Comment by MarkusWandel
20 hours ago
Wonderful but it irritates me that so many descriptions of internal combustion engines refer to "explosions" of the fuel. You don't want that. It causes knocking and pinging and engine damage. You want a controlled burn that generates heat smoothly.
Not exactly. You do want a deflagration and not a detonation, but "explosion" is more loosely defined and, depending on who you're talking to, a self-sustaining subsonic flame front and a sharp pressure spike are a perfectly valid explosion.
explosion/detonation causes engine knocking or pre-ignition which is both very bad. a properly working combustion engine is driven by controlled burning.
You’re replying to a post that says that “explosion” doesn’t imply “detonation”.
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Even more confusing to anyone who doesn't know the lingo, detonation in the context of an internal combustion engine means something specific. It is a synonym for pinging and knocking, and happens when unburnt fuel/air mixture explodes after the spark plug has already fired. It can damage the engine, but typically takes some time. Preignition is when the mixture ignites before the spark plug fires, and is typically much more damaging, often destroying the engine in just a few revolutions. It can pound through the boundary layer between the mixture and the face of the aluminum piston and melt it, or break something else in the engine like a rod.
It's been a minute, but at one point GM had some pretty interesting videos up on YT where they talked about preignition testing on Cadillac Northstar V8s and how quickly it would grenade the engine. Fascinating stuff.
There are videos on YouTube of what the combustion actually looks like in slow motion. It's fast, but far less violent than an "explosion".
I don't think it's any slower than the dust explosions that occasionally happen in factories or grain silos. Although those do appear more violent due to the scale & damage.
You don’t want detonation, but you do want deflagration.