静电雾化微滴模式下液滴周期性喷射的实验研究

Experimental Study on Periodic Emission of Micro-drops in Electro-spraying

为了探讨静电雾化微滴模式下荷电液滴形成的动力学规律,采用显微变焦的高速数码相机对微滴模式下无水乙醇的静电雾化过程进行了可视化研究,并采用位移法研究了微液滴的荷电量。通过记录弯液面释放的微液滴的体积长大、拉长、变形以及分离等过程,分析了静电雾化微滴释放的周期特性,探讨了微滴模式下液滴的长短轴之比、当量直径、弯液面长度等的微液滴形成过程的动力学特征。研究结果表明,微滴模式下静电雾化过程呈现一定的周期性,微液滴释放频率随静电Bond数增加;当液滴的释放频率范围在11.000~65.360Hz时,液体的流量几乎不影响微液滴的释放频率;在液滴的长、短轴特性中,短径比与长径比随无量纲流量的增加呈现出增长的趋势,而随着静电Bond数的变化趋势相对较小;雾化液滴的伸长特性呈现出明显的周期变化;随着静电Bond数的增加,当量直径呈现出降低趋势。

In order to explore the dynamics of drop formation in the form of micro-dripping regime in electro-spraying,the micro-dripping of anhydrous ethanol was studied by a high-speed digital camera with a microscopic zoom lens,and the charge of microdroplet was studied by displacement.By recording the process of liquid accumulation,meniscus growth,elongation,deformation and separation of drops,the periodic characteristics of the drops release in micro-dripping regime were analyzed,and the dynamic process of droplets formation with the long/short axis and the equivalent diameter was discussed.The results show that the electro-spraying process in the micro-dripping mode presents periodicity,and the droplet release frequency increases with an increase in the electric Bond number.When the droplet release frequency ranges from 11.000 Hz to 65.360 Hz,the liquid flow rate hardly affects the drops release frequency.In the long/short axis characteristics of drops,the values of short axis/pipe diameter and long axis/pipe diameter increase as the dimensionless flow rate increases,whereas negligibly vary as the electric Bond number increases.The equivalent diameter presents a decreasing trend with an increase in the electric Bond number.