摘要
依据内燃机碳氢燃料的特性，建立了正十二烷（C12H26）液滴在亚/超临界N2氛围下相变的分子动力学模型。将液滴温度与已有研究进行对比，验证了仿真模型的可靠性。在此基础上，对超临界环境下C12H26液滴的气液界面厚度、液滴直径的平方、均方位移（MSD）、扩散系数等参数随环境压力、温度和时间的变化规律进行分析。结果表明：当环境温度、压力高于C12H26的临界温度和压力时，随着时间的增加，C12H26液滴直径的平方与时间的关系不成正比，液滴界面厚度由18.43Å增加至23.25Å，MSD线性增加，由3.4×104 Å2增加至6.5×104Å2，扩散系数由2.8×10－3 cm2/s转变至4.37×10－3 cm2/s，液滴相变不再遵从d2定律，液滴由表面蒸发向以扩散为主的混合互溶过程转变。
Abstract
Based on the hydrocarbon fuel characteristics of internal combustion engine, a molecular dynamics model of phase transition for n-dodecane (C12H26) droplets under sub/supercritical nitrogen atmosphere was established. The droplet temperature was compared with the existing research results to verify the reliability of the model. The changing laws which the gas-liquid interface thickness, the square of droplet diameter, the mean square displacement (MSD) and the diffusion coefficient of C12H26 droplet changed with the ambient pressure, temperature and time respectively in a supercritical environment were analyzed. The results show that when the ambient temperature and pressure is higher than the corresponding critical value of C12H26, with the increase of time, the square of droplet diameter is not proportional to time, the interface thickness of droplet increases from 18.43Å to 23.25Å, MSD increases linearly from 3.4×104 Å2 to 6.5×104Å2, the diffusion coefficient increases from 2.8×10－3 cm2/s to 4.37×10－3 cm2/s, the droplet phase change no longer obeys the d2 law, and the droplet changes from surface evaporation to the process of mixing and mutual dissolution dominated by diffusion.
关键词
相变 /
柴油机 /
正构烷烃 /
超临界 /
分子动力学
Key words
phase transition /
diesel engine /
n-dodecane /
supercritical /
molecular dynamics
唐纯逸，王忠，李瑞娜，刘帅，李立琳.
亚/超临界环境正十二烷液滴相变过程分析[J]. 车用发动机. 2021, 0(1): 63 https://doi.org/10.3969/j.issn.1001-2222.2021.01.011
TANG Chunyi,WANG Zhong,LI Ruina,LIU Shuai,LI Lilin.
Phase Transition Process of N-Dodecane Droplets under Sub/Supercritical Environment[J]. Vehicle Engine. 2021, 0(1): 63 https://doi.org/10.3969/j.issn.1001-2222.2021.01.011
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