Flash boiling spray is a promising method to improve atomization, which subsequently affects the combustion phenomenon in engines. Therefore, an investigation on both macroscopic and microscopic characteristics of the flash boiling spray should be done to understand this behavior and mechanism. A mini-sac injector with a single hole was used under different injection pressures among 10, 15, and 20 MPa. Experiments were performed in a constant volume chamber with low ambient pressures varying from 5 to 100 kPa. First, macroscopic behaviors including morphology, spray tip penetration, spray angle, and spray cone angle were compared by a Mie scattering method. Then, microscopic characteristics of flash boiling spray were obtained with the help of particle image analysis technology. In order to analyze the droplet behaviors along the spray axis completely, a spray "slicer" was introduced to filter the spray. The influences of measurement location, injection pressure, and ambient pressure were discussed in detail. Results showed that although the injection pressure and measurement location have influences on the spray and atomization in both macroscopic and microscopic cases, the ambient pressure plays a more critical effect on it, indicating the low ambient pressure-induced flash boiling spray could improve the atomization much more efficiently.

中文翻译：

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低环境压力条件下单孔喷雾的宏观和微观特征

闪蒸喷雾是一种很有前途的改善雾化的方法，它随后会影响发动机的燃烧现象。因此，应该对闪蒸喷雾的宏观和微观特征进行研究，以了解这种行为和机制。在 10、15 和 20 MPa 的不同喷射压力下使用单孔微型囊式喷射器。实验在恒定容积的室内进行，环境压力从 5 到 100 kPa 不等。首先，通过 Mie 散射法比较宏观行为，包括形态、喷头穿透、喷雾角度和喷雾锥角。然后，借助粒子图像分析技术，获得了闪蒸喷雾的微观特征。为了完整地分析液滴沿喷雾轴的行为，引入了喷雾“切片器”来过滤喷雾。详细讨论了测量位置、注入压力和环境压力的影响。结果表明，虽然喷射压力和测量位置对喷雾和雾化在宏观和微观上都有影响，但环境压力对其影响更为关键，表明低环境压力引起的闪蒸喷雾可以大大改善雾化。更有效率。