What is the role of wavefront in high explosives?

[Nim]

How slow can an explosion possibly be?

 

[LURCH]

I think the generally accepted difference between "detonation" and "combustion" is wether the reaction takes place at supersonic speed for the medium being burned.

In an internal combustion engine, for example, care is taken to avoid a feul/O₂/pressure combination that will "detonate" the fuel in the cylinder, because such an explosion will damage the piston heads (this is one of the main engineering obsticals to Pulse Detonation Engines). Although I've never seen it explicitly stated, the difference between detonation and combustion is always discussed in terms of a supersonic or a subsonic shockwave.

For example, http://www.popsci.com/popsci/aviation/article/0,12543,473272-2,00.html no pulse detonation states that...

In deflagration—even in "fast flame" situations ordinarily called explosions—that reaction moves at tens of meters per second at most. But in detonation, a supersonic shock wave slams down the tube...

.

Not a clear-cut definition, as most people would refer to what goes on inside an engine cylinder as an "explosion".