Critical radius for sustained propagation of spark-ignited spherical flames

Andrew P. Kelley, Grunde Jomaas, Chung King Law

Research output: Contribution to journalArticlepeer-review

166 Scopus citations


An experimental study was performed to determine the requirements for sustained propagation of spark-ignited hydrogen-air and butane-air flames at atmospheric and elevated pressures. Results show that sustained propagation is always possible for mixtures whose Lewis number is less than unity, as long as a flame can be initially established. However, for mixtures whose Lewis number is greater than unity, sustained propagation depends on whether the initially ignited flame can attain a minimum radius. This minimum radius was determined for mixtures of different equivalence ratios and pressures, and was found to agree moderately well with the theoretically predicted critical radius beyond which there is no solution for the adiabatic, quasi-steady propagation of the spherical flame. The essential roles of pressure, detailed chemistry, and the need to use local values in the quantitative evaluation of the flame response parameters are emphasized.

Original languageEnglish (US)
Pages (from-to)1006-1013
Number of pages8
JournalCombustion and Flame
Issue number5
StatePublished - May 2009

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


  • Critical radius
  • Laminar flames
  • Minimum radius
  • Outwardly propagating flames
  • Spark ignition
  • Spherical flames


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