期刊
APPLIED THERMAL ENGINEERING
卷 83, 期 -, 页码 8-15出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.applthermaleng.2015.03.009
关键词
Microscale combustion; Cavity; Flame-splitting limit; Heat loss; Heat recirculation
资金
- Natural Science Foundation of China [51276073]
- Foundation of State Key Laboratory of Coal Combustion, China [FSKLCCA1503]
Heat transfer processes are of significance for combustion in microscale channel. In the present paper, three different values (i.e., epsilon = 0.1, 0.5 and 0.92) are selected to numerically investigate the effect of external surface emissivity on the flame-splitting limit (the critical velocity when the combustion efficiency drops to 80%) using Fluent 6.3. The results demonstrate that the flame-splitting limit has a negatively monotonic variation trend with the external surface emissivity. This feature is interpreted from viewpoints of heat-loss from the exterior wall and heat recirculation through the upstream wall. The analyses show that the heat-loss ratio decreases with the reduction of external surface emissivity, which gives rise to a more intense reaction in the cavity and a higher wall temperature level. Therefore, more heat is recirculated to upstream wall and a better preheating of the fresh mixture can be achieved. Consequently, the chain reactions of H-2/air mixture start earlier and the reaction rates are much faster for a smaller surface emissivity. The combined actions of heat loss and heat recirculation lead to a faster consumption of the hydrogen fuel at the flame tip, and a larger flame-splitting limit can be obtained for a smaller surface emissivity. (C) 2015 Elsevier Ltd. All rights reserved.
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