[Gasification] Prime Mover Knock

[AJH]

On Tue, 16 May 2006 01:37:45 -0400, Jeff Davis wrote:

>Early diesels used fuel injection by high pressure air. This atomized spray, 
>into the cylinder, made a soft combustion hense slower rate of pressure rise 
>after injection started. No diesel knock was heard.

Jeff, this was about the biggest mistake Rudolph Diesel made, it was
not rectified until a brit introduced fuel injection. I have seen one
of his early Sulzer's running at "internal fire museum" in Wales.

If you think about it using a compresses air blast is about the worst
think to do, in effect you are expanding an ambient temperature gas
into the hot post compression gas in the cylinder, this expanding
blast robs heat from the combustion chamber and slows combustion. This
produced the soft effect you describe but a high efficiency cost.

Also consider that there was a big power cost in adiabatic compressing
gas for the reservoir and then cooling it to maintain capacity, all
this power was just converted back to heat which was lost.

Similarly the indirect ignition diesels sacrificed efficiency for
smoothness in passenger vehicles but big engines always seem to have
favoured direct injection.

It's the move to common rail and high pressure injection systems with
electronic control that has enabled direct injection diesels to become
refined without sacrificing efficiency.

AJH