Absolute flammability limits and flame-balls

✍ Scribed by D. Lozinski; J. Buckmaster; P. Ronney

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 998 KB
• Volume: 97
• Category: Article
• ISSN: 0010-2180
• DOI: 10.1016/0010-2180(94)90023-x

✦ Synopsis

We examine flame balls that are not optically thin so that radiation from the hot burned gas is not lost but is reabsorbed by the surrounding cool gas. The steady solution is shown to be multivalued in general and defines an intrinsic (apparatus independent) flammability limit for a sufficiently small ignition source. Beyond the flammability limit a steady solution exists for arbitrarily weak mixtures, but is unrealizable since it is unstable to one-dimensional perturbations. An unsteady propagating flame solution is also possible for arbitrarily weak mixtures, but can only be generated by a large ignition source. Observations of flame-strings in SF6-diluted mixtures are reported and suggest that the peculiar nature of the radiative properties of SF 0 is responsible for peculiar dynamics.