TY - GEN
T1 - Effect of radical addition on extinction limits of H2 and CH4 flames
AU - Takita, Kenichi
AU - Ju, Yiguang
PY - 2006
Y1 - 2006
N2 - The effects of NOx and O, H and N radical additions on the extinction limits of H2/air and CH4/air mixtures were numerically investigated with detailed chemistry. The results showed that similar to the ignition limit, the extinction limits of both fuels were extended by the addition of radicals, though the effect on the extinction limit was much smaller than that on the ignition limit. In the case of low inlet temperature, where radicals initially added to a mixture were quickly quenched via recombination reactions, the combustion enhancement effect was mainly due to a thermal effect by heat release via recombination of radicals. The effect of radical addition on the extinction limit appeared more strongly when the inlet temperature was considerably increased. The addition of radicals to the H 2/air mixture at high inlet temperature caused a change of the extinction curve from the S-shaped curve to a monotonic single-valued curve. However, such a change in the flame curve by the addition of radicals did not occur for the CH4/air mixture, even at a much higher inlet temperature. On the other hand, it was shown that the addition of NO x, which is more stable than other active radicals at low temperatures, significantly extended the extinction limit of a lean CH 4/air mixture at high pressures.
AB - The effects of NOx and O, H and N radical additions on the extinction limits of H2/air and CH4/air mixtures were numerically investigated with detailed chemistry. The results showed that similar to the ignition limit, the extinction limits of both fuels were extended by the addition of radicals, though the effect on the extinction limit was much smaller than that on the ignition limit. In the case of low inlet temperature, where radicals initially added to a mixture were quickly quenched via recombination reactions, the combustion enhancement effect was mainly due to a thermal effect by heat release via recombination of radicals. The effect of radical addition on the extinction limit appeared more strongly when the inlet temperature was considerably increased. The addition of radicals to the H 2/air mixture at high inlet temperature caused a change of the extinction curve from the S-shaped curve to a monotonic single-valued curve. However, such a change in the flame curve by the addition of radicals did not occur for the CH4/air mixture, even at a much higher inlet temperature. On the other hand, it was shown that the addition of NO x, which is more stable than other active radicals at low temperatures, significantly extended the extinction limit of a lean CH 4/air mixture at high pressures.
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U2 - 10.2514/6.2006-1029
DO - 10.2514/6.2006-1029
M3 - Conference contribution
AN - SCOPUS:34250736914
SN - 1563478072
SN - 9781563478079
T3 - Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting
SP - 12348
EP - 12356
BT - Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting
PB - American Institute of Aeronautics and Astronautics Inc.
T2 - 44th AIAA Aerospace Sciences Meeting 2006
Y2 - 9 January 2006 through 12 January 2006
ER -