己酸乙酯/月桂酸乙酯及其二元混合物界面性质的分子动力学模拟

Molecular Dynamics Simulation of Surface Tension of Ethyl Hexanoate/Ethyl Dodecanoate and Their Binary Mixture

己酸乙酯和月桂酸乙酯是常用的化石燃料添加剂,其纯质及混合物的表面张力是设计燃料喷射系统所需的重要数据,在较宽的温度范围获取该物性参数非常必要。文章采用分子动力学模拟的方法分别研究了这两种纯质及其二元混合物在温度范围为298.15~448.15 K和308.15~413.15 K的界面性质,包括表面张力、界面层厚度和密度分布。己酸乙酯、月桂酸乙酯以及二者混合物的表面张力模拟值与实验值的平均绝对偏差分别为2.7%,5.1%,6.5%。采用“10-90”原则计算了体系随温度和组分变化的界面层厚度,发现界面层厚度随温度升高呈增大趋势,并且在高温条件下,界面层厚度增加的幅度与己酸乙酯的摩尔分数呈正相关。根据混合体系的密度分布可知,低温时己酸乙酯倾向于在汽-液界面区域出现,随着温度升高这一现象逐渐变弱。

Ethyl hexanoate and ethyl dodecanoate are commonly used as fuel additives,and the surface tension of pure substances and their mixtures is the crucial data for design or optimization of fuel injection system.In present work,the interfacial properties of ethyl hexanoate,ethyl dodecanoate and their binary mixtures,including surface tension,interfacial layer thickness and density were studied by molecular dynamics simulation.All properties were simulated in the temperature ranges between 298.15 and 448.15 K for ethyl hexanoate,ethyl dodecanoate and 308.15 and 413.15 K for their binary mixtures.The average absolute deviations of surface tension between the simulated and the experimental value were 2.7%,5.1%,6.5%for ethyl hexanoate,ethyl dodecanoate and their mixtures,respectively.Additionally,the variation of the interfacial layer thickness of the system with temperature and composition was calculated by the principle of“10-90”.As the temperature increases,the thickness of interface layer increases continuously,and is positively correlated with the molar fraction of ethyl hexanoate at high temperatures.According to the density distribution of the mixtures,ethyl hexanoate tends to appear at the vapor-liquid interface at low temperature,and the phenomenon becomes weaker as the temperature increases.