8/10/2019 Deflagration to Detonation Transition - Wikipedia, The Free Encyclopedia

1/2

10/7/2014 Deflagration to detonation transition - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Deflagration_to_detonation_transition

Deflagration to detonation transitionFrom Wikipedia, the free encyclopedia

Deflagration to detonation transition(DDT) refers to a phenomenon in ignitable mixturesof aflammable gas and air (or oxygen) when a sudden transition takes place from adeflagration type of combustion to a detonation type of combustion. The effects of adetonation are usually devastating.

A deflagration is characterized by a subsonic flame propagation velocity,typically farbelow 100 m/s, and relatively modest overpressures, say below 0.5 bar. The mainmechanism of combustion propagation is of a flame front that moves forward throughthe gas mixture - in technical terms the reaction zone (chemical combustion) progressesthroughthe medium by processes of diffusion of heat and mass. In its most benign form,a deflagration may simply be a flash fire. In contrast, a detonation is characterized bysupersonic flame propagation velocities, perhaps up to 2000 m/s, and substantialoverpressures, up to 20 bars. The main mechanism of combustion propagation is of apowerful 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 theshock are coincident, and the chemical reaction is initiated by the compressive heatingcaused by the shock wave.

Under certain conditions, mainly in terms of geometrical conditions such as partialconfinement and many obstacles in the flame path that cause turbulent flame eddycurrents, a subsonic flame may accelerate to supersonic speed, transitioning from

deflagration to detonation. The exact mechanism is not fully understood,[1]and whileexisting theories are able to explain and model both deflagrations and detonations,

there is no theory at present which can predict the transition phenomenon.

A deflagration to detonation transition has been a feature of several major industrialaccidents

1970 Propane vapour cloud explosion in Port Hudson

The Flixboroughdisaster

The 1989 Phillips Disaster in Pasadena, Texas

The damage observed in the Buncefield fire, see the 2005 Hertfordshire Oil Storage

Terminal fire

The phenomenon is exploited in pulse detonation engines because a detonationproduces 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.[2][3]

The mechanism has found military use in the thermobaric weapon.

http://en.wikipedia.org/wiki/Combustion_chamberhttp://en.wikipedia.org/wiki/Combustion_chamberhttp://en.wikipedia.org/wiki/Combustion_chamberhttp://en.wikipedia.org/wiki/Pulse_detonation_enginehttp://en.wikipedia.org/wiki/2005_Hertfordshire_Oil_Storage_Terminal_firehttp://en.wikipedia.org/wiki/2005_Hertfordshire_Oil_Storage_Terminal_firehttp://en.wikipedia.org/wiki/Phillips_Disasterhttp://en.wikipedia.org/wiki/Flixborough_disasterhttp://en.wikipedia.org/wiki/1970_Propane_vapour_cloud_explosion_in_Port_Hudsonhttp://en.wikipedia.org/wiki/Industrial_accidenthttp://en.wikipedia.org/wiki/Eddy_currenthttp://en.wikipedia.org/wiki/Eddy_currenthttp://en.wikipedia.org/wiki/Shock_wavehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Autoignitionhttp://en.wikipedia.org/wiki/Supersonichttp://en.wikipedia.org/wiki/Flash_firehttp://en.wikipedia.org/wiki/Detonationhttp://en.wikipedia.org/wiki/Deflagrationhttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Thermobaric_weaponhttp://en.wikipedia.org/wiki/Combustion_chamberhttp://en.wikipedia.org/wiki/Shchelkin_spiralhttp://en.wikipedia.org/wiki/Pulse_detonation_enginehttp://en.wikipedia.org/wiki/2005_Hertfordshire_Oil_Storage_Terminal_firehttp://en.wikipedia.org/wiki/Phillips_Disasterhttp://en.wikipedia.org/wiki/Flixborough_disasterhttp://en.wikipedia.org/wiki/1970_Propane_vapour_cloud_explosion_in_Port_Hudsonhttp://en.wikipedia.org/wiki/Industrial_accidenthttp://en.wikipedia.org/wiki/Eddy_currenthttp://en.wikipedia.org/wiki/Shock_wavehttp://en.wikipedia.org/wiki/Autoignitionhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Supersonichttp://en.wikipedia.org/wiki/Detonationhttp://en.wikipedia.org/wiki/Flash_firehttp://en.wikipedia.org/wiki/Bar_(unit)http://en.wikipedia.org/wiki/Overpressurehttp://en.wikipedia.org/wiki/M/shttp://en.wikipedia.org/wiki/Propagation_velocityhttp://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Deflagrationhttp://en.wikipedia.org/wiki/Detonationhttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Deflagrationhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Flammablehttp://en.wikipedia.org/wiki/Combustion

