Effect of radical addition on extinction limits of H2 and CH4 flames

Kenichi Takita, Yiguang Ju

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


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.

Original languageEnglish (US)
Title of host publicationCollection of Technical Papers - 44th AIAA Aerospace Sciences Meeting
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
Number of pages9
ISBN (Print)1563478072, 9781563478079
StatePublished - 2006
Event44th AIAA Aerospace Sciences Meeting 2006 - Reno, NV, United States
Duration: Jan 9 2006Jan 12 2006

Publication series

NameCollection of Technical Papers - 44th AIAA Aerospace Sciences Meeting


Other44th AIAA Aerospace Sciences Meeting 2006
Country/TerritoryUnited States
CityReno, NV

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Aerospace Engineering


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