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{{Short description|Type of explosion}}
{{more
'''Deflagration to detonation transition''' ('''DDT''') refers to a phenomenon in [[Combustion|ignitable]] mixtures of a [[flammable]] gas and [[air]] (or [[oxygen]]) when a sudden transition takes place from a [[deflagration]] type of [[combustion]] to a [[detonation]] type of explosion.
==Description==
A [[deflagration]] is characterized by a [[Speed of sound|subsonic]] flame [[propagation velocity]], typically far below {{convert|100|m/s|mph}}, and relatively modest [[overpressure]]s,
In contrast, a [[detonation]] is characterized by [[supersonic]] flame propagation velocities, perhaps up to {{convert|2000|m/s|mph}}, and substantial overpressures, up to {{convert|
Under certain conditions, mainly in terms of geometrical conditions (such as partial confinement and many obstacles in the flame path that cause turbulent flame
and while existing theories are able to explain and model both deflagrations and detonations, there is no theory {{as of|2023|alt=at present}} which can predict the transition phenomenon.
==Examples==
A deflagration to detonation transition has been a feature of several major [[industrial accident]]s:
* [[1970
* [[Flixborough disaster]]
* [[Phillips disaster of 1989]] in Pasadena, Texas
* Damage observed in the [[Buncefield fire]]
* [[2020 Beirut explosions]]
==Applications==
The phenomenon is exploited in [[pulse detonation engine]]s, because a detonation produces a more efficient combustion of the reactants than a deflagration does, i.e. giving a higher yields. Such engines typically employ a [[Shchelkin spiral]] in the [[combustion chamber]] to facilitate the deflagration to detonation transition.<ref>{{cite conference | first = TH | last = New
The mechanism has also found military use in [[thermobaric weapon]]s.
==Related phenomena==
An analogous deflagration to detonation transition (DDT) has also been proposed for thermonuclear reactions responsible for [[supernovae]] initiation.<ref>{{cite conference | first = Vadim N. | last = Gamezo
==See also==
*[[Zeldovich spontaneous wave]]
*[[Dust explosion]]
*[[Pressure piling]]
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==References==
{{reflist
* {{cite book
| last = Lea
| first = CJ
|author2=HS Ledin
| title = A Review of the State-of-the-Art in Gas Explosion Modelling, HSL/2002/02
| publisher = UK Health and Safety Laboratories
| year = 2002
| url = http://www.hse.gov.uk/research/hsl_pdf/2002/hsl02-02.pdf
}}
[[Category:Combustion]]
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