A flame will be extinguished when the time required for the chain reaction which sustains combustion exceeds the time it takes to replenish the necessary heat and reactants. A characteristic time for reaction can be estimated from the inverse of a global kinetic rate coefficient expressed in Arrhenius form as [equation] where B is a molecular collision frequency factor, Eo is a global activation energy, R is the ideal gas constant, and T is the gas temperature. Assuming reactant species and heat are transported at about the same rate (i.e., unity Lewis number), a characteristic time for replenishing both can be estimated from a convective flow velocity and a length scale by [equation].
Citation: Special Publication (NIST SP) - 861
NIST Pub Series: Special Publication (NIST SP)
Pub Type: NIST Pubs
halons, fire suppression, effectiveness, diffusion flames, turbulent flames, premixed flames, detonation, chain reactions