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液滴撞击壁面是一种常见的现象, 减少撞击过程中液滴在壁面的驻留时间在很多应用中非常重要. 本文在对液滴撞击加热壁面的动力学过程的研究中, 发现了一种能够大幅减少液滴驻留时间的弹起模式, 即雾化弹起模式. 与液滴撞击壁面过程中的回缩弹起模式相比, 雾化弹起模式的液滴驻留时间能减少约40%. 与其他试图减少液滴驻留时间的手段相比, 本文中驻留时间的减少仅需加热壁面, 因此该方法容易实施而且非常可靠. 最后, 本文对雾化弹起模式下液滴驻留时间减少的机理进行了讨论, 提出了一个针对膜态沸腾区域雾化弹起模式发生条件的简化理论模型, 并得出了膜态沸腾区域液滴从雾化弹起模式到回缩弹起模式过渡边界的幂次关系, 该幂次关系与实验数据吻合良好. 此外, 该理论模型也能解释过渡沸腾区域两种弹起模式的过渡边界的变化规律.
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关键词:
- 液滴撞击 /
- Leidenfrost效应 /
- 驻留时间 /
- 反弹
The impact of droplets on surfaces is a ubiquitous phenomenon, and reducing the droplet residence time is the aim of many studies because of the potential applications in self-cleaning, anti-icing, corrosion resistance, etc. This study identifies a mode of droplet bouncing (bouncing-with-spray) that can reduce the residence time significantly. And compared with the way of using complex microstructures on the substrate employed in previous studies, simply heating the substrate to reduce the residence time is novel and simple. The dimensionless residence time decreases down to about 40% compared with that from the traditional retraction-bouncing mode. The reduction in the residence time is due to the burst of vapor bubbles in the liquid film, which results in holes forming in the liquid film and consequently the liquid film recoiling from the holes. The reduction in the recoiling distance leads to the reduction in the recoiling time. Then a simplified theoretical model with considering the energy balance and the critical condition of the bubble burst is proposed. According to this theoretical model, a scaling law is proposed for the transition boundary between the retraction-bouncing mode and the bouncing-with-spray mode in the film boiling regime, and it accords well with our experimental data. This model can also explain the transition boundary between these two modes in the transition boiling regime.-
Keywords:
- droplet impact /
- Leidenfrost effect /
- residence time /
- bouncing








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