超临界环境下燃料液滴蒸发的分子动力学模拟

Molecular Dynamics Simulations of the Evaporation Process of a Fuel Droplet Under Supercritical Environment

本文采用分子动力学模拟的方法,研究了超临界压力下正十二烷液滴在氮气环境中的蒸发过程,环境温度覆盖了从亚临界到超临界的范围。研究表明,高压下的蒸发过程相对低压下的经典理论有明显偏离,其蒸发速率不符合D2定律的预测;环境压力和温度均对蒸发速率有明显影响,并且环境压力的提高还会使氮气溶解度和界面厚度显著增大。此外,分析还证明超临界环境下气液界面可能会变为连续相,从而使蒸发过程变成扩散主导的混合过程。

The evaporation process of an n-dodecane droplet surrounded by nitrogen ambient under supercritical pressures and sub- to super-critical temperatures is studied by molecular dynamics simulation. Results show that the evaporation process under high pressures depart considerably from the theoretical prediction of D2-1aw. Both environmental pressure and temperature have significant influence on the evaporation rate, and elevated pressure can greatly increase the nitrogen solubility in the liquid phase and also the liquid-vapor interface thickness. It is found that under supercritical environmental conditions, the expanded interface may enter the continuum regime, leading to a diffusion dominated mixing process, rather than a conventional evaporation.