Explosive velocity,also known asdetonation velocityorvelocity of detonation(VoD), is thevelocityat which theshock wavefront travels through adetonatedexplosive.Explosive velocities are always higher than the localspeed of soundin the material.
If the explosive is confined before detonation, such as in anartillery shell,theforceproduced is focused on a much smaller area, and thepressureis significantly intensified. This results in an explosive velocity that is higher than if the explosive had been detonated in open air. Unconfined velocities are often approximately 70 to 80 percent of confined velocities.[1]
Explosive velocity is increased with smaller particle size (i.e., increased spatial density), increased charge diameter, and increased confinement (i.e., higher pressure).[1]
Typicaldetonation velocitiesfor organicdust mixturesrange from 1400 to 1650m/s.[2]Gas explosionscan eitherdeflagrateor detonate based on confinement; detonation velocities are generally around 1700 m/s[3][4][5]but can be as high as 3000m/s.[6]Solid explosives often havedetonation velocitiesranging beyond 4000 m/s to 10300 m/s.
Detonation velocity can be measured by the Dautriche method. In essence, this method relies on the time lag between the initiation of two ends of adetonating fuseof a known detonation velocity, inserted radially at two points into the explosive charge at a known distance apart. When the explosive charge is detonated, it triggers one end of the fuse, then the second end. This causes two detonation fronts travelling in opposite direction along the length of the detonating fuse, which meet at a specific point away from the centre of the fuse. Knowing the distance along the detonation charge between the two ends of the fuse, the position of the collision of the detonation fronts, and the detonation velocity of the detonating fuse, the detonation velocity of the explosive is calculated and is expressed in km/s.
In other words "VOD is the velocity or rate of propagation of chemical decomposition/reaction." And for high explosives, it is generally above 1000m/s.
In the cases where a material has not received dedicated testing, rough predictions based upongas behavior theoryare sometimes used (seeChapman–Jouguet condition).
See also
editReferences
edit- ^ab"Explosives".
- ^Wolanski, Piotr."Dust Explosions".jstage.jst.go.jp.Warsaw University of Technology, Institute of Heat Engineering.Retrieved21 September2019.
- ^"TNT (Comparison to Pentane)".ch.ic.ac.uk.ChemWiki.
- ^"Glossary on Explosion Dynamics".shepherd.caltech.edu.California Institute of Technology.Retrieved7 October2019.
- ^"Review of Vapour Cloud Explosion Incidents"(PDF).hse.gov.uk.HSE 2017.Retrieved21 September2019.
- ^Egerton, Alfred C.; Gates, S.F. (1927)."Further experiments on explosions in gaseous mixtures of acetylene, of hydrogen and of pentane".Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character.116(775). The Royal Society: 516–529.Bibcode:1927RSPSA.116..516E.doi:10.1098/rspa.1927.0148.