Deflagraatio

Deflagration, sometimes referred to as deflagraatio in certain languages, is a mode of combustion in which a flame front propagates through an unburned gas mixture at subsonic speeds relative to the gas. The advance of the flame is driven primarily by heat transfer by conduction and by diffusion of reactive species, which preheats and ignites the fuel ahead of the front. Because the process is subsonic, information about the reaction can travel faster than the flame, but the overall pressure rise is typically smaller than in a detonation.

Laminar deflagration features a well-defined flame thickness and a characteristic burning velocity, the laminar burning velocity, which depends on mixture composition, temperature, and pressure. In practical systems turbulence develops, increasing the flame surface area and accelerating the apparent burning rate. Mixture stoichiometry, fuel–oxidizer ratio, temperature, and confinement influence the speed and behavior of deflagrations; near stoichiometric mixtures often burn most vigorously.

Deflagration is distinct from detonation, which propagates as a supersonic shock-driven wave. Under some conditions, deflagration can accelerate and transition to detonation (deflagration-to-detonation transition, DDT), especially in long tubes, porous media, or highly turbulent flows. In industry and safety contexts, deflagrations are managed with proper design, ventilation, inerting, and flame arrest features to limit pressure buildup and flame propagation.