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Detonation

From Wikipedia, the free encyclopedia
For detonation in spark-ignition engines, seeEngine knocking.
Not to be confused withDenotation.
Detonation ofTNT,andshock wave

Detonation(fromLatindetonare'to thunder down/forth')[1]is a type ofcombustioninvolving asupersonicexothermic front accelerating through a medium that eventually drives ashock frontpropagating directly in front of it. Detonations propagate supersonically throughshock waveswith speeds about 1 km/sec and differ fromdeflagrationswhich have subsonic flame speeds about 1 m/sec.[2]Detonation is anexplosionof fuel-air mixture. Compared to deflagration, detonation doesn't need to have an external oxidizer. Oxidizers and fuel mix when deflagration occurs. Detonation is more destructive than deflagrations. In detonation, the flame front travels through the air-fuel faster than sound; while in deflagration, the flame front travels through the air-fuel slower than sound.

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. Thevelocity of detonationin solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higherresolution).

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, andoxides 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 asacetylene,ozone,andhydrogen 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 scientistsMarcellin BerthelotandPaul Marie Eugène Vieille[6]andErnest-François MallardandHenry Louis Le Chatelier.[7]The mathematical predictions of propagation were carried out first byDavid Chapmanin 1899[8]and byÉmile Jouguetin 1905,[9]1906 and 1917.[10]The next advance in understanding detonation was made byJohn von Neumann[11]andWerner Döring[12]in the early 1940s andYakov B. Zel'dovichandAleksandr Solomonovich Kompaneetsin the 1960s.[13]

Theories

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The simplest theory to predict the behaviour of detonations in gases is known asChapman–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 byZel'dovich,von Neumann,andDöring.[13][11][12]This theory, now known asZND theory,admits finite-rate chemical reactions and thus describes a detonation as an infinitesimally thin shock wave, followed by a zone of exothermic chemical reaction. With a reference frame of a stationary shock, the following flow is subsonic, so that an acoustic reaction zone follows immediately behind the lead front, theChapman–Jouguet condition.[14][9]

There is also some evidence that the reaction zone issemi-metallicin 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

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A controlledbomb disposalinIraq,2006; detonating the bomb causes fire and smoke to propel upward.

When used in explosive devices, the main cause of damage from a detonation is the supersonic blast front (a powerfulshock wave) in the surrounding area. This is a significant distinction fromdeflagrationswhere the exothermic wave is subsonic and maximum pressures for non-metal specks of dust are approximately 7–10 times atmospheric pressure.[24]Therefore, detonation is a feature for destructive purposes while deflagration is favored for the acceleration offirearms' projectiles. However, detonation waves may also be used for less destructive purposes, including deposition of coatings to a surface[25]or cleaning of equipment (e.g. slag removal[26]) and evenexplosively weldingtogether metals that would otherwise fail to fuse.Pulse detonation enginesuse the detonation wave for aerospace propulsion.[27]The first flight of an aircraft powered by a pulse detonation engine took place at theMojave Air & Space Porton January 31, 2008.[28]

In engines and firearms

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Unintentional detonation whendeflagrationis desired is a problem in some devices. InOtto cycle,or gasoline engines it is calledengine knockingor 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 enginesare 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

