DNS Of the ignition process of n-heptane/air premixed combustion with low-temperature chemistry in turbulent boundary layer |
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| Affiliation: | 1. State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, PR China;2. Energy Systems Division, Argonne National Laboratory, Lemont, IL 60439, USA;3. Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550, USA;1. Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States of America;2. High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, United States of America;1. State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China;2. Institute for Combustion Technology, RWTH Aachen University, Templergraben 64, D-52056 Aachen, Germany;3. Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, TX 78712, USA;1. State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China;2. School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China;3. Department of Mechanical Engineering and Science, Kyoto University, Kyoto 615–8540, Japan;4. College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China |
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| Abstract: | In the present work, three-dimensional direct numerical simulation (DNS) of -heptane/air premixed combustion in turbulent boundary layer was performed to explore the near-wall ignition process with low-temperature chemistry. A reduced chemical mechanism with 58 species and 387 elementary reactions for -heptane combustion was used in the DNS. The general characteristics of the ignition process near the wall were examined. It was found that low-temperature ignition (LTI) dominates the upstream region, and high-temperature ignition (HTI) appears in the downstream region. The ignition process and the low-temperature chemistry pathways of the DNS are compared with those of a corresponding laminar case. It was found that the ignition process was affected by turbulence, which results in thickened reaction zones. However, the carbon flow analysis of low-temperature chemistry showed that turbulence rarely affects the low-temperature chemistry pathway. The combustion modes of various regions were scrutinized based on the budget terms of species transport equations and the chemical explosion mode analysis (CEMA). It was shown that the reaction term of is significant during the LTI process of the upstream region, and the reaction terms of and are evident in the downstream region, indicating the occurrence of HTI. It was also shown that auto-ignition is dominant in the upstream region. With increasing streamwise distance, the contribution of flame propagation increases, which takes over that of auto-ignition in the near-wall region. |
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