乙醇和柴油液滴的静电脱落和破碎特性研究

Study on Electrostatic Pinch-off and Breakup Characteristics of Ethanol and Diesel Droplets

液滴静电脱落和破碎特性研究是认识静电雾化的基础,以乙醇和柴油液滴为研究对象,开展其在静电场中的脱落及破碎行为研究。采用微泵驱动控制流量、静电发生装置形成稳定电场、氙灯照明和高速摄像仪获取脱落和破碎过程的动态行为,利用数字图像处理技术提取过程参数。结果表明:毛细管管径和流量不变的情况下,电场电压较低时,液滴发生偏移并脱落,柴油液滴的偏移角较乙醇的小,柴油脱落液滴粒径较乙醇的大;电场电压适中时,液滴发生闭塞而不脱落或变形为波条;仅当流量增大,且电场电压也较大时,液滴发生破碎,乙醇的破碎平均粒径较柴油的小,说明表面张力较小的乙醇静电雾化效果明显优于柴油。

The pinch-off and breakup characteristics of droplets in an electrostatic field are investigated to identify the mechanism of electrostatic atomization.This paper presents the electrostatic pinch-off and breakup behaviors of ethanol and diesel droplets.The micropump and the electrostatic equipment are used to control the rate of flow and to produce a controllable electrical field,respectively.Xenon lamp and the high-speed camera are used to illuminate the droplets and to record the dynamic behaviors of electrostatic pinch-off and breakup of droplets,respectively.The parameters are identified and measured by digit image processing technique.Experimental results demonstrate that the droplets deviates vertical direction and pinch-off in weak electric field.The deviation angle of diesel droplet is smaller than that of ethanol droplet.However,the pinch-off diameter of diesel droplet is larger than that of ethanol droplet.As the voltage enhanced slightly,the ethanol and diesel are clogged,resulting in that the droplets can not be formed.As both the electric field and the rate of flow are enhanced,the ethanol and diesel droplets deform and breakup.The breakup average diameter of diesel droplet is larger than that of ethanol droplet.The results demonstrated that the stability of electronic atomization of the ethanol is better than that of the diesel,since the surface tension of the ethanol is smaller than that of the diesel.