8/10/2019 Deflagration to Detonation Transition - Wikipedia, The Free Encyclopedia

2/2

10/7/2014 Deflagration to detonation transition - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Deflagration_to_detonation_transition

A deflagration to detonation transition (DDT) has also been proposed for thermonuclear

reactionsresponsible for supernovae initiation;[4]see also Carbon detonation. Apart fromthe name, this phenomenon is completely unrelated to the chemical combustion andflame acceleration phenomenon.

See also

Pressure piling

Boiling liquid expanding vapor explosion

References

1. ^"Gas explosion handbook" (http://www.gexcon.com/index.php?

src=handbook/GEXHBchap6.htm). Gexcon AS, Norway.

2. ^New, TH; PK Panicker; FK Lu; H M Tsai (2006). "Experimental Investigations on DDT

Enhancements by Schelkin Spirals in a PDE" (http://arc.uta.edu/publications/cp_files/aiaa-2006-7958.pdf). 44th AIAA Aerospace Sciences Meeting and Exhibit 912 January 2006, Reno

Nevada.

3. ^Schultz, E; E Wintenberger; J Shepherd (1999). "Investigation of Deflagration to Detonation

Transition for Application to Pulse Detonation Engine Ignition Systems"

(http://www.galcit.caltech.edu/EDL/publications/reprints/jannaf99_paper.pdf). Proceeding

of the 16th JANNAF Propulsion Symposium.

4. ^Gamezo, Vadim N.; Oran ES (2008). "Mechanisms for Detonation Initiation in Type Ia

Supernovae" (http://adsabs.harvard.edu/abs/2008AAS...21116208G). American Astronomica

Society, AAS Meeting #211, #162.08.

Lea, CJ; HS Ledin (2002).A Review of the State-of-the-Art in Gas Explosion Modelling

HSL/2002/02(http://www.hse.gov.uk/research/hsl_pdf/2002/hsl02-02.pdf). UK Health

andSafety Laboratories.

Retrievedfrom "http://en.wikipedia.org/w/index.php?

title=Deflagration_to_detonation_transition&oldid=628165559"

Categories: Combustion Industrial fires and explosions Explosives engineering

This page was last modified on 4 October 2014 at 03:55.

Textis available under the Creative Commons Attribution-ShareAlike License;

additional terms may apply. By using this site, you agree to the Terms of Use and

Privacy Policy. Wikipedia is a registered trademark of the Wikimedia Foundation,

Inc., a non-profit organization.

http://www.wikimediafoundation.org/http://wikimediafoundation.org/wiki/Privacy_policyhttp://wikimediafoundation.org/wiki/Terms_of_Usehttp://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_Licensehttp://en.wikipedia.org/wiki/Help:Categoryhttp://en.wikipedia.org/w/index.php?title=Deflagration_to_detonation_transition&oldid=628165559http://www.hse.gov.uk/research/hsl_pdf/2002/hsl02-02.pdfhttp://adsabs.harvard.edu/abs/2008AAS...21116208Ghttp://www.galcit.caltech.edu/EDL/publications/reprints/jannaf99_paper.pdfhttp://arc.uta.edu/publications/cp_files/aiaa-2006-7958.pdfhttp://www.gexcon.com/index.php?src=handbook/GEXHBchap6.htmhttp://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosionhttp://en.wikipedia.org/wiki/Pressure_pilinghttp://en.wikipedia.org/wiki/Carbon_detonationhttp://en.wikipedia.org/wiki/Supernovaehttp://en.wikipedia.org/wiki/Category:Explosives_engineeringhttp://en.wikipedia.org/wiki/Category:Industrial_fires_and_explosionshttp://en.wikipedia.org/wiki/Category:Combustion