Phase Transition Process of N-Dodecane Droplets under Sub/Supercritical Environment

TANG Chunyi; WANG Zhong; LI Ruina; LIU Shuai; LI Lilin

doi:10.3969/j.issn.1001-2222.2021.01.011

Vehicle Engine ›› 2021, Vol. 0 ›› Issue (1) : 63. DOI: 10.3969/j.issn.1001-2222.2021.01.011

Phase Transition Process of N-Dodecane Droplets under Sub/Supercritical Environment

TANG Chunyi¹,WANG Zhong¹,LI Ruina¹,LIU Shuai¹,LI Lilin²

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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 Å²to 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.

Key words

phase transition / diesel engine / n-dodecane / supercritical / molecular dynamics

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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