Abstract In view of the importance of atomization, droplet breakup induced by high Weber number and vapor bubble during droplet impacting onto a solid and heated surface has been studied extensively, but the understand on jet break-up phenomenon in the film boiling regime is still lacking. Thus, the work is trying to study the dynamic of jet break-up of n-butanol, a potential alternative biofuel for internal combustion engine, under the influence of Weber number. During experiment, a high-speed camera, set at 512 × 512 pixels, 10,000 fps, and 20 μs exposure time was used to visualize the droplet impacting behavior. The droplet falling height was set from 1 cm to 9 cm with interval of 0.5 cm, with corresponded Weber number around from 6.94 to 102.12. The heated surface temperature was set at 250 °C, to ensure the impact locates at the film-boiling regime. The results show that the jet break-up is dominated by Rayleigh-Plateau instability, the secondary droplet is formed through contraction of symmetric unstable surface waves since the waves are clearly observed on the jet column. Under tested wall conditions, the jet break-up only takes place when the Weber number of butanol droplet is around from 14.34 to 89.13. Within the jet break-up regime, the number of separated droplets first increases then decreases with Weber number increasing, and reaches the maximum at We = 65. The length of jet break-up first increases slowly then decreases rapidly and then increases with Weber number. While, the time of jet break-up first decrease then increase with Weber number and also reaches the minimum at We = 65.20. In addition, the timing of jet break-up is fitting well with the theory of Rayleigh instability.

中文翻译：

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薄膜沸腾状态下丁醇液滴撞击受热表面射流破碎特性的实验研究

摘要 鉴于雾化的重要性，液滴撞击固体受热表面时高韦伯数和蒸汽泡引起的液滴破裂已被广泛研究，但对薄膜沸腾状态下的射流破裂现象仍缺乏了解。 . 因此，这项工作正试图研究在韦伯数影响下正丁醇（一种潜在的内燃机替代生物燃料）射流破裂的动力学。在实验过程中，使用设置为 512 × 512 像素、10,000 fps 和 20 μs 曝光时间的高速相机来可视化液滴撞击行为。液滴下落高度设置为 1 cm 至 9 cm，间隔为 0.5 cm，对应的韦伯数约为 6.94 至 102.12。受热面温度设定为250℃，以确保冲击位于薄膜沸腾状态。结果表明，射流破裂以瑞利-高原不稳定性为主，由于在射流柱上清晰地观察到波，因此二次液滴是通过对称的不稳定表面波收缩形成的。在测试壁条件下，射流破裂仅在丁醇液滴的韦伯数在 14.34 到 89.13 左右时发生。在射流破碎范围内，分离的液滴数量随着韦伯数的增加先增加然后减少，并在 We = 65 时达到最大值。 射流破碎的长度先缓慢增加，然后迅速减少，然后随着韦伯数的增加而增加. 而射流分裂时间随着韦伯数的增加先减少后增加，并在 We = 65.20 处达到最小值。此外，