Deflagration to detonation transition: Difference between revisions

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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.
 
Under certain conditions, mainly in terms of geometrical conditions (such as partial confinement and many obstacles in the flame path that cause turbulent flame [[eddy current]]scurrents), a subsonic flame may accelerate to supersonic speed, transitioning from deflagration to detonation. The exact mechanism is not fully understood,<ref name=GexCon>{{cite web|title=Chapter 6: Detonation |url= http://www.gexcon.com/index.php?src=handbook/GEXHBchap6.htm |website=Gexcon AS |archivedate=October 4, 2011 |archiveurl=https://web.archive.org/web/20111004174240/http://www.gexcon.com/handbook/GEXHBchap6.htm}}</ref>
and while existing theories are able to explain and model both deflagrations and detonations, there is no theory at present which can predict the transition phenomenon.{{citation needed|date=February 2017}}