Gaining an insight into liquid fuel spray combustion is important to develop advanced internal combustion engines or gas turbines. In this paper, large-eddy simulation (LES) is adopted for investigation of the n-dodecane spray combustion process. To study the spray and combustion characteristics of n-dodecane, the corresponding velocity field and concentration field are analyzed by using proper orthogonal decomposition (POD). The results show that the increase of initial ambient temperature can enhance the convective heat transfer between the fuel and surrounding gas, accelerate liquid droplet breakup, and promote evaporation. Thus, large-scale structures of the spray concentration field are significantly correlated with the spatial distribution of the local vortices, and the temporal evolutions of energy/intensity of the two fields are similar. POD analysis can reveal the correlation of flow field and concentration field at different scales. In the combustion state, increasing the initial ambient temperature can change the ignition conditions and promote the temperature rise in the fuel-rich region, thus advancing the ignition delay time, decreasing the flame lift-off length, increasing the high-temperature reaction region area, promoting the reaction activity. In addition, POD analysis can also reflect the correlation between the unstable flame structure and the turbulent flow field.

中文翻译：

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基于适当正交分解的正十二烷喷雾燃烧分析

深入了解液体燃料喷雾燃烧对于开发先进的内燃机或燃气轮机非常重要。本文采用大涡模拟（LES）研究正十二烷喷雾燃烧过程。为研究正十二烷的喷雾和燃烧特性，采用适当正交分解（POD）方法分析了相应的速度场和浓度场。结果表明，初始环境温度的升高可以增强燃料与周围气体之间的对流传热，加速液滴破碎，促进蒸发。因此，喷雾浓度场的大尺度结构与局部涡旋的空间分布显着相关，并且两个场的能量/强度的时间演化相似。POD分析可以揭示不同尺度下流场和浓度场的相关性。在燃烧状态下，提高初始环境温度可以改变点火条件，促进富油区温度升高，从而提前点火延迟时间，缩短火焰升空长度，增加高温反应区面积，促进反应活性。此外，POD分析还可以反映不稳定火焰结构与湍流场的相关性。减小火焰升空长度，增大高温反应区面积，促进反应活性。此外，POD分析还可以反映不稳定火焰结构与湍流场的相关性。减小火焰升空长度，增大高温反应区面积，促进反应活性。此外，POD分析还可以反映不稳定火焰结构与湍流场的相关性。