Detonation
Detonation (from
Detonations occur in both conventional solid and liquid explosives,[3] as well as in reactive gases. TNT, dynamite, and C4 are examples of high power explosives that detonate. The velocity of detonation in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).
A very wide variety of fuels may occur as gases (e.g. hydrogen), droplet fogs, or dust suspensions. In addition to dioxygen, oxidants can include halogen compounds, ozone, hydrogen peroxide, and oxides of nitrogen. Gaseous detonations are often associated with a mixture of fuel and oxidant in a composition somewhat below conventional flammability ratios. They happen most often in confined systems, but they sometimes occur in large vapor clouds. Other materials, such as acetylene, ozone, and hydrogen peroxide, are detonable in the absence of an oxidant (or reductant). In these cases the energy released results from the rearrangement of the molecular constituents of the material.[4][5]
Detonation was discovered in 1881 by four French scientists
Theories
The simplest theory to predict the behaviour of detonations in gases is known as Chapman–Jouguet (CJ) theory, developed around the turn of the 20th century. This theory, described by a relatively simple set of algebraic equations, models the detonation as a propagating shock wave accompanied by exothermic heat release. Such a theory describes the chemistry and diffusive transport processes as occurring abruptly as the shock passes.
A more complex theory was advanced during World War II independently by
There is also some evidence that the reaction zone is semi-metallic in some explosives.[15]
Both theories describe one-dimensional and steady wavefronts. However, in the 1960s, experiments revealed that gas-phase detonations were most often characterized by unsteady, three-dimensional structures, which can only, in an averaged sense, be predicted by one-dimensional steady theories. Indeed, such waves are quenched as their structure is destroyed.[16][17] The Wood-Kirkwood detonation theory can correct some of these limitations.[18]
Experimental studies have revealed some of the conditions needed for the propagation of such fronts. In confinement, the range of composition of mixes of fuel and oxidant and self-decomposing substances with inerts are slightly below the flammability limits and, for spherically expanding fronts, well below them.[19] The influence of increasing the concentration of diluent on expanding individual detonation cells has been elegantly demonstrated.[20] Similarly, their size grows as the initial pressure falls.[21] Since cell widths must be matched with minimum dimension of containment, any wave overdriven by the initiator will be quenched.
Mathematical modeling has steadily advanced to predicting the complex flow fields behind shocks inducing reactions.[22][23] To date, none has adequately described how the structure is formed and sustained behind unconfined waves.
Applications
When used in explosive devices, the main cause of damage from a detonation is the supersonic blast front (a powerful
In engines and firearms
Unintentional detonation when deflagration is desired is a problem in some devices. In Otto cycle, or gasoline engines it is called engine knocking or pinging, and it causes a loss of power. It can also cause excessive heating, and harsh mechanical shock that can result in eventual engine failure.[29] In firearms, it may cause catastrophic and potentially lethal failure[citation needed].
Pulse detonation engines are a form of pulsed jet engine that has been experimented with on several occasions as this offers the potential for good fuel efficiency[citation needed].
See also
- Carbon detonation
- Detonator
- Detonation of an explosive charge
- Detonation diamond
- Detonation flame arrester
- Sympathetic detonation
- Nuclear testing
- Predetonation
- Chapman–Jouguet condition
- Engine knocking
- Deflagration
- Relative effectiveness factor
References
- Oxford Living Dictionaries. "detonate". British & World English. Oxford University Press. Archived from the originalon February 22, 2019. Retrieved 21 February 2019.
- ^ Handbook of Fire Protection Engineering (5 ed.). Society of Fire Protection Engineers. 2016. p. 390.
- ISBN 978-0-486-41456-0.
- ISBN 978-0-816903-91-7.
- ISBN 978-0-123725-63-9.
- ^ Berthelot, Marcellin; and Vieille, Paul Marie Eugène; « Sur la vitesse de propagation des phénomènes explosifs dans les gaz » ["On the velocity of propagation of explosive processes in gases"], Comptes rendus hebdomadaires des séances de l'Académie des sciences, vol. 93, pp. 18–22, 1881
- ^ Mallard, Ernest-François; and Le Chatelier, Henry Louis; « Sur les vitesses de propagation de l’inflammation dans les mélanges gazeux explosifs » ["On the propagation velocity of burning in gaseous explosive mixtures"], Comptes rendus hebdomadaires des séances de l'Académie des sciences, vol. 93, pp. 145–148, 1881
- ^ Chapman, David Leonard (1899). "VI. On the rate of explosion in gases", The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 47(284), 90-104.
- ^ a b Jouguet, Jacques Charles Émile (1905). "Sur la propagation des réactions chimiques dans les gaz" ["On the propagation of chemical reactions in gases"] (PDF). Journal de mathématiques pures et appliquées. 6. 1: 347–425. Archived from the original (PDF) on 2013-10-19. Retrieved 2013-10-19. Continued in Jouguet, Jacques Charles Émile (1906). "Sur la propagation des réactions chimiques dans les gaz" ["On the propagation of chemical reactions in gases"] (PDF). Journal de mathématiques pures et appliquées. 6. 2: 5–85. Archived from the original (PDF) on 2015-10-16.
- ^ Jouguet, Jacques Charles Émile (1917). L'Œuvre scientifique de Pierre Duhem, Doin.
- ^ a b von Neumann, John (1942). Progress report on "Theory of Detonation Waves" (Report). OSRD Report No. 549. Ascension number ADB967734. Archived from the original on 2011-07-17. Retrieved 2017-12-22.
- ^ .
- ^ OCLC 974679.
- LCCN sn86025845.
- doi:10.1038/nphys806.
- S2CID 123018814.
- ISBN 978-0-915928-46-0.
- S2CID 95326309.
- ISSN 0305-7844.
- S2CID 93720416.
- .
- ^ Oran; Boris (1987). Numerical Simulation of Reactive Flows. Elsevier Publishers.
- (PDF) from the original on 2017-07-05.
- ^ Handbook of Fire Protection Engineering (5 ed.). Society of Fire Protection Engineers. 2016. Table 70.1 Explosivity Data for representative powders and dusts, page 2770.
- S2CID 93125699.
- .
- doi:10.2514/2.1156.
- ^ Norris, G. (2008). "Pulse Power: Pulse Detonation Engine-powered Flight Demonstration Marks Milestone in Mojave". Aviation Week & Space Technology. 168 (7): 60.
- ^ Simon, Andre. "Don't Waste Your Time Listening for Knock..." High Performance Academy.