Parameters influencing the burning rate of laminar flames propagating into a reacting mixture

被引:22
作者
Ansari, Abtin [1 ]
Jayachandran, Jagannath [1 ]
Egolfopoulos, Fokion N. [1 ]
机构
[1] Univ Southern Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA
关键词
Laminar flame propagation; Auto-ignition; Low temperature chemistry; Sensitivity analysis; REACTION FRONT PROPAGATION; NUMERICAL-SIMULATION; COMBUSTION; IGNITION; AUTOIGNITION; CHEMISTRY;
D O I
10.1016/j.proci.2018.05.163
中图分类号
O414.1 [热力学];
学科分类号
摘要
The laminar flame speed is an important property of a reacting mixture and it is used extensively for the characterization of the combustion process in practical devices. However, under engine-relevant conditions, considerable reactivity may be present in the unburned mixture, introducing thus challenges due to couplings of auto-ignition and flame propagation phenomena. In this study, the propagation of transient, one-dimensional laminar flames into a reacting unburned mixture was investigated numerically in order to identify the parameters influencing the flame burning rate in the conduction-reaction controlled regime at constant pressure. It was found that the fuel chemical classification significantly influences the burning rate. More specifically, for hydrogen flames, the "evolution" of the burning rate does not depend on the initial unburned mixture temperature. On the other hand, for n-heptane flames that exhibit low temperature chemistry, the burning rate depends on the instantaneous temperature and composition of the unburned mixture in a coupled way. A new approach was developed allowing for the decoupling the flame chemistry from the ignition dynamics as well as for the decoupling of parameters influencing the burning rate, so that meaningful sensitivity analysis could be performed. It was determined that the burning rate is not directly affected by fuel specific reactions even in the presence of low temperature chemistry whose effect is indirect through the modification of the reactants composition entering the flame. The controlling parameters include but not limited to mixture conductivity, enthalpy, and the species composition evolution in the unburned mixture. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
引用
收藏
页码:1513 / 1520
页数:8
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