基于热力学相平衡模型的多组分燃料低温特性研究

Low temperature performance of multi-component fuel based on thermodynamic phase equilibrium model

该文采用差示扫描量热仪对比研究了棕榈油生物柴油(palm methyl ester,PME)-柴油二元燃料和PME-乙醇-柴油三元燃料的结晶和熔融特性,并基于热力学相平衡理论构建模型计算多元燃料的析晶点。结果表明,在正十二烷(C12)中加入PME和乙醇可以显著提高析晶点,其中三元燃料的析晶点明显低于二元燃料。这是因为PME内含较多的高饱和度脂肪酸甲酯,其长链结构促使燃料更易结晶。而乙醇的加入使得燃油分子间作用力增大,阻碍了分子间运动趋势,并加剧非均匀成核,致使三元燃料的结晶难度高于二元燃料。此外,不同比例下混合燃料的析晶点计算值与试验值具有较好的一致性,证明该热力学模型可用于预测多组分燃料的低温特性。

The crystallization and melting characteristics of palm methyl ester(PME)-diesel binary blend and PME-ethanol-diesel ternary blend were compared and analyzed by differential scanning calorimeter,and the crystallization point of multi-component fuel was calculated by thermodynamic phase equilibrium model.The results showed that the crystallization points of fuel blends were significantly increased by adding PME and ethanol to n-dodecane(C12).The crystallization points of ternary blends were significantly lower than those of binary blends.The early crystallization of multi-component fuel was attributed to the long-chain structure of major saturated fatty acid methyl esters in PME.Moreover,the hindered intermolecular motion and the intensification of heterogeneous nucleation of ternary blend were rooted in ethanol,which directly exhibited its high crystallization difficulty compared to binary blend.It should be noted that the computed values of crystallization points of multi-component fuel were in good agreement with the experimental values.This indicated that the calculation thermodynamics model can be used to predict the low temperature performance of multi-component fuel.