TY - JOUR
T1 - Ignition of premixed hydrogen/air by heated counterflow
AU - Zheng, X. L.
AU - Blouch, J. D.
AU - Zhu, D. L.
AU - Kreutz, T. G.
AU - Law, C. K.
N1 - Funding Information:
This work was primarily sponsored by the Army Research Office under the technical monitoring of Dr. D. Mann. T.G.K. was supported by a block grant from the British Petroleum Corp. to the Center for Carbon Mitigation Initiative at Princeton University.
PY - 2002
Y1 - 2002
N2 - The inert temperature required to ignite a lean premixed hydrogen/air mixture in a counterflow was determined experimentally and numerically using detailed chemistry and transport. It was found that above φ = 0.2, the ignition temperatures increased with increasing equivalence ratio. This effect is due to the fact that the ignition kernel is located on the hot, inert side of the flow and preferential diffusion of hydrogen makes the flow self-stratifying, resulting in a rich mixture in the ignition kernel even for a very lean freestream mixture. The dearth of O2 in the kernel reduces the reaction rates to the point where diffusive loss becomes significant relative to the rates of kinetic production and consumption. In the presence of this significant transport loss mechanism, premixed ignition temperatures are much higher than non-premixed ignition temperatures and the influence of the strain rate is likewise increased. Adding a few percent of O2 to the hot inert side of the flow lowers the kernel equivalence ratio and increases the reaction rates to the point where diffusive effects are no longer of the same order as kinetic effects. In these cases, the ignition temperatures drop significantly to values close to those of non-premixed ignition even though the free-stream flow is still predominantly premixed.
AB - The inert temperature required to ignite a lean premixed hydrogen/air mixture in a counterflow was determined experimentally and numerically using detailed chemistry and transport. It was found that above φ = 0.2, the ignition temperatures increased with increasing equivalence ratio. This effect is due to the fact that the ignition kernel is located on the hot, inert side of the flow and preferential diffusion of hydrogen makes the flow self-stratifying, resulting in a rich mixture in the ignition kernel even for a very lean freestream mixture. The dearth of O2 in the kernel reduces the reaction rates to the point where diffusive loss becomes significant relative to the rates of kinetic production and consumption. In the presence of this significant transport loss mechanism, premixed ignition temperatures are much higher than non-premixed ignition temperatures and the influence of the strain rate is likewise increased. Adding a few percent of O2 to the hot inert side of the flow lowers the kernel equivalence ratio and increases the reaction rates to the point where diffusive effects are no longer of the same order as kinetic effects. In these cases, the ignition temperatures drop significantly to values close to those of non-premixed ignition even though the free-stream flow is still predominantly premixed.
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U2 - 10.1016/S1540-7489(02)80201-2
DO - 10.1016/S1540-7489(02)80201-2
M3 - Conference article
AN - SCOPUS:84915752958
SN - 1540-7489
VL - 29
SP - 1637
EP - 1643
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 2
T2 - 30th International Symposium on Combustion
Y2 - 25 July 2004 through 30 July 2004
ER -