TY - JOUR
T1 - Ignition of hydrogen/air mixtures by a heated kernel
T2 - Role of Soret diffusion
AU - Liang, Wenkai
AU - Law, Chung K.
AU - Chen, Zheng
N1 - Funding Information:
The work at Princeton University was supported by the US National Science Foundation (CBET, Grant # 1510142 ) under the technical monitoring of Dr. Song-Charng Kong, while that at Peking University by the National Natural Science Foundation of China (Nos. 91741126 and 91541204 ). WL was in addition supported by a Guggenheim Fellowship and a Harari Fellowship of Princeton University.
Funding Information:
The work at Princeton University was supported by the US National Science Foundation (CBET, Grant # 1510142) under the technical monitoring of Dr. Song-Charng Kong, while that at Peking University by the National Natural Science Foundation of China (Nos. 91741126 and 91541204). WL was in addition supported by a Guggenheim Fellowship and a Harari Fellowship of Princeton University.
Publisher Copyright:
© 2018 The Combustion Institute
PY - 2018/11
Y1 - 2018/11
N2 - Effects of Soret diffusion on the ignition of hydrogen/air mixtures by a heated kernel, and the structure and dynamics of the embryonic flame that is subsequently formed, were investigated numerically with detailed chemistry and transport. Results show that Soret diffusion leads to larger (smaller) minimum ignition energy (MIE) for relatively rich (lean) mixtures, that this effect is mainly engendered by the Soret diffusion of H2 while that of the H radical is almost negligible, and that Soret diffusion also leads to an increase (decrease) of the Markstein length for rich (lean) mixtures. Satisfactory agreement with literature experimental data on the MIE is shown, especially for the critical states near lean and rich flammability limits. Evolvement of the flame structure shows that before the self-sustained flame is formed, the high temperature gradient associated with the ignition kernel has driven the H2 in the mixture towards the ignition kernel and formed a locally high H2 concentration region, which consequently renders lean (rich) mixtures easier (harder) to ignite. It is further shown that Soret diffusion of both H and H2 affect the propagation dynamics of the stretched spherical flame that is subsequently formed, from its embryonic state until that of free propagation, in that Soret diffusion of H2 is the dominant mode at small flame radius with the large strain rate, while that of H is the dominant mode at large flame radius with the small strain rate similar to that of the unstretched adiabatic planar flame.
AB - Effects of Soret diffusion on the ignition of hydrogen/air mixtures by a heated kernel, and the structure and dynamics of the embryonic flame that is subsequently formed, were investigated numerically with detailed chemistry and transport. Results show that Soret diffusion leads to larger (smaller) minimum ignition energy (MIE) for relatively rich (lean) mixtures, that this effect is mainly engendered by the Soret diffusion of H2 while that of the H radical is almost negligible, and that Soret diffusion also leads to an increase (decrease) of the Markstein length for rich (lean) mixtures. Satisfactory agreement with literature experimental data on the MIE is shown, especially for the critical states near lean and rich flammability limits. Evolvement of the flame structure shows that before the self-sustained flame is formed, the high temperature gradient associated with the ignition kernel has driven the H2 in the mixture towards the ignition kernel and formed a locally high H2 concentration region, which consequently renders lean (rich) mixtures easier (harder) to ignite. It is further shown that Soret diffusion of both H and H2 affect the propagation dynamics of the stretched spherical flame that is subsequently formed, from its embryonic state until that of free propagation, in that Soret diffusion of H2 is the dominant mode at small flame radius with the large strain rate, while that of H is the dominant mode at large flame radius with the small strain rate similar to that of the unstretched adiabatic planar flame.
KW - Hydrogen
KW - Minimum ignition energy
KW - Soret diffusion
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U2 - 10.1016/j.combustflame.2018.08.015
DO - 10.1016/j.combustflame.2018.08.015
M3 - Article
AN - SCOPUS:85053042065
SN - 0010-2180
VL - 197
SP - 416
EP - 422
JO - Combustion and Flame
JF - Combustion and Flame
ER -