超临界CO_(2)与PAG润滑油互溶性的分子动力学模拟

Molecular Dynamics Simulation of Miscibility of Supercritical CO_(2) WithPAG Lubricating Oil

选取超临界CO_(2)和聚乙二醇合成油(PAG润滑油)作为研究对象,采用分子动力学模拟方法,考察超临界CO_(2)体系、PAG润滑油体系及二者混合体系在不同温度、压力、CO_(2)含量、PAG润滑油含量等条件下CO_(2)和PAG润滑油的互溶性变化规律。结果表明:对于CO_(2)摩尔分数100%、PAG润滑油质量分数22.23%的混合体系,在压力为10 MPa、温度由313.15 K升至353.15 K时,混合体系的溶解度参数差值增大80.5%,分子间结合能减小13.8%,CO_(2)和PAG润滑油互溶性减弱;在温度为393.15 K、压力由10 MPa升至50 MPa时,混合体系溶解度参数差值减小55.7%,分子间结合能增大19.1%,CO_(2)和PAG润滑油互溶性增强;混合体系中CO_(2)摩尔分数由25%升高至100%时,体系密度和溶解度参数均增大,CO_(2)溶解性能提高,此时溶解度参数差值降低了52.9%,CO_(2)和PAG润滑油互溶性增强。当混合体系中PAG润滑油的质量分数增加至60%以上时,CO_(2)和PAG润滑油的互溶性主要与润滑油含量有关。CO_(2)和润滑油互溶性变化规律的研究结果为海上高压超临界CO_(2)压缩机的研发和应用提供理论支撑。

Supercritical CO_(2)and polyethylene glycol synthetic oil(PAG lubricating oil)were selected as the research object,and molecular dynamics simulation method was used to investigate the change law of miscibility of CO_(2)and PAG lubricating oil in supercritical CO_(2)system,PAG lubricating oil system and their mixed system under different conditions of temperature,pressure,CO_(2)content and PAG lubricating oil content.The results show that for the mixed system with CO_(2)molar fraction of 100%and PAG lubricating oil mass fraction of 22.23%,when the pressure is 10 MPa and the temperature rises from 313.15 K tO_(3)53.15 K,the difference of solubility parameter increases by 80.5%,the intermolecular binding energy decreases by 13.8%,and the miscibility of CO_(2)and PAG lubricating oil is weakened;when the temperature is 393.15 K and the pressure rises from 10 MPa to 50 MPa,the difference of the solubility parameters decreases by 55.7%,the intermolecular binding energy increases by 19.1%,and the miscibility of CO_(2)and PAG lubricating oil is enhanced;when the molar fraction of CO_(2)in the mixed system increases from^(2)5%to 100%,the system density and solubility parameters both increase,and the solubility of CO_(2)is improved,as a result of which the solubility parameter difference decreases by 52.9%,and the miscibility of CO_(2)and PAG lubricating oil is enhanced.When the mass fraction of PAG lubricating oil in the mixed system increases to more than 60%,the miscibility of CO_(2)and PAG lubricating oil is mainly related to the content of lubricating oil.Research results for the change law of miscibility of CO_(2)and lubricating oil provide theoretical support for the development and application of offshore high-pressure supercritical CO_(2)compressors.