Detonation

Detonation (from Latin detonare 'to thunder down/forth'[1]) is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations occur in both conventional solid and liquid explosives,[2] as well as in reactive gases. 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).

For detonation in spark-ignition engines, see Engine knocking.
Not to be confused with Denotation.
Detonation of a 500-ton TNT explosive charge during Operation Sailor Hat. The passing blast-wave left behind a white water surface. A white condensation cloud is visible overhead.

A very wide variety of fuels may occur as gases, droplet fogs, or dust suspensions. Oxidants include halogens, 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 dioxygen.[3][4]

Detonation was discovered in 1881 by two pairs of French scientists Marcellin Berthelot and P. Vieille[5] and Ernest-François Mallard and Henry Louis Le Chatelier.[6] The mathematical predictions of propagation were carried out first by David Chapman in 1899[7] and by Émile Jouguet in 1905,[8] 1906[9] and 1917.[10] The next advance in understanding detonation was made by Zel'dovich, von Neumann, and W. Doering in the early 1940s.

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 confines the chemistry and diffusive transport processes to an infinitesimally thin zone.

A more complex theory was advanced during World War II independently by Zel'dovich, von Neumann, and W. Doering.[11][12][13] This theory, now known as ZND 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, the Chapman-Jouguet condition.[14][15] There is also some evidence that the reaction zone is semi-metallic in some explosives.[16]

Both theories describe one-dimensional and steady wave fronts. 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.[17][18] The Wood-Kirkwood detonation theory can correct for some of these limitations.[19]

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.[20] The influence of increasing the concentration of diluent on expanding individual detonation cells has been elegantly demonstrated.[21] Similarly their size grows as the initial pressure falls.[22] 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.[23][24] To date, none has adequately described how 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 shock wave) in the surrounding area. This is a significant distinction from deflagrations where the exothermic wave is subsonic and maximum pressures are at most one eighth as great. Therefore, detonation is a feature for destructive purpose while deflagration is favored for the acceleration of firearms' 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 even explosively welding together metals that would otherwise fail to fuse. Pulse detonation engines use the detonation wave for aerospace propulsion.[27] The first flight of an aircraft powered by a pulse detonation engine took place at the Mojave Air & Space Port on January 31, 2008.[28]

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 or pinking, and it causes a loss of power, excessive heating, and harsh mechanical shock that can result in eventual engine failure.[29][30] In firearms, it may cause catastrophic and potentially lethal failure.

Pulse detonation engines are a form of pulsed jet engine that have been experimented with on several occasions as this offers the potential for good fuel efficiency.

See also

References
  1. Oxford Living Dictionaries. "detonate". British & World English. Oxford University Press. Retrieved 21 Feb 2019.
  2. Fickett; Davis (1979). Detonation. Univ. California Press. ISBN 978-0-486-41456-0.
  3. Stull (1977). Fundamentals of fire and explosion. Monograph Series. 10. A.I.Chem.E. p. 73.
  4. Urben, Peter; Bretherick, Leslie (2006). Bretherick's Handbook of Reactive Chemical Hazards (7th ed.). London: Butterworths. ISBN 978-0-12-372563-9.
  5. 6 M. Berthelot and P. Vieille, “On the velocity of propagation of explosive processes in gases,” Comp. Rend. Hebd. Séances Acad. Sci., Vol. 93, pp. 18-21, 1881
  6. 5 E. Mallard and H. L. Le Chatelier, “On the propagation velocity of burning in gaseous explosive mixtures,” Comp. Rend. Hebd. Séances Acad. Sci., Vol. 93, pp. 145-148, 1881
  7. Chapman, D. L. (1899). VI. On the rate of explosion in gases. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 47(284), 90-104.
  8. Jouguet, E. (1905). On the propagation of chemical reactions in gases. J. de mathematiques Pures et Appliquees, 1(347-425), 2.
  9. Jouguet, E. J. (1906). Mathem. Pures Appl. 1. 1905. P. 347-425. And 2.
  10. Jouguet, É. (1917). L'œuvre scientifique de Pierre Duhem. Doin.
  11. Zel'dovich; Kompaneets (1960). Theory of Detonation. New York: Academic Press. ASIN B000WB4XGE. OCLC 974679.
  12. von Neumann, John (1942). Progress report on "Theory of Detonation Waves" (Report). OSRD Report No. 549. Ascension number ADB967734.
  13. Doring, W. (1943). "Über den Detonationsvorgang in Gasen". Annalen der Physik. 43 (6–7): 421–436. Bibcode:1943AnP...435..421D. doi:10.1002/andp.19434350605.
  14. Chapman, David Leonard (January 1899). "On the rate of explosion in gases". Philosophical Magazine. Series 5. London. 47 (284): 90–104. doi:10.1080/14786449908621243. ISSN 1941-5982. LCCN sn86025845.
  15. Jouguet, Jacques Charles Emile (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 Continued in Jouguet, Jacques Charles Emile (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.
  16. 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.
  17. 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.
  18. D. H. Edwards; G. O. Thomas; M. A. Nettleton (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. ISBN 978-0-915928-46-0.
  19. 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. S2CID 95326309.
  20. Nettleton, M. A. (1980). "Detonation and flammability limits of gases in confined and unconfined situations". Fire Prevention Science and Technology (23): 29. ISSN 0305-7844.
  21. 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. S2CID 93720416.
  22. 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.
  23. Oran; Boris (1987). Numerical Simulation of Reactive Flows. Elsevier Publishers.
  24. 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:2007CTM....12....1S. doi:10.1080/13647830701335749. S2CID 73601951.
  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. S2CID 93125699.
  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. See article on engine knocking
  30. Andre Simon. "Don't Waste Your Time Listening for Knock..." High Performance Academy.
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