Жарылысқа әкеп соқтыратын жану процесі

Combustion that leads on to an explosion

Deflagration (Lat: de + flagrare, 'to burn down') is subsonic combustion in which a pre mixed flame propagates through an explosive or a mixture of fuel and oxidizer. Deflagrations in high and low explosives or fuel–oxidizer mixtures may transition to a detonation depending upon confinement and other factors. Most fires found in daily life are diffusion flames. Deflagrations with flame speeds in the range of 1 m/s differ from detonations which propagate supersonically with detonation velocities in the range of km/s.

Deflagrations are often used in engineering applications when the force of the expanding gas is used to move an object such as a projectile down a barrel, or a piston in an internal combustion engine. Deflagration systems and products can also be used in mining, demolition and stone quarrying via gas pressure blasting as a beneficial alternative to high explosives.

When studying or discussing explosive safety, or the safety of systems containing explosives, the terms deflagration, detonation and deflagration to detonation transition (commonly referred to as DDT) must be understood and used appropriately to convey relevant information. As explained above, a deflagration is a subsonic reaction, whereas a detonation is a supersonic (greater than the sound speed of the material) reaction. Distinguishing between a deflagration or a detonation can be difficult to impossible to the casual observer. Rather, confidently differentiating between the two requires instrumentation and diagnostics to ascertain reaction speed in the affected material. Therefore, when an unexpected event or an accident occurs with an explosive material or an explosive containing system it is usually impossible to know whether the explosive deflagrated or detonated as both can appear as very violent, energetic reactions. Therefore, the energetic materials community coined the term "high explosive violent reaction" or "HEVR" to describe a violent reaction that, because it lacked diagnostics to measure sound speed, could have been either a deflagration or a detonation.

Damage to buildings, equipment and people can result from a large scale, short duration deflagration. The potential damage is primarily a function of the total amount of fuel burned in the event (total energy available), the maximum reaction velocity that is achieved, and the manner in which the expansion of the combustion gases is contained. Vented deflagrations tend to be less violent or damaging than contained deflagrations. In free air deflagrations, there is a continuous variation in deflagration effects relative to the maximum flame velocity. When flame velocities are low, the effect of a deflagration is to release heat, such as in a flash fire. At flame velocities near the speed of sound, the energy released is in the form of pressure, and the resulting high pressure can damage equipment and buildings.