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References

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  1. ^Oxford Living Dictionaries."detonate".British & World English.Oxford University Press. Archived fromthe originalon February 22, 2019.Retrieved21 February2019.
  2. ^Handbook of Fire Protection Engineering(5 ed.). Society of Fire Protection Engineers. 2016. p. 390.
  3. ^Fickett, Wildon; Davis, William C. (1979).Detonation.University of California Press.ISBN978-0-486-41456-0.
  4. ^Stull, Daniel Richard (1977).Fundamentals of fire and explosion.Monograph Series. Vol. 10.American Institute of Chemical Engineers.p. 73.ISBN978-0-816903-91-7.
  5. ^Urben, Peter; Bretherick, Leslie (2006).Bretherick's Handbook of Reactive Chemical Hazards(7th ed.). London: Butterworths.ISBN978-0-123725-63-9.
  6. ^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
  7. ^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
  8. ^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.
  9. ^abJouguet, 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 fromthe original(PDF)on 2013-10-19.Retrieved2013-10-19.Continued inJouguet, 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 fromthe original(PDF)on 2015-10-16.
  10. ^Jouguet, Jacques Charles Émile (1917).L'Œuvre scientifique de Pierre Duhem,Doin.
  11. ^abvon Neumann, John (1942).Progress report on "Theory of Detonation Waves"(Report). OSRD Report No. 549. Ascension number ADB967734. Archived fromthe originalon 2011-07-17.Retrieved2017-12-22.
  12. ^abDöring, Werner (1943). ""Über den Detonationsvorgang in Gasen""[" On the detonation process in gases "].Annalen der Physik.43(6–7): 421–436.Bibcode:1943AnP...435..421D.doi:10.1002/andp.19434350605.
  13. ^abZel'dovich, Yakov B.; Kompaneets, Aleksandr Solomonovich (1960).Theory of Detonation.New York: Academic Press.ASINB000WB4XGE.OCLC974679.
  14. ^Chapman, David Leonard (January 1899)."On the rate of explosion in gases".Philosophical Magazine.Series 5.47(284). London: 90–104.doi:10.1080/14786449908621243.ISSN1941-5982.LCCNsn86025845.
  15. ^Reed, Evan J.; Riad Manaa, M.; Fried, Laurence E.; Glaesemann, Kurt R.; Joannopoulos, J. D. (2007). "A transient semimetallic layer in detonating nitromethane".Nature Physics.4(1): 72–76.Bibcode:2008NatPh...4...72R.doi:10.1038/nphys806.
  16. ^Edwards, D. H.; Thomas, G. O. & Nettleton, M. A. (1979). "The Diffraction of a Planar Detonation Wave at an Abrupt Area Change".Journal of Fluid Mechanics.95(1): 79–96.Bibcode:1979JFM....95...79E.doi:10.1017/S002211207900135X.S2CID123018814.
  17. ^Edwards, D. H.; Thomas, G. O.; Nettleton, M. A. (1981). A. K. Oppenheim; N. Manson; R. I. Soloukhin; J. R. Bowen (eds.). "Diffraction of a Planar Detonation in Various Fuel-Oxygen Mixtures at an Area Change".Progress in Astronautics & Aeronautics.75:341–357.doi:10.2514/5.9781600865497.0341.0357.ISBN978-0-915928-46-0.
  18. ^Glaesemann, Kurt R.; Fried, Laurence E. (2007)."Improved Wood–Kirkwood detonation chemical kinetics".Theoretical Chemistry Accounts.120(1–3): 37–43.doi:10.1007/s00214-007-0303-9.S2CID95326309.
  19. ^Nettleton, M. A. (1980). "Detonation and flammability limits of gases in confined and unconfined situations".Fire Prevention Science and Technology(23): 29.ISSN0305-7844.
  20. ^Munday, G.; Ubbelohde, A. R. & Wood, I. F. (1968). "Fluctuating Detonation in Gases".Proceedings of the Royal Society A.306(1485): 171–178.Bibcode:1968RSPSA.306..171M.doi:10.1098/rspa.1968.0143.S2CID93720416.
  21. ^Barthel, H. O. (1974). "Predicted Spacings in Hydrogen-Oxygen-Argon Detonations".Physics of Fluids.17(8): 1547–1553.Bibcode:1974PhFl...17.1547B.doi:10.1063/1.1694932.
  22. ^Oran; Boris (1987).Numerical Simulation of Reactive Flows.Elsevier Publishers.
  23. ^Sharpe, G. J.; Quirk, J. J. (2008)."Nonlinear cellular dynamics of the idealized detonation model: Regular cells"(PDF).Combustion Theory and Modelling.12(1): 1–21.Bibcode:2008CTM....12....1S.doi:10.1080/13647830701335749.S2CID73601951.Archived(PDF)from the original on 2017-07-05.
  24. ^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.
  25. ^Nikolaev, Yu. A.; Vasil'ev, A. A. & Ul'yanitskii, B. Yu. (2003). "Gas Detonation and its Application in Engineering and Technologies (Review)".Combustion, Explosion, and Shock Waves.39(4): 382–410.doi:10.1023/A:1024726619703.S2CID93125699.
  26. ^Huque, Z.; Ali, M. R. & Kommalapati, R. (2009). "Application of pulse detonation technology for boiler slag removal".Fuel Processing Technology.90(4): 558–569.doi:10.1016/j.fuproc.2009.01.004.
  27. ^Kailasanath, K. (2000). "Review of Propulsion Applications of Detonation Waves".AIAA Journal.39(9): 1698–1708.Bibcode:2000AIAAJ..38.1698K.doi:10.2514/2.1156.
  28. ^Norris, G. (2008)."Pulse Power: Pulse Detonation Engine-powered Flight Demonstration Marks Milestone in Mojave".Aviation Week & Space Technology.168(7): 60.
  29. ^Simon, Andre."Don't Waste Your Time Listening for Knock..."High Performance Academy.
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