Modeling and simulation of primary jet breakup at aircraft engine relevant conditions

该项目第二学期的主要目标是开发一种方法，使用嵌入式域名系统来预测在真实的空气冲击式雾化器几何形状中液体燃料的一次裂解。嵌入式数值模拟(EDNS)是在项目的第一阶段引入的，指的是一种方法，在这种方法中，使用嵌入整个空气喷射雾化器的大涡模拟(LES)的直接数值模拟(DNS)来计算一次破裂，而不需要基本的简化假设。因此，计算昂贵的域名系统的使用被减少到最重要的区域，这使得能够将域名系统用于现实的技术应用。在项目的第一阶段，该方法被成功地应用于计算一般几何图形。详细的比较表明，预测的初级裂解与实验数据吻合得很好。建议的项目将计算真实空气喷雾器雾化边缘的一次破碎。提取了飞机发动机相关条件下的液滴分布，使其能够转换为Euler-Lagrange描述，用于随后的燃烧模拟，这不是拟议项目的一部分。这项工作的目标是生成嵌入区域(雾化器的大涡模拟)的边界条件，通过耦合VOF和Level-Set方法以及初级破裂的EDNS来提高相界面的分辨率。第一项的工作表明，由于液滴的比例很大，特别是小液滴，完全分辨液体质量是不可行的。重建未分辨液滴和评估重建方法的质量的两个目标由此而来。另一个目标是分析物理分手的机制，这是最初分手的根源。第二个学期的工作使我们能够第一次详细地了解在现实的操作条件下，真实的空气喷射雾化器几何形状的主要分解。所获得的见解将有助于显著提高预测飞机发动机燃烧室的能力。

The main goal of the second term of the project is the development of a method to predict the primary breakup of liquid fuel in a realistic airblast atomizer geometry using embedded DNS. The embedded DNS (eDNS) was introduced in the first term of the project and refers to a method in which the primary breakup is computed without underlying simplifying assumptions using a Direct Numerical Simulation (DNS) which is embedded in a Large-Eddy-Simulation (LES) of the whole airblast atomizer. The usage of the computationally expensive DNS is therefore reduced to the most important regions which enables the usage of DNS for realistic technical applications. In the first term of the project, the method was successfully employed to compute a generic geometry. Detailed comparison showed a good agreement of the predicted primary breakup to experimental data. The proposed project will compute the primary breakup at the atomizing edge of a real airblast atomizer. The droplet distributions at aircraft engine relevant conditions are extracted, enabling the transformation in to the Euler-Lagrange description for the subsequent simulation of the combustion, which is not part of the proposed project. The objectives of the work are to generate boundary conditions of the embedded domain (LES of the atomizer), an enhanced resolution of the phase interface through a coupling of VOF- and Level-Set method and the eDNS of the primary breakup. The work of the first term has shown that the complete resolution of the liquid mass is not feasible due to the large proportion of especially small droplets. The two objectives to reconstruct the non-resolved droplets and to evaluate the quality of the reconstruction method follow from this. Another objective is to analyse the physical breakup mechanism, which originate the primary breakup. The work of the second term enables the very first detailed insight into the primary breakup of a realistic airblast atomizer geometry at realistic operating conditions. The gained insights will contribute to significantly improve the capabilities to predict combustion chambers of aircraft engines.