In this paper, the importance of turbulence effects on the procedure of droplet’s secondary breakup is studied. In the process of modeling the secondary breakup of a droplet, it is a common practice to presume that the droplet is moving in a laminar flow. However, it is evident that the critical Weber number is profoundly affected by the intensity of turbulence presented in the flow. As a result, the abovementioned supposition may lead to significant computational inaccuracy. This paper tends to perform a modification that considers the effects of turbulent flow on the secondary breakup of droplets. It is shown that the results obtained by the modified model are more precise and in a better agreement with experimental data. In this paper, spray behavior is predicted by a conventional breakup model and the one obtained by a modified model, which are both implemented in an in-house computer code. This CFD code accounts for engine simulation by solving the governing two-phase-flow equations using the Eulerian-Lagrangian approach in a three-dimensional coordinate system. To show the effects of turbulence, the changes in spray parameters such as droplet size distribution, spray tip penetration, and spray mean diameter, which is extracted from the two models are compared. Results have shown that the turbulence causes droplets to break in an earlier time, which leads to a higher rate of evaporation and lower penetration length. An interesting fact concluded in this paper is that the difference between the results of the two models decreases as the gas pressure is increased, which means the effects of turbulence become less important as the gas pressure increases.

中文翻译：

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湍流对柴油燃料喷雾中液滴二次破碎的影响

本文研究了湍流效应对液滴二次破碎过程的重要性。在对液滴的二次破碎进行建模的过程中，通常的做法是假设液滴在层流中移动。然而，很明显，临界韦伯数受到流动中湍流强度的深刻影响。结果，上述假设可能导致显着的计算不准确。本文倾向于进行修改，考虑湍流对液滴二次破碎的影响。结果表明，改进后的模型得到的结果更加精确，与实验数据更加吻合。在本文中，喷雾行为是通过传统的破碎模型和通过修改模型获得的模型来预测的，它们都在内部计算机代码中实现。该 CFD 代码通过在三维坐标系中使用欧拉-拉格朗日方法求解控制两相流方程来解释发动机仿真。为了显示湍流的影响，比较了从两个模型中提取的喷雾参数的变化，例如液滴尺寸分布、喷雾尖端穿透和喷雾平均直径。结果表明，湍流导致液滴在较早的时间内破裂，从而导致更高的蒸发速率和更短的穿透长度。本文得出的一个有趣的事实是，随着气压的增加，两个模型的结果之间的差异会减小，这意味着随着气压的增加，湍流的影响变得不那么重要。