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中文核心期刊

液滴在气流中的破碎和蒸发研究进展

RECENT ADVANCES ON FRAGMENTATION AND EVAPORATION OF DROPLETS IN AIRFLOW

  • 摘要: 冷气体动力喷涂是一种高效低成本构筑纳米复合结构电极的方案, 但采用传统的冷喷涂方法直接沉积纳米粉末存在严重的激波减速问题, 通过微米液滴携带纳米粉末实现沉积成为极具潜力的解决方案之一. 高速流动中, 受到气流的作用液滴会发生变形、破碎和蒸发等现象, 在破碎特性方面, 气流中液滴破碎在惯性力、表面张力和黏性力主导下有袋状破碎和多袋状破碎等多种破碎模式; 蒸发特性上, 液滴蒸发受扩散现象和Marangoni 效应等影响, 因此液滴的破碎和蒸发行为将影响到液滴的流动加速进而影响纳米粉末的撞击速度和沉积效果. 基于此, 本文综述了近年来液滴在气流中破碎和蒸发的研究进展, 归纳了液滴破碎的动力学机制及液滴蒸发的传热传质特性; 总结了流动液滴破碎和蒸发的主要影响因素, 包括液滴自身性质如黏度、组分及粒径等, 以及气流状态如温度、压力、速度、湿度和激波等; 同时介绍了液滴在气流中破碎和蒸发的主要实验方案; 最后对液滴的破碎和蒸发研究进行了展望, 提出了需要进一步解决的问题和未来可能的研究方向.

     

    Abstract: Cold gas dynamic spraying is an efficient and low-cost solution to build nanocomposite electrodes. However, there is a serious bow shock near the substrate causing a sudden drop in velocity when nano powder is directly deposited by traditional cold spraying methods. Nano powder carried by micro droplets has become one of the most potential solutions to deposit nano powder. In high-speed flow, droplets will deform, break up, and evaporate under the influence of airflow. In terms of fragmentation characteristics, the fragmentation of droplets in the airflow is dominated by inertial force, surface tension, and viscous force, resulting in various fragmentation modes such as bag fragmentation and multi-bag fragmentation. In terms of evaporation characteristics, the evaporation of droplets is affected by diffusion phenomenon, Marangoni effect, etc. Therefore, the fragmentation and evaporation behaviors of droplets will affect the acceleration of droplet flow, and further affect the impact velocity and deposition effect of nano powders. Based on this, this article reviews the recent advance of droplet fragmentation and evaporation in airflow in recent years, summarizes the dynamic mechanism of droplet fragmentation in airflow and the heat and mass transfer characteristics of droplet evaporation; Summarized the main influencing factors of droplet fragmentation and evaporation, including droplet properties such as viscosity, composition, and particle size, as well as airflow states such as temperature, pressure, velocity, humidity, and shock waves; At the same time, the main experimental schemes for the fragmentation and evaporation of droplets in airflow were introduced. Finally, prospects were made for the study of fragmentation and evaporation of droplets in the air, and further issues that need to be addressed and possible future research directions were proposed.

     

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