Talk:Detonation

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)

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)

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)

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.

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)

I provided some further examples of what some explosives are that detonate — Preceding unsigned comment added by SUChem04 (talk • contribs) 02:16, 25 October 2023 (UTC)

detonation in engines

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)

We should add more detail to the firearm side of this topic, not just one sentence worth of information. The section title is "In engines and firearms" yet there's only a sentence worth of information on the topic relating to firearms — Preceding unsigned comment added by SUChem04 (talk • contribs) 02:27, 27 September 2023 (UTC)

Lead

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

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)

Introduction, and contrast with deflagration

The introduction seems (to me) to be too technical - in the first sentence it uses two terms, "exothermic" and "shock front", that I think are not right that early in the article. It then immediately goes on to mention which kinds of detonation are easier to study, which would be appropriate to much later in the article.

The other thing is that the contrast with deflagration, which from what I've read is an important and informative one, is not made until the last quarter of the article. Shouldn't this contrast be made right at the beginning: it helps inform us what is special about a detonation. It's also important to do this because in common speech, people use "detonation" to mean any explosion, so making it clear straight away that not all explosions are detonations would be doing a useful service.

I don't feel qualified to make any changes myself, but from what I've read, what makes a detonation distinct from a deflagration is:

1. In a detonation the combustion front travels faster than the speed of sound in the material; in a deflagration it travels more slowly.

2. In a detonation the initiation of combustion at any point is caused by the pressure rise (and consequent heating) caused by the supersonic shock wave; in a deflagration the initiation of combustion is by normal transfer of heat from the adjacent combusting material.

3. Detonations are much more violent than deflagrations; a deflagration can be an entirely tranquil affair.

The introduction to the article on deflagration is much more the sort of thing that is needed. Macboff (talk) 11:01, 9 April 2021 (UTC)

I provided the changes similar to what you're saying above about the contrast between detonation and deflagration in the introduction section. — Preceding unsigned comment added by SUChem04 (talk • contribs) 01:35, 25 October 2023 (UTC)

The first paragraph is a mess now.

It now contains contradictory and incorrect information presented in poor English. It reads like it was cobbled together from a book about combustion and ignores detonation in explosives without external oxidizers. I’ll dig out a book on the subject and have a go at fixing it when I get time unless someone else wants to have a go. NBeddoe (talk) 22:38, 8 August 2024 (UTC)

Wiki Education assignment: Big Ideas in Chemistry

This article was the subject of a Wiki Education Foundation-supported course assignment, between 29 August 2023 and 19 December 2023. Further details are available on the course page. Student editor(s): SUChem04 (article contribs). Peer reviewers: Kmcfarland11222, Chemlearn11.

— Assignment last updated by Pringlesandluffy (talk) 17:45, 3 October 2023 (UTC)