Talk:Detonation

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Two classes of combustion?[edit]

While detonation and deflagration represent the two classes of premixed flame wave structure, they certainly are not all encompassing of "combustion". At the very least, where is the deflagration or detonation in a diesel engine? In a candle flame? Not only are diffusive flames completely ignored, it is also certainly possible to have combustion chemistry occur without a wave structure (i.e. HCCI engines, knock, flow reactors, shock tubes...). I'll do a major rewrite of this unless there is a complaint in the next few weeks. Thermodude 17:30, 10 July 2007 (UTC)

pressure waves[edit]

"This is in contrast to deflagration, where the pressure waves are subsonic."

Wouldn't a pressure wave just travel at the speed of sound, by definition, making it sonic? - Omegatron 18:51, Nov 16, 2004 (UTC)
Only if it's only an small disturbance. Large pressure increases sharpen into shocks where the flow enters the shock supersonically, but leaves, compressed and slowed, subsonically.
If it's a pressure decrease, then usually it spreads out (rarefaction) and every bit of it travels at the _local_ speed of sound. See any book on Gas Dynamics Linuxlad 10:36, 28 January 2006 (UTC)
Deflagration is more of a process than a true wave. Imagine very rapid burning, driven mainly by heat rather than by only pressure.--BillFlis 10:33, 16 July 2006 (UTC)
Looks like this was fixed in the article. Linuxlad, wave speeds are quoted from the stationary observer stand point and are thus always the upstream speed. Thus, the slowest speed a pressure wave will travel at will be the speed of sound. I don't know where BillFlis gets his info, but a deflagration is a true wave, which emerges from the coupling of the species and energy transport equations in a reactive flow. Thermodude 17:17, 10 July 2007 (UTC)

Latin "detonare"[edit]

The etymology section is wrong. The 'de' in detonare is closer in meaning to the English particle off as in to sound off or to give off (cf. Merriam-Webster etymology for detonate: French détoner to explode, from Latin detonare to expend thunder, from de- + tonare to thunder). --Rcgy 16:59, 20 December 2006 (UTC)

Combustion[edit]

"Detonation is a process of supersonic combustion..."

Defining detonation as a form of combustion would imply the presence of an oxidizer, would it not? This definition would exclude the exothermic decomposition of certain compounds in the absence of oxygen, including obvious explosives such as TNT or nitroglycerin. Jp69091 05:05, 13 February 2007 (UTC)

I agree. The definition should be more along the lines of "the coupling of a compressive wave with a subsequent exothermic reaction which in turn resupplies energy to the leading compression." I think this is sufficiently general for all detonation phenomena.

Detonation and explosion[edit]

Is a detonation same as an explosion ? -- Myth (Talk) 01:28, 6 July 2007 (UTC)

No. A detonation involves continued heat release. A steam explosion, for example, would not be a detonation. Thermodude 17:25, 10 July 2007 (UTC)

detonation in engines[edit]

This passage is completely wrong

"High compression ratios or high temperatures can cause the flame speed of combustion to exceed the sound barrier, resulting in an explosion or detonation and a pressure shockwave"

There is no supersonic flame speed involved at all. Here is the correct information.

Knock is the name given to the noise which is transmitted through the engine structure when essentially spontaneous ignition of a portion of the end-gas-the fuel, air, residual gas, mixture ahead of the propagating flame occurs. When this abnormal combustion process takes place, there is an extremely rapid release of much of the chemical energy in the end-gas, causing very high local pressures and the propagation of pressure waves of substantial amplitude across the combustion chamber- from "fundamentals of internal combustion engines" by J. Heywood

I rewrote the passage with the correct information but it keeps being undone. You can refer to engine knock detonation in wikipedia for more info --=Motorhead (talk) 01:08, 17 August 2008 (UTC)

Lead[edit]

The lead should probably be only the first paragraph. Can we make a section title for the remainder of the current lead?

In the third paragraph: "In terms of external damage, it is important to distinguish between detonations and deflagrations where the exothermic wave is subsonic and maximum pressures are at most a quarter[citation needed] of those generated by the former."

If this is covered in reference 4, remove the {{Citation needed|date=February 2010}}. :- ) DCS 18:08, 1 March 2012 (UTC)

Confinement[edit]

Why is there no mentioning of the most relevant distinction between explosion and detonation like it is e.g. in the German Wiki article? So here it is: a detonating explosive like e.g. TNT by an ignitor (e.g. PbN3) does not need to be CONFINED to do produce the desired effect! Whereas, e.g. gunpowder HAS to be confined - if you light a handful of unconfined gunpowder, it will just burn off. If you light the PbN3 ignitor stuck in a handful of unconfined TNT your are dead. (Btw if you light TNT without an ignitor it will also just burn off. It needs the initial shock wave provided by the detonating PbN3!)

--Felix Tritschler (talk) 18:55, 16 November 2013 (UTC)

  • There are many topics not covered in the article. It needs attention from an expert in the subject. Unfortunately, there are not so many not only in WP, but also in real life, because detonation is a very complex topic of the physics of combustion and explosions. The most relevant distinction between explosion and detonation is that detonation is a physico-chemical phenomenon of self-sustained supersonic wave propagation in a reactive substance, while explosion (chemical, not nuclear) is a phenomenon related to mechanical work done by rapidly expanding gaseous products of detonation or combustion. I'm working on this article ((ru:детонация) in Russian Wikipedia. --Fedor Babkin (talk) 16:20, 17 November 2013 (UTC)