Investigation of Non-Spherical Droplets in High-Pressure Fuel Sprays

了解导致液体分解和蒸发的机制是设计高效清洁燃烧系统的关键一步。涉及柴油雾化过程的复杂性是这样的，涉及的许多方面仍然不了解。典型的柴油喷雾的形态组成包括韧带、无定形液滴和球形液滴等结构，但完美的球形液滴所占的燃料量只占总喷射体积的一小部分。这些相对较大的非球形结构从未在高压喷雾中进行过彻底的研究和记录，尽管变形液滴的传热表面积的增加是预测柴油喷雾蒸发正确趋势的一个影响因素。燃料喷雾液滴的表征通常使用激光诊断来进行，激光诊断可以高精度地测量液滴的直径，但它们从根本上无法测量非球形液滴和韧带的大小或形状。因此，通过这些诊断技术获得的数据提供了喷雾的部分和有偏见的特征。由于模拟变形液滴的加热和蒸发的复杂性，实验偏向于球形液滴。因此，液体燃料雾化和汽化的理论模型是基于许多简化的假设，包括分散的球形液滴的假设。我们的建议旨在通过开发诊断和数值模型，特别是专注于非球形液滴和韧带，从而对石油和生物燃料喷雾形成的描述进行一步改变。我们的方法将建立在显微成像的最新进展之上，以建立新的诊断和算法，可以测量单个液滴和韧带的形状、大小、速度和气体周围。这种形态分类以及速度测量将用于开发新的现象和数值模型，用于喷雾破裂，加热和蒸发。然后，这些模型将被实现到计算流体动力学（CFD）代码中，以模拟现代发动机条件下的喷雾混合，并生成光学诊断无法应用的信息。这些目标将通过将学术和工业合作伙伴的专业知识与来自贝加莫大学、科里亚大学和莫斯科国立大学的国际专家的专业知识相结合来实现。该项目的协同方法旨在消除对球形液滴的实验和数值偏差，将建立一个独特的世界领先的研究能力，并对许多实际喷雾应用产生潜在影响。该项目将支持依赖液体雾化或蒸发的领域的研究，包括液体燃料、药物、冷冻剂、润滑剂和选择性催化还原剂的有效输送。

Understanding the mechanisms that lead to the breakup and evaporation of liquids is a key step towards the design of efficient and clean combustion systems. The complexity of the processes involved in the atomisation of Diesel fuels is such that many facets involved are still not understood.The morphological composition of a typical Diesel spray includes structures such as ligaments, amorphous and spherical droplets, but the quantity of fuel occupied by perfectly spherical droplets can represent a small proportion of the total injected volume. These relatively large non-spherical structures have never been thoroughly investigated and documented in high-pressure sprays, even though the increase in heat transfer surface area of deformed droplets is an influential factor for predicting the correct trend of evaporating Diesel sprays. The characterisation of fuel spray droplets is generally conducted using laser diagnostics that can measure droplet diameters with a high level of accuracy, but they are fundamentally unable to measure the size or shape of non-spherical droplets and ligaments. Hence the data obtained through these diagnostic techniques provide a partial and biased characterisation of the spray. The experimental bias towards spherical droplets is compounded by the complexity of modelling the heating and evaporation of deformed droplets. Consequently, theoretical models for liquid fuel atomisation and vaporisation are based on a number of simplifying hypotheses including the assumption of dispersed spherical droplets.Our proposal seeks to initiate a step change in the description of petroleum and bio fuel spray formation by developing diagnostics and numerical models specifically focused on non-spherical droplets and ligaments. Our approach will build upon recent advances with microscopic imaging to build novel diagnostics and algorithms that can measure the shape, size, velocity and gaseous surrounding of individual droplets and ligaments. This morphological classification, along with the velocity measurements, will be used to develop new phenomenological and numerical models for spray breakup, heating and evaporation. The models will then be implemented into computational fluid dynamics (CFD) codes to simulate spray mixing under modern engine conditions, and generate information where optical diagnostics cannot be applied. These goals will be achieved by combining the expertise of the academic and industrial partners with that of international experts from the University of Bergamo, CORIA, and Moscow State University.The project's concerted approach, aimed at removing the experimental and numerical biases towards spherical droplets, will establish a unique world leading research capability with potential impact for numerous practical spray applications. The project would underpin research in areas that rely upon the atomisation or evaporation of liquids, including the efficient delivery of liquid fuel, pharmaceutical drugs, cryogens, lubricants and selective catalytic reductants.