Estimation of laminar flame speeds using axisymmetric bunsen flames: Molecular transport effects |
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| Institution: | 1. Department of Mechanical Engineering and Aeronautics, University of Patras, Patras, 26504, Greece;2. Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90089-1453,USA;1. State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, China;2. Dalian National Laboratory for Clean Energy, Dalian 116023, China;1. McGill University, 817 Sherbrooke St W,Montréal, QC H3A 0C3, Canada;2. Siemens Energy Canada Limited, 9545 Chemin de la Côte-de-Liesse, Dorval, QC H9P 1A5, Canada;1. State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China;2. School of Astronautics, Beihang University, Beijing 100191, China;1. Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen 76344, Germany;2. Engler-Bunte-Institute, Division of Combustion Technology, Karlsruhe Institute of Technology, Engler-Bunte-Ring 1, Karlsruhe 76131, Germany;3. SKLTCS, CAPT, BIC-ESAT, College of Engineering, Peking University, Beijing 100871, China |
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| Abstract: | Intricacies associated with the estimation of laminar flame speed using the axisymmetric Bunsen flame technique were assessed, through parametric direct numerical simulations. The study involved methane-air mixtures at atmospheric pressure and temperature, and both the flame cone angle and flame surface area methods were utilized to estimate the laminar flame speeds based on conditions used in recent relevant experimental studies. The results provided insight into the details of the flame structure and allowed for the assessment of various non-idealities and the attendant uncertainties associated with the estimation of laminar flame speeds. Additionally, molecular transport effects were investigated by altering the fuel diffusivity, in order to evaluate its impact on the flame structure and propagation under the presence of negative stretch. The modification of fuel diffusivity was found to affect the burning rate as stretch varies. Under fuel rich conditions, decreasing the fuel diffusivity was found to have an opposite effect on the heat release and thus the burning rate, when compared to positively stretched flames that have been investigated recently in a similar manner. The reported results are expected to provide guidance in flame propagation experiments using the convenient Bunsen flame method at near-atmospheric or elevated pressures, as well as insight into the effects of negative stretch that has, compared to positive, attracted less attention in past studies. |
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