Abstract: In the majority of prior research, the phenomenon of droplet impact on solid surfaces has predominantly been examined under conditions involving flat substrates, with pure water serving as the most frequently utilized working fluid. While such studies have provided foundational insights into droplet dynamics, their applicability remains limited, as they fail to address the complexities encountered in many industrial and engineering scenarios. By contrast, investigating the impact behavior of ethanol droplets on cylindrical curved surfaces offers substantial practical value, particularly in optimizing critical industrial processes such as spray cooling and surface coating. Beyond industrial applications, this research also contributes to advancing fundamental knowledge in multiphase flow systems, particularly in understanding how interfacial interactions between liquids and curved substrates influence spreading, rebound, and heat transfer mechanisms. This study employs experimental methods to investigate the dynamics and heat transfer mechanisms of pure ethanol droplets and ethanol-glycerol mixture droplets (with a certain amount of glycerol added) impacting overheated curved surfaces. The dynamic analysis reveals that for pure ethanol droplets, the behavioral differences caused by surface curvature primarily occur in the high Weber number (We) regime. After adding glycerol, the maximum spreading factor on concave surfaces increases with higher glycerol concentration in the droplet, whereas on convex surfaces, this relationship no longer follows a linear trend. In terms of heat transfer, the study demonstrates that the heat transfer mechanisms differ between low and high wall temperature conditions during continuous ethanol droplet impact on overheated surfaces. Moreover, there is a coupling effect between glycerol concentration and surface curvature on heat transfer characteristics. For the impact of droplets on concave surfaces, the addition of glycerol enhances heat transfer performance at low wall temperatures; whereas at high wall temperatures, when the temperature increases to a certain extent, the addition of glycerol has no significant effect. In contrast, for droplet impact on convex surfaces, glycerol addition enhances heat transfer performance only under high wall temperature conditions.

Key words: droplet impact, convex surface, concave surface, droplets dynamics, heat transfer

摘要： 在过去的大部分研究中，液滴撞击表面大多集中在平面，且所用工质大多为纯水，这无法满足一些实际应用的需求。探究乙醇液滴撞击圆柱曲面对于优化喷雾冷却和表面涂覆等工业应用具有重要意义，也可为多相流界面相互作用的基础研究提供新见解。本工作采用实验方法研究了纯乙醇液滴和添加了一定量甘油的乙醇-甘油混合液滴撞击过热曲面的动力学及传热机理。动力学研究表明，纯乙醇液滴撞击时，表面形状造成的行为差异主要发生在高韦伯数(We)阶段；添加甘油后，在凹表面上，最大铺展因子随着液滴中甘油浓度的升高而增大，而在凸表面上则不再呈线性规律。在传热方面，乙醇液滴连续撞击过热表面时，低壁面温度与高壁面温度下的传热机理并不相同，且甘油浓度与表面形状对传热特性的影响存在耦合机制。对于液滴撞击凹表面，低壁面温度下甘油的添加能够提高传热性能；而高壁面温度下，当温度升高到一定程度时，添加甘油无显著影响。对于液滴撞击凸表面，只有在高壁面温度下，添加甘油才有助于提高传热性能。

关键词: 液滴撞击, 凸表面, 凹表面, 液滴动力学, 传热