Talk:Detonation

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Contents 1 Two classes of combustion? 2 pressure waves 3 Latin "detonare" 4 Combustion 5 Detonation and explosion

[edit] Two classes of combustion?

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)

[edit] pressure waves

"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)

[edit] Latin "detonare"

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)

[edit] Combustion

"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.

[edit] Detonation and explosion

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)