Investigation of Entrainment and its Effect on Flame Stabilization in a Turbulent High Karlovitz Number Premixed Jet Flame using Direct Numerical Simulation

IF 2 3区工程技术 Q3 MECHANICS

Flow, Turbulence and Combustion Pub Date : 2023-10-24 DOI:10.1007/s10494-023-00500-8

Jiahao Ren, Haiou Wang, Kun Luo, Jianren Fan

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Abstract

The stabilization of high Karlovitz number (Ka) jet flames is challenging due to the strong mean shear, and the role of entrainment on high Ka flame stabilization is not well understood. In the present work, a direct numerical simulation study of fluid entrainment and its effect on the flame stabilization in a three-dimensional turbulent high Ka premixed jet flame with a strong mean shear was carried out. The global entrainment characteristics in the turbulent jet flame was analyzed, which shows that the mass flow of the jet increases almost linearly with the streamwise distance. The turbulent/non-turbulent (T/NT) interface was investigated and the conditional statistics near the T/NT interface were analyzed. It was found that the enstrophy transport is generally balanced by the vortex stretching term and the viscous dissipation term. In the region close to the interface, the enstrophy generation from the viscous diffusion term is dominant, which has significant impact on the T/NT interface propagation. Overall, the T/NT interface propagates towards the non-turbulent region. Therefore, the species in the coflow of the non-turbulent region are entrained into the turbulent region across the T/NT interface. Various terms of species transport equations conditioned on the T/NT interface were analyzed. It was concluded that the entrainment of species such as OH plays an important role in flame stabilization in the upstream region.

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利用直接数值模拟研究高卡尔洛维茨数湍流预混合喷射火焰中的夹带及其对火焰稳定的影响

高卡尔洛维茨数（Karlovitz number，Ka）喷射火焰由于具有很强的平均剪切力，其稳定化具有挑战性，而夹带对高Ka火焰稳定化的作用尚未得到很好的理解。本研究对具有强平均剪切力的三维湍流高 Ka 预混射流火焰中的流体夹带及其对火焰稳定的影响进行了直接数值模拟研究。分析了湍流射流火焰中的全局夹带特性，结果表明射流的质量流几乎随着流向距离的增加而线性增加。研究了湍流/非湍流（T/NT）界面，并分析了 T/NT 界面附近的条件统计量。研究发现，涡流输送一般由涡旋拉伸项和粘性耗散项来平衡。在靠近界面的区域，粘性扩散项产生的能耗占主导地位，这对 T/NT 界面传播有重大影响。总体而言，T/NT 界面向非湍流区传播。因此，非湍流区共流中的物种会穿过 T/NT 界面进入湍流区。分析了以 T/NT 界面为条件的物种输运方程的各种项。结论是，OH 等物种的夹带对上游区域的火焰稳定起着重要作用。

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来源期刊

Flow, Turbulence and Combustion 工程技术-力学

CiteScore

5.70

自引率

8.30%

发文量

审稿时长

2 months

期刊介绍： Flow, Turbulence and Combustion provides a global forum for the publication of original and innovative research results that contribute to the solution of fundamental and applied problems encountered in single-phase, multi-phase and reacting flows, in both idealized and real systems. The scope of coverage encompasses topics in fluid dynamics, scalar transport, multi-physics interactions and flow control. From time to time the journal publishes Special or Theme Issues featuring invited articles. Contributions may report research that falls within the broad spectrum of analytical, computational and experimental methods. This includes research conducted in academia, industry and a variety of environmental and geophysical sectors. Turbulence, transition and associated phenomena are expected to play a significant role in the majority of studies reported, although non-turbulent flows, typical of those in micro-devices, would be regarded as falling within the scope covered. The emphasis is on originality, timeliness, quality and thematic fit, as exemplified by the title of the journal and the qualifications described above. Relevance to real-world problems and industrial applications are regarded as strengths.