Large Eddy Simulation of Swirled Spray Flame Using Detailed and Tabulated Chemical Descriptions
Large Eddy Simulation of Swirled Spray Flame Using Detailed and Tabulated Chemical Descriptions
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DOI：
10.1007/s10494-016-9763-0
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
B. Franzelli;A. Vié;M. Boileau;B. Fiorina;N. Darabiha
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作者：
B. Franzelli;A. Vié;M. Boileau;B. Fiorina;N. Darabiha
旋流火焰的准确表征是开发更高效、更安全的航空发动机的关键点。对于喷射系统来说，这项任务更具挑战性。一方面，喷雾与湍流和火焰相互作用，最终影响火焰动力学。另一方面，由于蒸发和混合过程引起的当量比不均匀性，湍流喷射火焰的结构非常复杂。这项工作的第一个目标是对旋流喷射火焰的结构和动力学进行数值表征。目标配置是名为 MERCATO 的实验基准，代表实际的涡轮喷气发动机喷射系统。由于火焰的复杂性，化学动力学的详细描述是必要的，这里通过使用 24 种化学方案来获得，该方案是为喷雾火焰的数值模拟而开发的。这里首次使用如此详细的化学描述对旋流喷雾火焰进行大涡模拟 (LES)，并分析结果以研究喷雾、湍流和火焰之间的复杂相互作用。据观察，这种耦合对火焰结构有影响，并且火焰动力学由喷雾、进动涡核和火焰锋之间的相互作用控制。即使如此详细的动力学描述可以准确表征火焰，但就 CPU 时间而言仍然非常昂贵。已明确开发了表格技术，以减少纯气态配置中的计算成本，以解释详细的化学反应。第二个目标是验证 FPI 表格化学方法通过执行 LES 正确再现喷涂火焰特性的能力。为此，将 FPI 方法的结果与实验数据库以及通过 24 种描述获得的结果在平均和波动轴向气体速度和液相特征（液滴直径和液体速度）方面进行比较。此外，通过 FPI 方法获得的火焰特征与 24 种方案的结果进行了比较，重点关注火焰结构、主要和次要物质浓度以及污染物排放。最后评估了喷雾火焰表格方法的潜力和局限性。
Accurate characterization of swirled flames is a key point in the development of more efficient and safer aeronautical engines. The task is even more challenging for spray injection systems. On the one side, spray interacts with both turbulence and flame, eventually affecting the flame dynamics. On the other side, the structure of turbulent spray flame is highly complex due to equivalence ratio inhomogeneities caused by evaporation and mixing processes. The first objective of this work is to numerically characterize the structure and dynamics of a swirled spray flame. The target configuration is the experimental benchmark named MERCATO, representative of an actual turbojet injection system. Due to the complex nature of the flame, a detailed description of chemical kinetics is necessary and is here obtained by using a 24-species chemical scheme, which has been developed for numerical simulations of spray flames. The first Large Eddy Simulation (LES) of a swirled spray flame using such a detailed chemical description is performed here and results are analyzed to study the complex interactions between the spray, the turbulent flow and the flame. It is observed that this coupling has an effect on the flame structure and that flame dynamics are governed by the interactions between spray, precessing vortex core and flame front. Even if such a detailed kinetic description leads to an accurate characterization of the flame, it is still highly expensive in terms of CPU time. Tabulated techniques have been expressly developed to account for detailed chemistry at a reduced computational cost in purely gaseous configurations. The second objective is then to verify the capability of the FPI tabulated chemistry method to correctly reproduce the spray flame characteristics by performing LES. To do this, results with the FPI method are compared to the experimental database and to the results obtained with the 24-species description in terms of mean and fluctuating axial gas velocity and liquid phase characteristics (droplet diameter and liquid velocity). Moreover, the flame characterization obtained with the FPI approach is compared to the results of the 24-species scheme focusing on the flame structure, on major and minor species concentrations as well as on pollutant emissions. The potential and the limits of the tabulated approach for spray flame are finally assessed.