论文标题
Lodletsmoke ++:用于多维燃油液滴蒸发的全面多相CFD框架
DropletSMOKE++: a comprehensive multiphase CFD framework for the evaporation of multidimensional fuel droplets
论文作者
论文摘要
本文旨在介绍液滴++求解器,这是一个综合的多维计算框架,用于在重力场和外部流体流的影响下蒸发燃料液滴。采用流体(VOF)方法的体积来动态跟踪界面以及能量和物种方程的溶液。基于相边界处的蒸气浓度梯度直接评估蒸发速率,而无需半经验蒸发子模型。由于存在寄生水流,因此强烈的表面张力力通常会阻止小滴蒸发。在这项工作中,我们绕过这个问题,消除了表面张力,并将中心力引入液滴中心。这种权宜之计代表了这项工作的主要新颖性,该工作允许在正常重力条件下在纤维上悬挂一滴液滴,而不会对表面张力进行建模。寄生流得到完全抑制,可以准确地对蒸发过程进行任何液滴尺寸的建模。在自然和强迫对流的各种燃料和初始液滴直径的各种燃料和初始液滴直径方面,在广泛的操作条件下,与实验数据显示出了极好的一致性。与在微重力条件下建模的相同病例的比较突出了外部流体流对蒸发机制的影响,尤其是在高压下。包括用于相平衡的非理想热力学,以在高压下正确捕获蒸发速率,否则理想的气体假设不会很好地预测。最后,讨论了液相中流动循环的存在及其对内部温度场的影响。 Lodletsmoke ++将以开源代码发布,并接受科学界的贡献。
This paper aims at presenting the DropletSMOKE++ solver, a comprehensive multidimensional computational framework for the evaporation of fuel droplets, under the influence of a gravity field and an external fluid flow. The Volume Of Fluid (VOF) methodology is adopted to dynamically track the interface, coupled with the solution of energy and species equations. The evaporation rate is directly evaluated based on the vapor concentration gradient at the phase boundary, with no need of semi-empirical evaporation sub-models. The strong surface tension forces often prevent to model small droplets evaporation, because of the presence of parasitic currents. In this work we by-pass the problem, eliminating surface tension and introducing a centripetal force toward the center of the droplet. This expedient represents a major novelty of this work, which allows to numerically hang a droplet on a fiber in normal gravity conditions without modeling surface tension. Parasitic currents are completely suppressed, allowing to accurately model the evaporation process whatever the droplet size. DropletSMOKE++ shows an excellent agreement with the experimental data in a wide range of operating conditions, for various fuels and initial droplet diameters, both in natural and forced convection. The comparison with the same cases modeled in microgravity conditions highlights the impact of an external fluid flow on the evaporation mechanism, especially at high pressures. Non-ideal thermodynamics for phase-equilibrium is included to correctly capture evaporation rates at high pressures, otherwise not well predicted by an ideal gas assumption. Finally, the presence of flow circulation in the liquid phase is discussed, as well as its influence on the internal temperature field. DropletSMOKE++ will be released as an open-source code, open to contributions from the scientific community.