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The phenomenon is exploited in pulse detonation engines, because a detonation produces a more efficient combustion of the reactants than a deflagration does, i.e. giving a higher yields. Such engines typically employ a Shchelkin spiral in the combustion chamber to facilitate the deflagration to detonation transition. [2] [3]
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]
Deflagration (Lat: de + flagrare, 'to burn down') is subsonic combustion in which a pre-mixed flame propagates through an explosive or a mixture of fuel and oxidizer. [1] [2] Deflagrations in high and low explosives or fuel–oxidizer mixtures may transition to a detonation depending upon confinement and other factors.
Explosion of unserviceable ammunition and other military items The explosion of the Castle Bravo nuclear bomb. An explosion is a rapid expansion in volume of a given amount of matter associated with an extreme outward release of energy , usually with the generation of high temperatures and release of high-pressure gases .
A blast injury is a complex type of physical trauma resulting from direct or indirect exposure to an explosion. [1] Blast injuries occur with the detonation of high-order explosives as well as the deflagration of low order explosives. These injuries are compounded when the explosion occurs in a confined space.
If detonation is allowed to persist under extreme conditions or over many engine cycles, engine parts can be damaged or destroyed. The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine's oil system and cause wear on other parts before being trapped by the oil filter.
A 5 psi blast overpressure will rupture eardrums in about 1% of subjects, and a 45 psi overpressure will cause eardrum rupture in about 99% of all subjects. The threshold for lung damage occurs at about 15 psi blast overpressure. A 35-45 psi overpressure may cause 1% fatalities, and 55 to 65 psi overpressure may cause 99% fatalities. [3]
In more detail (in the ZND model) in the frame of the leading shock of the detonation wave, gases enter at supersonic velocity and are compressed through the shock to a high-density, subsonic flow. This sudden change in pressure initiates the chemical (or sometimes, as in steam explosions, physical) energy release. The energy release re ...