study, and the results will be compared with those without adding nano particles. The proposed study will answer the following specific questions: (1) Does the droplet burning follow the conventional d-square law due to the presence of particles and why? (2) Can the existing theory explain the non-d-square behavior? (3) How does the droplet burn when the droplet is electrically charged? (4) Is there secondary atomization during the single-droplet evaporation due to the Rayleigh charge limit (the critical charge density of a droplet)? (5) How does the aluminum particle affect the secondary atomization, Rayleigh limit, ignition, and burning? The proposed study is of great significance in advancing the power density of energy systems. This work has the main application in propulsion as adding metal energetic particles to liquid propellants can increase both the gravimetric and volumetric energy density of the propellant, thus increasing the range of the atmospheric flights and space vehicles. In addition to combustion, this work is also relevant to the dynamics of functional droplets, sprays, and heat/mass transfer. The results also have implications for other applications, such as food, pharmaceutical, ceramic, chemical, and nanotechnology.