Detonation & Deflagration Difference(Basic)

7/23/2019 Detonation & Deflagration Difference(Basic)

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DETONATIONAND

DEFLAGARATION

- Jigar D



Deflagration (Lat: de + flagrare, "to burn down")

Subsonic combustion propagating through heat transfer; hot burning materialheats the next layer of cold material and ignites it.

A deflagration is characterized by a subsonic flame propagation velocity,typically far below 100 m/s, and relatively modest overpressures, say below

0.5 bar.

Most "fire" found in daily life, from flames to explosions, is deflagration.

Eg. Combustion in Gas stove, Fuel air mixture in IC Engine, Rapid burning ofgunpowder in firearm, pyrotechnic mixture in fireworks.

Applications in mining, demolition and stone quarrying via gas pressureblasting.



Detonation (detonare, meaning “to expend thunder”)

Combustion propagation is of a powerful pressure wave that compresses theunburnt gas ahead of the wave to a temperature above the autoignition

temperature.

The velocity of detonation in solid and liquid explosives is much higher than

that in gaseous ones.

A detonation is characterized by supersonic flame propagation velocities,

perhaps up to 2000 m/s, and substantial overpressures, up to 20 bars. Detonation is most often used for explosives and the acceleration of

projectiles.

Pulse detonation engines use the detonation wave for aerospace propulsion.







The Hugoniot-diagram



Deflagration to Detonation

The natural acceleration of a flame in a long pipe

The forced acceleration of a less confined mixture

within a region containing obstacles

In both cases, gas phase turbulence enhances combustion rates to a point where a shoahead of the flame front. If further flame acceleration occurs, the leading shock waveuntil a transition to detonation occurs.



Deflagration-to-Detonation Transition

(DDT)

Deflagration-to-detonation transition (DDT) is the transient phenomenonresulting from the acceleration of a deflagration flame to detonation via

combustion-generated turbulent flow and compressive heat effects.

During the DDT, the initial peak pressure reached is higher than the final

pressure reached when the stable detonation phase occurs, and thedetonation wave is described as “overdriven.”



Deflagration to Detonation Transition Ca

Industrial Accidents1970 Propane vapor cloud explosion in Port Hudson




Industrial AccidentsThe Flixborough disaster




Industrial AccidentsThe1989 Phillips Disaster in Pasadena, Texas




Industrial AccidentsThe damage observed in the Buncefield fire, see the 2005 Hertfordshire Oil Storage Ter



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Detonation & Deflagration Difference(Basic)