![TNT detonation on Kaho'olawe Island during Operation Sailor Hat, shot Bravo, 1965](https://upload.wikimedia.org/wikipedia/commons/a/ac/TNT_detonation_on_Kaho%27olawe_Island_during_Operation_Sailor_Hat%2C_shot_Bravo%2C_1965.jpg)
Detonation () is a type of
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
involving a
supersonic
Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
exothermic front accelerating through a medium that eventually drives a
shock front propagating directly in front of it. Detonations propagate supersonically through
shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
s with speeds in the range of 1 km/sec and differ from
deflagration
Deflagration (Lat: ''de + flagrare'', "to burn down") is subsonic combustion in which a pre-mixed flame propagates through a mixture of fuel and oxidizer. Deflagrations can only occur in pre-mixed fuels. Most fires found in daily life are diffu ...
s which have subsonic flame speeds in the range of 1 m/sec.
Detonations occur in both conventional solid and liquid explosives, 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
Resolution(s) may refer to:
Common meanings
* Resolution (debate), the statement which is debated in policy debate
* Resolution (law), a written motion adopted by a deliberative body
* New Year's resolution, a commitment that an individual mak ...
).
A very wide variety of fuels may occur as gases (e.g.
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
), 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
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
,
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
, and
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...
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.
Detonation was discovered in 1881 by four French scientists
Marcellin Berthelot and
Paul Marie Eugène Vieille and
Ernest-François Mallard
Ernest-François Mallard (4 February 1833 – 6 July 1894) was a French mineralogist and a member of the French Academy of Sciences. He is also notable for his work with Henri Louis Le Chatelier in combustion as applied to mining safety.< ...
and
Henry Louis Le Chatelier. The mathematical predictions of propagation were carried out first by
David Chapman in 1899 and by
Émile Jouguet Jacques Charles Émile Jouguet (5 January 1871, in Bessèges (Gard) – 2 April 1943, in Montpellier) was a French engineer and scientist, whose name is attached to the Chapman–Jouguet condition.
He was the son of Félix Jouguet (1831–1887), ...
in 1905,
1906 and 1917. The next advance in understanding detonation was made by
John von Neumann
John von Neumann (; hu, Neumann János Lajos, ; December 28, 1903 – February 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. He was regarded as having perhaps the widest cove ...
and
Werner Döring in the early 1940s and
Yakov B. Zel'dovich
Yakov Borisovich Zeldovich ( be, Я́каў Бары́савіч Зяльдо́віч, russian: Я́ков Бори́сович Зельдо́вич; 8 March 1914 – 2 December 1987), also known as YaB, was a leading Soviet physicist of Bel ...
and
Aleksandr Solomonovich Kompaneets in the 1960s.
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
Zel'dovich
Yakov Borisovich Zeldovich ( be, Я́каў Бары́савіч Зяльдо́віч, russian: Я́ков Бори́сович Зельдо́вич; 8 March 1914 – 2 December 1987), also known as YaB, was a leading Soviet physicist of Bel ...
,
von Neumann, and
Döring.
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.
[ Continued in ]
There is also some evidence that the reaction zone is
semi-metallic in some explosives.
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. The Wood-Kirkwood detonation theory can correct for some of these limitations.
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. The influence of increasing the concentration of diluent on expanding individual detonation cells has been elegantly demonstrated. Similarly their size grows as the initial pressure falls. 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. 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 physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
) in the surrounding area. This is a significant distinction from
deflagration
Deflagration (Lat: ''de + flagrare'', "to burn down") is subsonic combustion in which a pre-mixed flame propagates through a mixture of fuel and oxidizer. Deflagrations can only occur in pre-mixed fuels. Most fires found in daily life are diffu ...
s where the exothermic wave is subsonic and maximum pressures for non-metal dusts are approximately 7 - 10 times atmospheric pressure. Therefore, detonation is a feature for destructive purpose while deflagration is favored for the acceleration of
firearm
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
s' projectiles. However, detonation waves may also be used for less destructive purposes, including deposition of coatings to a surface or cleaning of equipment (e.g. slag removal) and even
explosively welding together metals that would otherwise fail to fuse.
Pulse detonation engines use the detonation wave for aerospace propulsion. The first flight of an aircraft powered by a pulse detonation engine took place at the
Mojave Air & Space Port
The Mojave Air and Space Port at Rutan Field is in Mojave, California, United States, at an elevation of . It is the first facility to be licensed in the United States for horizontal launches of reusable spacecraft, being certified as a sp ...
on January 31, 2008.
In engines and firearms
Unintentional detonation when
deflagration
Deflagration (Lat: ''de + flagrare'', "to burn down") is subsonic combustion in which a pre-mixed flame propagates through a mixture of fuel and oxidizer. Deflagrations can only occur in pre-mixed fuels. Most fires found in daily life are diffu ...
is desired is a problem in some devices. In
Otto cycle, or gasoline engines it is called
engine knocking
In spark ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignite ...
or pinging or pinking or pre-ignition, and it causes a loss of power, excessive heating, and harsh mechanical shock that can result in eventual engine failure.
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
*
Carbon detonation
Carbon detonation or carbon deflagration is the violent reignition of thermonuclear fusion in a white dwarf star that was previously slowly cooling. It involves a runaway thermonuclear process which spreads through the white dwarf in a matter of s ...
*
Detonator
A detonator, frequently a blasting cap, is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the last two being the most common.
The commercial use of explosives uses electri ...
*
Detonation of an explosive charge
*
Detonation diamond
Detonation nanodiamond (DND), also known as ultradispersed diamond (UDD), is diamond that originates from a detonation. When an oxygen-deficient explosive mixture of TNT/RDX is detonated in a closed chamber, diamond particles with a diameter of ...
*
Detonation flame arrester
*
Sympathetic detonation
*
Nuclear testing
Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by ...
*
Predetonation
In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series of these reactions. The specific nu ...
*
Chapman-Jouguet condition
*
Engine knocking
In spark ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignite ...
*
Deflagration
Deflagration (Lat: ''de + flagrare'', "to burn down") is subsonic combustion in which a pre-mixed flame propagates through a mixture of fuel and oxidizer. Deflagrations can only occur in pre-mixed fuels. Most fires found in daily life are diffu ...
*
Relative effectiveness factor
References
External links
Youtube video demonstrating physics of a blast wave
{{Authority control
Explosives engineering
Combustion