[Vwdiesel] New to list

[Bill Truesdell]

Anton Largiader wrote:

>Actually I don't think it's accurate to say that it runs by detonation.
>Detonation is the premature auto-ignition of fuel/air mixture that's already
>in the combustion chamber, which is sort of an explosion in the case of
>gasoline.  Diesel is compression-ignited, but the fuel is only added when
>combustion is wanted, and has a more controlled burn.
>
>
Deflagration is probably the correct term for both. Deflagration is a
more controlled burn. Can be very fast, so it seems like detonation
(both can be called an explosion, which is where the confusion starts),
but detonation implies a shock wave propagation of the explosive front
and is more chemical in nature while deflagration implies a burning
front. Detonation fronts, since they are shock waves, can move in the
thousand of feet per second and all the material is in transition at
approximately the same time, so the effect is deadly.
For example, gunpowder deflagrates and does not detonate. Burn it in the
open and it does little but encase it in a rifle bullet and, because of
pressure and temperature, it burns more quickly and an explosion
(deflagration contained) results. But no detonation. If it did detonate,
it would shatter the bullet chamber.

Either can be started at a specific point or points, blasting cap for
detonation and spark plug or hot spot for deflagration. Deflagration can
transform to detonation under the right circumstances and material. You
can burn HMX (a military explosive) but in the process, it might detonate.

Bill T