基于分子模拟的铁表面含酯燃油油膜吸附特性分析

Adsorption of Esters Contained Fuel on the Fe Surface: A Molecular Dynamics Study

将肉豆蔻酸甲酯(C14)、棕榈酸甲酯(C16)、硬脂酸甲酯(C18)、油酸甲酯(C18∶1)、亚麻油酸甲酯(C18∶2)及蓖麻油酸甲酯(C18∶1OH)添加至柴油中,基于Materials Studio软件建立酯/正十四烷在铁表面吸附构型,分析含酯油膜的能量构成。结果表明:对于C14酯/正十四烷混合物,随着酯体积分数增加,油膜的吸附能大幅增加,而内聚能总体差异较小;对于5%(体积分数)酯/正十四烷混合物,含不同酯油膜的吸附能总体上较为接近,但内聚能随着碳链长度、不饱和程度及极性基团等因素变化较大,其由大到小的顺序为C18∶1OH、C18∶2、C18∶1、C18、C16、C14。对比酯体积分数与组分引起的油膜吸附能变化可见,酯体积分数是更重要的因子,但酯组分变化可引起内聚能显著的差异。酯体积分数增加和酯组分改变均为提升低硫柴油润滑性能的有效措施。

Proper additives for low sulfur diesel are necessary to enhance its lubrication properties.Therefore,appropriate amount of methyl myristate (C 14 ),methyl palmitate (C 16 ),methyl stearate (C 18 ),methyl oleate (C 18 ∶1 ),methyl linoleate (C 18 ∶2 ) and methyl ricinoleate (C 18 ∶1 OH) were added into diesel fuel.Based on the Materials Studio software,constructions of various fatty acid methyl ester/ n -tetradecane mixtures adsorbed on the Fe surface were built up,and then the energy composition of esters contained oil film was analyzed.The results show that for the C 14 / n -tetradecane mixture,adsorption energies significantly increase with the increase of C 14 volume fraction,while cohesive energies differ slightly.For 5% volume fraction of esters /n -tetradecane mixtures,adsorption energies are almost the same,while cohesive energies change with the carbon chain length,the degree of unsaturation and the polar groups in descend order of C 18 ∶1 OH,C 18 ∶2,C 18 ∶1,C 18,C 16,C 14.Overall,it is found that the ester fraction has more influence on adsorption energies,while the ester composition has more influence on cohesive energies.In conclusion,both the increase of ester fraction and the change of ester composition are effective ways to improve the lubrication properties of low sulfur diesel fuel.