Deflagration to detonation transition: Difference between revisions

Revision as of 22:52, 1 May 2020

Revision as of 17:39, 5 August 2020

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==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, saytypically below {{convert|0.5|bar|psi}}. The main mechanism of combustion propagation is of a flame front that moves forward through the gas mixture - in technical terms the reaction zone (chemical combustion) progresses through the medium by processes of [[diffusion]] of [[mass transfer|heat and mass]]. In its most benign form, a deflagration may simply be a [[flash fire]].

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|20|bar|psi}}. The main mechanism of detonation propagation is of a powerful [[pressure]] wave that compresses the unburnt gas ahead of the wave to a [[temperature]] above the [[autoignition]] temperature. In technical terms, the reaction zone (chemical combustion) is a self-driven [[shock wave]] where the reaction zone and the shock are coincident, and the chemical reaction is initiated by the [[Compression heating ignition|compressive heating]] caused by the shock wave. The process is similar to ignition in a [[Diesel engine]], but much more sudden and violent.