Abstract The aeronautical sector has been, in the last decade, one of those that most invested in more efficient and ecological solutions in order to reduce significantly greenhouse gas and pollutant emissions. The introduction of biofuels in fuel mixtures for aircraft engines is a promising alternative in this sector. The main objective of this experimental study is understanding the influence of crossflow variation on droplet deformation and consequent impact outcomes. An experimental facility was developed and validated to study the impact of single droplets onto a dry, smooth aluminium impact surface under the influence of several crossflow velocities. Different crossflow velocities of 4 , 5 , 6 , 7 and 8 m/s were tested. A combination of conventional jet fuel and a biofuel was considered to understand the behavior of jet fuel and biofuel mixtures, and three fluids were used: 100% jet fuel, 75% jet fuel/25% biofuel and 50% jet fuel/50% biofuel. Several parameters, including velocity components, impact angle and eccentricity, were analysed for the different crossflow velocities, and the spread and splash regimes were also defined for the different fluids. The results display that, for each crossflow velocity, an increase in the droplet impact velocity causes a shift from the spread to the splash regime. The presence of a crossflow induces deformation on the droplet, altering its outcome. Ellipsoidal droplets promote the occurrence of spreading, whereas splashing tends to occur for spherical forms, corresponding to higher and lower eccentricity values, respectively. A substantial increase in the crossflow velocity leads to aerodynamic breakup of the droplet.

中文翻译：

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液滴变形研究：横流速度对喷气燃料和生物燃料液滴撞击干燥光滑表面的影响

摘要 在过去十年中，航空业一直是投资于更高效和生态解决方案以显着减少温室气体和污染物排放的行业之一。在飞机发动机的燃料混合物中引入生物燃料是该领域的一个有前途的替代方案。本实验研究的主要目的是了解横流变化对液滴变形和随之而来的影响结果的影响。开发并验证了一种实验设施，以研究在几种错流速度的影响下，单个液滴对干燥、光滑的铝质撞击表面的影响。测试了 4、5、6、7 和 8 m/s 的不同错流速度。考虑使用传统喷气燃料和生物燃料的组合来了解喷气燃料和生物燃料混合物的行为，并使用了三种流体：100% 喷气燃料、75% 喷气燃料/25% 生物燃料和 50% 喷气燃料/50% 生物燃料. 针对不同的横流速度分析了几个参数，包括速度分量、冲击角和偏心率，并且还为不同的流体定义了扩散和飞溅状态。结果显示，对于每个横流速度，液滴撞击速度的增加导致从扩散到飞溅状态的转变。交叉流的存在会导致液滴变形，从而改变其结果。椭圆形液滴促进扩散的发生，而球形液滴倾向于发生飞溅，分别对应较高和较低的偏心率值。