亚/超临界环境下多组分燃料液滴相变的模拟-《内燃机学报》

文章信息/Info

Title:: Simulation on Phase Transitions of Multi-Component Fuel Droplets Under Sub- and Supercritical Conditions

作者:: 巩艺飞; 马骁; 肖国炜; 罗开红; 徐宏明; 帅石金; 1. 清华大学汽车安全与节能国家重点实验室，北京100084；2. 伦敦大学学院机械工程系，伦敦 WC1E 7JE，英国；3. 伯明翰大学机械工程系，伯明翰 B15 2TT，英国

Author(s):: Gong Yifei; Ma Xiao; Xiao Guowei; Luo Kaihong; Xu Hongming; Shuai Shijin; 1. State Key Laboratory of Automotive Safety and Energy，Tsinghua University，Beijing 100084，China；2. Department of Mechanical Engineering，University College London，London WC1E 7JE，United Kingdom；3. Department of Mechanical Engineering，University of Birmingham，Birmingham B15 2TT，United Kingdom

Keywords:: supercritical; phase transitions; multi-component fuel; droplet; molecular dynamics simulations; dominant mixing mode

摘要:: 采用分子动力学模拟的方法，研究了一种三组分碳氢燃料液滴在亚/超临界氮气环境下的相变过程，并与单组分正十六烷液滴进行了对比，液滴初始直径约为26nm．分析了液滴寿命、初始加热时间和蒸发速率常数等常规的液滴蒸发特性．提出了一种针对单/多组分燃料油、气混合过程主导模式的判据，探讨了环境温度和环境压力对主导混合模式转变的影响．结果表明：当环境压力为2～10MPa、环境温度为750～1200K、环境压力升高或环境温度降低时，气/液密度差逐渐减小，主导混合模式逐渐从蒸发向扩散转变．得到了正十六烷液滴和三组分燃料液滴蒸发系统在p-T图上的主导混合模式的分区图，并分析了不同混合模式下的燃料分子分布差异．

Abstract:: Phase transitions of three-component hydrocarbon fuel droplets in sub- and supercritical nitrogen environments were studied in detail using molecular dynamics，in?comparison with those of single-component n-hexadecane droplets. The initial diameters of the two droplets were about 26nm. The droplet evaporation lifetime，initial heat-up time and evaporation rate constant were analyzed for all simulation cases. A criterion to determine the dominant mixing mode of single/multi-component fuel in fuel-ambient gas mixing process was proposed. Effects of ambient temperature and ambient pressure on the transition of dominant mixing mode were discussed. The results show that，when the ambient pressure ranges from 2MPa to 10MPa and the ambient temperature ranges from 750K to 1200K，the density?difference between the vapor phase and the liquid phase decreases gradually with increasing ambient pressure or decreasing ambient temperature. The dominant mixing mode gradually transitions from?evaporation to diffusion，simultaneously. Dominant mixing mode partition maps on the p-T diagram for evaporation systems of n-hexadecane droplets and three-component fuel droplets were presented. Atomic-level insights into the differences between the mixing modes were obtained via the molecular distributions of fuel droplets.