On multiple criticality in hydrocarbon ignition

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

2 Scopus citations


The counterflow ignition of nitrogen-diluted methane by heated air was computationally studied, with particular interest on the role of thermal- versus radical-induced runaway. Results show that for situations with low methane concentrations, the characteristic ignition-extinction S-curve has two ignition turning points, implying that ignition could occur in two stages as the air temperature is increased. It is further shown that the first ignition event, occurring at the lower temperature, is controlled by radical runaway and does not involve thermal feedback, while the second ignition event does require thermal feedback. The crucial reaction that effects the folding of the first ignition turning point is CH3 + HO2 → CH3O + OH, which converts the nominally inactive HO2to two reactive radicals. The analogy of this reaction with H + HO2 → OH + OH in the ignition of hydrogen is noted, and the importance of HO2 in inducing ignition in general is discussed. The study in addition emphasizes the need to have accurate knowledge of the rate constants of the key reactions, such as that involving HO2 branching, as moderate differences or uncertainties in their values could lead to qualitatively different descriptions of the combustion response, including the presence/absence of the radical-induced ignition event.

Original languageEnglish (US)
Title of host publicationCollection of Technical Papers - 45th AIAA Aerospace Sciences Meeting
Number of pages8
StatePublished - 2007
Event45th AIAA Aerospace Sciences Meeting 2007 - Reno, NV, United States
Duration: Jan 8 2007Jan 11 2007

Publication series

NameCollection of Technical Papers - 45th AIAA Aerospace Sciences Meeting


Other45th AIAA Aerospace Sciences Meeting 2007
Country/TerritoryUnited States
CityReno, NV

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Aerospace Engineering


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