DNS Study of Freely Propagating Turbulent Lean-Premixed Flames with Low-Temperature Chemistry in the Broken Reaction Zone Regime

Yi Zhang, Yinhu Kang (), Xiaomei Huang, Pengyuan Zhang and Xiaolin Tang
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Yi Zhang: Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education of China, Chongqing 400044, China
Yinhu Kang: Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education of China, Chongqing 400044, China
Xiaomei Huang: School of Civil Engineering, Chongqing University, Chongqing 400044, China
Pengyuan Zhang: School of Civil Engineering and Architecture, Anhui University of Technology, Ma’anshan 243032, China
Xiaolin Tang: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Energies, 2025, vol. 18, issue 16, 1-22

Abstract: The novel engines nowadays with high efficiency are operated under the superpressure, supercritical, and supersonic extreme conditions that are situated in the broken reaction zone regime. In this article, the propagation and heat/radical diffusion physics of a high-pressure dimethyl ether (DME)/air turbulent lean-premixed flame are investigated numerically by direct numerical simulation (DNS). A wide range of statistical and diagnostic methods, including Lagrangian fluid tracking, Joint Probability Density Distribution (JPDF), and chemical explosive mode analysis (CEMA), are applied to reveal the local combustion modes and dynamics evolution, as well as the roles of heat/mass transport and cool/hot flame interaction in the turbulent combustion, which would be beneficial to the design of novel engines with high performances. It is found that the three-staged combustion, including cool-flame, warm-flame, and hot-flame fronts, is a unique behavior of DME flame under the elevated-pressure, lean-premixed condition. In the broken reaction zone regime, the reaction zone thickness increases remarkably, and the heat release rate (HRR) and fuel consumption rate in the cool-flame zone are increased by 16% and 19%, respectively. The diffusion effect not only enhances flame propagation, but also suppresses the local HRR or fuel consumption. The strong turbulence interplaying with diffusive transports is the underlying physics for the enhancements in cool- and hot-flame fronts. The dominating diffusive sub-processes are revealed by the aid of the diffusion index.

Keywords: DNS simulation; turbulent premixed combustion; broken reaction zone; diffusion; flame front thickening (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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