基于流体体积方法的燃油液滴蒸发过程数值模拟研究

Numerical Study of Fuel Droplet Evaporation Process by Using VOF Model

建立了基于气液两相流流体体积(VOF)方法的燃油液滴蒸发的数学计算模型,研究了燃油液滴蒸发过程中的传热传质特性及强制对流流场对传热传质特性的影响。研究发现,燃油液滴在蒸发过程中,液滴内部并不是均匀加热,而是热点区域加热较快,其他区域缓慢加热。在初始时刻时,燃油液滴相界面处的蒸气与周围气体之间的浓度梯度较大,因此初期的蒸发速率较快,其谢伍德数Sh也较大。不同气液相温度差能促进液滴的蒸发过程,随着气液相温度差增大,液滴蒸发速率逐渐增大。随着雷诺数的增大,高温热点区域的分界线逐渐模糊,液滴内部加热逐渐趋于均匀。雷诺数越大,液滴的温度越高,但液滴温度差别较小。不同雷诺数能有效促进液滴的蒸发过程。

A large eddy simulation VOF model is established for the fuel droplet evaporation. The heat and mass transfer characteristics of fuel droplet evaporation in forced convection flow field are investigated. The trend of droplet evaporation is researched by comparing and analyzing the results of heat and mass transfers. The results show that the heat transfer of droplet is not uniformly, but the hot zone is rapidly heated while other zone is slowly heated in the process of droplet evaporation. At the initial time, since the concentration gradient of the fuel droplet at the interface between the vapor and the surrounding gas is high, the initial evaporation rate is rapid and Sh number is larger. Different temperature difference can promote the evaporation process of the droplets. The evaporation rate increases with the increase of the temperature difference.